And if they are indeed meant to be flipped around then they will render that "Thick" switch useless. ...and on that matter, any voicing via cathode bypass.
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Or there may be some effective low frequency cathode bypass through the RC..and more clipping high frequencies from the diode in that case. Which is normally what is needed to reduce low frequency distortions ''farty'' sound etc.. But that is just IMHO, what the original intention was and what is right or wrong in this circuit..not for me to defend or justify. But is fun and interesting...so anybody want to email Struth and ask?
Hi Guys
The cathode diodes were an artifact of a previous wiring someone had done. They were still in place when the final circuit was documented and as they were not hurting anything they were left in place. TUT made no claim for their presence or what they do wired in reverse.
Elsewhere in the Preamp chapters diode biasing is illustrated, with the diodes in correct orientation. The problem with diode biasing is that the tube runs flat out all the time and is essentially "fixed biased". The low dynamic impedance of the cathode diode leaves little room for focusing the gain with bypass caps, so personally I never use it and advise against it for most hobbyists/builders.
No snake oil; just a shortage of white out.
Have fun
Kevin O'Connor
londonpower.com
The cathode diodes were an artifact of a previous wiring someone had done. They were still in place when the final circuit was documented and as they were not hurting anything they were left in place. TUT made no claim for their presence or what they do wired in reverse.
Elsewhere in the Preamp chapters diode biasing is illustrated, with the diodes in correct orientation. The problem with diode biasing is that the tube runs flat out all the time and is essentially "fixed biased". The low dynamic impedance of the cathode diode leaves little room for focusing the gain with bypass caps, so personally I never use it and advise against it for most hobbyists/builders.
No snake oil; just a shortage of white out.
Have fun
Kevin O'Connor
londonpower.com
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