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Old 9th September 2012, 08:40 PM   #1
400kg is offline 400kg  Turkey
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Default ultra hifi amp new

šok temiz ses . tam simetrik yapı
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Last edited by 400kg; 9th September 2012 at 08:43 PM.
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Old 9th September 2012, 08:46 PM   #2
400kg is offline 400kg  Turkey
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If someone from PCB designers lurking this forum has extra time to design PCB, this can become serious competitor for the DIY-ers best option of choice to built their first (and maybe the last) solid state amplifier.
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Old 10th September 2012, 01:32 AM   #3
Struth is offline Struth  Canada
Join Date: Aug 2012
Location: books at londonpower.com
Hi Guys

Did you measure the THD and bandwidth or are these "optimistic guesses" based on similar circuits? Is the 100db S/N based on full output?

Personally I would change the Miller compensation to a single cap going from the top of the bias reg filter cap to the feedback node - maybe with a small R in series. This separates slew rate from bandwidth and allows a bit more feedback to reduce high-frequency distortion. It made sense to me back in 1982 or so when I saw Cordell's article about his high-performance mosfet amp in the Siliconix app book.

The BD139/140 are only rated for 80V, so won't survive in your +/-60V circuit. Many amps use the MJE340/350 (300V) pairs. I like the 2SC4739/2SA1837 pair (230V).

I built an amp similar to this in 1980. One issue is the gate turn-off speed is slow and causes a lot of high-freq distortion. A possible fix is to add current sources where the 330R gate-leaks are.

You don't need back-to-back zeners for the mosfets as there is no reversing voltage. Single polarity protection is ample.

One last thing: I always add a 1k or so from the output node to ground. This provides a DC path to ground for leakage currents and gives the output stage a ground reference, making the DC centering task easier for the front-end.

Have fun
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