[Bill Thomas]

Dear Dave,

     At the moment I can't *swear* about the spacing, but there is no reason why you can't assemble the binding posts with the black one in the middle.  Just remember to wire them accordingly.  I am assembling the unit this way because I am following Frank's Assembly Instructions closely.  (And I would probably forget which post was 4 Ohms and which was 8 Ohms anyway.)  Also, since I change connections between MANY "vintage" amplifiers and equally "vintage" speakers, much of the time I am dealing with bare wires, rather than neatly terminated cables.

     When I get back "on site", I'll try to remember to check the spacing, but it looks pretty close to me.

Sincerely,

Bill Thomas

[avahifi]

The output terminal spacing does not support dual banana plugs on 3/4 inch centers.  There was not enough room for this without cutting sheet metal and our kit does not do this.

Regards,

Frank Van Alstine

[Bill Thomas]

Dear Frank,

     Thanks for the information.  I *thought* they looked a little bit closer than "standard" 3/4" spacing.  (My previous post was a bit ambiguous.)  When I said they look "close", it could easily be taken to mean that they look "close" to 3/4" spacing.  I *MEANT* that they look a bit closer together than standard 3/4" spacing!

     Words are sometimes my friend, sometimes my enemy!  Sorry for the confusion.  Thank you VERY much for clearing this up.  (I wouldn't want to "hack-up" a Stereo 70 chassis either!)

Sincerely,

Bill

[Bill Thomas]

December 3rd, 2008 - Update:  "This Is About As Much Fun As Watching Paint Dry!"

     Come to think of it, I *HAVE* been watching paint dry!  Here's a picture of our Output Transformer end bells, primed and properly cured.  Here's the Outside:

                             

     And here's a picture of the Inside of the end bells:

                             

     You might be wondering why I bothered spraying primer on the *inside* of the end bells; after all, who's going to see it?  Well, after the bells were glass-bead blasted, the metal was completely exposed and unprotected.  A coat of primer will keep the metal from rusting due to the humidity in the atmosphere.

     I should mention that this application of primer was actually sprayed IMMEDIATELY after the bells were returned from the glass-bead blasting process.  Since the metal was totally bare and unprotected, it could quickly develop a "tainted" surface - again, from only the moisture in the atmosphere.  Before applying the primer, it is important to blow any remnants from the glass-bead blasting process.  (Those little beads get into EVERYTHING and cling tighter than plastic wrap.)  Once you blow the remaining glass beads from the surface, wipe the bare metal with lacquer thinner - both inside and out.  Allow the thinner to evaporate completely and apply the primer to the inside of the bells.  Follow the directions on the can and make SURE to keep shaking the can often in between the spraying applications.  I have said this before, but remember to apply the primer in several light coats until the entire surface is covered.  Again, follow the paint manufacturer's recommendations regarding the "wait time" between coats of primer.  Every nook and cranny needs complete coverage so our color coat will bond properly.  Once you are satisfied that the coverage is complete, allow the bells to dry.  The manufacturer of the paint I used said that the paint would be dry to the touch in about ten minutes, but the parts shouldn't really be "handled" for about an hour.

     Once you have waited for that time to elapse, *CAREFULLY* turn the end bells over and apply the primer to the Outside.  Again, several *light* coats are MUCH better than a thick, heavy coat.  You must use EXTREME caution during this step because you want the edges of the metal to retain the primer.  Don't just invert the bells on the same surface you just used to paint the inside.  Instead, put down a fresh surface so the primer on the edges of the metal doesn't stick to the "overspray" on the previous work surface.  While newspaper works *ok* for the task, it'll pay you to go to your local "Moving and Packing" supplier to pick up some unprinted "newsprint" paper.  It's cheap and you can lay down a fresh surface for every painting operation.  Remember, the quality of your finished paint job DEPENDS upon keeping everything CLEAN!

     The pictures above were taken after the paint had cured for five days.  The manufacturer of the paint said the part would be cured in about 24 hours, but we want to make SURE the coating is as tough as possible.  It takes time for the solvents in the primer to completely "outgas" and evaporate.  Waiting a little longer than the minimum "curing time" will give us just a *little* more "insurance" against working with a primer coat that can be easily damaged or worn through.

     Our next step is to smooth the Primer Coat.  If this were a car, we'd block sand the primer, but since we're dealing with SO many "nooks and crannies" we're going to use common automotive rubbing compound to smooth the surface a bit.  We DON'T want a perfectly smooth surface!  We still want a surface that will have a bit of "tooth" to it in order to help the color coat to properly bond with the primer coat.  Somewhat smooth is ok, but polished is not!

     I realize that this project is taking a LONG time to complete due to these little "extra" cosmetic steps.  But, when we're finished, we *should* have an amplifier that will not only SOUND beautiful, it will also LOOK beautiful.  And I don't know about YOU, but *I* would rather take the time to "do it right" the FIRST time, rather than goof it up and have to remove the paint and start all over again; or worse, wind up with an amplifier that needs to be "hidden" because it looks "cruddy!"

     In our next update, we'll proceed on to the color coat (weather permitting) and then *hopefully* we can reassemble the Output Transformers and the Power Transformer, mount them to our chassis, and then wire the whole thing up.  We've still got a ways to go, but so far, things are working out the way they should.

     Expect a few days delay before the next update.  In the meantime, I'll be busy watching the paint dry!  Yes, it's "excitement on TOP of excitement" around the ol' hacienda!  But the best is yet to come!  Stay tuned!

Sincerely,

Bill Thomas

[jtwrace]

Bill,

Looks great as always.  If you have any interest you could send them down to Charlotte for some electroless nickel.  That would look HOT.

[Bill Thomas]

     While I might be inclined to agree with an original nickel-plated chassis, (I DO love the look of nickel!),  since this chassis has been re-plated in chrome, it just *might* be a bit like mixing "Cardinal Red" and "Barbie Pink" on the same unit.

     But more importantly, (and even though I actually DID "farm out" the re-plating of the chassis), I really wanted to show people what could be accomplished "at home" with a couple of cans of spray paint (and some serious "sweat equity") to take some old "gnarly" looking transformers and make 'em look nice and pretty again.

     Besides, since our green circuit board will be displayed on a pedestal, the contrast between the chrome and the black will tend to make the green circuit board "pop" (visually speaking)!

