[JoshK]

Couple of questions for you Jeff, if you don't mind.  First, what did you draw your schematic in?  I still haven't found a schematic drawing program I like.

Second, have you had success with making macros in FPE?  I was poking around with FPD, first try and wanted to make a macro for my different tube sockets.   I looked in the help file and that is pretty laughable.   Edit: nevermind, I figured out the macro thing.  Their forum had the answer.

[jeffdavison]

Josh,

I'm using AutoCad.  I created my own symbol library. Any drwing program can do the same. Once you do one schematic it's easy to save the symbols you've created for another project.

I've never tried or used macros in FPE. I just "hard input" the co-ordinats of the holes.  I  probably make it more difficult then I have to. I create the top plate I want first in AutoCad then I dimension the drawing using baseline coordinates. I print the drawing out then manually enter the coordinates of the hole in FPE. mucho labor and tedious but it works for me. FPE has an AutoCad DXF or DWG into FPE translator, but the charge a pretty penny for that extra bit of software.


JD

Couple of questions for you Jeff, if you don't mind.  First, what did you draw your schematic in?  I still haven't found a schematic drawing program I like.

Second, have you had success with making macros in FPE?  I was poking around with FPD, first try and wanted to make a macro for my different tube sockets.   I looked in the help file and that is pretty laughable.   Edit: nevermind, I figured out the macro thing.  Their forum had the answer.

[JoshK]

Thanks.  I guess I am going to stick with putzing around with the programs I got for drawing.  I don't want to shell out the dough for autocad.  Plus I wouldn't have a clue how to use it.

I figured out the macro thing and it is pretty easy and nice.  I just opened up a new fpd, make the area a bit larger then what you need.  Then you draw the holes where you need them, I change the center of the large hole, for a tube socket for instance, to be the coordinate center, then draw the screw holes relative to it.   When your done drawing out the holes, group it all together.  Then go to create macro object and create a new one.  You will see your group in the preview.  You need to type a new macro name also in the box, which was nice as I was able to create a macro of macros (tube sockets, which is a group of macros for each socket size I wanted).  I did the same with transformers, even if I only wanted to use them once. 

With the macros, you can insert and then move it around where you want it or later move it somewhere else without messing up the relation of those holes to eachother.  You might be able to do the same thing with just grouping, but macros was a nice way to do it too. 

I don't know if I'll use FPE to make my topplate since I have a drill press and usually make my own.  I actually just wanted to use FPD to figure the layout of my Karna topplate.  The drawing program in FPD is exactly what I've been trying to find and haven't found it.  Depending on how much the price comes out to be, I might just have FPE do it, otherwise I'll print it out and do it myself.

[JoshK]

I am getting itchy.....very darn close.  Actually just need to hook up power entry wiring and then figure out where/how I want to ground the filament supply.  Then it will be double/triple checking wiring and testing. 

Funny, I don't even have suitable speakers yet.  Will try them with the 90db 4ohm MTM's, but they ultimately won't be very happy with that load.

Maybe I organize the shop a little better so I can start cutting baffles for my Abbey clones. 

[JoshK]

IT LIVES!!!   

Or should I say it GLOWS?

Haven't heard it yet, as the D3A biases a bit off from one channel to the other, so I have to tweak some resistors in the front end.  The output stage biases up the same from channel to channel and B+ is equal. 

This was my first fire up of a tube amp that I built, so nerves were a little high.  I am happy to report that the only mistake I found was that I goofed in the filament wiring of the KT88s and they didn't light up.  I got one half right but the other side I wired to pin 6 instead of pin 7.    I guess I can't count. 2 minutes later it fired up and all things glowed and voltages were where they were suppose to be.

Vacuum tube voltage regulators are cool. The lavendar glow is pretty sexy.  I fired it up and the wife turned out the lights, she wanted to see it glow in the dark.

George of tubelab had a nice procedure written up for your first fire up.  I had read it a while ago, so I followed same idea.  No tubes at first, and check secondary voltages and AC filament voltages, to check the transformers were wired correctly. Second, put the rectifiers in (in my case damper diodes) and check [unloaded] B+. Then I put in the OD3's and checked their voltages, then KT88's, then D3A's (including load, bias, screens, etc).

