The CMOQ-4 would result in much lower gain, right? So, you are using that transformer plus a high-output preamp?
I've had a pair of Cinemags with close to the same turns ratio as the original Edcors for almost a year, but have never got around to testing them in an M2-style circuit... Maybe this year?
I've had a pair of Cinemags with close to the same turns ratio as the original Edcors for almost a year, but have never got around to testing them in an M2-style circuit... Maybe this year?
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absolutely not
if you cascode input JFets , change few values around optocoupler , say that 35V rails are still OK , considering 50W on each mosfet , if you keep them cool enough , with great care of thermal interface
Last night I listened to M2 singing with grimberg's board and Fairchild mosfets from buzzforb (FQA12P20/FQA16N25C).
Was able to zero output offset so the amp was dead quite.
At turn on (when amp is cold), you need to wait few secs. (~15) to stabilize before you can hear output from speakers.
However, I noticed the supply voltage sag different from both polarity (~0.3-1Vdc). Also, Vgs between N and P channel is different being 3.7Vdc from the N and 4.3Vdc from the P channel.
Is this normal due to the variation of N and P channel mosfets?
Was able to zero output offset so the amp was dead quite.
At turn on (when amp is cold), you need to wait few secs. (~15) to stabilize before you can hear output from speakers.
However, I noticed the supply voltage sag different from both polarity (~0.3-1Vdc). Also, Vgs between N and P channel is different being 3.7Vdc from the N and 4.3Vdc from the P channel.
Is this normal due to the variation of N and P channel mosfets?
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In Teabags instructions, he noted that it was just a personal thing, and made the Harris unit available.
There is an anomaly with the one unit, I have used them with no personal issue, and as I remember back when I was building F5, Peter Daniels noted it, and had no issue with it. In that amp I found it rather nice.
As to the M2, I personally have only used Teabags sets, which included the Harris mosfet. If I was in posession of just the Vishay units, I dont think I myself would be alarmed.
Russellc
Thanks Dennis & Russel for your reply.
Tried the Toshiba OPT 2SK1530 & 2SJ201 been keeping some time, I thought its a good place to put this. I bought it from Blues intended for F5 few years ago. Highs and low significantly improved compared with FQA.
Vgs +/- diff now the same and supply drop tends to get closer probably because of the closely matched outputs. Slightly higher bias (R13/R14 drop 0.6Vdc compared with 0.4/0.5 of the FQA).
Used 1KVA torroid tranffo from a defective UPS having secondary 21.5Vac (14Vdc). Several hours playing did not even get warm
This amp got the attention of my wife in terms of how voices are sung.
Grimberg, thanks for sharing the M2 boards.
Thanks so much Nelson for a unique and special amplifier.
Tried the Toshiba OPT 2SK1530 & 2SJ201 been keeping some time, I thought its a good place to put this. I bought it from Blues intended for F5 few years ago. Highs and low significantly improved compared with FQA.
Vgs +/- diff now the same and supply drop tends to get closer probably because of the closely matched outputs. Slightly higher bias (R13/R14 drop 0.6Vdc compared with 0.4/0.5 of the FQA).
Used 1KVA torroid tranffo from a defective UPS having secondary 21.5Vac (14Vdc). Several hours playing did not even get warm
This amp got the attention of my wife in terms of how voices are sung.
Grimberg, thanks for sharing the M2 boards.
Thanks so much Nelson for a unique and special amplifier.
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