     Then again, each of these "rebuild projects" tends to have a "life of it's own."  When I started this one, I had originally planned to just take a nice looking chassis and do a "normal" rebuild using the "Ultimate Stereo 70" rebuild kit.  As it turned out, my "nice looking chassis" wound up being a completely "stock" factory-wired Stereo 70 that was in EXTREMELY good cosmetic condition.  I just didn't have the heart to drill out all those rivets and "carve-up" a perfectly operating original unit that way.  The chassis I DID wind up using was a pretty ugly beast with SERIOUS rust and pitting problems.  A re-plating job was the BEST option to "make it pretty" again.  I had toyed with the idea of powder-coating, but since this was going to be a really "special" amplifier, I wanted it to "sparkle and shine" with a true chrome-plated chassis.

     When the chassis came back from the plating company, I took a good look at the transformers.  (You saw the pictures!)  There comes a time when you simply have to have your "moment of decision" about these things.  In all good conscience, I just *couldn't* stick those grubby transformers on such a pretty foundation.  But, it gave me an opportunity to show folks what could be accomplished using standard "spray-bomb" paint and a little effort.

     It's kind of like your typical car restoration project that gets out of hand.  You start with a "daily driver" and decide to start "making it prettier" and by the time you're done, you have a concours 100+ point "trailer queen" that'll NEVER see the open road again!  (Along with a totally evacuated wallet!)

     Of course, this is no concours restoration.  It is a "resto-mod" that definitely WILL see real use!  Cars were meant to be DRIVEN and amplifiers were meant to make music!

Sincerely,

Bill Thomas

[Atlplasma]

Hi Bill:

How do you handle cleaning up the cores? I'm sure you want them to look as good as the end bells.

Steve

[Bill Thomas]

     You want to be cautious with the cores.  Any abrasives used should be mild and you should avoid excessive removal of the lacquer.  Generally speaking, after VERY carefully masking the windings to avoid any contamination, a mild polishing compound can be used.  It can be removed with a dampened shop towel.  Once the surface is cleaned a bit, a *light* mist of color can be applied to the Output Transformers, or they can be left "au naturel."

     Hope this helps.

Sincerely,

Bill Thomas

[Bill Thomas]

January 20th, 2009 - Update:  "Goodbye NEW Paint!"

     You never really know where a particular "stumbling block" is going to come from.  In the case of our "Ultimate Stereo 70" build, the prevailing climate conditions have been delaying our project for quite some time now.  You simply can't paint when the temperature is too low, or there is too much falling moisture.  (This has been going on for quite a few weeks now.)

     To get around this problem, I worked out a "deal" to do the final painting in a heated garage MANY miles away from here.  Unfortunately, the owner of that garage was out of town over most of the Holiday Season, so everything has been "on-hold" pending his return.  The GOOD news is, he HAS returned.  The BAD news is, we suffered a BIG setback!

     It all started out innocently enough.  I just had to do a little "touch-up" of the finish coat on our Output Transformer end bells.  Of course, that meant another coat of paint.  When that final coat was applied, THIS was the result:

                                       

     Oops!  Not *exactly* what we were hoping for, is it?  The problem was nobody's fault but MINE!  In the past, I have STRESSED the need to follow the manufacturer's recommendations when applying paint or glue.  You would think that I would follow my own "sage" advice, but again, you'd be wrong!  Here's why we wound up with something resembling an alligator wallet.

     We were using an enamel paint for a nice, glossy look with a minimum of extra "finishing" work.  We used the correct primer, allowed MORE than enough "curing time" for the primer to "set up" properly for the finish coat, and applied a pretty nice final coat.  BUT, there were a few "flaws" in the final coat that required us to sand it down to get rid of the flaws so we could apply another final coat.  HERE is where the problem (and my stupidity) came to a head.

     The first finish coat was sprayed on two days prior to our sanding and repainting.  Now, in my haste to complete these "pesky" little end bells, I completely forgot to re-read the instructions on the paint can.  Of course, once the paint began to "alligator", THEN I looked at the instructions.  They clearly said, "apply a second coat within one hour, OR after a week of curing time."  Well, "Duh!"  You see the result of my stupidity.  When something like this happens, there is only ONE way to properly address it - start over!

     It took approximately five applications of "Aircraft Grade" paint stripper to get our end bells back to bare metal.  Yes indeed, the primer had certainly cured VERY well!  I should mention that even though we had one set of "nicely finished" end bells already assembled to one of the Output Transformers, we took them off and stripped them as well.  The reason was simple:  We decided to change the type of paint we were going to use to refinish these pieces and there was no way a lacquer paint job is going to perfectly match an enamel paint job.

     Why change to lacquer?  Time!  (Not to mention a REALLY beautiful finish!)  While our original enamel paint has quite a few "restrictions" regarding additional coats, lacquer cures VERY rapidly.  By using lacquer, we were able to apply MANY coats during a single evening.  Starting with our bare-metal end bells, we applied several coats of the proper "high-build" primer for lacquer.  The first couple of coats built up a reasonable surface to allow a good bit of sanding to "smooth out" the surface and provide "tooth" for additional coats.  In all, five coats of primer were applied - sanding between coats.  All this took place during one "marathon" session of painting over an eight hour period.

     The next day, the color coats were applied in a similar manner.  It's a pretty tedious process:  Apply a coat, sand it down smooth, clean it and apply *another* coat.  Then repeat as necessary.  The BIG difference between the application of enamel and the application of lacquer is the number of coats and the amount of surface sanding that is required.  With enamel, one coat of primer and one (or two) color coats will do the trick.  With lacquer, the final total was five coats of primer and six coats of color, sanding between coats.  That may sound like a LOT of paint "buildup", but the lacquer coats are a LOT thinner than the enamel coats.  Here's a picture of the painted end bells, prior to compounding and polishing:

                   

     In all, over 32 HOURS has been devoted to painting our transformers (and REPAINTING our transformers!)  By the way, I can't take the credit for the lacquer paint job.  Quite honestly, I was busy back "on site" preparing for the "final assault" in assembling our "Ultimate Stereo 70."  (Boy do THOSE words really ring true now!)  The lacquer paint job, along with all the requisite sanding and finishing, were provided by a "Maestro of the Paint Booth."  I am truly in his debt!  I *can* take responsibility for the paint work on our Power Transformer:

                         

     This brings us "up to date" on the "Ultimate Stereo 70" build.  In our next update, I'll show you the result of compounding and polishing the end bells, reassembly of the Output Transformers, and *hopefully*, how this will all look when assembled to our nice, chrome-plated chassis.  Updates will be coming a LOT faster now.  Hang on for dear life 'cause I ain't stoppin' for NOBODY!

