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"WHAMMY" Pass DIY headphone amp guide
"WHAMMY" Pass DIY headphone amp guide
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Old 12th July 2019, 05:46 AM   #1461
Gaz2613 is online now Gaz2613  United Kingdom
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I had oscillation issues and crackling/buzzing with a 50K alps at either extreme which I fixed on a build of a different amp by adding a 100 ohm resistor to the left and right channel wiper (middle pins) of the pot. This is a trick I picked up from a fellow member at head fi.
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Old 13th July 2019, 03:17 AM   #1462
MadHatterRyu is offline MadHatterRyu
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Hey my builds been done for quite a while and I love it with less sensitive cans.

Just wondering about one thing, there's this extremely low volume hiss on extra sensitive cans like the AD2000X.

The hiss doesn't increase in volume with pot position at all.. does this mean it's coming post the amplification? What would be the best solution to this?
I was thinking of trying the output ground to the chassis too.

Or is it due to some other reason
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Old 13th July 2019, 05:37 PM   #1463
meldano is offline meldano  Germany
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Hello,

can someone (Wayne?) explain the function of the caps C12,17,22,25?

Thanks
Daniel
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Old 13th July 2019, 07:02 PM   #1464
6L6 is offline 6L6  United States
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"WHAMMY" Pass DIY headphone amp guide
The four 10k resistors are there to set the maximum DC bias voltage available to the gates of the mosfets. The optocoupler then reduces the bias voltage as needed.

The capacitors allow the AC signal to get to the gates and make music.
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Old 13th July 2019, 07:08 PM   #1465
meldano is offline meldano  Germany
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Thanks!
But in a spice model the output stage run without these caps.
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Old 13th July 2019, 07:41 PM   #1466
6L6 is offline 6L6  United States
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And the signal will have to fight the 10k resistor. Hopefully Wayne will jump in and explain it better...

Last edited by 6L6; 13th July 2019 at 07:51 PM.
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Old 13th July 2019, 08:08 PM   #1467
generg is offline generg  Germany
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I thought this combo of 10k and caps is used to have the output stage swing near the rails voltage.
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Old 14th July 2019, 01:57 AM   #1468
AllanMarcus is offline AllanMarcus  United States
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Hi all. The guide on page 1 says "25VA 22V+22V is best and used in this guide.". There is discussion in the thread about using a 15V with no LEDs. The advantage of the 15V is that is runs cooler. Any advantage to the 22V over the 15V? I'm building yet another WHAMMY for a friend, and ordering parts. Given the voice, which to build with?
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Old 14th July 2019, 03:22 AM   #1469
AllanMarcus is offline AllanMarcus  United States
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oops, I mean given the choice, which to build with?
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Old 14th July 2019, 03:36 AM   #1470
6L6 is offline 6L6  United States
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Whichever you can get more easily.

The 22v transformer is if you want the full +/-24v rails, which is mainly for people driving a F4 or MoFo amp. If just headphones or normal line stage duty, 15v is great.
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