Does tube make a difference in the sound?

[Chuck H]

If you read Stan's post above you'll have to agree that saying "tubes do sound different!" and then "Its all about preference, expectation and natural human caprice...no science there..." are entirely contradictory. You can't make a definitive statement and then back it up by saying there is no proof but it's true by virtue of your nature. Tubes aren't all created equal, but they all do the same thing in the same way under controlled operating conditions. If the operating conditions aren't adjusted the circumstances are not the same and there is no basis for judgment.

That said, I agree that the difference between the various versions and makes of 12--7 tubes is profound. There is good reason to experiment and find out what sounds best in any individual amp (sans adjustment to the circuit itself). I do want to point out that every amp presents it's own circumstances and how well it works with any given tube will vary. So it would be wrong to assume that a particular tube sounds best in all amps only because it sounds best in your amp.

[tedmich]

I disagree, I can also say "people fall in love" and there is no science there either. Identifying complex differences in complex systems does not necessarily mean they will respond well, or indeed at all, to the scientific method, especially when human brains are involved.

How do EL84s sound different than 6V6, 6L6...? They do, some numbers can be discussed but the bottom line is human preference & caprice, like the majority of life.

[Chuck H]

Tubes aren't nearly as complex as the human brain Understanding why tubes sound different is easy done by evaluating their parameters and operating conditions. All of which are inventions and principals we know about. Who knows all there is about love?

Suppose we had only one tube, but a whole bunch of amps. The scenario would no longer be which tube sounds good but which amp sounds good. But we are a very self centered bunch so whatever amps we own will automatically become the criteria by which judgments are made. Suppose your amp circuit were a drinking glass. Now suppose your tubes were different amounts of water. One of the amounts fills your glass just the way you like it. That doesn't mean the rest of the amounts are wrong. They're just wrong for you and your glass. There are many glasses of many different volumes. For some of them a different amount of water might fill them just the way you like it. Whereas the amount of water you chose for your glass would be wrong for many of these other glasses. But all the different amounts of water do the same thing in the right circumstances.

This would apply mostly to tubes of the same designation and basic specifications. The construction of 6V6's and EL84's is very different and they do indeed behave differently. But two different brand EL84 tubes will be virtually the same if the circuit were adjusted for either tube.

[Jazz P Bass]

I simply want to note that my RCA stereo amp came with RCA EL84 Black Plates.
I was offered $150.00 for the quad & I sold them.

I installed a quad of Sovtek EL84 tubes & the amp sounded like ass.

Lucky for me, the seller was most cooperative & sent me a bag of used, old style tubes.
I picked four that had the same current draw (grey plates) & the sound came alive.

I am not knocking the Sovtek tubes but I do believe that the old tubes had much more going for them than new ones.

At least in this case.

[Alan0354]

If you read Stan's post above you'll have to agree that saying "tubes do sound different!" and then "Its all about preference, expectation and natural human caprice...no science there..." are entirely contradictory. You can't make a definitive statement and then back it up by saying there is no proof but it's true by virtue of your nature. Tubes aren't all created equal, but they all do the same thing in the same way under controlled operating conditions. If the operating conditions aren't adjusted the circumstances are not the same and there is no basis for judgment.

That said, I agree that the difference between the various versions and makes of 12--7 tubes is profound. There is good reason to experiment and find out what sounds best in any individual amp (sans adjustment to the circuit itself). I do want to point out that every amp presents it's own circumstances and how well it works with any given tube will vary. So it would be wrong to assume that a particular tube sounds best in all amps only because it sounds best in your amp.

That's really the point. Yes, if you just plug in any tube of the same number, they do sound MINOR difference. But if you go in and tune to the exact plate voltage( plate current), I believe you can make them sound a lot closer and it become a non issue. The same tube with 20V difference plate voltage is operating at a slightly different load line, the distortion is different, clipping is different. Unlike BJT, triode is very non ideal device, every change in parameter result in different operating characteristics. This is what I believe and that's the reason I post this to let people have a lot of experience to comment.

FYI, I just received a set of JJ 12AX7. When I replace into the amp, the plate voltage dropped by 15V. I bet it will sound different from the original tube. I did not even care enough to compare.

[Alan0354]

I disagree, I can also say "people fall in love" and there is no science there either. Identifying complex differences in complex systems does not necessarily mean they will respond well, or indeed at all, to the scientific method, especially when human brains are involved.

How do EL84s sound different than 6V6, 6L6...? They do, some numbers can be discussed but the bottom line is human preference & caprice, like the majority of life.

