TUBE BIAS, socket to me!

In each case the tube was in the +/- tolerance range for satisfactory operating performance?

I wish I find the article I read years ago about "tube matching" by an engineer who determined it’s baloney-at least for audio equipment. Maybe a rocket ship to Mars it may be critical

Let’s be honest-who hears a 1ma MM reading? Perhaps it shows on test equipment, but your ears? .

That said, I still do everything in an owners manual.

The issue with balanced valves is just that "Balanced", left to right in volume and bottom to top, if it's a single, double, or triple.

Sometimes the left and right share the same valve, they need to be the same, bottom to top. Incorrect bias can cause the valve to distort to quick, (to high) or sound muddy and thin (to low).

If you're picky, and the amps are revealing enough, you'll hear the difference, no problem.. Gotta keep the pin pockets tight and clean and the unit tuned..

Regards

What really counts? (personally I don't care about either heat or life, but would like to understand)

Heat?
Life?
Output stays Matched when adjusted?
Acoustic Performance?
_________?

First off, why do we do it at all? In very general layman's terms its to improve signal response and sound quality. Okay, but how?

What happens when we send a signal through a cold tube? Not much, right? Tube has to warm up first. Because a tube is a kind of valve that controls the flow of electrons we have to have some electrons to start with, of which there are damn few when its cold. 

But even after we warm it up we find every time we send a signal the first little bit that comes out isn't as good as later on. Like it has to go through warm-up all over again only this time on a very fine small scale. But the details in music are all very fine small scale so even this little bit matters.

What we do to solve this is keep the tube up in its optimal response zone by adding a small steady bias current. How small? There is no one answer. Its a judgment call, and a trade off. More bias, more current, more heat, more power, more wear, less tube life. In a nutshell.

oldhvymec

no need to LOL about same gear forever, much of my setup is ’old vintage’.

The 47 years begin in 1973 when I inherited my uncle’s Fisher President II console. My OMG moment, the awareness of high quality sound. All components made in 1958 still work. It’s Fisher Mono Amps, 80Z: the transformers seem indestructible, I bought a spare on eBay just in case. I used original EL37’s, EL34’s, 5881’s I think, a 4th type I seem to remember. All legit substitutes, bias never adjusted.

Over the years, I found a few burnt resistors, replaced them. Had them checked by pros just because they are so old, a few innards replaced, nothing really.

They still are dead quiet (so quiet I left them on many times) and sound great, but for convenience I got the current Cayin A88T (1st and only Cayin), Liked it equally, and wanted to hear difference of it’s optional Triode/Ultra-Linear modes. And KT88’s for the first time. Goodbye Triode. Fishers ready if disaster strikes current gear.

The receivers: two Fisher 500C (1964 to ?) and Fisher 800C all sound great. 7591’s, perhaps I tried substitutes, I can’t remember. Bill has the 800C (500C with AM added) we traded for his Mitsubishi Vertical TT LV-5V.

Sherwood I gave to a friend who collects Sherwood’s.

Dynaco Preamp I sold, just because it was ugly IMO.

current McIntosh tube tuner/preamp mx110z (1962-1969), best purchase ever! Love it’s tuner and phono. Dead quiet up to 12 o’clock vol, I leave it at 10 o’clock, Cayin at 12 oclock, use my Chase Remote Line Controller for remote increased volume, and it’s automatic Fletcher Munson Loudness progressively engaged when lowered from it’s startup vol. level. (you need to find the correct interactive Chase/McIntosh/Cayin mix so normal listening starts at Chase factory start up level), many use it wrong and complain about it’s auto loudness, used properly it’s a great feature to retain involvement at low listening levels. I digress.

Current speakers are new custom enclosures with all the drivers from the Fisher console, all made in 1958. Re-coned the 15" woofers twice, once pro, once myself, gonna check em soon just to verify they are ok.

So, that’s all the stuff I never biased, the current issue is the internal bias controls of the Cayin.

MC conveniently forgot the 'more electric bill" part.