[SET Man]

IT LIVES!!!   

Or should I say it GLOWS?

...

Hey!

   Congratulation Josh. Wasn't that exciting and nerve recking at the same time?

Take care,
Buddy

[JoshK]

Well, I've been listening to it all day and all morning.  Going through different music.  I understand the appeal.   Pete Millet suggests that this amp produces 10 watts at 1% and starts to clip at 15w. 

I have it pushing my 4 ohm 89db MTMs.  Not the easiest load, some receivers can't push them.  I am using my Lite DAC 60 into my TVC (no gain) into the KT88 set.  I have enough volume, no problem, at least with the louder recordings and comfortable with softer ones, although I have settings left on the volume.

Compared to my UCD 400s, there isn't as much bass, but what is there is very articulate.  Midrange is everything you would think of a SET amp, more clear than the 400s.  The overall sound is a bit further back, rather than forward in presentation.  Felicia noticed that too. 

On Rodrigo Y Gabriela - Tamicun, I immediately noticed how the body of the guitar sounded very realistic.  It was a bit other-worldly.  I've never been captured by the sound of their guitars on this recording that way before.  I have listened to the recording, many many times before.

That said, putting on some Tool 10,000 Days and things started out pretty good.  Presentation was a bit more redicent in the vocals then I am used to, but still good.  I did notice some "confusion" when music got really dense and layered.  I think I was pushing the limits of 15watts and was at the onset of clipping.  Other recordings, with less density have not shown this again.

This amp isn't for NYAR, not with Chris present at least, but it is nice for personal listening time.

When I first set it up, hum was pretty loud.  Then it dawned on me that I forgot to ground the filaments, as I was debating how I wanted to do it.  I then took a few minutes to ground the filaments and then hum dropped to low levels.  I still have a bit of hum to track down, but it is constant with volume level (doesn't go up) and it isn't very loud. 

I tried to measure the AC volts for hum, but my volt meter wasn't very constant.  Maybe the impedance isn't high enough, or maybe I have to put a dummy load on the amp to measure the hum. 

I have a few ideas where the hum might be coming from so I'll be playing some more over the coming days.  Still it is very tolerable to listen to right now.

[lonewolfny42]

Nice to see a project finished Josh....

This amp isn't for NYAR, not with Chris present at least, but it is nice for personal listening time.

You enjoyment is what counts...but in the future...I'm sure we'd (NYAR) all enjoy a listen.

[JoshK]

I threw that in there to see if you would read this.  Ha!  I'm pulling your leg.  Of course, we can turn the dial up but it may not be very graceful that loud.  Still I am listening right now to NIN at ~80-85db average and not noticing any clipping, distortion or congestion.  So we aren't talking real quiet.

[lonewolfny42]

I threw that in there to see if you would read this.

I read almost everything that's posted....

"80-85db average"....that's a good range....very comfortable.

[JoshK]

I am excited to hear them on my Abbey clones, as they will be ~96db/w and impedance of 8 ohms. 

I swear I am hearing the bass open up...I've put ~10 hours on them so far.  Maybe my ears are adjusting, but I think there is more going on here.

[SET Man]

Well, I've been listening to it all day and all morning.  Going through different music.  I understand the appeal.   Pete Millet suggests that this amp produces 10 watts at 1% and starts to clip at 15w. 

I have it pushing my 4 ohm 89db MTMs.  Not the easiest load, some receivers can't push them.  I am using my Lite DAC 60 into my TVC (no gain) into the KT88 set.  I have enough volume, no problem, at least with the louder recordings and comfortable with softer ones, although I have settings left on the volume.

Compared to my UCD 400s, there isn't as much bass, but what is there is very articulate.  Midrange is everything you would think of a SET amp, more clear than the 400s.  The overall sound is a bit further back, rather than forward in presentation.  Felicia noticed that too. 

On Rodrigo Y Gabriela - Tamicun, I immediately noticed how the body of the guitar sounded very realistic.  It was a bit other-worldly.  I've never been captured by the sound of their guitars on this recording that way before.  I have listened to the recording, many many times before.

