[DrewWinters]

I know nothing about tube amps or tubes themselves - but I am considering buying a tube amp... so they've been on my mind lately. I'm not sure exactly what sparked this thought but I figured I'd pass it along to yall in case it was actually a good idea rather than my usual crackpot ones...

My understanding is that in an amp like the PPX3 - that each channel has a seperate output tube. If that is the case, and you wanted to compare different tubes in the output stage, why not just run one of each and make a recording with the same music in one channel at a time and alternate. I.e. You could rip a song into .WAV format and use an audio program like Adobe Audition to combine the channels into a mono signal and then run it only in the left channel for five seconds, then only in the right channel for five seconds...or something along those lines... then burn it to a CD. You might add a little jitter into the recording - but all in all the quality of the recording shouldn't be degraded much and it might help in comparing tubes.

Just a thought from a newb, take it for what it's worth...

 

[Zanth]

From my pretty limited knowledge in the world of EE and tubes I gather that especially power tubes, they have to be the same type, matched fairly closely or bad things can happen, certainly not the greatest sound.

Though audio memory is short, the differences between some tubes is NOT subtle. Thus you won't really need to worry about swapping and then getting a feel for the tube. In my amp, even though they are inputs (with mosfets at the output) I can easily discern the differences between various tube manufacturers and even between families (Amperex Bugle Boys vs. Amperex PQ 7316 for example).

 

[DrewWinters]

I can see how that might be a problem - I thought that any tube of a certain kind would be electronically similar enough to any other tube of that same kind that it wouldn't matter. I thought that tube-matching was for sonic reasons rather than electric ones.

I have a hard time describing the differences between things even when I can hear a distinct difference - but I guess that's just my inexperience speaking. Then again, it seems (from what I've heard from others) that the difference between tubes can be much more dramatic than..umm... "normal" stuff. <shrug> Perhaps I will find out sooner or later...

 

[Len]

The output tubes should always be the same tubes. In some designs such as most push pull, the output tubes should also be very closely matched to avoid damage to the transformers.

Listening to music through one speaker/headphone isn't going to give you the big picture. There are many things you're going to be missing by combining two channels into mono from a recording that was originally mastered for stereo. Listening in mono will give you a rough sense about the characteristic of the tube, but it's going to be impossible to fully appreciate the tonality, soundstage, detail, coherency, speed, ad nasueum of these tubes compared to stereo playback.

I agree; tubes' sonic differences are prominent.

 

[Len]

Quote:

Originally Posted by DrewWinters I can see how that might be a problem - I thought that any tube of a certain kind would be electronically similar enough to any other tube of that same kind that it wouldn't matter. I thought that tube-matching was for sonic reasons rather than electric ones.

Tube matching is important to avoid damage in some designs. Tubes of the same type (and even of the same make and vintage) can have enough deviation to cause long-term damage to an amp. In almost every headphone amps I'm aware of, you're not likely to have problems with mismatched output tubes due to the way these headphone amps are designed, but given the choice for peace of mind, I'd still use tubes of the same type. Tube matching for gain/pre tubes is less important.

 

[Mikey01]

NEVER MIND.

 

[DrewWinters]

I see. I knew that it wouldn't give an idea of imaging or spaciousness - but tonal qualities would still have come through. Too bad it won't work. Oh well... I guess it was just another crackpot idea.

I'll get a good one sooner or later!

 

[Hirsch]

In the PPX-3 (and all of the Singlepower amps I know of so far), the triodes are run single-ended. The amps stay in Class A all the time, so there is never any push-pull involved. This makes triode matching within a tube a bit less critical than it is in some other amps.

There is absolutely no reason you couldn't run completely different brands of tube in each output socket (and in fact at least one person has posted that he prefers this). Each tube is output for one channel. Each channel is independent, so there would be no risk of damage that I can think of. No way to damage an output transformer, since the PPX doesn't have them. It could sound pretty strange, though.

Note: this is not necessarily true of other amps. In a push-pull design, mismatched outputs could cause an amp to become unstable. As Len indicated, this could damage tubes and output transformers, if present.

 

[DrewWinters]

Yay!

But the real question is: merely for comparing tonal qualities - would it be useful at all to have a recording that swapped an identical mono signal from left to right?

Having never even heard a tube amp before, much less swapped tubes in and out of one, I haven't a clue how useful it would be. Obviously it's not a panacea - or even the best thing since sliced bread - but maybe someone will find it useful... If anyone does chose to play with it, Good luck, I hope you don't blow up your amp!

I look forward to having a tube amp, myself.

 

[Hirsch]

Interesting concept that can actually be measured.

I've got a device for setting up cartridges that takes two channels (of a mono recording), puts one channel out of phase, and sums the channels. If the cartridge is set up properly, there should be almost no signal. If antiskate or azimuth is not correct, you'll get signal from one of the channels, which will be louder or have distortion not present in the other.

Take this concept to tubes. Put two different tubes in the outputs, then use this device. You'll get signal if one channel has different gain than the other, which is actually pretty likely in most tube amplifiers to at least a small degree. However, you'll get higher level output at frequencies where one of the tubes is outputting significantly more than the other. In other words, one thing this will do is to take the tubes' frequency response, and subtract them. The remainder would be those frequencies where the tubes' response differed significantly.

A frequency analyzer could tell you exactly which frequency levels showed differences. I may have software that can do this. An interesting possibility to explore.