• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Problem with old tube amp

If Tim says class A, he ought to know;) I would say the 859 was nominally 13 watt, and later (869) 15 watts, Half 32 watts is 16 so I suspect it is. Also I would imagine if the amp was run significantly into class B it would mess up the DC feedback and introduce strange artefacts with the 2 feedback loops. I haven't studied the circuit enough to state that with certainty but it would seem likely.
 
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Rait

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Paid Member
2015-04-12 4:24 pm
If Tim says class A, he ought to know;) I would say the 859 was nominally 13 watt, and later (869) 15 watts, Half 32 watts is 16 so I suspect it is. Also I would imagine if the amp was run significantly into class B it would mess up the DC feedback and introduce strange artefacts with the 2 feedback loops. I haven't studied the circuit enough to state that with certainty but it would seem likely.

Thanks for you time. Fun is the amplifier top plate. Surely they late understand that this statement is too much. Seen photos from some years late made 861 and there aren't this statement any more. Here photo.
 

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Rait

Member
Paid Member
2015-04-12 4:24 pm
Hi!
Problem solved😊. Had time today to change all ordered resistors. Now both channels identical. Attached new scope photo.
All thanks to Diyaudio members, specially to Chris who studied diagram and pointed correct point to check out.🙏

Rait
 

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