Tube Amp question:TUBE replacements: explain MATCHED?

@wspohn

That’s what I told the individual who was helping me troubleshoot my Cary when he told me about how he had to bias his ARC. I said, "That’s interesting." But, I also said that I thought that it must make for a better tuned amp. I once had a pair of ARC VTM120s, & I vaguely remember hooking up leads for the multimeter to legs of resistors on the circuit board, and then adjusting the bias pot (on the board) with one of those plastic screw drivers you referred to. That typed,  on those ARCs that I owned each bank of four 6550s were adjusted together.

As far as checking bias, I bought a dozen new reissued Tungsols going on a year or so ago, and I have actually been checking mine after every several hours of play time. Mainly what I am watching for is to see that the small changes in bias that occur are happening on both sides simultaneously (which for now, they are).

@moose89 -

     The information that blackdoghifi gave you, regarding YOUR Cary amp’s output tubes and why THEY should be a matched set, is absolutely correct.

      Given that all 4 of your valves share one bias voltage; not having a matched set MAY result in crossover/notch distortion, which is never good.

                                   Also: immathewj’s instructions = +1

I just looked at the bias instructions for the 808 and the bias is adjusted by the same procedure as the two Cary amps that I own. A plug (with a + lead and a - lead) insert into a receptacle in the back of the amp; you will need a multimeter that will read DC milliamps. Connect the leads from the bias plug to the leads on the multimeter (the Cary bias plug leads have alligator clips on them) and after the amp is warmed up, you can adjust the bias pot. I always back my bias pot all the way down and start from scratch when installing new output tubes or lugging the amp in at an unfamiliar environment.

Y’all are great! Yes, I ordered the plug-ins and accompanying meter from Caryaudio.com  $120.

and I’m hoping there are some reasonable NOS quads for output. I’ll wait til we get past our newest tragedy distraction in our political world, and like toilet paper, supply and demand will settle $  down. 

     I WISH there were yet honest-to-goodness, NOS KT88/6550 valves out there, that could be described as, "reasonable".

     The supplies of Sylvania, GE, Genelex and Tung-Sol output valves, have long been dwindling and the prices (if they can be found): breathtaking.

     Even the authentic (before the St Petersburg plant was destroyed) SED =C= tubes are way up in price, IF/WHEN available (not often).    Funny (to older-than-dirt me, anyway), that tubes made as late as 2012, should be considered, "NOS", BUT: they did come close to the presentation of the afore-mentioned champs.

It is always a good idea to put matched power tubes in your amp or integrated. Do this even if it isnt required. You have a much better chance of similar longevity if you start out with matched tubes. Best to buy power tubes that have been burned in for 25 to 50 hours when possible. This is no guarantee that there tubes will age similarly but it doesnt hurt. Further there is no reason not to buy this way and no good seller will charge significantly more for matched tubes.