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Old 7th January 2013, 09:24 AM   #11
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Avincenty, thanks for reply. You are correct. I found and did a download. I am going to buy a Photofact and think about building a replica.I want to build one cuz i love, to say I could and to enjoy what I can't afford to buy. It is remarkably designed like the Madison Fielding 360 I am restoring. I will keep status posted. Cheers, Paul
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Old 8th January 2013, 12:43 AM   #12
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I did build a quasi clone. Quasi because it doesn't have the phono stage, also it only has bass and treble control. From what i can remember, the a300,a500 and a700 are all similar, the output valve changes for more power. I built mine with jj7591 and Hammond 1650 transformers. It sounds very good. The one fault I find is a very slight hiss coming from the first gain stage when I place my ear close to my 99db sensitive speakers.

12ax7 gain stage to bandaxal tone to 12ax7 gain stage to 12au7 concertina to 7591a.

Alfredo
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Old 8th January 2013, 02:03 AM   #13
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Alfredo, I was looking over the photofact. You have my admiration for building this design. I am planning my first DIY amp. I am a novice so I am going to start with a kit. If nothing else it will insure I end up with a completed project. I am confident I could complete a project but do not have the equipment needed at the end. Speaking of 12AU7's, gain and hum, would a 5965 in place of a 12AU7 make sense due to it's lower gain. I have read allot of differant opinions on this tube. I have never read anyone comment in a before and after application. Have you substituted the 5965 for a 12AU7? I am curious to hear about them. Any thoughts?
Cheers, Paul
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Old 8th January 2013, 03:39 AM   #14
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My 12au7 is used in the concertina with unity gain irrespective of individual tube gain so i am not sure if it will make a sonic difference.

Afredo
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Last edited by avincenty; 8th January 2013 at 03:43 AM.
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Old 10th January 2013, 04:38 AM   #15
zoe is offline zoe  United States
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I have rebuilt this amp.
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Old 10th January 2013, 04:50 AM   #16
zoe is offline zoe  United States
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This is the first amp that I've work on. Its been quite a evolution. I probably started seven years ago or so. Its still got the same 12AX7 driver tube and 12AU7 is still used
as the phase splitter but its a different kind its a cathode coupled splitter.I also now have a adjustable bias scheme with its own power supply so I can use different tubes.
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Old 10th January 2013, 04:54 AM   #17
zoe is offline zoe  United States
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pix
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Old 10th January 2013, 04:57 AM   #18
zoe is offline zoe  United States
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I have three of these now. I brought one to burning amp.
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Old 10th January 2013, 05:27 AM   #19
zoe is offline zoe  United States
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heespaul
Sherman audio has a lot of info.
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