Sincerely,

Bill Thomas

[Bill Thomas]

January 22nd, 2009 - Update:  "A Beautiful Transformation!"

     After our recent paint "difficulties", I thought you might like to see something truly pretty, for a change!  Our painted end bells have been reunited with our transformer cores and the completed transformers have been installed onto our chassis.  Here's a picture from head-on:

                   

     And here's a picture from the back of the amplifier:

                   

     And to give you an idea of how the completed Output Transformers look after assembly, here's a somewhat elevated view from the back of the amplifier:

                   

     While our "Ultimate Stereo 70" driver board hasn't been installed yet, the standoffs have been mounted "finger-tight" in anticipation of the "great event."  We're actually about halfway finished with the amplifier at this point.  In our next update, we'll take a look at the under-chassis wiring and the installation of that beautiful Driver Board.  In other words, we'll show you the completed amplifier from top to bottom!  This is turning into a VERY lovely amplifier.  You won't want to miss our next update, coming VERY soon!  Hang in there!  At LONG last, we're nearly done!

Sincerely,

Bill Thomas

[Bill Thomas]

January 24th, 2009 - Update:  "Some Assembly Required!"

     In our last update, we showed you how pretty those transformers looked on the chrome-plated chassis.  Now it's time to actually DO something with them!

     When building ANY Stereo 70, once the mechanical assembly is done, the FIRST place to start "connecting things up" is here:

         

     This is the socket for the GZ34/5AR4 rectifier.  While there aren't a lot of connections to deal with, since we are re-using an existing Power Transformer, the wires are pretty short.  You'll notice a tiny place on one of the filament wires where the cloth covering was "chafed", but the actual insulation on the wire is still just fine.  This is not ALWAYS the case.  Manipulating these old wires can have disastrous results.  Spend a little time heating them up a bit with a hair dryer.  Don't scorch them, just get them warm and a bit more pliable.  (Frank Van Alstine recommends this technique in his instructions for building the "Ultimate Stereo 70" and it is truly sage advice!)  As I usually do, I have applied a little bit of heat-shrink tubing over the ends of the cloth-covered insulation, just to keep the covering from fraying and to make things look a little neater.  Pin 8 of this socket gets an additional wire, so it has not yet been soldered, but the other three pins are completed and soldered.

     Once the rectifier socket has been wired, we can move on to a truly CRITICAL part of the amplifier - the central ground point here:

    

     In the "Ultimate Stereo 70" kit, Frank includes a terminal strip that is mounted in place of the old selenium rectifier.  The center lug of this terminal strip is the central ground point for the entire amplifier, so it is CRUCIAL that it makes a GOOD mechanical AND electrical connection to the chassis.  In the "Ultimate Stereo 70" kit, Frank includes VERY high-quality hardware (screw, nuts, etc.); everything you need to correctly build/rebuild the amplifier.  In this case, an "inside-star" lock washer is used to INSURE a good electrical connection at this ground point.  (It also keeps the terminal strip from "movin' around.")

     Once the terminal strip is securely mounted, you can connect the red/yellow wire from the Power Transformer.  Of course, like *this* transformer, nearly all of the red has disappeared and the yellow has faded, so this wire looks "sorta tan."  So how do you figure out which wire?  Well, the DEFINITE way is to measure the resistance of the Power Transformer secondaries.  But you *usually* don't have to go that far.  Since this transformer has been previously installed in an amplifier, there are only two *possible* wires that *could be* the center-tap: the one you see connected to the center lug, or the wire connected to the lug directly below the center lug.  *That* wire is the "Bias Tap" wire and is *supposed* to be a black/red wire.  In the case of our transformer, the "red" is completely gone from that wire, but the "black" strip remains.  This helps!  But to be *completely* sure, use your Ohm meter to check the resistance of the High Voltage Secondary.  Measure between the two ends of the High-Voltage wires that connect to the rectifier tube socket.  As you might guess, if you measure between one of the High Voltage wires on the rectifier socket, the Center Tap should be one-half the resistance value.  The bias tap will be either higher, or lower than one-half the resistance of the full Secondary winding.  Simple!

     Once you identify the Center Tap, the remaining short wire is the Bias Tap.  This needs to connect to a terminal on the "Ultimate Stereo 70" Driver Board assembly.  Unless you have a "wire-stretcher" handy,  the BEST way to "extend" this wire is to connect it to the lug below the center lug of the terminal strip, as we have done here.  The orange wire will route through the hole originally used for the can capacitor (no longer needed) and connect to the Driver Board.

     Located on either side of the terminal strip are the new Spectrol 10-turn potentiometers we're using as Bias Potentiometers.  The extended shaft will poke up *slightly* above the surface of the Driver Board, making them VERY easy to adjust, and the VERY high quality of the parts will insure a long life with little chance that they will fail and cause an expensive set of tubes to runaway and melt.  We'll wire those potentiometers a bit later.

     Right now, it's time to finish the connections from the Power Transformer.  We still have two filament windings to connect.  The pair of Green wires connect to the filament pins (2 and 7) of the Left-rear EL34.  Here's how that works out:

         

     Route those green wires close to the chassis.

     A twisted pair of wires (white and green) connect from pins 2 and 7 of the left-rear EL34, to pins 2 and 7 of the left *front* El34.  Route *that* twisted pair against the chassis as well.  Another twisted pair runs from pins 2 and 7 of the left-front EL34, to the left channel of the "Ultimate Stereo 70" Driver board.  Since we won't be mounting that until a bit later, we've just made SURE we'll have enough "twisted-pair" available to route around the front of the chassis, UNDER the Biaset socket, and then to the Driver board.  We'll cut it to length when we wire up the Driver Board.

     While we're looking at this picture, notice that we have also connected the four wires from the Output Transformer to the two left-channel EL34's.  The solid-color blue and green wires connect to the left front EL34 pins 3 and 4, respectively.  Don't solder pin 4 of the front EL34 *just* yet, we'll be adding a "feedback" wire to that terminal when we install the Driver Board.  You CAN solder pin 3 and BOTH pins 3 and 4 of the left-rear EL34.

     By the way, we're using the same color-coding Dynaco used in their factory-wired amplifiers (for the *most* part).  For the Left channel filaments, Dynaco used green-white twisted pairs, so we are too.  Onward!

