Tremoverb with Matched Duets or Matched Quad

[TremoJem]

Is there any reason or added benefit to using a matched Quad of 6L6's over Matched Duets? I read something about push/pull but was confused.

Please feel free to elaborate.

Oh and matching and stuff does not apply to preamp and 12AX7's right...I don't think so anyway.


Thanks

 

[blazer986]

Matched duets should be fine as long as all tubes fall within an acceptable tolerance for your amp. Anything mesa labels is ok and any tube vendor should be able to give you what you are looking for. The guys at tube depot told me that most tubes naturally fall within an acceptable range for mesa amps, but it is good to let them know when you are buying.

as for preamp tubes no matching needed.

 

[94Tremoverb]

It's perfectly OK to use two different matched pairs instead of one matched quad, but remember to put them in the correct sockets. If you have two pairs A and B, they must be arranged with one A and one B in the left hand pair of sockets and one A and one B in the right-hand pair. It's conventional to arrange them in 'inside' and 'outside' pairs, ie ABBA or BAAB, although this doesn't strictly matter and you can have ABAB or BABA too . Just avoid AABB or BBAA.

A friend just brought a Dual Rectifier over for a check-up and he had two pairs arranged AABB. It was very noticeable how much better the amp sounded after I swapped them to ABBA. (And yes I like ABBA too but that's another story .)

You're correct that this is to maintain the symmetry of the push-pull output.

 

[TremoJem]

Thanks.

Mesa finally got back to me and they said the same thing.

 

[droptrd]

although this doesn't strictly matter and you can have ABAB or BABA too . Just avoid AABB or BBAA.

Isnt that the same thing?

 

[94Tremoverb]

No. Sockets 1 and 2 are the "push" and sockets 3 and 4 are the "pull". As long as you have one A tube and one B tube in push and one A tube and one B tube in pull, it doesn't matter which way round they are within each pair, so ABAB is not the same as AABB. I'm not sure why you would actually want to do that, it was just to point out that the "outside" and "inside" pairs are just for convention and there is no electrical distinction between the two sockets on each side, they are wired in parallel.

It *does* make a difference in any amp with a half-power (or Simul/Class A) switch that turns off one pair though. But the Tremoverb isn't one of these amps.

 

[droptrd]

Ah so you want to split the pairs up so it balances the push pull so to speak?

 

[94Tremoverb]

Yes, exactly. It doesn't matter if the tubes on each side of the push-pull are mismatched - the total current in each half is just the sum of the current from both tubes - but you want the push to match the pull! So you need the *same* mismatch on each side.

NB - this is made even more confusing by amps which have separate bias adjustment per side, eg Marshall JCM2000s, modern Fender Twins etc. - there you *do* probably want the tubes arranged AABB, so you can match the two sides to each other using the individual bias controls and end up with a match overall.


There is even a possibility - which I tend to agree with, at least a bit - that deliberately using two mismatched pairs (arranged correctly) can sound better than a matched quad, since it causes a bit more harmonic complexity.

 

[TremoJem]

Interesting...