The difference a tube can make

[BluesDude]

I am a little green on knowledge about vacuum tubes and the differences that certain tubes might make in an amps sound.

I have read quite a bit about NOS tubes, different tube brands, etc. It seems some people are big believers in the tone improvement that certain tubes can make in their amps.

Can someone give me a little background on why one tube may be better than another (assuming both are in good working order). For example what might make one 12ay7 tube yield better tone than another?

I am not opposed to paying up for tubes if I really thought they would make a huge difference... but from what I have read, it sounds more like buy a bunch of tubes and swap them in and out and try to find a combo that yields an improvement. That sounds a little like a hit or miss approach which could be a bit expensive and not yield much if any improvement.

Thanks

[Enzo]

First off, take all such comments with a grain of salt. What does it really mean when Joe Blow Guitar-god comes online and claims Tube-X is "better" than some other? He likes it better, OK fine. DO you have the same taste in tone as he? Is his amp identical to yours? Does he play the same guitar and pickups? Same speaker? AT best it is a suggestion. It is like someone saying lobster is better than steak. Maybe for some guys it is, but for others it ain't.

What makes tubes sound different? SUbtle differences in the internal element spacing, slight differences in interelement capacitances, maybe some cathodic material differences. whatever.
Depending upon the circuit and how you play through the amp, you may or may not notice a lot of difference.

To me, the tube differences are about on the order of the differences betwen brands of guitar strings.

Remember that NOS doesn;t specify any particular tube, it just means old tubes that have not been used.

And remember also, that each socket in the amp does a different job. There are inoput stages, tone stack recovery stages, phase inverter stages, and reverbs and trems, and other things. SOme amps have extra tube stages added in for OD channels, while others use separate channel paths.

Really, ther is no scientific procedure for netting your tone from tube specs. You get yourself a selection of tubes, and pick a socket. Try the various tubes in that socket. You may or may not notice a lot of difference. If you do, great, use the tube you lihe. Then move to the next socket. DO it all again.

Hit or miss? Maybe. Or maybe it is like going to the same restaurant and trying a diferent entree each time. The tubes you don;t use will be fine as spares. Can you tie up $100 in tubes? Sure, but that is the price of glory.


This is of course just my opinion, others may disagree.

[BluesDude]

Thanks for the comment.

It sounds like your experience has been that certain tubes might make a marginal difference, but not transform the sound and tone to a completely different level.

I have read many comments from people (their opinions). I must admit, I am a bit skeptical about claims of transforming of the amp (unless the tubes were bad)... I do believe there might be marginal improvement.

Here is an example I was reading... it is a review: Torres Tweed Deluxe 5E3

The author describes swapping out the tubes with NOS tubes and describe a complete transformation.

He also claimed orange drop caps are harsh in fender amps??


I was wondering... are different tube manufacturers' designs for a given tube type (e.g., 12ax7 or 6V6) different... or are they typically very similar (in design and spec)?

[Steve Conner]

I agree with Enzo. If you swap one brand of 12AX7 or EL34 or whatever, for another tube of the same type but different brand, it makes about as much difference as guitar strings.

As an example, I analyzed the differences between two 12AX7s in this thread, and posted sound clips etc. http://music-electronics-forum.com/t9221/

You can achieve more of a difference by swapping a different type of tube in: a popular tweak is to substitute a 12AT7 or 12AY7 for a 12AX7. Or changing EL34s in your power amp for 6550s, etc. But be aware that power tube swaps sometimes need mods to the amp ("rebiasing") for safe operation. And, some swaps are just plain verboten: if you stuff an EL34 into a Champ, you'll burn out the transformer.

You asked whether different tube manufacturers have different designs for the same type of tube:
my answer is "Mostly not." However, the thread I linked above dealt with a tube design that was completely new and different, and even then, the differences were fairly subtle, although many people could identify them from the sound clips.

I don't believe that changing the brand of capacitors makes the slightest tonal difference, and this point of view seems to be reasonably accepted, on this forum at least. But changing the VALUE of them does. If you swap a 0.1uF coupling capacitor for a 4700pF, it'll change the voicing of your amp radically.

So, in order of influence on tone:

1) Topology
2) Resistor and capacitor values
3) Tube types
4) Tube brands
5) ?

