Tube driven Diode Clipper

[petemoore]

Why me no see ?/
 Somebody tried this once. Is there a reason I've never seen diodes from signal path to ground after a tube stage on a schematic?

[R.G.]

(a) I've seen it. Some Marshalls do it with two pairs of diodes. I don't think it's for clipping, though. It's likely for preventing bias shift when the grid is driven positive.
(b) It's not a particularly good match. Diodes clip at under a volt, LEDs a couple of volts. The sharpness of clipping depends on both the clipping voltageof the diode and how far they're overdriven. With a tube stage putting ten to seventy volts into a diode clipping pair, every signal is driven to razor-sharp square waves, and the tube sounds no better than a cheap opamp clipper. Every fifty volt high signal looks alike to silicon diodes...

To get softer clipping, the driving signal must be near the clipping threshold. If one could guarantee that a silicon diode would never meet a signal more than 0.7V high, it would be quite soft in clipping.  That's the basis of a set of distortion thingies I've been working on for quite a while. That guarantee is the hard part.

[puretube]

Ampeg SVT V9;

[puretube]

HIWATT L50R & L100R; (1989)
uses same configuration as a.m. Marshall, however switchable.
M. usually doesn`t care about bias-shift...

[Johnny G]

posablly stupid question that ive been wondering about fora little while, if you can get tube diodes would it be posable to use those for clipping? i dont actually know anything about them hence why i realise that this could be a very stupid question but its always intrigued me as to what it might be like

[puretube]

tube-diode clipping is used in the Pure-Tube-Technology`s
Tube-Fuzz (R) :
http://www.puretube.com/T-FUZZ%20D-C%20cor.2.jpg;

Fender got a relative recent patent using tube-diodes for that purpose;
of course I was first (and others have done it in the `30s...);

[puretube]

(solidstate-)diodes after the second gainstage - driven by cathode-follower also in Randall RGT-100;

[puretube]

R.L. Haynes filed a patent in 1943 (us pat.#2434155),
for compressing/expanding signals with a row of successively higher biased tube-diodes with series-resistors shunting to ground  in a chain;
exactly the configuration like the tri-to-sine converters used in synths...

[runmikeyrun]

Pure Tube, how do those ampeg V9 SVT's sound on bass?  I've always wondered how the distortion sounded but due to their rarity i've never had the opportunity to try one...  Right now my dream rig is an old SVT with my big muff distortion pushing it, would a V9 be close to that?

[puretube]

tube-diode clipping is used in the Pure-Tube-Technology`s
Tube-Fuzz (R) :
http://www.puretube.com/T-FUZZ%20D-C%20cor.2.jpg;

inside a TUBE-FUZZ(TM):



runmikeyrun: sorry, I got that info only from the schematic...