     To finish the "pre-wiring" of the Left Channel Output Transformer, lets take a look at the wiring to the Left Channel Output terminals.  Here's a picture:

         

     This is pretty straightforward, but notice that the 16 Ohm tap is routed to a tiny terminal strip, rather than a Binding Post.  Another "feedback" wire will run from this terminal strip to the Driver board (when we install it, that is.)  Don't solder the Black (Common) wire yet.  We'll also be connecting a wire that runs from here, to the common ground point between the Bias Potentiometers.  Again, we'll get to that a bit later.

     In this picture you'll also notice a three-lug terminal strip.  I replaced the LONG 7-lug terminal strip with this one because I just *might* need it for another Stereo 70 down the road, AND it really "cleans up" this area of the amplifier.  Notice that the center taps of the filament windings connect to the two Outside lugs of the terminal strip.  We'll install that "funny, little 3-legged capacitor to these three lugs later.  The center terminal will have a ground wire that runs from *it*, back to our "common ground point" between the Bias Pots.  (That'll come later too.)

     One of the black wires from the Power Transformer connects to the center contact of the fuse holder.  It can be soldered at this time.  The heat-shrink tubing helps (a *little*) to prevent a nasty shock.  It's NOT a total solution, as the side contact of the fuse holder will still be easily "touchable" by "foolish fingers" so just be careful and keep 'em out of harm's way when the amp is plugged in.

    With the Left Channel "pre-wired", we can move on the the Right Channel.  Here's a picture of the Power and Output Transformer connections at the Right EL34's:

                   

     Basically, it's the same story as the Left Channel pre-wiring, except we used a brown-white twisted pair of wires for the filament connections.  Now, here are the Output connections for the Right Channel:

         

     You can also see the .02 uF disc capacitor Frank has included in the "Ultimate Stereo 70" kit.  This reduces switching "transients" and extends the life of the Power Switch, as well as serving to minimize a loud "POP!" when the amplifier is turned off.  The black wire is the other Primary Wire from the Power Transformer and can be soldered at this time.

     Put it all together, and THIS is the result:

         

     And *this* looks like a good place to wrap up this chapter of the "Ultimate Stereo 70" saga.  We're getting REALLY close to some BEAUTIFUL music now.  The Best (and the REST) is yet to come!  Stay tuned!

Sincerely,

Bill Thomas

     

[Bill Thomas]

January 25th, 2009 - Update:  "Final Wiring - Part One"

     Let's start out our coverage of the final wiring by taking a look at the Bias Potentiometers.  Here's a picture of the final wiring at the Bias Pots and our "Common Ground Point":

                   

     On the left side of this picture, you can see the completed wiring of the rectifier socket.  The thick red wire soldered to Pin 8 of the tube socket carries full B+ Voltage to the "Ultimate Stereo 70" Driver Board where the filter capacitors for the amplifier now reside.  Connection to the Driver Board is made through the hole where the original can capacitor once "lived."

     The orange wire from the Bias Tap of the Power Transformer also connects to the Driver Board through that same hole.  When soldering the six wires that connect to the Driver Board through this hole, you will need to poke the soldering iron through the hole.  There isn't a lot of space here, so the BEST way to handle the soldering chores without melting something is to work in a clockwise fashion, starting with the orange Bias wire.  Next, solder in the B+ feed from the rectifier.  Then, solder in the wires from the Filter Choke.  And finally, the two red wires from the two Output Transformers.  When soldering in a stranded wire, prepare the end of the wire first by twisting the strands tightly and "tinning" them with solder.  Slide the tinned end of the wire into the hole until it *almost* bottoms out against the circuit board.  Leave *just* enough exposed wire so you can apply the tip of the soldering iron to the Printed Circuit Board "pad" and the wire, at the same time.  Allow solder to flow until the entire  circuit board pad is covered and the solder flows to surround the tinned wire.  Work CAREFULLY to make a good electrical AND mechanical joint at each circuit board pad.

     We used a new Filter Choke for this build, so there was more than enough wire to make it to the Driver Board.  If you are re-using an existing Filter Choke, you will need to add more wire to the choke leads.  The "proper" way to do this is to use what is called a "Western-Union Splice".  This results in a mechanical connection that is strong, but keeps the diameter of the soldered splice about the same thickness as the original insulation of the wires.  Then, a piece of heat-shrink tubing over each joint will finish the task and there won't be a big "lump" to get in the way.  Remember, this wires carries nearly 500 Volts, so make SURE it is thoroughly insulated.  Another tip?  Shorten the choke leads a bit more so the splices actually occur under the chassis instead of inside the hole to the Driver Board.  You're welcome!

     One of the nice things about our Spectrol 10-turn potentiometers is that there is a little diagram on the body of the potentiometer.  The connections are numbered, and those numbers correspond to the original numbering scheme of the old bias pots.  Wire the two "Terminal 1's" together and solder another wire from the Left Bias Potentiometer's "Pin 1" to connect it to the Driver Board.  Each of the "Pin 3's" on the Bias Pots connects to separate pads on the Driver Board, so just solder a wire and leave enough length to properly dress the wire when you make the connection to the Driver Board.  Each Pin 2 connects to the left and right sides of the driver board, respectively.  Don't be stingy!  Leave plenty of extra wire on the "pigtails" so you will be able to route this wiring properly - away from other potential sources of noise and hum.  (We'll show you a picture later to demonstrate the "3D" nature of the wire routing to minimize hum and noise.)

     Our "Common Ground Point", the center lug of the terminal strip, has five wires soldered to it.  One comes from the Center-Tap of the High Voltage winding of the Power Supply, two wires connect to the "Common" binding post terminals at the Speaker Outputs, another wire goes to the center terminal of our added 3-lug terminal strip for connection to the 3-legged capacitor and the fifth wire provides the ground connection to our Driver Board.  Using the solid black wire Frank supplies in the "Ultimate Stereo 70" kit, makes this a simple task with no need to use more than one lug of the central terminal strip.

     OK, now let's take a look at the completed wiring of the Left Channel EL34 sockets:

                             

     There's a good bit going on here, so let's cover the additional wiring.  The 15.6 Ohm Cathode resistor is connected to the rear EL34 Cathode and the blue wire on the far left connects the Cathodes of the front and rear EL34's together.  Another blue wire connects from the Front EL34's Cathode, to Pin 8 of the Left "Biaset" socket.

     Notice the green wire from Pin 4 of the Front EL34 socket?  It connects to the Driver Board and is part of the feedback arrangement in the amplifier.  While it looks like this wire is next to the twisted pair of wires, there is actually some space between them.  Keep the green wire away from the Driver Board circuit traces as well.

