MKI Screeching noise?

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mam8dg
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Re: MKI Screeching noise?

Post by mam8dg »

To echo what others have said, that is pretty normal for the decay of a MK1.
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Nostalgia
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Re: MKI Screeching noise?

Post by Nostalgia »

With 8nf cap from input to ground. Changed the tone a bit. Will try lower cap maybe 3nf-5nf.

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Electric Warrior
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Re: MKI Screeching noise?

Post by Electric Warrior »

Maybe try a slightly bigger resistor between Q2B and -9V. What did you use there?
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Nostalgia
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Re: MKI Screeching noise?

Post by Nostalgia »

Electric Warrior wrote:Maybe try a slightly bigger resistor between Q2B and -9V. What did you use there?
I used 2k2 and 280k on Q2 base and 2k2 on Q2C. Maybe my gain transistors are low side? Q1 60hfe, Q2 95hfe and Q3 80hfe.
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Electric Warrior
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Re: MKI Screeching noise?

Post by Electric Warrior »

Gains should be fine. I fixed my screeching noise problem (far worse than yours) by using a bigger resistor. Try a 330k instead of the 280k. That might be enough.
They used quite a range of different resistor values in that spot in vintage units...
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Nostalgia
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Re: MKI Screeching noise?

Post by Nostalgia »

Electric Warrior wrote:Gains should be fine. I fixed my screeching noise problem (far worse than yours) by using a bigger resistor. Try a 330k instead of the 280k. That might be enough.
They used quite a range of different resistor values in that spot in vintage units...
Well that's true. Mine does not screech at all when I reaches above -6v on Q2C or -9.2v on Q3C. But I don't like the tone and feel when it goes above -4.5v. I try to bias mine around -1.5 to 3.3v at Q2C.
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anemochore
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Re: MKI Screeching noise?

Post by anemochore »

Nostalgia wrote:With 8nf cap from input to ground. Changed the tone a bit. Will try lower cap maybe 3nf-5nf.
This sounds great :tu:
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