dowto1000
Junior Member
Since I was censored from StevenZ's amp thread, I will start my own. Forum members probably are very unhappy with your amplifier build problems. I know I am, to say the least. So........ to serve you, I will " step up to the plate".
StevenZ, relax some, I have a proposal for your consideration. If you can wait till February 2018, ( when I have some time ) I will re-DO your amp with NO labor charge at all, only parts costs ( which we can economize upon ).
We would do a direct coupled 2A3 amplifier circuit, REAL triodes StevenZ, imagine THAT , as inexpensively as I know how to do, so your amplifier problem will be optimally resolved, long term.
We could re-use your pretty chassis. Perhaps even re-use your output transformers ( especially if they are 6K Z or less ).
We could re-use the 12AX7 tube sockets and tubes !! The high gain ( mu of 100 times ) 12AX7 is LOTS of FUN to listen to in our 2A3 DC amp implementation, mentally-engaging to hear.
Since 1984, I have on my shelf, a "cool" looking vintage power transformer, nicely enclosed / potted, that is a fabulous piece. It weighs sixteen pounds, made by ADC ( Audio Development Corporation ) for B+ only. It is rated 115 VAC to 370-0-370 VAC..... at 750 whopping milliamperes. This power transformer's total high voltage winding ( 740 VAC, end-to-end ) measures ONLY 18.20 Ohms, which is superbly-low.
Since the amp proposed only draws about 120 milliamperes, a 750 milliampere rated power transformer will LOAF, and as a by-product, provide top-notch bass, electronic self-regulation, and superior inner-definition of all the music.
In preparation for this post, I load-tested and measured this power transformer yesterday. A change from zero load, to a full 120 milliampere load, is only a 0.6% drop in the secondary's VAC. ( 0.994 of the original NO-Load measurement.) Fabulous natural stability !!
I can sell off your existing Hammond ( 54 Ohm DCR / 287 milliampere rated ) power transformer, and that ineptly-chosen, very nasty-to-hear 82 Ohm Hammond choke, to defray the value of the vintage ADC 750 mA. power transformer. ....18.2 Ohms !!
You will need to go, out of pocket, for four small filament transformers. They will go below deck. One for the 12AX7 filaments. One for the 5U4GB tube rectifier, and two, one each for the 2A3 filaments. Maybe $75 or so.
I will apply a unique and effective power supply design, refined over the past 35 years. We would use a LSES supply ( LOW STORED ENERGY SUPPLY ). It is a special ultra high performance L1/C1/L2/C2 B+ filter configuration to the 2A3's, ( L is a inductor or choke, C is a capacitor ).
The first choke, L1, will be a single 6 Ohm DCR Hammond 159ZA, capable of 1,000 milliamperes. The L2 chokes will be " split" ( fed by C1) as one L2/C2 for EACH 2A3 . The two L2 chokes will measure 10 Ohms DCR each, lovely sounding chokes, no longer available / made.
Total choke associated resistances will be only ( 6 + 10 ) 16 Ohms to each 2A3 channel. Versus 82 Ohms ( or more ) most people UNconsciously all use. Sixteen Ohms is simply outstanding to hear, with a 2A3 tube !!! You will be out of pocket $76 for the three new chokes, and I will convert their lead outs, from their stock, usually 22 AWG, to Mil Spec 14 AWG high quality / wide-band lead wire, for free.
Quality resistors will be $60.00 for both channels. NO PC boards, point to point.
We would ONLY use a DIRECTLY heated TUBE rectifier, because that simply sounds the best of all options. 5U4GB, $15.00.
I'll provide the amp's wire internal, no cost, all top quality Military Specuification, super high quality, various gauges as needed, just as I do in my own builds.
OUT OF TIME....finish tomorrow ..
Tommorow is NOW !!
I have vintage ceramic tube sockets, USA classic parts, for the two 2A3s, and the rectifier tube, which I will donate.
A SET amp I might do will have NO electrolytics , use all quality / good sounding film caps. Every capacitor position ( about 11 in a stereo amp ) , will have multiple bypassing, to allow the SET to play WIDEBAND. This means about 34 film caps. I'd estimate, when not using boutique caps, we can get it to within 80% of the best possible botique caps' sound, for $200. That is 5 to 7 % in the cost, of what " I " would like to use, boutique / quality wise. Five to seven percentof the cost, getting 80 percent of the results, the performance, is A-OK in my book !!
