power tubes: tone related question

Si G X

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There is a difference. The materials used have changed. Up to, say, 75% of the rated output ( number pulled from ass, wiped clean and given a pep talk ), they'll sound the same. More or less. It's when clipping and compression come into play that subtle differences can be heard by the user, not neccessarily anyone else.

I agree with this comment.

Personally I don't hear (or feel) much (if any) difference between valves until they are distorting/compressing. So unless I was really driving the output stage then I wouldn't usually hear any significant difference in output valves.

.. and because I almost always push the front end with boosts then it's not something I worry about. I do play around with pre-amp valves a little though.
 

Greg70

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Getting back to the OP's question, and I think kingfan hit on, is that a tube tester only tests a few parameters of the tube. Two tubes can look the same on a tester but sound different installed because their response at different frequencies and voltages may be different. Look at a tube response chart and you will quickly see that a tube has a window of operating voltages that are linear and once it is operated outside that window the response becomes non-linear, which is distortion. A tube tester will not tell you where a particular tube's linear response would be.
 

telemnemonics

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Let's say I have two completely different sets of power tubes (let's assume two sets of 2X6L6GC for a super reverb)

  • One set is a vintage RCA set
  • the other set a modern JJ or whatever

Let's assume that both set of tubes present all the exact same readings on a professional tube tester.

What - if any - could explain tonal differences between both sets? If ALL electric values are the same?

Could there be any difference??

thanks

Tube testers don't test ALL "electric values".

In fact they test very very little.
 

telemnemonics

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I am vastly aware of differences in construction, quality & reliability, among tubes........ & how much an old RCA set is hard to beat for stability, reliability, consistency, etc...

YET, again:

How could that "better construction/materials" translate to the OPT & Speaker?

What would the OPT read/get from the tubes other than electric values?

Maybe consider tube tester "electrical values" to MD giving two men a physical.
Find two men who measure the same in height, weight, waist and chest, body fat, BP and respiration, even age and all organ functions.

Does that tell you which one wins an MMA fight, wins a dance contest, shoots hoops best or even benches the most weight?
 

slider313

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How could that translate to the OPT & Speaker?

What would the OPT read from the tubes other than electric values?

As mad dog has stated, different amp circuits will determine which tube sounds best. There's no given that a pair of RCA blackplate 6L6GC's will sound better than anything else just because of their use in blackface Fender amps.

Micanol bases were use on certain JAN power tubes for the purpose of being a better RF insulator, being able to withstand more heat and absorb less moisture. Everything going into a tubes construction has something to do with how it will react/sound in any given circuit.

Will the "overbuilt" tube always sound better? No. I've tried pairs of Bendix 5992 tubes (the most overbuilt 6V6GT type) in a few Fender amps and really didn't care for the sound at all.
 

KokoTele

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Getting back to the OP's question, and I think kingfan hit on, is that a tube tester only tests a few parameters of the tube. Two tubes can look the same on a tester but sound different installed because their response at different frequencies and voltages may be different. Look at a tube response chart and you will quickly see that a tube has a window of operating voltages that are linear and once it is operated outside that window the response becomes non-linear, which is distortion. A tube tester will not tell you where a particular tube's linear response would be.

This. If you were using an oscilloscope with a very high resolution, you could see some of those differences, and those are parameters that a tube tester won't record.

There have got to be dozens of things that affect the way tubes make electrons jump from the cathode to the anode, and dozens of things that affect the way the grid influences them.

The OPT and the speaker see voltages and frequencies. Change those a tiny bit and you alter the sound.
 

telemnemonics

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As mad dog has stated, different amp circuits will determine which tube sounds best. There's no given that a pair of RCA blackplate 6L6GC's will sound better than anything else just because of their use in blackface Fender amps.

Micanol bases were use on certain JAN power tubes for the purpose of being a better RF insulator, being able to withstand more heat and absorb less moisture. Everything going into a tubes construction has something to do with how it will react/sound in any given circuit.

Will the "overbuilt" tube always sound better? No. I've tried pairs of Bendix 5992 tubes (the most overbuilt 6V6GT type) in a few Fender amps and really didn't care for the sound at all.

