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Capacitance is a byproduct of 2 (or more) conductors whilst inductance is a property of a single conductor. Sent from my SM-A715F using Tapatalk

Thin, wide conductors have lower inductance. Inductance increases in a wire if you coil it like a spring (it is now an air-cored inductor - wrap the wire round a magnetic metal and you have a traditional inductor). Capacitance results from how close the conductors are to one another. Braided...

That is a beautiful machine - can it interface or display on a PC? Sent from my SM-A715F using Tapatalk

When CDs and THX came out output was standardised at 2V and yip, the need for preamps pretty much disappeared. It was assumed that vinyl would die - hehehe - and power amps would have roughly 1V input sensitivity therefore the need for a preamp with gain would be superfluous. Passive preamps...

Also what size signal are you putting into the device?

Measure the voltage across the 270R resistors - this is the bias voltage it could be too low and that may be causing your squishing. Sent from my SM-A715F using Tapatalk

The PSU on that pre seems to be a zener-follower - this is a stabilised not filtered, supply. So pull the valves and measure the HT voltages - this will eliminate the valve's and their associated circuitry as problems and confirm that the PSU is indeed working properly. The asymmetrical waveform...

Also, post a schematic

Remove the tubes and re-measure the HT rail. Something could be pulling too much current thus dragging your output voltage down.

That circuit has a constant-current loaded cascode (LOT of gain) plus another gain stage (even more LOT of gain) plus a constant current loaded cathode follower all wrapped up in a feedback loop that uses very large (12 Meg) resistance - the potential for oscillation is very, very, very large...

Who needs bluetooth? https://www.youtube.com/watch?v=xbiesrBby1M

The sequence of powering up audio equipment always should be: Switching on - from the beginning of the chain e.g turntable/laptop, then DAC, then amplifier Switching off - from the end of the chain e.g amplifier then DAC then laptop This is especially relevant with power amplifiers as they are...

Your summing resistors will increase the preamp?s output resistance so best to put them in the mono power amp

Valve amplifiers draw much lower currents than their SS siblings. More importantly, they draw much less signal current. Because of this we don't really need large conductors in a valve amplifier ergo 22AWG will be fine in almost all situations. Your earth wire should be much larger though...

Use a potentiometer of no more than 10k - worst case output impedance is 0.25x pot impedance. So 2k5 for a 10k pot. 1k25 (better) for a 5k pot. Be sure your source can drive pot impedance thats no issue for any modern solids state devices - not so good for valve equipment with a 10k pot. Ideally...

Then again silver-plated copper could make Jim Reeves sound like Angus Young....

Very interesting commentary on the coupling caps here: http://www.keith-snook.info/quad-ii-valve-power-amplifier.html Snook contends that the capacitors capacitance to the chassis determines the dominant pole of the amplifier and thus instability could be provoked by replacement caps not mounted...

Changing the input capacitor will affect the amount of bass in the input signal that the amplifier ?sees? as such the amplifier?s transfer function etc is not affected. Changing the values of capacitors within the amplifier can affect phase angles which could affect how the this amplifier...

Viewed at single frequency yes, the capacitor size will attenuate the signal. But amplifiers are designed to pass the many frequencies in the audio bandwidth at once and so, in the real world your attenuation is manifested as a rolling of of low frequencies. Changing capacitor size therefore as...

Stunning! Suggestion: next batch should say "Designed and made in RSA"