Do preamp tubes have to be matched?

[Markk]

I'm looking to buy some tubes (to have spares on hand along with extra fuses, just in case. The next little while might see the amp travel more) for my TSL 601.

I know that power amp tubes (the El34's in my case) should be matched. And I'll probably buy either a pair or a quad of them.

I was wondering about the ECC83/12AX7 tubes. Do they have to be matched as well? Because I'm thinking the preamp tubes control different channels (distortion/clean) and wouldn't really be affected by being mismatched in terms of bias.

If that would be true, then could you also interchange with tubes (like JJ/svetlana/sovtek) and any from the 12A_7 family in order to 'customize' your channels?

And for the Euro people on here, any good place in Europe to buy tubes from?

 

[zzmoore]

Re: Do preamp tubes have to be matched?

There is no need for your pre tubes to be matched. Yes you can change the brands around if you like. It can make a pretty noticeable difference sometimes. I think the TungSol reissue is a great 12AX7, but buy a few different brands and see (hear) what you think. Most of the tubes made come from your side of the world, but as far as where to buy.... I will let one of your neighbors give that advice.
Good Luck

 

[wixedmords]

Re: Do preamp tubes have to be matched?

Markk, I think most of the resellers that are popular on forums ship to Poland, but most of the UK guys seem to speak well of Watford Valves.

 

[marvar]

Re: Do preamp tubes have to be matched?

Some folks prefer the sound of a matched phase inverter tube (myself included) the phase inverter tube is usually a 12 ax7 or 12 at7, the one located closest to the power tubes. It's a personal preference, the amp manufacturers certainly don't use a matched/balanced tube in that position, but lot's of people like to use one in that spot.

 

[Markk]

Re: Do preamp tubes have to be matched?

There is no need for your pre tubes to be matched. Yes you can change the brands around if you like. It can make a pretty noticeable difference sometimes. I think the TungSol reissue is a great 12AX7, but buy a few different brands and see (hear) what you think. Most of the tubes made come from your side of the world, but as far as where to buy.... I will let one of your neighbors give that advice.
Good Luck

I looked around and finally found the distributor for Poland. And even though I'm neighbours with the country of production the prices aren't anything to be crazy about.

Price list

Yahoo puts 1 USD ~ 3 PLN (But more exactly, 1 USD will buy 2.82zl and 3.02zl will buy one USD as of today in my city)

A set of four 12AX7 (without a balanced one for the PI) and a pair of EL34 (all from JJ) would cost me 236zl (that amount would get me 78 USD)
The retube kit from Eurotubes costs 68 USD! Which is roughly 200zl

Some folks prefer the sound of a matched phase inverter tube (myself included) the phase inverter tube is usually a 12 ax7 or 12 at7, the one located closest to the power tubes. It's a personal preference, the amp manufacturers certainly don't use a matched/balanced tube in that position, but lot's of people like to use one in that spot.

I was actually going to ask the question if I can just put any 12AX7 into the PI and are there matched ones specially made or is 'matched' really a normal 12AX7 that just happens to be (more) balanced and is therefore classifed as a matched/balanced PI?

 

[glassman]

Re: Do preamp tubes have to be matched?

The PI circuit in almost all guitar amps (exceptions include some silver face Fenders) are imbalanced by design. To match the two triodes in a 12ax7 or 12at7 really has no actual value.

 

[idsnowdog]

Re: Do preamp tubes have to be matched?

Short answer no. Matching tubes in the preamp can help with getting consistent performance, but having mismatched tubes doesn't hurt either and can actually lead to a more diverse and balanced sound.

I have a ADA MP-1 which uses two 12AX style tubes. There's a separate drive control for each tube. When using two 12AX7's the distortion is thicker and darker but I don't think it is very dynamic. So I put a 5751 in the second position and the two distort in very different ways and when combined they have a great lively balance.

 

[StillLearnin']

Re: Do preamp tubes have to be matched?

Matching preamp tubes is not of any value. The only reason why output tubes are matched is because they are in a push/pull Class AB circuit (assuming you don't have a class A amp) sharing a common bias voltage. Preamp tubes are in a common voltage multiplier setup not requiring any DC voltage on the grids (except in a follower config which drives tone circuits in Marshalls and many other amps). Depending on the design of the amp and the input resistance to the grids, swapping preamp tubes can have profound effects on tone. This is because the Miller capacitance variations in the tubes themselves. That's why one brand of tube may sound better to you in a preamp stage than another - due to their construction variations. There are amp designs which are very sensitive to these differences and show it in the way the tone is affected. At the same time, some amp designs purposely mitigate the effects of Miller capacitance in the gain stages which makes changes in tube brands almost negligible.

So, best thing to get a few different brands of 12AX7s and try swapping them in and out of the early gain stage tubes and see what ones make a difference if at all...

 

[wixedmords]

Re: Do preamp tubes have to be matched?

I have never bought a preamp tube with balanced triodes.

Never had a problem.

 

[StillLearnin']

Re: Do preamp tubes have to be matched?

I have never bought a preamp tube with balanced triodes.

Never had a problem.

Yup and you won't... That is an anal audiophile thing and maybe has credence in UltraLinear tube power amps but has no place in a guitar amp. As Glassman said, the PI circuit in almost all guitar amps is unbalanced by design which would be about the only place you want to possibly use a matched dual triode.

 

[marvar]

Re: Do preamp tubes have to be matched?

Some folks prefer the sound of a matched phase inverter tube (myself included) the phase inverter tube is usually a 12 ax7 or 12 at7, the one located closest to the power tubes. It's a personal preference, the amp manufacturers certainly don't use a matched/balanced tube in that position, but lot's of people like to use one in that spot.

Yup and you won't... That is an anal audiophile thing and maybe has credence in UltraLinear tube power amps but has no place in a guitar amp. As Glassman said, the PI circuit in almost all guitar amps is unbalanced by design which would be about the only place you want to possibly use a matched dual triode.

I was very careful in the wording of my original post as to not open that balanced PI can of worms.
I CAN hear a difference, I like what I hear, and I will continue to use a balanced PI.
I don't think you should automatically disregard the option of trying a balanced PI, nor call someone that uses one anal. Heck it's usually only a couple of bucks for the balanced option, and you might like what you hear, in any case, you would still have a useable preamp tube, if you decided you didn't care for the sound.