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Starting to look around for my next bread board project. I have always threatened to try a PP 2A3 amp, so now might be a good time. Looking for designs/schematics that are considered good ones. All input apprecaited.PS Has anyone here built or boarded the "feral eye" 2a3 amp?
Edits: 09/17/17Follow Ups:
NOT PP but way different then anything else I have seen easy to build!
http://diyaudioprojects.com/Technical/Papers/Direct-Coupled-6V6-Cathode-Follower-Amplifier/
definetly different ....
pm'd
What is pm'd ?
Sorry - "private message" - aka email on this forum.
Reply with your email address, I will send you my PP 6B4G schematic. A few people built it back in the day (2001 or so) and liked it. Similar to the Seth, but choke input supply and fixed bias.
Please, I'd like a copy of your schematic too, if you don't mind
David
D_tsue@yahoo.com
vince@vrhea.com ..... sounds interesting
Hey Vinnie I've built a few transformer coupled PPDHT amps . I've used both choke coupled and transformer coupled PPDHT amps.
If you're interested .... send me a PM !
Willie
Willie
Tried to send a PM but it said your email address was no longer working???
Chip67 showed the schematic in his post to this thread.
I built 4 PP45/2A3 stereo amps, one using a Para-feed E-P choke ,like as shown in the Seth 2A3 design ....another PP45/2A3 stereo amp used a small Edcor inter-stage to couple the input to PP outputs.... and another PP45/2A3 stereo amp that used E-P Inter-stages.
Of the 4 ,all of which have new homes, the one with the E-P iknter-stages sound best
I still own a Stereo PP45/2A3 with custom iron amp and a pair of Wurlitzer PP45 mono-blocks with custom iron also.
...........Last word PPDHT is very good , but there's magic in SETDHT done right !
Willie
Chip647 showed the schematic in his post to this thread.I built 4 PP45/2A3 stereo amps, one using a Para-feed E-P choke ,like as shown in the Seth 2A3 design ....another PP45/2A3 stereo amp used a small Edcor inter-stage to couple the input to PP outputs.... and another PP45/2A3 stereo amp that used E-P Inter-stages.
Of the 4 ,all of which have new homes, the one with the E-P iknter-stages sound best
I still own a Stereo PP45/2A3 with custom iron amp and a pair of Wurlitzer PP45 mono-blocks with custom iron also.
...........Last word PPDHT is very good , but there's magic in SETDHT done right !
Willie
Edits: 09/18/17
Done done it , Willie, it is one I am considering. Thanks.
I know a pair you can probably acquire. They got replaced by a pair of E-Linear 807 monoblocks...:)
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
It would be a lot of fun to A-B the Seth 2a3 against an E-linear 807 amplifier.
It was not as much fun as you might think...LOL As far as the comparison went it was a bit of a 'WOW' for both of us. Seth went back in a few times and we sat there giggling about how those old pentodes were so much cleaner and clear-er than the 2A3's.
Was wishing I had a grid choke for the finals, just to even out the comparison in terms of parts. The front end was a 6H6/FQP1N50 cascode. FET's on top.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Vinnie if you can spend a little money now might be a good time to pick up a couple of interstage transformers. In a push pull they do 4 things I really like: choke load, low voltage drop, phase splitter, and no coupling cap.
Not sure if Dave below is using that set up on his pp 300b but he could wind you some killer units to get the job done with various tubes so you could bread board different amps. On the cheap Hammond makes some units which Andy has played with some success.
Audio design guide on the web has a ton of schematics. Look at the parts count on a interstaged 2 stage pp amp. You could clip board one up in a few hours. Keep up the good fight.
Enjoy the ride
Tom
I will have to look into that. Thanks for the tip. Want to stay on the cheap side for now as this is just an experiment.
I'm sure you already know this, but the one significant advantage to PP DHT (Class A) is that you get the magic without the hum. If I had it to do over, I'd strongly consider building PP 211 instead of SET.
--------------------------
Buy Chinese. Bury freedom.
Hmmmmmmmm. Hadn't thought about that, but it sounds interesting. Best take a look at those before I get too far along. Know of any good designs/schematics? Would the same be true for PP 845? Same questions if so.
Edits: 09/18/17
There are schematics for SE and PP DHTs at the Bonavolta Audio site (link below). As always, approach all online schematics with caution. Many are wannabe musings and have never been built or tested.
--------------------------
Buy Chinese. Bury freedom.
Edits: 09/18/17
Looks like only one each for 211 nd 845. Guess I will have to do some surfing.
thanks
I lived with the feral eye for a few weeks with single plate 2A3's no less... It was one of the better PP amps I have heard if you are into that kind of thing :-)
dave
Into what? PP, 2a3 or ??. Thanks.
Push Pull... I was using lowthers at the time.... today with quad ESL57's of sorts I am actually 'gasp' using pp 300B's
dave
Dave you have to be in midrange heaven. With your front end options I bet it is a system that needs to be heard.
Enjoy the ride
Tom
I was surprised by how good the triode conneted PP 6bq5 I just finsihed a week ago sounds, so I thought I would try amother PP. Or is it the "triode connected" part that gives it such a lush sound. Not at all what I expected from a PP amp.
Vinnie, Perhaps I am the only one here who does not know what speakers you use with all these amplifiers, but... what speakers? Thanks.
I have a pair of Altec Granadas. They are two way horn units of about 95db efficency I think. They work well with the lower powered amps I build.
I would look at starting with something like the Mullard 20W amp as a starting point.
You'll need to lower the B+ a little bit for the 2A3, and I'd assume that you'll run cathode bias instead of fixed bias.
Substitute a 12AU7 or 6CG7 for the 12AX7 (you don't need the gain), adjust the biasing in that stage to account for the tube change. With lower available B+, the AU7/CG7 will be plenty happy with a lower impedance pair of plate resistors.
Lastly, remove the compensation on the driver plate load and disconnect the feedback.
Gain is likely a little higher still than you'd want, and perhaps using half of another 6CG7 instead of the EF86 will give you a driver stage that isn't overly sensitive.
I will take a look at it, but that sounds like a few more mods to make than I want at this time. Thanks.
Oh, don't be too nervous about such things. Going through such an exercise is a good way to learn.
Seth is pretty well respected.
I built this from a design that was in the Welborne Labs catalog. I changed it to fixed bias and ironed up the power supply
That's a very nice looking amplifier. Congrats!
--------------------------
Buy Chinese. Bury freedom.
Interesting. Do you happen to know if T1 in the hand drawn schem is also MQ S-258A? Man, that's a lot of iron on the one you built!
Thanks
Edits: 09/17/17 09/17/17
BCP-16NiGC
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Thanks for the link Tre', that will have all the info I need I think.
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