( We have today, industrial film caps, typically made by WIMA in Germany, that, carefully selected, are extremely high in performance. Industrially priced. I'd know what to order. )
The amp uses a modern day variant of the 1929 Loftin White direct coupled circuit. No solid state parts in it. Tube rectifiers....directly HEATED tube rectifiers, which sound the best. 5U4GB is about 15 dollars. Hardware, nuts, bolts, mounting terminals ( point to point ) is another 30 dollars.
No coupling caps, G-d AWFUL things to use in a circuit. Just half a 12AX7, directly coupled to the grid of a 2A3. KISS,... KISS rules !!
One has to be smart to chose a real triode and NOT ever a triode-connected-pentode. Why?? It sounds better, always, that is why...good enough reason to discard second-best designs. " There is no substitute................ for the real thing. "
Amp will have a high performance fully-shunt-regulated B+ supply to the 12AX7 driver stage, ( which hardly any one else ever does ) - a BIG plus. Puts out about 3 Watts per channel, and will play DYNAMICALLY like you and others have never ever heard before.
Nothing known to me personally, anywhere in audio, can out-do this basic simple circuit, as it would be implemented, when used on high efficiency speakers. I am building my own monaural amps, using JJ 2A3-40s, over 12- 2017 and 01-2018. Yours would be after mine. Your call StevenZ, I am willing to serve you, if you are able to be patient and wait 60 days. Looks like parts cost is $476, plus shipping TX to MO and back to TX.
Dowto1000
PS:
Regarding 2A3s: I would like to see someone on this Forum also " step up to the plate" and offer either one, or both 2A3's for StevenZ to simply borrow for 6 to 12 months. I have no old biplates left. The tubes would loaf, 10.5 Watts design center on a 15 Watt rated plate. When StevenZ financially recovers, he will go out and get JJs for himself, and send the borrowed tubes back to Forum Members. One or two would be fine!! Who reading this, will help the fellow ?? He'd appreciate the loan, and so would I.
Thanks, regards,
Dowto1000
StevenZ, relax some, I have a proposal for your consideration. If you can wait till February 2018, ( when I have some time ) I will re-DO your amp with NO labor charge at all, only parts costs ( which we can economize upon ).
We would do a direct coupled 2A3 amplifier circuit, REAL triodes StevenZ, imagine THAT , as inexpensively as I know how to do, so your amplifier problem will be optimally resolved, long term.
We could re-use your pretty chassis. Perhaps even re-use your output transformers ( especially if they are 6K Z or less ).
We could re-use the 12AX7 tube sockets and tubes !! The high gain ( mu of 100 times ) 12AX7 is LOTS of FUN to listen to in our 2A3 DC amp implementation, mentally-engaging to hear.
Since 1984, I have on my shelf, a "cool" looking vintage power transformer, nicely enclosed / potted, that is a fabulous piece. It weighs sixteen pounds, made by ADC ( Audio Development Corporation ) for B+ only. It is rated 115 VAC to 370-0-370 VAC..... at 750 whopping milliamperes. This power transformer's total high voltage winding ( 740 VAC, end-to-end ) measures ONLY 18.20 Ohms, which is superbly-low.
Since the amp proposed only draws about 120 milliamperes, a 750 milliampere rated power transformer will LOAF, and as a by-product, provide top-notch bass, electronic self-regulation, and superior inner-definition of all the music.
In preparation for this post, I load-tested and measured this power transformer yesterday. A change from zero load, to a full 120 milliampere load, is only a 0.6% drop in the secondary's VAC. ( 0.994 of the original NO-Load measurement.) Fabulous natural stability !!
I can sell off your existing Hammond ( 54 Ohm DCR / 287 milliampere rated ) power transformer, and that ineptly-chosen, very nasty-to-hear 82 Ohm Hammond choke, to defray the value of the vintage ADC 750 mA. power transformer. ....18.2 Ohms !!
You will need to go, out of pocket, for four small filament transformers. They will go below deck. One for the 12AX7 filaments. One for the 5U4GB tube rectifier, and two, one each for the 2A3 filaments. Maybe $75 or so.