     Regarding the green and white twisted pair, notice that the wires are routed against the chassis, under the left "Biaset" socket and away from the circuit traces of the Driver Board.  These wires carry 6.3 Volts AC for the Left Channel 6GH8A Driver Tube, so we want them as far away from the sensitive grid circuitry as we can get!

     You can also see where the yellow wire from the Left Bias Potentiometer connects.  This is a "High Impedance, High Sensitivity" area too, so keep this wire away from the twisted pair.

     The two resistors are the "grid stopper" resistors that actually couple the audio signal from the Driver Board, to the two EL34's.  Make SURE you insulate the resistor leads so they don't short out against the chassis.

     The black wire that connects to Circuit Pad #8 comes from the 16 Ohm tap of the Output Transformer.  It's part of the feedback arrangement.  Route it away from the Power Transformer as shown.

     You can also see where the rest of the Bias Potentiometer wires connect to the Driver Board.  Keep them close to the chassis.

     Now, let's look at the Output section of the Left Channel:

                             

     The two black wires from the Common and the 16 Ohm Taps of the Output Transformer are the wires that provide negative feedback to the Input circuitry of the Driver Board.  The Black wire at the "Common" terminal goes to our "Common Ground Point" terminal strip and the other black wire routes from the 16 Ohm Tap of the Output transformer back to Circuit Pad #8 of the Driver Board.

     See the 3-legged capacitor?  While this is an "unusual" part, it is actually a dual .02 uF capacitor with a common center connection.  If your original part is broken, or if the leads are too short, you can replace this part with two discrete .02 uF capacitors.  (You'll never notice a difference in sound quality.)  This little part provides an AC ground reference to the center tap of each filament winding.  Without this part, your amplifier will have a LOT of HUM!  The center connection of the capacitor routes via the black wire to our Common Ground Point.

     One wire of our new Power Cord (included in the "Ultimate Stereo 70" kit - Thanks, Frank!) connects to the side terminal of the fuse holder.  I have added a bit of clear heat-shrink to minimize the shock hazard, but the silver ring around the center of the fuse holder carries full Line Voltage.  When the amplifier is plugged in, DON'T TOUCH!

     We'll finish up or description of the wiring and the *routing* of the wiring in our next update - following immediately.

Sincerely,

Bill Thomas

     

[Bill Thomas]

January 25th, 2009 - Update:  "Final Wiring - Part Two"

     Here's a look at the Final Wiring of the Right Channel EL34's:

         

     This is basically a "mirror-image" of the Left Channel.  I won't bore you with a detailed description of the same stuff we covered in the Left Channel wiring, but you can get a better look at the wiring from the Input Jacks to the Driver Board.  The "hot" wires are VERY susceptible to hum pickup, so it is VERY important to keep these wires away from the twisted pairs that supply AC to the tube filaments on the Driver Board.

     Now, let's look at the Output Connections for the Right Channel:

         

     Notice that the feedback wires are routed away from the Power Transformer.  You can also see the other wire of our new Power Cord connected to the remaining terminal of the Power Switch.  This picture also gives you some idea of just how cramped the connections are through the old can capacitor mounting hole.  While soldering these six wires IS a bit of a challenge, if you work carefully, you'll be just fine!

     I mentioned earlier that there is a "3-D quality to the wiring of the Driver Board.  This picture will help you visualize what I am talking about:

     

     While it's impossible to get a camera down into the "guts" of the amplifier to show you the various "levels" of the wiring, this picture shows you how the various wires that NEED to be separated, ARE separated.  Wires that could potentially pick up hum are kept as far away from the twisted pairs as possible.  Wires from the Bias Potentiometers are kept away from the feedback wires.  The feedback wires are routed close to the chassis.  The "Hot" wires from the Input Jacks are kept away from the twisted pairs and the circuit board traces.  Everything has a proper "place" in order to keep hum and noise pickup to a minimum.  You can also see that the twisted pairs that supply the filament Voltage to the two 6GH8A's are routed close to the chassis, but away from the Driver Board circuit traces AND other wires.

     Put it all together and THIS is the result:

     

     And that's it!  We have an amplifier!  Here's what it looks like in "test configuration" with a quad of Electro-Harmonix EL34EH's, a NOS Mullard-manufactured GZ34/5AR4 (branded as a GE) and the two NOS Philips/ECG 6GH8A's.  The 6GH8A's are supplied in the "Ultimate Stereo 70" kit.  (The rest of the tubes come from my stock of NOS and NEW tubes):

              

     Yes, I know the EL34's aren't inserted completely.  Yes, they CAN be, but I wanted to keep wear and tear on the new tube sockets to a minimum.  These VERY high quality Eby tube sockets grip like a first-time trapeze artist.  What a WONDERFUL change from the original (cheap) Cinch plastic sockets!  I don't think we'll suffer any "intermittent contact" problems with THESE babies!

     Here's a view "from the top":

               

     Yes, that's a tiny "dent" in the cover for the Power Transformer.  (I wish I had taken a little more time to try to remove it, but I *probably* would have made things worse.  As they say, "First, do no harm.")  To be honest, it's not THAT noticeable at most viewing angles.  Still, all things considered, this is a FAR cry from what we started with, remember?

         

     Compare that with THIS:

                   

     While the amplifier is now wired, we still have a little more to cover.  We WILL, in our next update coming soon!  Right now, it's time for some BEAUTIFUL music while we "burn-in" our "Ultimate Stereo 70!"  More to come!

Sincerely,

Bill Thomas

[Bill Thomas]

January 25th, 2009 - Update Three:  "So, What's It Gonna Cost for ME to Build One for Myself?"

     In previous rebuild articles, I haven't covered the "Dollar Aspect" of the construction.  This project took just a *tad* over four months to bring to fruition.  Was it worth it?  You BET it was!  (We'll cover the actual "sound quality" of the finished amplifier in our next update.)  First, let's discuss the "Ultimate Stereo 70" kit itself.

     The most striking thing I noticed about the kit was the EXTREMELY high quality of every component selected for the "kit."  EVERY resistor and EVERY capacitor was of truly high quality.  The Printed Circuit board itself is absolutely STUNNING.  You WON'T have a problem with circuit traces lifting from the substrate with THIS board.  The silk-screen parts placement printing is clear and completely unambiguous.  The Driver Board tube sockets are of the highest quality available today.  Everything you need to transform your old Stereo 70 into the "Ultimate Stereo 70" is included in the kit - hookup wire, solder, even a new Power Cord.  It's ALL in the kit.  The mounting hardware is of MUCH higher quality than the original Dynaco hardware.  The 4-40 nuts have captive star lock washers and the machine screws are MUCH more durable than the "stock" screws and nuts used in existing Stereo 70's.