[Enzo]

You will often read comments like this: "I replaced the Sovtek 12AX7 with a TungSol reissue and it made all this difference..." Maybe it did, but what I bet that same person did NOT do was try a differnt Sovtek tube of the same type. When you do note differences, you might just as easily see as much difference between two tubes of the same brand and model as between two different brands.

Replacing a 12AX7 with a 5751 or 12AY7 is bound to sound different. The tubes have different gains and everything else. That is a separate isue from brands of one type tube.

Some people are genuinely excited by changes in their amps, but they are not careful reporters. Numerous times I read reports that start out, "I swear by the orange drop caps, they made a tremendous difference in my amp." Then as we read on we find that not only did he replace all his caps with orange drops, he also changed values in his tone stack, performed someone's mod from some web site, put in a lower gain tube in the phase splitter, changed his speaker out for a hemp tone something. Added a bright switch and converted to cathode bias. Now how on earth can he say the orange drops made all this difference?

The 12AX7 type tube has certain defining characteristics. Individual tube makers can build them as they see fit. Gather 10 different 12AX7 tubes and look through the glass at the innards. There are tall plates and short plates, different heater arrangements, and various things that may not meet the eye.

[yescaster]

I 'll disagree with one brand over another not imediately sounding different. It prolly depends on your listening. But I will also say...it seems no two tubes are identical, even the same make. Like guitars.

An example... I had a 12ax7 EH tube...and I wasn't quite getting what i wanted from that amp.. the shop gave me a high end mesaboogie tube. It was very grainy, and seemed brittle in tone compared to the EH which was creamier.

Tone IS subjective. but.. yea... get a bunch...pick a socket. True. I did. I presently have a 12ay or a 12au in place of the 12ax in the second socket (which is the reverb channel)... and i love it.. it gives alittle cleaner tone, and breaks up smoother than the full gain tube.

I haven't experimented with switching power tubes as much (just a few)...because it is more more costly than swapping preamps... but yes...that would make a huge difference in the amps reactive character.
Even changing the rectifier would change the character.
compression or sag punch or warmth... yea.. tubes make a difference.

one thing I will say I learned.

You may like what a tube swap does at studio room volumes...or in a certain room... then take it out to a bar and crank it... and it may not do what you like in that room's accoustic scenario, or in a band mix. Because certainly the amp will respond differently when played harder than studio setting. Also power soaking from all the electrical draw at a bar will make a difference.

One thing a fellow who is a Furman tech told me: "If you want the same sound always, use a power conditioner unit."
That is true.... amp sounds different in every place i play, and also depends who i'm playing with.

So tubes.. will get you in there. But crank it, and play as hard as you would when you play out.. because the tube swap will suprise you at the new character it gives the amp at higher volumes.

I think push the amp, that is where you will see the difference easily, withoput squinting to hear a difference.

anyway.. go for the preamps. it's cheap and values (ax, au, ay, 1575, etc..) can be swapped without rebiasing anything. It really amazed me how easily i could change the character of my amp.

So far I can tell you I personally prefer an EH, or milspec, to a Mesaboogie pre.

[Chuck H]

Many 12ax7's sound different (mostly high or low balance and slight gain differences) this will make a difference but it's a very small one in all but the first preamp stage. Changing the V1 12ax7 can make a very marked difference IME and it's worth experimenting. Power tubes vary a bit too. Some break up a little sooner and, as mentioned, have different balance when overdriven. This can also be worth experimenting with IF you want that last 5% to 10% of polish on your sound. But, as mentioned, it's about YOUR sound. Your ears, your guitar, etc. The results are more subjective than "improvements". So, V1 and power tubes are where you'll really hear a difference. As for V2, PI tubes, reverb drivers, etc... Not so much unless you change tube type rather than just tube brand.

Now. Steve mentioned that he doesn't think cap type makes the slightest difference in tone unless there is a change in value. This is true for the most part, but, if you were to change ALL the film caps in your amp with EXACT VALUE replacements of a different dielectric you MAY hear a SLIGHT difference. More significant are the dielectric characteristics. I use polypropylene caps because I got tired of my amps changing tone as they went from cold to warm to hot. Polypropylene caps in general have better temperature stability and I have noticed a significant improvement in this regard. So, since most amps that work do warm up I would say that different caps DO sound different. But it's not because of some fundamental difference in performance. It's because some caps change VALUE more than others as the amp warms up. As Steve said, a caps value can make a significant difference. That and cheap ceramic caps are best avoided all together.

