diyAudio - The Kuartlotron - keantoken's simple error-correction superbuffer

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- - The Kuartlotron - keantoken's simple error-correction superbuffer (https://www.diyaudio.com/forums/analog-line-level/251413-kuartlotron-keantokens-simple-error-correction-superbuffer.html)

Hello @ keantoken, I have adjusted the TP terminal to half of the positive voltage, R1 and R2 are 56R, when using Onsemibc550c/560c, the output voltage can not be adjusted to 0, there are tens of MV, and the output voltage will jump around. And the TP terminal voltage will change from time to time 5.8-5.3v. When I add R9 to 4M, the output can be adjusted to 0, but it is also unstable and will change. But when using PHILIPSbc550c/560c transistors, the TP terminal voltage and output voltage are very stable and will not change, but R9 also needs to be added to 4M to adjust to 0v.

R1R2 = 56R, power supply ± 10vTP = 5V, working points are normal, play some high level CD, high frequency will break, how is it?

Now that On-Semi BC560C is obsolete are there any suggestions for alternative devices to the BC550/560C?

Which parameters are important when selecting parts for this circuit?

Mouser has OnSemi BC5x0C and they are actually the same Fairchild parts I original recommended, now that OnSemi has acquired Fairchild.

Quote:

Originally Posted by qq33006498 (https://www.diyaudio.com/forums/analog-line-level/251413-kuartlotron-keantokens-simple-error-correction-superbuffer-post6030252.html#post6030252)

It sounds like oscillation, or perhaps a bad connection somewhere. It could be you have an unusual layout that is causing a problem. You can use the Phillips transistors if they work better, but they have higher noise and I designed the Kuartlotron for the Fairchild (now OnSemi) parts.

Quote:

Originally Posted by keantoken (https://www.diyaudio.com/forums/analog-line-level/251413-kuartlotron-keantokens-simple-error-correction-superbuffer-post6047548.html#post6047548)

Mouser has OnSemi BC5x0C and they are actually the same Fairchild parts I original recommended, now that OnSemi has acquired Fairchild.

I don't see anything available

BC550CTA ON Semiconductor / Fairchild | Mouser Denmark

No more bc560 it seems, Mark Johnson bought them all :o)

I was looking at the NPN, looks like the PNP is now obsolete. Hmm.

I use the DIY dartZeel nhb108 Amplifiers, then your Superbuffer Amplifiers midpoint voltage will rise from tens of MV to 700-800mv, what is the reason for this? Do I add 4.7 UF capacitors to the input or output? Superbuffer output midpoint is already within 10mv

I have used the same Fairchild BC550CTABC560CTA (HFE/800) as you listed, when R9 = 2.7M, the lowest midpoint voltage is still tens of MV, when R9 = 4M, the midpoint voltage is still 10mv, TP = 5V, sometimes 4.8v and sometimes 5.2v. With PHILIPSbc550c/560c won't such, what reason is this?