     The use of 6GH8A's eliminates the added expense of trying to find 7199's at a reasonable price, since 6GH8A's are VERY common tubes; even NOS American-made tubes are readily available at about a TENTH of the current price for NOS 7199's!  But you won't need to look for any for *quite* a while.  two NOS Philips/ECG 6GH8A's were included with this kit.

     The "upgraded" Input and Output connector kit is WELL worth the added cost.  The wider spacing of the Input RCA jacks makes it possible to use high quality interconnects and the 5-way Binding Posts make it "dead-simple" to swap speaker cables quickly and easily.  Quite honestly, it's OBVIOUS that Frank has spent a LOT of time putting all the right parts together to make these kits a true JOY to build and use!

     So, let's get down to the cost of "Ultimate" joy:

     First, we need to include the cost of our "donor" Stereo 70.  As you might guess, this "basket-case" of a donor came from eBay.  It was *touted* as an "upgraded" unit, but in reality, it was on its last legs.  (It wasn't much to look at either!)  It cost a TOTALLY unreasonable $250.00!  From the donor we salvaged the chassis (such as it was), the Output Transformers, and the three-legged capacitor.  That's it!

     The cost of replating the chassis was $200.00.  This was the charge to plate the main chassis only.  The bottom cover from our donor was in such poor condition that we are replacing it with a new part that came from Sound Values a few years ago.  It cost $35.00.  (Thanks, John and Joy - wherever you two are today!)

     The "Ultimate Stereo 70" kit is currently listed at $449.00 and the upgraded connector kit is an additional $75.00.

     Those high quality Eby tube sockets were $10.00 each (and worth EVERY cent!) and the two "standard" Cinch sockets for the "Biaset" sockets were $2.00 each.

     The ten-turn Spectrol potentiometers were a "Surplus Steal" at $10.00 each.  (Is that a Dollar a turn?) and you can figure in about $50.00 (or a little more) for wire, hardware, paint, rubbing and polishing compounds, a terminal strip, the Power Switch and the strain relief for the Power Cord.

     The NOS GZ34/5AR4 is a $125.00 item.  The NEW matched quad of Electro-Harmonix EL34EH tubes is an additional $60.00.

     So, let's add it all up:

Donor.................................. ........... $250.00
Plating................................ ............ $200.00
Bottom Cover.................................. . $ 35.00
"Ultimate Stereo 70" kit...................... $449.00
Upgraded connector kit...................... $ 75.00
Tube Sockets................................ ... $ 54.00
Potentiometers......................... ........ $ 20.00
Miscellaneous Items........................... $ 50.00
Tubes.................................. ........... $185.00

Grand Total.................................. ... $1318.00

     But an amplifier THIS nice "cries out" for MUCH better EL34's.  Let's add two matched pairs of NOS Mullard EL34's.  The going rate for THOSE beauties is around $450.00 for the quad, so let's add another $390.00 to the total cost.  That brings us to a GRAND grand total of:  $1708.00!

     Remember, this is what it would cost you if you were "starting from scratch" with the build.  If you have a good Stereo 70 to begin with, you can shave $485.00 off the cost of this build.  That brings the cost down to $1223.00.  Got a good set of Mullard tubes available?  That brings the cost down to $648.00!

     It's all a matter of priorities.  If you don't care how nice your finished amplifier looks, you can shave some bucks.  If you have some of the items "on hand", you can shave some MORE bucks.  I CAN tell you *this* much:  Even at $1708.00 for the "Full Monty" version, you'll have an amplifier that is the rival of units costing five times as much or MORE!  It really IS *that* good!

     We'll get into THAT aspect of the "Ultimate Stereo 70" build in our next update when we discuss the actual "sound" of the final result.  Stay with us!

Sincerely,

Bill Thomas

[avahifi]

I really appreciate your efforts in this project Bill.

However you are overestimating the cost a bit.

Note that we will do a complete factory installation of the U70 circuits in your tired but working ST-70 for $899 including all new tubes and the AVA jack set installed.

My builder does do a partial strip of the chassis and cleans it up as much as is reasonable, but of course not to your wonderful "glow in the dark" standards.  They do come up looking pretty darn good with all marginal wiring replaced and solder connections made solid.  And of course if you own a decent ST-70 with good tubes and want to do it yourself, the cost will just be $499 plus your labor time.

We operate on the philosophy of "its the music" first.  The visual clean up is frosting on the cake, important to some, but not all that much to others.

But gee, it sure is nice seeing that old ST-70 turn into something one can be really proud of again.

Best regards,

Frank Van Alstine

[Bill Thomas]

Dear Frank,

     I was trying to illustrate the costs involved in this particular "Extreme Rebuild", but of course, I *should* have also listed the prices for your "factory installation" of the complete kit in an existing Stereo 70.  The costs I listed include the "visual" items like the replating of the chassis and the new bottom cover.  I also included the cost of using NOS Mullard tubes for the rectifier and the EL34's.  I also mentioned that if someone had an existing Stereo 70 and a set of good tubes, the "do it yourself" cost would drop to $648.00, but that price includes the cost of the new, high quality tube sockets, the Spectrol 10-turn bias pots and the miscellaneous items, so I don't think there is THAT much difference in the prices I stated.  Considering the amount of "sweat equity" involved in this particular "Extreme Rebuild", your complete "factory rebuild" price of $899.00 (including new tubes and the upgraded jack set) is a REAL deal!  If you add the cost of purchasing an existing Stereo 70 (in *this* case, $250.00), that raises the full price to $1149.00.

     Still, for an amplifier of this "sonic quality", that is an absolute "Screaming Steal!"  Then again, to duplicate the "visual aspect" of this "extreme rebuild", the costs DO mount up.  I'm not sure that ANYONE would actually spend over 32 hours and several hundred miles of travel to apply five coats of lacquer primer and six coats of lacquer color coating, with hand sanding and compounding between the coats, *just* to repaint the Transformer bells, but this was a "no holds barred" exercise in showing someone what *could* be done with enough persistence, enough time (and enough dead presidents), in order to make a visually stunning amplifier from something that originally looked like a rusted bumper on a '47 Dodge.