Chuck

[yescaster]

Changing the V1 12ax7 can make a very marked difference IME and it's worth experimenting. So, V1 and power tubes are where you'll really hear a difference. As for V2, PI tubes, reverb drivers, etc... Not so much unless you change tube type rather than just tube brand.

Chuck

why wouldn't you hear a difference swapping v2 in an amp?

if you do play through the "normal" channel...and you play through the reverb or tremolo channel, then v1 is not your preamp.

For instance. I've removed the V1 pre, at times altogether because I was not using that channel.

If you use. V2 is for reverb side of (a "fender" amp for instance) your amp, and v1 is the normal side. You wont hear a difference swapping v1, or eliminating it, if you are playing through the reverb channel. maybe (and probably) a current/voltage character difference (because you are not heating v1 if it is absent), but the v1 and v2 positions are not both used unless you are jumping channels (using both channels) on fender amps (deluxe reverb as a plain example).

I've never pulled v2 while playing through v1...although I wouldn't see that not working.

[BluesDude]

Seems like the general consensus is: for a given tube type the brand at best might make a marginal difference and two tubes from the same manufacturer could exhibit differences (due to variability in the tubes).

It also sounds like there could be many other variables at play including the environment.

Right now my weber 5e3 has the low cost chinese tubes in it. They sound pretty good to me. I switched the 12ax7 in v1 with an 12ay7 (EH tube). I could hear the difference... it help with headroom some.

Well I was a bit skeptical anyway. I will probably not chase the elusive tube upgrade too much. Perhaps when I need to swap... I will try a different brand.

Too bad there is not a try before you buy option... but then again, I suspect that would drastically reduce tube sales

[uvacom]

Steve, thanks for posting those examples comparing the Mullard to the Techtube (which unfortunately already seems to be OOP). I wish there were more audio examples A/B'ing alike tubes in different positions in different amps.

[Chuck H]

I probably shouldn't even be responding, but...

if you do play through the "normal" channel...and you play through the reverb or tremolo channel, then v1 is not your preamp.

For instance. I've removed the V1 pre, at times altogether because I was not using that channel.

If you use. V2 is for reverb side of (a "fender" amp for instance) your amp, and v1 is the normal side. You wont hear a difference swapping v1, or eliminating it, if you are playing through the reverb channel. maybe (and probably) a current/voltage character difference (because you are not heating v1 if it is absent), but the v1 and v2 positions are not both used unless you are jumping channels (using both channels) on fender amps (deluxe reverb as a plain example).

I've never pulled v2 while playing through v1...although I wouldn't see that not working.

In my example V1 represents the first tube in the signal chain regardless of what specific preamp you happen to be using. How else could you explain this phenomenon in this scenario without going through the specifics of every guitar preamp ever built? In the case of a typical two channel BF Fender, if you happen to be playing through the reverb or vibrato channel, my reference to "V1" is V2 of the actual circuit. If the poster is using a Fender 5E3 Deluxe my reference to "V1" would actually be V1. So, in the future, just assume when no specific preamp schematic is referenced that when someone says "V1" they mean the first preamp tube in the signal chain, ok.

Chuck

[Enzo]

I'm with you Chuck. One shouldn;t have to explain that. Maybe we have to use terms like "input stage."

[yescaster]

So, in the future, just assume when no specific preamp schematic is referenced that when someone says "V1" they mean the first preamp tube in the signal chain, ok.

Chuck

ok. I misunderstood.

[MWJB]

"You wont hear a difference swapping v1, or eliminating it, if you are playing through the reverb channel. maybe (and probably) a current/voltage character difference (because you are not heating v1 if it is absent)," Pulling the Normal Channel input tube reduces the effective value of the shared cathode resistor at pin 8 of both input tubes. This will noticably drop the voltage on pin 6 of the Reverb Channel input tube, voltage on pin 1 of the Reverb Channel input tube may well rise - this is what causes the marked change in tone, not the heaters.

[Chuck H]

True that. In fact, it's a common "mod" to simply pull the preamp tube your NOT using on a BF Fender. I missed that in light of the issue I covered.

But Enzo is right. I should have said "input tube" or something like that as V1, V2, etc. actually IS how tubes are designated on schematics. I just wanted to recognize my part of the mistake here.

Chuck