As long as we're quibbling over subtle stuff here, RCA black plates were not used in Blackface Fender amps.
Then while RCA black plates are collector tubes, only a few guitar players prefer them over all other tube production.
And hell, I don't even think black face Fender amps sound all that great!

The only black plate tubes I distinctly consider special are Raytheon 12ax7, because they cut like no other.
Limited application though, like chili powder.
I do use NOS Sylvania black plates in brit amps but that's hardly pop tube selecting!
They were cheap.
Those are my favorite NOS tubes: cheap ones.
Some of the best were actually made in the '80s.
Some superb welded plate 6L6, 6ca7, 6550 etc then.
 

Dacious

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How could that translate to the OPT & Speaker?

What would the OPT read from the tubes other than electric values?

Difference in emission. Different damping standards. Different voltage swing between cathode and anode.

Your signal appearing at the grid is disrupting the flow of electrons in the pattern of the sine wave, which is creating that sine wave at the transformer taps and driving the speaker.

Everything at that point is part of the equation. Mass of the iron. Windings - number and gauge and interweave. Speaker impedance and type.

So two different manufacture tubes may react differently to the same signal. One may augment treble frequencies, one may augment bass. One may be noticeably louder. One may be sharper, one may be softer.

It's like the EL34 and 6CA7. Arguably they're interchangeable. But some 6CA7s are a bit beam-forming tetrode and not a pure pentode.

I haven't intensively listened but some people say there's a discernable difference.

Ditto 6V6s. JJs are a big plate tube that are loud and with good bass response. They also seem to handle higher voltage and current well.

Some people insist they're not a true 6V6GT even though the spec sheet says they are.

Vintage tubes can be more delicate sounding. Or livelier. Depending again on element design and placement.

You only have to look at long plate 12AX7s compared to show to short plates. They can be considerably different sounding although interchangeable.
 
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Dunedin2019

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Getting back to the OP's question, and I think kingfan hit on, is that a tube tester only tests a few parameters of the tube. Two tubes can look the same on a tester but sound different installed because their response at different frequencies and voltages may be different. Look at a tube response chart and you will quickly see that a tube has a window of operating voltages that are linear and once it is operated outside that window the response becomes non-linear, which is distortion. A tube tester will not tell you where a particular tube's linear response would be.

Yes, non-linearities and microphony effects are likely to make a difference. Audible? Better? YMMV.
 

Wallaby

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Pardon me, I didn't realize NOS *power* tubes are a thing. Preamp tubes, yes, but power tubes?

My understanding is that power tubes are the ones that wear out and get replaced, no?
 

VintageSG

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Pardon me, I didn't realize NOS *power* tubes are a thing. Preamp tubes, yes, but power tubes?

My understanding is that power tubes are the ones that wear out and get replaced, no?

They're a thing. You can still buy JAN VT-107 ( and others ) with mid 1940's production dates for the same price as modern production, if you hunt them down. War surplus!

The Soviet Union produced valves in enormous amounts from WWII up to the early 1990's. The 6p6s ( 6V6GT ) and 6p14p ( EL84 ) variants were produced in numbers that boggle the mind. European and Japanese production was more limited when it came to overproduction, but they're available.

Whether they're for you or not is your decision. They amplify that which the preamp supplies. Spend on the preamp first.
 

slider313

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As long as we're quibbling over subtle stuff here, RCA black plates were not used in Blackface Fender amps.

I'm guessing you haven't seen too many blackface Vibrolux, Pro, Super, or Twin Reverb amps built between 1963 and 1967? Most, if not all were shipped with RCA blackplate 6L6GC's.
 

printer2

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There was a web page that had a shootout of about 20 tubes, can not seem to find it. But on the variability of the tubes, the physical makeup changes how the lines are displayed on a curve tracer. How much is audibly different, I will leave it up to others.

vBoCGdm.jpeg
 

meric

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Double blind experiment should answer the question.
Run a statistically significant number of tests with a statistically significant number of tubes and get tone gurus to predict which tube is which ( cork sniffing boutique tube or generic tube). If a statistically significant number of predictions are correct....I would consider that humans can hear a difference....otherwise....OPINION ONLY.
 




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