     Quite honestly, I originally had NO plans to take things this far, but once I built the "Ultimate Stereo 70" Driver Board and saw the quality of the result, I just didn't have the heart to install it in an old "rust bucket" of a Stereo 70.  Then again, when the chassis arrived back from being replated, (well worth the $200.00 outlay), it just raised the bar that much higher and spurred me on to go the "whole nine yards" in finishing EVERY aspect of the visuals to match the quality of the "sonics" YOU engineered into the electronics.

     To my mind, I think it is safe to say that the end result of this "project" is an "Ultimate Stereo 70", from both the "sonic standpoint" AND the "visual aesthetic standpoint."  Overkill?  No question about it!  But the end result is an amplifier that deserves to be displayed under a spotlight, rather than tucked into a corner.

     I'm sure you know that a "no holds barred" project like this takes on a life of its own.  It's not unlike the guy who buys a 1965 Mustang that "needs a little work" to make it drivable.  He starts out by rebuilding the mechanicals.  Then he decides to "spiff it up a little."  Before he's finished, he has a concours restoration that becomes a "trailer queen" because it's too valuable to drive.  The GREAT thing about *this* build is that it won't hurt it one bit to "drive it" every day from now on!

     I WILL say this much, I don't think I'll be spending this amount of time, money or effort on another Stereo 70 anytime soon.  But it sure was nice to make it happen, just this once.

     I salute you, Frank.  I can safely say that this project has been an honest attempt to show you just how much I respect your contribution to the audio community over these many decades.  In my next "update", I'll be discussing the "sonic rewards" of the "Ultimate Stereo 70" kit.

With DEEPEST respect and appreciation,

Bill Thomas

[Bill Thomas]

January 25th, 2009 - Update Three:  "It Sounds Like a Stereo 70 - Only Better!"

     Before we get to the discussion of "sound quality", I wanted to report on the initial "turn-on" of the "Ultimate Stereo 70" amplifier.

     I completed the wiring of the amplifier around 2:00 AM Thursday morning.  I simply couldn't wait, so...  I stuffed it with the supplied 6GH8A driver tubes, a NOS Mullard GZ34/5AR4 and added a new factory-matched quad of Electro-Harmonix EL34EH Output tubes.  (These are the tubes I use to "test" new amplifier projects.  In case something goes *drastically* wrong, I'm not out a bunch of bucks.)  I plugged the amplifier into my trusty Variac and slowly brought up the Voltage.  No signs of stress or strain, everything powered up nicely.  But there was no sound!  With a stock Stereo 70, when you put your ear next to the speaker, you can *usually* hear SOME trace of "thermionic emission."  And when you power up a stock Stereo 70 without the bottom cover installed, there is almost always *some* trace of hum.  Not THIS time.  Total silence!

     Not quite believing that things should be this quiet, I fired up a little portable CD player I had plugged into those nice, new, gold RCA Input Jacks.  And - there it was!  GORGEOUS music from a dead silent background!  Even those "less than perfect" Electro-Harmonix EL34EH's couldn't disguise the fact that something truly SPECIAL was going on!

     When "burning-in" an amplifier, I use a wide variety of music.  Fortunately, I have a pretty extensive library of material that has been ripped uncompressed to hard drives (approximately 10 TB worth of audio at this point).  It's no big deal for me to put together "test CD's" of material I am *intimately* familiar with.  I decided to burn a "test CD" with some cuts that would "tell the tale" clearly.

          I was especially impressed with the clarity of the Banjo in the left channel of "Take It Easy" by the Eagles.  It was a truly noticeable improvement over a stock Stereo 70.  (Funny how those "little things" jump out at you.)

     "Remember" by Harry Nilsson was quite a revelation as well.  "Branded Man" by Merle Haggard was less "strained" than with a stock 70.  (Usually, the guitar just tried to peel your face off, but here, it had a lot of "point", but wasn't excessively searing - as it SHOULD be.)

     Randy Travis' "Honky-Tonk Moon" was just GORGEOUS.  Full, rich, and crystal clear.  Not a BIT of Randy's "nasality" was lost.  The harmonica was right in the room.  But, the BASS was absolutely STUNNING!

     "Hear To Heart" by Kenny Loggins is an especially well-produced piece.  The intro showed the significant improvement in the bass region clearly.  Kenny's vocals were dead-centered and you could hear every nuance of the vocals.  But it positively sent chills up my spine when I listened to "Crying" by Roy Orbison.  Despite the flaws in the Master Tape (you can CLEARLY hear a dropout that is usually only audible in headphones), Roy was about eight feet away from me - dead center.  Simply STUNNING!

     As I type this, Ray Charles is just wrapping up "Take These Chains From My Heart and Set Me Free."  The tape hiss on the master tapes is clearly audible, but Ray is alive again, dead-center between my near-field monitors.

     One of the most striking aspects of the "Ultimate Stereo 70" is the improvement in the bass region.  Due to design compromises, a stock Stereo 70 tends to be a little "muddy" (or what I call "flubbery") in the bass region.  This has to do with a combination of things.  If you have the time, let's discuss it a little.

     The Stereo 70 depends upon relatively high amounts of negative feedback to minimize distortion.  But for this principle to work properly, the feedback signal has to contain the entire audio passband presented to the input of the amplifier.  In a stock Stereo 70, the Input is directly coupled to the grids of the 7199 driver tubes.  This means that the 7199's are presented with a signal "from DC to light" (well, *almost* anyway.)  The problems begin when the signal travels through the amplifier.  The 0.1 uF coupling capacitors are simply too small to pass the lower bass frequencies without rolloff.  By the same token, the Output Transformers also have some rolloff when the frequencies dip below 20 Hz or so.

     On the top end, the Output Transformers become a limiting factor.  While the "iron" in a Stereo 70 is REALLY good (after all, that's were Dynaco spent the "big bucks"!), ANY audio transformer is a compromise.  Make it good for bass, and the top end begins to suffer.  Make it IDEAL for high frequencies, then the bass will roll off.  David Hafler's contribution was to design a transformer that was a GREAT compromise, with good response at both ends of the audio spectrum.  BUT, it doesn't work "from DC to light"!

     What this all means is that the feedback signal delivered to the Input section is not *exactly* an inverted replica of the Input signal.  Hit a stock Stereo 70 with a 32 foot organ pipe and things get REALLY "muddy".  The feedback signal has less bass content in it than the Input signal.  That means the necessary reduction in Voltage at the Input stage simply isn't there and the tube is swamped.  This leads to VERY high levels of distortion in the bass region, but it ALSO means the REST of the audio passband is full of distortion products as well.  A similar effect also occurs at the upper extreme of the audio passband.  The limits of the Output Transformer cause a gradual rolloff of the extreme top end, but the Input stage is still receiving the full spectrum.  The result?  MORE distortion!

