This amp is a version of Grant Wills ultralinear PP amp based on 12AX7 preamp and driver stages driving pairs of PL36 line output TV valves and using 100V line PA transformers, a budget priced amplifier concept! I modified it to use the equally low budget Russian valves 6N2P drivers and 6P7S output pairs. It was my first valve amp build (I was always more of a microprocessor circuit constructor in the past!) and it took me six months sourcing the parts and the drilling, filing, sanding and other mechanical details that are so time consuming with a valve amplifier, but I am very happy with the result. It's in daily use and I love the sound of it!
Nice work! I like the way it reminds me of a band. http://www.iviewtube.com/uploads/thumbs/e2l9upwqvmxac0xcxfx.jpg
Nice work! I like the way it reminds me of a band. http://www.iviewtube.com/uploads/thumbs/e2l9upwqvmxac0xcxfx.jpg
Haha DEVO amp ! Nice !
What is that rectifier tube ? Seen it before but never searched for it.
Nice looking...that metal treatment always reminds me of the Spirit of St Louis aircraft.....http://t2.gstatic.com/images?q=tbn:ANd9GcQisjo42Tf0ZeCqkre3uVFqt4GOErzjsPI5id1y89ablArZMLHZ
This amp is a version of Grant Wills ultralinear PP amp based on 12AX7 preamp and driver stages driving pairs of PL36 line output TV valves and using 100V line PA transformers, a budget priced amplifier concept! I modified it to use the equally low budget Russian valves 6N2P drivers and 6P7S output pairs. It was my first valve amp build (I was always more of a microprocessor circuit constructor in the past!) and it took me six months sourcing the parts and the drilling, filing, sanding and other mechanical details that are so time consuming with a valve amplifier, but I am very happy with the result. It's in daily use and I love the sound of it!
Top looking amp
.Cheers
Lol @ Evenharmonics, I see what you mean about the band. Long time since I heard anything by DEVO!
The tube in the middle isn't a rectifier (I cheated there... 1N4007s inside), its a VR105 voltage stabiliser / gas discharge valve made by RCA circa 1945 as far as I know. I was lucky enough to pick up two of these for a couple of quid (as we say here). Glows light purple inside when it strikes up.
Well spotted and identified!
Those are Russian versions of the 6AU6, the 6J4P, and they are front end preamps in this amplifier as per the slightly modified version of Grants amp that I based my version on.
As I modded the output stages to take the big old G-807 (or 6P7S Russian octal versions anyway), the amplifier is slowly morphing away from Grants version. I rejigged the bias to use a pot on each side so I could adjust the 6P7S pairs bias voltage as the circuit as it stood didn't bias them correctly... not surprising as it was designed to run PL36 pairs!
I run them at a modest 25mA idle current and they seem very happy there.
Thanks, I may try them sometime, although at the moment I am in the middle of a small SE stereo test amp using parallel pairs of EL34s with adjustable bias, to be used to burn in and match EL34 quads.
The next version of it will be a simplified one with only one output valve per channel using some Russian 6P3S I have and cathode bias.
Both amps will have 12AX7 (actually 6N2P) preamp and cathode follower driver stages and the 6P3S version with just 4 valves will get finished more tidily than the test amp, as its going to be a late birthday present for my son, who has been bugging me for one since he saw and heard my PP amp.
New work in progress, 3rd day...
In the MAN CAVE...
This is an amp that I have up and running, but is still unfinished.
It still needs the IEC power connector (on order) and the wood sides.
I have hooked up a pair of 6973's UL, SE, driven by a 6cg7 and I have a bias selector switch to swap the cg7 for a 6dj8. This setup sounds spectacular, much better than my 6bq5 amps.
The 6973's are running at Plate 290Vdc 44mA, g1 at -19V close to spec.
Planning to add a selector switch for triode mode in the near future, just for fun and to test other sensitive speakers...
In the MAN CAVE...
This is an amp that I have up and running, but is still unfinished.
It still needs the IEC power connector (on order) and the wood sides.
I have hooked up a pair of 6973's UL, SE, driven by a 6cg7 and I have a bias selector switch to swap the cg7 for a 6dj8. This setup sounds spectacular, much better than my 6bq5 amps.
The 6973's are running at Plate 290Vdc 44mA, g1 at -19V close to spec.
Planning to add a selector switch for triode mode in the near future, just for fun and to test other sensitive speakers...
Attachments
Thank you for your reply polyphase . More pictures mar available here :
Audiyofan.org • Afficher le sujet - Bloc MONO PP KT88
@ + Philippe.
I like the finish on the top plate. Your wiring methods look similar to mine. I just don't run the big bare copper earth or ground as you do.
