any damage from mismatching tubes?

[wyomingrocks]

Hi group, I have a quad of EL34 SED winged c tubes that are marked 35's and another quad marked 34's and two that are 32's. I will naturally keep my quads together but eventually they will go bad and I will have to rematch. My question is can I mix say two 35's with two 32's? I would probably put a 35 and a 32 on one side and another grouping of 35 and 32 on the other side. Will this put any undue stress on the amp and would that be the way to set them up if it can be ran like that? By the way this would most likely be on my tsl. Thanks for any feedback

[Enzo]

There is no stress to be made on the tubes or anything else by a mismatch. Amp makers don;t bother with matched tubes, and certainly no one was thinking matched tubes in Leo Fender's day. Matching helps reduce hum and maybe distortion. That was the point of the bias balance control in some Fenders - you could balance mismatched tubes for least hum.

[wyomingrocks]

great

Thanks "again" Enzo. That makes me feel better, these are all brand new tubes so I am happy to hear that. That is interesting that amp makers don't bother with matched tubes, I would think they would want to give there best sound with each and every amp they produce. Sometimes I feel like a bozo by asking what may appear to be simple questions to some but I learned long ago. The only stupid question is the one that is not ask. I have also found that if I don't know or understand something there is probably someone else with the same question. As always thanks for all your help.

[Enzo]

You have to draw the line somewhere. What is the "best" sound? To make an amp with the best sound, a maker would have to sit down with each customer and determine his tastes, then modify the basic amp circuits to suit. Then the maker would have to select the speaker that best matched the owner's taste. SOme would want Sovtek tubes, and some JJs, and some who knows what. Those tubes would have to be carefully matched - unless the particular customer preferred the sound of the mis-match.

But of course then you have a custom built amp. Mass produced amps can't be made that way. Peavey/Fender/Crate/Marshall/whoever has to buy tubes by the tens of thousands. They could sit technicians down and have them sorted and matched up. But that takes time and would cost serious money, not to mention a substantial portion of the tubes purchased would not match any and would be waste. But would that extra expense add to sales? Very doubtful. When you buy an amp in the store, you liked the sound. And that was without matched tubes. That is a lot of expense to add just the tiniest bit to the amp appeal.

I like car analogies. The car maker really does try to make a good car. But would mom or dad realy be more likely to purchase if the tires were kept inflated within a quarter pouind of pressure? How about headers and a tuned exhaust? Rally tuned suspension would be better for safety and road handling. They have to draw the line and stop at good enough, or they are selling $100,000 cars.

All those famous old fine vintage Fender amps were made with 20% resistors - Leo wasn't going to pay extra for 5% resistors. SO a 100k plate resistor in the preamp could be 80k to 120k and be a good part. And the electrolytic filter caps of that era had - and I am not making this up - tolerances of +80/-20%. That means your 100uf cap could be anywhere from 80uf to 180uf and still be within specifications. You could put matched tubes in that and it wouldn;t even notice.

Here is an experiement. YOu have two pairs of tubes - 32 and 35. You plan to split the pairs so each side gets one of each. That is the balanced approach. That is fine. INstall them that way and play the amp for a while. Get a good idea what it sounds like. Now turn it off and swap to of the tubes so both 32s are on one end and both 35s on the other end. That is as mis-matched as those four tubes can get. Now see what it sounds like. That is the difference between matched and mis-matched tubes. I'd bet you don't hear much difference. Slight increase in hum.