[Dmason]

Jim, curious, what did you decide upon?

Josh, how 'bout, Uber 5 Series Beam Machine? AMG-Schnitzer Tetrode? 

Robert Simpson is currently building one for Alex Lifeson, for home stereo useage...

[jrebman]

Dan,


I got a pair of 5k primary 100 mA and 43% UL tap, with single 6 ohm secondaries and M6 laminations.  I skipped on the potting as it both makes them pretty large, but also adds cost.  I didn't opt for the partial silver secondaries -- again too much dough, and sonically may be too much of a good thing for this amp.

My cabinetmaker friend was by last night to look over the Koa with me, and although it is decent, he had something else to offer which I could not pass up -- Bird's Eye Brazillian Chitawba (spelling?)  Could look killer with the solid copper .125" top plate I have andit's seasoned about 10 years now.

All of this is just way more time consuming than I remember, and with the tools he has access to on his job, he can knock the chassis out in well under an hour -- including planing, dimensioning, rabbetting and chamfering, and glued up, and it would take me that long to just get the saw setup and get the rough boards out.  Yes, I'm starting to farm out some of my DIY stuff so I can actually get something done, but all the design, electronic construction, wiring and finishing will still be up to me -- the stuff I can do without a good wood or metal shop.

I'm also going to leave this as a straight power amp and pair it with the 24v aikido 6gm8 preamp/headamp.  That simplifies things just that much more, and I have everything for the preamp except a chassis, some resistors, and 4 big coupling caps.

-- Jim

[AKSA]

Jim,

Do you think your friend would be interested in building speaker boxes for me?  Does he have the facilities to produce them routinely?

I'm trying to find someone in the Denver area who can do good speaker boxes, since I would like to produce them for the US market and hefting them across the pond is hugely expensive.

Cheers,

Hugh

[jrebman]

Hugh,

I don't even have to ask him as I know he would want nothing to do withthis .  He's a cabinetmaker that works for a very high end architectural millwork company, and that's his day job, and that's where it ends.  As far as anything related to woodworking goes beyond that, his real passion is building classical guitars.

I wish, and I mean, really wish I could help you with this!

-- Jim

[jeffdavison]

Can we keep the thread on track? If you need something besidess info on the uber beam machine, please PM or email each other..

jd

[jrebman]

Ok, answered my own question about the filament supply, and now Jack has the specs for the quote.  Other than 4 BG FK caps for the cathod bypass, all PS caps will be film types -- 100 uF motor runs following the choke, and a Mundorf M-tube loading the rectifier.

Would the more experienced guys comment on whether it would be better to use 30 uF or 47 uF for the rectifier cap?  I know 60 is max for a 5ar4, so the 47 works, but I much more often see 30-33 here.  Unfortunately, I don't know the resistance of the HV secondary.

-- Jim

[nodiak]

Hi Jim,
Congrats on the Electra Print iron choice, I've heard them described as having big soundstage, power and great tone. I haven't ordered a PT yet so will be interested in the price from Electra Print, please let me know.
Sounds like your going for some nice wood. How are you going to keep the copper from tarnishing, or is that a problem?
Josh thanks for answering my question, I can get my order in now.
Hey Dan, looks like I'm ordering a 7'0 mini longboard and selling off the 9'4. Should tuck into these steep waves mo betta.
Don

[andrewbee]

comment on whether it would be better to use 30 uF or 47 uF for the rectifier cap

Any or neither of these may work. The first cap after the rectifier can also be used to adjust the voltage of the power supply. The smaller the cap the lower the voltage. If you have a copy of PSU designer then it can steer you in the correct direction wrt to voltage and ripple.

http://www.duncanamps.com/psud2/index.html

Andrew

[jrebman]

Don,

I'm not sure what I'll do with the copper yet -- I'm interested to hear more about this hand-rubbed oil finish Josh was talking about many pages back, but also my sister-in-law is a metal artist who developed a very unique finish for copper, but it may not stand up to the heat, and is easily marred, so it may have to be clear powdercoated, and she's not sure if that will work either.  If the wood will look better with brass or bronze, then I'll have the copper plated and polished, and that will be that.  Aesthetically probably can't go wrong with either.