That said, putting on some Tool 10,000 Days and things started out pretty good.  Presentation was a bit more redicent in the vocals then I am used to, but still good.  I did notice some "confusion" when music got really dense and layered.  I think I was pushing the limits of 15watts and was at the onset of clipping.  Other recordings, with less density have not shown this again.

This amp isn't for NYAR, not with Chris present at least, but it is nice for personal listening time.

....

Hey!

    Welcome to the world of SET/SE Josh.

    A good SET can give you another "D" or dimension and more!

   And of course it could play louder than most people think with just a few watts. With a right higher-eff they system could play at Chris' level

    See, all you need is a couple of good watts. I can bet that you and Felicia will have a hard time going back to that UCD amp or any other amps type now.

Take care,
Buddy

[JoshK]

FWIW, my posts thus far are not a rave review, so much as a 10,000 ft view of the differences in sound.  It is a sound I like, but I would like higher efficiency speakers with this amp ultimately.  It is adequate power for much of my listening, but I like a bit more headroom.

I have enjoyed listening to this amp for the last week or two.  I have some residual hum that can be heard near the speaker but not at the seat.  It also does not increase with volume, so as soon as music plays you can not hear it.  Still it bothers me a bit to know it is there.  This is most likely from the AC heaters.  I will try a couple of things to see if I can't reduce it to near nothing.  If I can't I'll experiment with DC heating.

[JoshK]

Ok, my camera battery charger finally came.  I lost my old one.

Here it is fired up. 


Here is a lousy pic, since I didn't set up the tripod and took it without flash.  But it shows a bit more of the glow.



And closeup of the tubes...

[poseidonsvoice]

Josh,

That looks awesome! I love the way you staggered the tubes so you can see them all in their glory...

Now where is the schematic? And the pics under the hood?

Best,
Anand.

[JoshK]

The circuit is Pete Millett's E-linear amp.   The schematic can be seen here.

I've thrown the acronym SET around, but technically this is not SET.  It is SE UL. 

[BillB]

Gorgeous. 

[SET Man]

Hey!

   Beautiful work Josh. And you started this from scratch, amazing.

   Looking forward to hear this someday.

Take care,
Buddy

[jeffdavison]

Josh.... great job.... I know the feeling of finishing your own handiwork and having, not only, it looking great, but sounding fantastic as well. I think from now on the only "commercial gear" will be the software... tho I also play guitar, but if I listened only to myself, I'd get bored too quickly...
Even after all the tedious planning, parts acquisition, designing, Building, soldering, procrastinating, it's worth it in the end.

Re.. the hummmmm. Have you tried all the tricks that you can do with AC?  Is your filament transformer center tapped?.. try putting the center tap to ground. If the filament transformer isn't, you can use a couple of resistors from each tap to each other and connect the common to ground. You can also bias the ground to a positive voltage....some tubes need a smaller cathode to heater voltage differential.
Of coarse I assume the the filament wires are set up as a twisted pair as not to radiate 60Hz noise.

I'm currently getting ready to test my WE437A / EML 320B-XLS mono blocks. I used a vccs for the power tube, but I'm using AC for the driver. I'm using a transformer that does not have a center tap and using the two resistor method as mentioned, BUT in a different sort of way.... I'm using a 50R pot with the wiper towards ground (actually a +46v bias above ground ) and each end of the pot to a tap. The potentiometer will act as a "hum pot", where I can balance out the hum. Even tho the driver is an IDHT the adjustable humpot idea is still valid.

I've posted a thread in the Asylum... any interest here, I'll post the pics here, but this is supposed to be the 6550/KT88 thread.... which by the way if y'all seen the number of reads, its almost the highest viewed thread!

What ever happended to the others from the early posts? Be nice to see their work ( if they didn't loos interest along the way).

Anyways... great job.... and also a Huge thanks for starting the thread! it has been very motivational.

Jeff

[nullspace]

Excellent job Josh; very nicely done. For sure you'll want to track down that hum. Once you move to more efficient speakers, I would expect that you'd be able to hear it at your seat. Or, you could be like me and just practise willful ignorance...

Regards,
John