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DIY 6AV5 Amplifier- Want To Build One (or Two)

idadude

idadude

Super Member
This request was posted in the DIY forum also, and I'm reposting it here in case I can get some additional responses.

I'd like to find a source for plans to build a 6AV5 push-pull and/or single ended amplifier. I have several dozens of these tubes and would like to construct an amp from some of them.
I have previously owned an Elite 80 6AV5 based push-pull amp made by Ideal Innovations of Canada and was impressed with the sound it put out. I'm open to the single -ended option since I have a set of very efficient speakers (100db SPL).
I tried searching through the forums here, but I did not find anything. I have a tough time finding anything using the 'search' option on AK. I thought this might be the faster way to get to my destination.
I'm not necessarily looking to build a cheap amp, just want good sound and don't mind putting some bucks into it. So, if anyone would be so inclined to steer me in the right direction to some good plans, schematics, and sources for parts, anything..... I would deeply appreciate it. Thanks.

Larry D.
 
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As I remember, Tubelab over at DIYaudio did extensive work with the 6AV5. I think he even melted a couple down.:yes::D
 
Google?

Yes I did. Found a lot of interesting information on the TubeLab website. What I'm looking for is an amp that has been built and possibly used for a while, which the builder is very happy with and the majority (if not all) of the bugs have been worked out.
I may have to go the experimental route, but if possible, I'd prefer to build it from a proven plan. Yeah, that would be 'ideal'. Just trying to find out if such a beast exists.
 
idadude said:
Yes I did. Found a lot of interesting information on the TubeLab website. What I'm looking for is an amp that has been built and possibly used for a while, which the builder is very happy with and the majority (if not all) of the bugs have been worked out.
I may have to go the experimental route, but if possible, I'd prefer to build it from a proven plan. Yeah, that would be 'ideal'. Just trying to find out if such a beast exists.
Click to expand...

Ahem, Paging Kegger. :music:
 
Not many options, so far....

Yeah, if Kegger is willing to share his info, that would be great, but he may not have it down on paper. It may not be so bad putting one together from scratch, but I would save some money and time if I could complete it on the first build. (There goes that 'ideal' situation idea again.) Another alternative would be to clone a Bogen 6AV5 push-pull model.
I'll wait & see if anyone else has some input. No immediate hurry to start this project. You can't start something without some sort of plan first.
 
What led you to get rid of the Ideal Innovations amp? I have had one for 6 years
now, also with 6AV5GAs, and I'm still happy with it. I guess the way to improve
on their design would be to use beefier output transformers. Good luck!

P.S.: this link will provide some interesting reading, including a reference to AK.

http://www.idealinnovations.biz/elite-models.htm
 
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Alright, alright, I'll get my act together and finish up the schem then post it..
(mine is push pull triode wired for 12-15wpc using the Sansui 1000A outputs)
 
When I bought the Elite 80 and used it a short while, I said I'd never sell it. Then I got the 'try something different' bug a couple years later and then sold it. The only three things I did not like about the amp was its compactness, (which made it tough to swap out caps & resistors, which I never did anyway), it ran on the hot side, and it had fixed bias which meant I had to have a matched set of output tubes if I were to try and roll some other OP tubes. The sound was very good in the stock form though. That's why I kept it so long.
Yeah, I was looking at some of Edcors OPTs and they looked to be much beefier than the Elite 80's. Those, with an oversized PT should make for a cooler running unit (which is one of my goals in building this amp) and should help slightly on the lower frequencies also (though the 80 did well in the LF area too).
The link you sent is full of good information. Thanks for sending it. I need to read it more thoroughly and take a closer look at the Bogen schematic.

Larry D.
 
I have one. It was hand drawn by a friend that's been doing this stuff for years. I built the amp a year ago. It sounds nice. I can scan and post if you are interested.

I want to see Keggers schematic!
 
That would be great..........

Yes, please scan and post. As much info as possible is better than not enough. I'd like to have both a push-pull and a single-ended set of plans/schematics. It seems that this amplifier may end up being put together in an experimental fashion first, even though I originally didn't want to. The TubeLab site had a tube lab experimental amp building board that looked to be a great idea to put together an amp and be able to switch out various components and hear how they might make a difference.
Anyway, yes, scan & post please. I definitely appreciate the help.

Larry D.
 