Andrew, I do have PSUDII installed on my computer, but it doesn't work very well -- not at all, really -- with my screen reader.  I may be ale to make it work with some programming of the screen reader, but that just isn't on the priority list right now.

I'll probably start with one value, and try different ones at a later date.

-- Jim

[JoshK]

Jim,
I agree with Andrew.  If you can play with PSUD, that would be best, but the results are more a graphical display so I don't know if that'll work for you. 

Dan,
I don't really care so much about the name, was just saying. 

I ordered a new choke, one that could handle a great deal more current than the 5H/200mA one.  This is because I am planning to build Pete Millet's E-linear amp first (with the 6550 of course).  This topology has really got me interested.  It also is the most demanding in terms of power supply due to the gas regulators pulling an extra 30mA per channel.  This will give me the room to go in many directions if I wish.

I ordered up all the parts for the e-linear amp, except for a couple resistors that digikey didn't stock, like a 82K metal oxide 10+watt resistor.  I think I figured out a nice way to prototype the amp, making it semi permanent but also flexible enough to try out other things too.  I'll do this by subdividing the top plate into sections.  That way I can sub in another front section without rebuilding a whole new plate.  I've seen this done in a few other diy amps and I have a bunch of aluminum sheets to work with. 

[mgalusha]

I ordered a new choke, one that could handle a great deal more current than the 5H/200mA one.  This is because I am planning to build Pete Millet's E-linear amp first (with the 6550 of course).  This topology has really got me interested.  It also is the most demanding in terms of power supply due to the gas regulators pulling an extra 30mA per channel.  This will give me the room to go in many directions if I wish.

I ordered up all the parts for the e-linear amp, except for a couple resistors that digikey didn't stock, like a 82K metal oxide 10+watt resistor.  I think I figured out a nice way to prototype the amp, making it semi permanent but also flexible enough to try out other things too.  I'll do this by subdividing the top plate into sections.  That way I can sub in another front section without rebuilding a whole new plate.  I've seen this done in a few other diy amps and I have a bunch of aluminum sheets to work with. 

Slightly off topic - Josh, I'm really interested in hearing how your e-linear project turns out. I remember when Pete's article appeared in AX and at the time I didn't have anything that could be driven by a lower power amp but it might be splendid to drive my mids and tweeters with active crossovers. There was also an interesting (to me) SE amp using parallel 6550's in the November 2006 issue of AX. I've been wanting to build it as well. Not sure how it would compare the the project in this thread but it would interesting to listen to them both.

mike

[jrebman]

Mike,

Tell me more about this PSE 6550 amp -- how many output tubes per chanel, how much power, what kind of ps voltages?

I ask because I know somewhere down the line I want to look into a big PSE valve amp for the Sapphires.  The PUBM -- Penultimate Uber Beam Machine (M7 Series if you will, and to keep things "on topic" :: )

-- Jim

[JoshK]

Mike,

I don't consider that off topic because this was intended more as a build thread than a design thread.  I am working, right now, on laying out the top plate(s) for the amp. I, for now, have bailed on google sketchup as I can't seem to do some obvious things like precise placement of objects within the plate.  So I am sticking to the graph paper and pencil for now.

I am really intrigued by the local feedback techniques I've been reading about lately.  Gary Pimm's Tabor amp employs local feedback in a couple forms, the e-linear uses a combo of two in one hybrid type of local feedback and then there is cathode feedback.  There has been a lot of discussion recently on the DIYaudio tube forum on local feedback and it seems the more experienced guys really advocate its use.  I really admire Pete's designs and knowledge so I thought it fits in with the topological experimentation of this amp. 

I think this amp (around 10+watts with e-linear fb) should be able to drive my 89db 4 ohm Modula's at more moderate levels, enough to get a sense of its performance until I finish on my hi-eff OB 3 ways.  I intend to use this amp to drive the mid/tweet in that project.  It will be actively crossover between the mid & woofer and from the woofer over to IB subs using the DEQX.  The mid/tweet I plan to cross passively, but that will be a project to tackle as compression drivers need quite a bit of impedance compensation networks and some notches.  The Modulas will be used to just hear it, but I don't expect to be able to drive them to levels my wife and I like to listen with all the music we like to listen to.

I didn't subscribe to AudioXpress till about a year ago.  So I had to order the back issue CD, which is pretty nice though.   I might order other years on CD after I digest the ones I have. 