     Frank investigated this "problem" and freely published a reasonable "solution" to the problem MANY years ago.  To solve this problem requires a multi-faceted attack.  First, limit the audio passband going IN to the Input of the Driver tube.  A relatively simple bandpass filter does the deed.  This allows the amplifier to do exactly what it SHOULD do, and not waste "audio resources" trying to pass signals that are beyond the range of human hearing (or beyond the capabilities of its circuitry or transformers!)  The result is a much CLEANER signal.  Lower distortion and MUCH less "modulation" of the distortion products.  But there's more left to do.

     As I mentioned, the stock 0.1 uF capacitors are simply too small to pass the lower bass frequencies without significant rolloff.  Frank resolves THIS problem by increasing the coupling capacitor size to a total of 4.4 uF of high-quality film capacitors!  Now, the low frequencies can pass through the amplifier without attenuation and since the bandpass filter limits the extreme low frequencies presented to the grid of the driver stage, the feedback signal does the proper attenuation across the entire audio signal presented to the grid.  The result?  EXTREMELY reduced distortion products and a much "cleaner" sound presented to the speakers!  It is *especially* noticeable in the lower bass region, but the benefits extend across the entire audio passband.  Now, the bass is "controlled" and "tight", rather than "muddy" or "flubbery."  This all makes the "Ultimate Stereo 70" sound like a much more powerful amplifier in the bass region.  It's CERTAINLY more "accurate!"

     The benefits on the top end are impressive as well.  While a stock Stereo 70 is said to have a "magical mid-range", the "Ultimate Stereo 70" extends this magic into the upper frequencies as well.  There is improved "clarity" and better "definition" to cymbals, triangles and even the "point" of a good snare drum.

     While a stock Stereo 70 does a LOT of things well, the "Ultimate Stereo 70" does it all MORE well!  I also need to mention one other aspect of the finished product - the soundstage is remarkably richer, wider and has more "depth" than a stock unit.  Separation seems improved and the center-channel image is absolutely ROCK-solid!  At the moment, Sinatra is snapping his fingers.  Clear and clean.  Nothing excessive, just RIGHT!

     And THAT is the gist of the "Ultimate Stereo 70."  With a stock Stereo 70, you notice how GOOD this inexpensive amplifier sounds.  With the "Ultimate Stereo 70", the amplifier gets out of the way and let's the MUSIC prevail!  (Of course, you also notice shortcomings of some recordings as well.)

     The end result is an amplifier that will brings true joy to ANY audio enthusiast.  Frank has taken a really GOOD amplifier and turned it into a truly GREAT amplifier.

     By the way, some Stereo 70 Power Transformers tend to mechanically "hum" a bit, but this one is nicely quiet.  It's quite warm to the touch, but after several hours of running at about two-thirds maximum Volume, you can still keep your hand on it.  Not bad for a transformer made in 1962!

     When Norah Jones sings "Come Away With Me" through THIS amplifier, you'll be ready to sell your children in order to buy the tickets!

     We'll have one final update coming up, but right now, I think I need a cigarette!  Whew!

Sincerely,

Bill Thomas

[smbrown]

Bill, what a great write-up, wonderful work and workmanship! Thanks for taking the time to document all this. I sure wish it was around 15 years ago when I started "back" into tubes. I'm wondering, too, have you taken the "road less traveled" and done an ST70 with your own mods - for example, eliminating feedback, or using triode connected EL34's? If so, any advice or guidance you care to offer?

[Bill Thomas]

Hi there, smbrown!

     First off, thanks for the VERY kind words.  But ALWAYS remember that the REAL kudos go out to Frank Van Alstine for this OUTSTANDING kit.  I'm just the "grease monkey."

     As for my own "personal" mods, I'm really not smart enough to "re-invent the wheel" and I'm WAAAYYYY too lazy to try! (lol)  Seriously though, I DO believe that "good" can be made "better" until there is an optimum point where any further pursuit results in diminishing returns.  I'm also a big believer in the concept of "good enough."  But I'm always willing to keep an open mind when presented with other (better?) possibilities.

     I generally believe that sound engineering practices generally trump the "tweak du jour" nearly every time.  While overall sound quality is the most important thing, it isn't the ONLY thing.  Long-term reliability, cost considerations, "fussiness", repeatability and "the point of diminishing returns" all enter into the "Big Picture."

     ALWAYS remember that some of our most *cherished* recordings were made on equipment that more closely resembles a washing machine than a finely-honed piece of space-age engineering.  Take a look at some of the Ampex tape recorders of the 1950's.  They didn't have the best specs in the industry.  (Actually, Crown made tape recorders in the late 60's that put EVERY other tape recorder manufacturer to shame!  Sadly, a fire at their plant put them out of the Tape Recorder business!)  What Ampex recorders DID have was long-term reliability.  Those things would operate day-in and day-out with a minimum of hassle.  Sure, you had to adjust and clean things, but for the most part, they were as durable as an anvil.  Without them, Capitol Records wouldn't have achieved "sonic superiority" while everyone else was still cutting tracks on decidedly inferior disc cutters from the 40's.

     It can always be argued that "direct to disc" is better than "tape to disc."  Perhaps so, but as one who has been responsible for vinyl production in the 80's, as well as distribution of material on various tape formats, a LOT more can go wrong with direct to disc production that can render a one-time performance lost forever.

     Earlier today, while "burning-in" the Stereo 70, I was listening to Cliff Edwards doing "When You Wish Upon a Star."  It was recorded in 1938.  Sure, the recording was a little "pinched", yet it was the "performance" that evokes all those childhood memories of seeing "Pinocchio" for the first time.  Still, for what it started out on, (Optical Film, I believe) it sounded AMAZINGLY good!  Sometimes that's all that's necessary.

Sincerely,

Bill Thomas

[poseidonsvoice]

Bill,

What truly excellent work! I've been reading your thread diligently since when you started 4 months ago!

Mr.Van Alstine,

Can you describe or point to a link where your Ultimate Stereo 70 board circuit topology is described? Some of us diy'ers are interested in the details, of course without divulging any proprietary information. How is the phase splitting performed? Do you use a long tail differential pair, etc...

Best,

Anand.