High gain pre-amp tube / valve - Question

[skeitaridaudans]

I'm wondering...
If I use a tube that is rated high gain or tested for high gain as the pre-amp gain tube (V1) will the amp:

a) have more distortion, smoother sustain?

OR

b) distort later when I turn up the gain control? That is, will the tube handle higher gain WITHOUT distorting?

To a more specific question:
If I can choose between "JJ /Tesla ECC-83-S" (JJ's regular 12AX7) and "JJ / Tesla ECC-803-S", described as a "High-gain 12AX7" to use as the pre-amp gain tube (V1) in a JCM800 2204 50W amp, which would give me a warmer, fatter, "endless sustain" type sound?

Thanks!

[Steve Conner]

The answer is that a higher gain tube will give more distortion and more sustain, but not necessarily any of those other buzzwords like "warmer, fatter, smoother". You could maybe even replace the first two tubes with those high-gain types for an even bigger effect.

[Jammin'John]

Awful

It might even sound awful,or buzzy,or spikey.
Swappin' tubes is a blast !





JJ

[Brad166]

Iv ordered an entire tube set with high gain testing for all except the PI tube. In all honesty, I didnt notice realy any diffrence. I wouldnt pay the extra cash to get them tested. But....thats just my opinion.

[yankeerob]

Higher gain in the earlier stages usually means harsher distortion in the end product... you usually get the creamiest tone if you're more subtle earlier on in the chain... Another fallacy is power tube distortion... it's a myth... output tubes would sound awful if they were actually distorting... what people are actually referring to is the phase inverter or 'splitter' as it is know colloquially in Britain being overdriven... the smoother the earlier stages are the better this effect sounds...

You are far better advised to get as lush a clean tone as you can with your 1st stage... the rest will just follow...

[J M Fahey]

Higher gain in the earlier stages usually means harsher distortion in the end product... you usually get the creamiest tone if you're more subtle earlier on in the chain... Another fallacy is power tube distortion... it's a myth... output tubes would sound awful if they were actually distorting... what people are actually referring to is the phase inverter or 'splitter' as it is know colloquially in Britain being overdriven... the smoother the earlier stages are the better this effect sounds...

You are far better advised to get as lush a clean tone as you can with your 1st stage... the rest will just follow...

Tell that to, among others,

18 watt Marshall with cathode bias in extreme overdrive

owners :

[Justin Thomas]

Oh, I don't know... "awful" is subjective! That scope shot looks good to me!

Justin

[tedmich]

I love my Peavey Ultra series amps (XXX, ULTRA+) specifically because the active tone controls allow me to squash the preamp signal down to almost nothing when set to full cut (-15 db) and run the power amp full on pegged. Put some attenuating device into the FX loop and you have seething creamy distortion at very low volume levels. Lessening the PA gain removes a wonderful grittiness from the sound which I maximize with a NFB presence/resonance circuit stolen from a JSX. It is a little dangerous because if I accidentally bypass the FX loop attenuation, minimally my dog will be frightened to death by the resultant volume spike

That said many a "ultra high gain amp" was designed to provide almost solely preamp distortion with fairly clean PAs with wide bandwidth OTs etc. Perhaps this is one of the reasons few people are truly happy with the way their SLOs sound at low volume; they really open up when you go to the ear splitting volume where the PA is pushed. Really driving the PA like I've described above also results in replacing the current (fairly poor quality) power tubes much more frequently.

[g1]

The PI will almost always appear to be clipping when the power tubes do. Pull the power tubes to see what the true headroom of the PI is. Then you will probably find the PI appears to clip much sooner when the power tubes are installed.
This is the power tube grids conducting and clamping the PI output as it can't supply the current. Maybe a "chicken or the egg" scenario?

[J M Fahey]

Yes.

In fact the real power stage clippers are the power tubes, period.

That the PI plate signal clips at about the same time is just a design choice, power tube load impedance is chosen so they clip when their grids reach 0 volt, simply because that's when you can pull maximum current out of them.

And once grids become positive the power tubes will make the PI clip.

As said by g-one: pulling the power tubes from their sockets will "magically" correct PI plate clipping ... because you are removing clipping diodes (grid-cathode) from the circuit.

So no matter how you look at it, power tubes are main responsible for clipping.

Rant/side note: I had to search through a couple google pages to find a true plate waveform scope image, after pages and pages of DRAWN waveforms posted in countless pages (and even in books, ahem!!!) purporting to show and explain how tubes clip.
Absolutely wrong and misleading, of course.

A couple examples:



"Tube" vs. "SS":





Blue: original
Yellow: "Tube"
Red: "SS"



From a Boutique amp maker page:
(by the way, I'd LOVE to know what he means by "-Ve" .... PNP tubes? .... Isaac Asimov's "Positronics?" ):



and so on.

Special thanks to Loudthud who generously experiments and posts tube scope screens of real tubes driving real loads

[yankeerob]

The PI will almost always appear to be clipping when the power tubes do. Pull the power tubes to see what the true headroom of the PI is. Then you will probably find the PI appears to clip much sooner when the power tubes are installed.
This is the power tube grids conducting and clamping the PI output as it can't supply the current. Maybe a "chicken or the egg" scenario?

I would call it more of a 're-invent the wheel' scenario than a 'chicken or egg' one g-one... If anyone is happy with the sound of the waveform as posted earlier in this thread then who am I to spoil their joy?... horses for courses

I would say that having a good variety of pre-amp tubes hanging around is not a terrible idea but one should not be terribly surprised if a good ol' JJ ECC83S sounds better in certain scenarios than your prized Mullard or otherwise... most people will themselves to believe one is better than the other (because they have no doubt spent considerably more obtaining the said 'holy grail' article) but the reality is that in most cases - it's like plugging a '58 Les Paul Custom into a Vox Valvetronix amp... whilst the amp may produce a better sound with such a fab guitar plugged into it you will get a much better sound out of the guitar if you plug it into a better amp...

For me it's about being able to duplicate the same thing over and over and I've found that the quality of the build - ie ensuring the signal path is preserved at all costs with good quality wire/cable and wiring methods followed by selecting components that are going to support that ethos far outweighs valve choice... if you accomplish the former - the rest will follow... rant over