[JoshK]

Jim/Mike,

Here is a site I stumbled upon recently.  I really like a lot of the designs of this guy, not everything about the design, but his approach is pretty cool.  The amp designs that he built are all interesting for different applications and reasons.

http://www.turneraudio.com.au/se35cfbmonobloc.html

The above linked amp is a 4x EL34 PSE amp, but could be modified to other pentode tubes pretty easily.  It makes me want to try a higher powered PSE design at some point. 

Broskie has shown a couple PSE designs, including the Aikido as a front end for a SE amp that I posted near the begining of this thread, which parrallels two KT88s.  From memory, he shows a 5 x EL84 PSE amp further back in the archives.  That ought to be a good sounding medium powered SET amp.

Jim, parralleling output tubes wouldn't raise the B+.  It would be the same B+ as with one tube but you multiply the current drawn (from bias) making the power supply big.  This makes it a bit more dangerous as well because a bigger supply will hold more energy and most likely be a lower impedance supply.  So for the same voltage you have a lot more amps the PSU can deliver, which in turn is more watts it can deliver.  We often think the higher the voltage the more dangerous, but for a given voltage the lower the impedance of the supply the more dangerous it is.

[jrebman]

Josh,

Thanks for the pointer to the web site -- will check that out shortly.

The main reason I was asking about power supply really has to do with the availability and price of good electrolytics and higher value film caps (at reasonable sizes.)  There are a lot more choices if you stay at 400 v or lower.

I used to work on 120 kv 100 amp DC power supplies, so even though 120 volts gets due respect, it's not so much the voltage.  Hell, I'd build an Ongaku, but at those voltages the parts would be prohibitively expensive.

Slightly off topic, but I ordered the enclosure for my 24v Aidido which will be the pre for the UBM.

-- Jim

[JoshK]

Jim & everyone else,

Just for the record, if I respond in a too simplistic way, don't think think it is because I am talking down to you or anyone else, or that I think you aren't experienced.   I respond with such detail and simple explaination, particuliarly with safety, because I am responding in public and I am trying to speak to a common denominator for everyone's benefit.   

I get nervous in particular when discussing high voltage projects in public because I don't want to make some wife a widow even inadvertently.   So I try to be as clear as possible about risks.  I think all the posters in this thread are knowlegdeable enough, but I don't know who all is lurking and might embark on this project. 

[jrebman]

Josh,

Sorry, didn't mean to imply anything by my responnse.  I'm just finding out first hand how price goes way up, and choices way down as B+ goes up.

I do appreciate the tutorial nature of the responses from you and the other experienced folks out there -- it helps revive those long unused brain cells.  Once I get setup with my new computer, I just decided that I'm going to hire a local EE student to enter schematics, tube curves etc. in my tactile graphics software, so I can get a better handle on all this.

-- Jim

[JoshK]

Josh,

Sorry, didn't mean to imply anything by my responnse. 

No problem, I didn't take it as that.  Just reminded me that I should mention why I respond the way I do sometimes.

[mgalusha]

Tell me more about this PSE 6550 amp -- how many output tubes per chanel, how much power, what kind of ps voltages?

I ask because I know somewhere down the line I want to look into a big PSE valve amp for the Sapphires.  The PUBM -- Penultimate Uber Beam Machine (M7 Series if you will, and to keep things "on topic" :: )

Jim,

The amp in the article uses 2 6550's in parallel and a pair of 5687's, one as a cascade preamp and the second as the driver stage amplifier. The B+ voltage is 500V with no load and 455V loaded. The schematic shows the PS as capable of 500V at 200mA, so plenty of hazard for the unwary. I know you are experienced but like Josh I'm paranoid about folks who have never built or dealt with high voltage electronics before. For the PS caps the author is using 400V caps in series to get the necessary voltage support.

The author claims 25W with .6% distortion in triode mode and 25W with .64% distortion in ultra linear mode. It does use 7dB of feedback to get the low distortion and some other tricks he describes, mainly the use of a degererative output stage.

mike

[jeffdavison]

Now THIS is what I'm talking about!  or rather, the amp I want to build. This is exactly the tube compliment I want to use. Now if there is some way to get a schematic 

http://www.quicksilveraudio.com/products/SET%20Mono.html


JD