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β22

beta22

Re: β22

Postby KASaudio » March 17th, 2019, 5:48 am

Replaced C2-C5 with ground chanel at 100pf and now I'm almost happy, the noise is completely gone in the entire range of the volume control. The amplifier is very stable, the quiescent current does not change, the output bias is also within normal limits.
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Re: β22

Postby amb » March 17th, 2019, 8:41 am

What is the voltage gain of the amplifier? It’s probably too high for your Audio Technica headphones.
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Re: β22

Postby KASaudio » March 17th, 2019, 9:59 am

I told you that I have HD-650 and AD-2000X, only on AD noise was obviously heard, and on HD it is almost imperceptibly. But all the same I rejoiced too early, with 0 to 7% volume there is some noise, a feeling like an electrical hum. From 7 to 95% everything is very quiet and comfortable.Then from 95 to 100% again there is noise. It's all with an unconnected sound source.
Last edited by KASaudio on March 17th, 2019, 11:30 am, edited 1 time in total.
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Re: β22

Postby KASaudio » March 17th, 2019, 10:03 am

amb wrote:What is the voltage gain of the amplifier? It’s probably too high for your Audio Technica headphones.

I know that this amplifier has a very high power, I very carefully use headphones Audio Technica, otherwise they can spoil.
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Re: β22

Postby KASaudio » March 17th, 2019, 11:39 am

I noticed an interesting effect, after a while from 0 to 7% and from 95 to 100% the noise completely disappears. What could it possibly be?. I have the feeling that at first there is self-excitation, and then calms down, after 10-15 minutes.
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Re: β22

Postby amb » March 17th, 2019, 1:05 pm

Have you installed zobel networks at the output? If not, you probably need it.
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Re: β22

Postby DEFL » March 17th, 2019, 2:46 pm

I noticed that when LSK input devices came into stage, amp became much more prone to oscillation. That didn't happen with Toshiba jfets. I had chance to see the difference by building many betas, so maybe this is not coincidence.
Ti would you mind checking that?

KASaudio, install these on the wires to output jacks and your problem will be gone:
goo.gl/g3YQZv

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Re: β22

Postby KASaudio » March 17th, 2019, 2:54 pm

amb wrote:Have you installed zobel networks at the output? If not, you probably need it.

Ti, I installed a Zobel circuit at the output of the amplifier. But still the effect is present.
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Re: β22

Postby KASaudio » March 17th, 2019, 2:58 pm

DEFL wrote:I noticed that when LSK input devices came into stage, amp became much more prone to oscillation. That didn't happen with Toshiba jfets. I had chance to see the difference by building many betas, so maybe this is not coincidence.
Ti would you mind checking that?

KASaudio, install these on the wires to output jacks and your problem will be gone:
goo.gl/g3YQZv

I noticed that the effect disappears if the ground channel to reduce the quiescent current of 40-50 mA. Sorry I did not quite understand where and what to install? If there is opportunity throw off please photo.
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Re: β22

Postby DEFL » March 17th, 2019, 3:07 pm

Where: Clamp the wires that go from beta boards to output jack (TRS in your case?) in the hinged ferrite beads. What: The link is quite self explanatory what you need. Just try it and report back if it helps.
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