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50w Single-Ended BAF2015 Schade Enabled
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Old Today, 12:31 AM   #1221
OllBoll is offline OllBoll  Sweden
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Join Date: Nov 2010
I have now built #1196 and so far it kinda works, but at the same time not as well as I'd hoped.

I slightly reduced the reistance of one of the 910k resistors and added a 25K trimpot to let me trim the last offset.

And it does work, but it oscillates a bit. It is not as fast as the CCS so on startup there is still a 10V+ DC offset. I replaced the 1000uF cap for the lower FET with a 220uF one and it reduced it a bit. There is also a bit of DC offset oscillation after playing some 1khz sine waves. It wobbles around 1V and steadily gets smaller until after 15 seconds or so when it is down to below 10 mV again.

It might be the bias servo, but it might also be the active ground, post #8 in Virtual ground in power amp applications I'm using that is causing problems. It hasn't caused problems when I tried with the F6 though.

Click the image to open in full size.

I'll do some experiments to see if I can stabilize it but if that doesn't work I'll probably try to build an Aleph J / J2 clone and keep it as a voltage feedback amplifier with a slight difference. I'd reduce the voltage feedback to ~ 10 dB or so and then wrap a current feedback loop around it with the rest of the feedback.
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Old Today, 01:08 AM   #1222
Ben Mah is offline Ben Mah  Canada
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Join Date: May 2012
Location: Vancouver
50w Single-Ended BAF2015 Schade Enabled
Originally Posted by MEGA_amp View Post

question...I've read the Tokin 2SK182ES needs to have it's bias supply on prior to applying power to the rails. As I'm using IXFN here, does this have that same requirement? I'd like to eventually use just one power switch when I finish the chassis instead of powering up things separately as I'm doing now.
If your main supply has lots of capacitance and your bias supply has much less, the bias supply will come up ahead of the main supply so one power switch should work. So that should work for the Tokin.

Another thing, the IXFN is an enhancement mode MOSFET so it is off until the Vgs comes up.

Last edited by Ben Mah; Today at 01:18 AM.
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Old Today, 03:12 AM   #1223
MEGA_amp is offline MEGA_amp  United States
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Join Date: Oct 2003
50w Single-Ended BAF2015 Schade Enabled
Thank you Ben.
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