Now, comparing different tubes is a little more extreme as they have different structures. I sure hope they are a little different!!!!

[Alan0354]

Bottom line is, I can't get over people buying a used Fender Blues Jr or a Hot Rod Deluxe for about $300 to $400, then they automatically goes out and spend $100 to buy a set of new tubes!!!! AND I was being criticized for saying stop, listen first before spending the money!!!!

I can truly understand if people buy a vintage late 60s or very early 70s Fender SF amp and want to change the tubes. These are more collectable, more expensive, has the high quality sound that made Fender famous. But spending $100 for any el cheapo amp and expecting to have good return is another matter.

For the record, I bought a 73 Pro Reverb in good condition. I have not change the tubes as it sounds good. I did change all the filter caps as they were all original!!!

[soundmasterg]

I have a RCA "console pull" amp, it's a RCA RS177J with EL84's in push-pull. I totally refurbished it: completely recapped it (including coupling caps) and replaced all the resistors. Hooked to real speakers (ancient Radio Shack Mach Ones) and driven with a SS preamp, it's got very good bass response. In fact when I first fired it up I was surprised at the "oomph" that little amp produces. I'm certain that if it were back in the console, with the open-back original speakers, and if had not been refurbished, and if it were still being driven by the original tube preamp, I would not have been impressed. It's not the use of EL84's that limits bass response but rather everything else.

My RCA console doesn't lack bass per se, given what it is and how old it is....it lacks bass presence in comparison to a 70's Sherwood solid state amp I use in the garage, but of course they use different speakers. I also have only rebuilt the power amp on the RCA and not the rest of it. I do have to do that one of these days as the FM doesn't work anymore on the RCA and the tubes are all good, so something is amiss in the tuner/preamp portion. This console stereo has one EL84 per side, so its probably 9 watts a side or something, but it is plenty loud for a small house.

My comment on EL84's lacking bass in comparison to 6L6's is more directed towards guitar amps....a typical 2x6L6 amp seems to have more bass than a 4xEL84 amp....and the EL84 amp tends to have a sweeter top end with more harmonics present....so if that isn't the tubes then what is it? You could build identical amps, but use different power tubes....but then to get proper operation of each tube type you would need different OT's with different impedances....and there would be different value grid resistors on the power tubes....and an EL84 is easier to drive than a 6L6 so in the end you can't really get exact between two amps in this example to have an A/B test without there being differences....but these slight circuit or transformer changes can't account for all of the sound difference between two amps....so if not the tubes then what is it? Internal capacitances will make a difference in each tube type's response would it not?

Greg

[teemuk]

EL84's and El34's have much gradual curve towards saturation than 6V6's or 6L6's. Basically, EL84's and alike will "soft clip" whereas 6V6's and alike will "hard clip". People will hear the difference of overloading behaviour according to harmonic content: hard clipping is more higher order harmonics and sounds brighter than soft clipping which has less higher order harmonic content. People may also hear the headroom of more linear tubes as improved low end because the low frequencies won't fart out like they do when the amplifier is discernibly distorting. Output transformer may have different limits and slopes in its response depending on loading. If one tube requires a certain load impedance you can't often substitute it with another tube of different load impedance without effecting the overall response.

So, if you cange the design by changing the tubes a chance is the design itself will be effected somehow. If you design two circuits with different tubes paying attentiontion to proper specs you propably end up with less differences. For example, Egnater made amps with switchable output tubes and caught a lot of flak because in the end the switch didn't do as much as people expected it should. Under usual operating conditions both tubes in the circuit actually sounded almost identical. That said, usually you won't even encounter any differences before you overdrive the tubes out of their linear range of operation. Especially with power tubes this clause is often way too loud to fulfill in practice.

[Jazz P Bass]

I do have to do that one of these days as the FM doesn't work anymore on the RCA and the tubes are all good, so something is amiss in the tuner/preamp portion. g

I got real lucky when my FM tuner started acting up.
I replaced the tuner tube, 6C9 (VHF dual tetrode), and that fixed it.

[soundmasterg]

I got real lucky when my FM tuner started acting up.
I replaced the tuner tube, 6C9 (VHF dual tetrode), and that fixed it.
[ATTACH=CONFIG]27670[/ATTACH]

Yah I was hoping that would fix it as several tubes were bad in that part of the circuit, but it didn't...so when I get time I need to check into it. It works fine to play anything input from the RCA ins, in this case a CD player, so I can use it fine as long as I don't want to listen to FM. Nothing good on the radio anyway...haha.

Greg