Ok, here it is. My buddy drew this up one day as we were eating lunch. The amp works well as drawn. It has amazing seperation and soundstage. I played around with different 6AV5 cathode resistors until the outputs are drawing about 50ma. I also bought some good quality bypass caps and they really made a difference. I don't have a copy of the p/s schematic. I did as you plan to do and just played around with the amp during the build. I ended up with modeling the p/s and using a 7 henry choke and two RC sections. I think I have no more than $100 in this amp with the new Edcor OPT's I bought. Have fun with it.:banana:

Oh ya. I forgot to mention I had no luck running my 6AV5's as hard as the Tubelabs guy did. One of my first tries triode strapped the 6AV5's. My b+ was around 275 Volts and man were the screens glowing!
 

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Thanks!

Thanks a bunch for the schematic. This is the single-ended plan I could try out. I have 1/2 drawer of cherry picked old tall bottle 7N7s I could pick from to use with this.... plenty of 6SN7/ 5692s too. You think 7F7/6SL7 might add some useful gain?
I have a local buddy who's very knowledgeable at building tube amps (I'm an amature at it) and I'll bet he will be ready to jump in with both feet on either this one or Kegger's or both. Yeah, would like to hear this triode strapped, but not with the glowing screens, ha!. I won't want to run the 6AV5s hard. I like it when tubes last for years & years. Just want to get the best sound out of them without killing them prematurely.
Thanks again for the schematic and if I have any questions I'll post or send a PM.

Larry D.
 
Glad to be able to pass it along. One of the nice things about this amp is the screens of the 6AV5 are fed by 1/2 of the b+ from the driver section. My screens are running at 150V

7F7's do work but I prefer the sound of the 7N7. Try it out and see what you think. A nice loktal that I use in this amp is the 7AF7. They have a bit less gain than the 7N7 but a bit more transconductance. The 7AF7 is a more rare than the 7N7 but still not expensive.

I bet I've logged 300 hours on my amp in the last year. It is still using the same RCA 6AV5's. This amp seems to be a good runner.

I had to use a choke input filter and some healthy caps in the power supply to get rid of the hum. My wife used to laugh when I told her I was going out to the shop to work on the "Humming Bastard".

Keep us posted on the progress. I'd like to build another 6AV5 if a schematic turns up.
 
Slightly off topic but you mentioned trouble with the search engine...the "Search AK with Google" option works well, and if that doesn't get it I use the Advanced Search.

PS interested in this amp as well, they must have made a billion of those tubes.
 
How does the search work correctly? I have wasted a couple hours looking at non-related posts when I try regular 'search'.
 
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I noticed better results with Google in AK 'search' too. Never tried the advanced search. Regular search is a waste of time.
Yeah, they made plenty 6AV5GAs and they're cheap (at times) too. Just bought a few dozen of NOS Sylvanias for $2 each.
I'd like to find some more people in the Boise area that are interested in building amps and make these tubes available to them at my cost. For now I'll just work on getting a few successful amps put together and sounding fine.

Larry D.
 
What is best OPT for push-pull?

I noticed that Bogen used an output transformer with a 7500 ohm input rating on their push-pull 6AV5 amp. I wonder if that's the optimum rating to use. From what I've read, Kegger is very happy with his....I'm curious as to what the Sansui OPTs are rated at.
Looks as if the 5K input rating is the way to go for the single ended, but I haven't nailed down the P-P rating for sure.

Larry D.
 
Remember I ran mine "triode", in triode mode the 6AV5 is "basically" an 2A3, push pull
2A3 fixed bias a 5K is generally used/suggested, cathode bias a bit higher is the norm.

Mine is using a tad of cathode feedback so an even higher load would be wanted, so
I believe the Sansui outputs are 6K which just happens to fit nicely in that circuit. ;)
(mine is cathode biased)

Believe I'm about 265v plate to cathode on my output tubes, I'm running the Sylvania's
which seemed Tubelab found to be the beefier ones of the bunch, mine still test as new. :)
 
I might be limited if I go Edcor...

Edcor is only offering 5K and 6.6K on their pushpull OPTs. If one were to go triode strapped/cathode biased w/cathode feedback, would the 6.6K work well or should I try another brand OPT that's at 6K?
It may be that I'll have to go triode w/fixed bias at 5K if I can't find a suitable OPT that's as reasonably priced as the Edcor CXPP series. I have heard that cathode biased configurations have better sound though. I would prefer to go the better sound route.

Larry D.
 
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