I will apply a unique and effective power supply design, refined over the past 35 years. We would use a LSES supply ( LOW STORED ENERGY SUPPLY ). It is a special ultra high performance L1/C1/L2/C2 B+ filter configuration to the 2A3's, ( L is a inductor or choke, C is a capacitor ).
The first choke, L1, will be a single 6 Ohm DCR Hammond 159ZA, capable of 1,000 milliamperes. The L2 chokes will be " split" ( fed by C1) as one L2/C2 for EACH 2A3 . The two L2 chokes will measure 10 Ohms DCR each, lovely sounding chokes, no longer available / made.
Total choke associated resistances will be only ( 6 + 10 ) 16 Ohms to each 2A3 channel. Versus 82 Ohms ( or more ) most people UNconsciously all use. Sixteen Ohms is simply outstanding to hear, with a 2A3 tube !!! You will be out of pocket $76 for the three new chokes, and I will convert their lead outs, from their stock, usually 22 AWG, to Mil Spec 14 AWG high quality / wide-band lead wire, for free.
Quality resistors will be $60.00 for both channels. NO PC boards, point to point.
We would ONLY use a DIRECTLY heated TUBE rectifier, because that simply sounds the best of all options. 5U4GB, $15.00.
I'll provide the amp's wire internal, no cost, all top quality Military Specuification, super high quality, various gauges as needed, just as I do in my own builds.
OUT OF TIME....finish tomorrow ..
Tommorow is NOW !!
I have vintage ceramic tube sockets, USA classic parts, for the two 2A3s, and the rectifier tube, which I will donate.
A SET amp I might do will have NO electrolytics , use all quality / good sounding film caps. Every capacitor position ( about 11 in a stereo amp ) , will have multiple bypassing, to allow the SET to play WIDEBAND. This means about 34 film caps. I'd estimate, when not using boutique caps, we can get it to within 80% of the best possible botique caps' sound, for $200. That is 5 to 7 % in the cost, of what " I " would like to use, boutique / quality wise. Five to seven percentof the cost, getting 80 percent of the results, the performance, is A-OK in my book !!
( We have today, industrial film caps, typically made by WIMA in Germany, that, carefully selected, are extremely high in performance. Industrially priced. I'd know what to order. )
The amp uses a modern day variant of the 1929 Loftin White direct coupled circuit. No solid state parts in it. Tube rectifiers....directly HEATED tube rectifiers, which sound the best. 5U4GB is about 15 dollars. Hardware, nuts, bolts, mounting terminals ( point to point ) is another 30 dollars.
No coupling caps, G-d AWFUL things to use in a circuit. Just half a 12AX7, directly coupled to the grid of a 2A3. KISS,... KISS rules !!
One has to be smart to chose a real triode and NOT ever a triode-connected-pentode. Why?? It sounds better, always, that is why...good enough reason to discard second-best designs. " There is no substitute................ for the real thing. "
Amp will have a high performance fully-shunt-regulated B+ supply to the 12AX7 driver stage, ( which hardly any one else ever does ) - a BIG plus. Puts out about 3 Watts per channel, and will play DYNAMICALLY like you and others have never ever heard before.
Nothing known to me personally, anywhere in audio, can out-do this basic simple circuit, as it would be implemented, when used on high efficiency speakers. I am building my own monaural amps, using JJ 2A3-40s, over 12- 2017 and 01-2018. Yours would be after mine. Your call StevenZ, I am willing to serve you, if you are able to be patient and wait 60 days. Looks like parts cost is $476, plus shipping TX to MO and back to TX.
Dowto1000
PS:
Regarding 2A3s: I would like to see someone on this Forum also " step up to the plate" and offer either one, or both 2A3's for StevenZ to simply borrow for 6 to 12 months. I have no old biplates left. The tubes would loaf, 10.5 Watts design center on a 15 Watt rated plate. When StevenZ financially recovers, he will go out and get JJs for himself, and send the borrowed tubes back to Forum Members. One or two would be fine!! Who reading this, will help the fellow ?? He'd appreciate the loan, and so would I.
Thanks, regards,
Dowto1000
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