You guys ever play with diode limiters? I'm messing with my Princeton reverb clone and when I bypass the tone stack for a boost I can at times get out of control osciallations out of my reverb section because I am jamming so much signal into it. I know I can always just lower the input impedance on the driver tube and that would likely solve it, but it got me thinking about using some type of diode limiter on the input of the reverb tube driver to shunt the extra signal to ground once it reaches X value.
Is there a schematic I can check out for this type of thing?
Diode Limiters?
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Leo_Gnardo
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Re: Diode Limiters?
Input to the reverb drive tube is taken thru a 500 pF cap with 1M to ground. Try a pair of back-to-back diodes across the 1 Meg, fuzz box style. No fancy diodes needed either, 1n914 or 1N4001 or whatever you have in your parts box. You'll be clamping the signal to about 0.6V peak.
If you reduce the value of that 1 Meg you'll be reducing drive to the reverb driver at all times. With the diode pair, it will be normal at low volumes but clamped with a big signal, hopefully enough to keep you out of trouble
Note I've never had to do this sort of thing & proposed solution is my best "back of the envelope" attempt. At least it's cheap and fast. Tack a couple of diodes on, give 'er a go and let us know how/if it works.
If you reduce the value of that 1 Meg you'll be reducing drive to the reverb driver at all times. With the diode pair, it will be normal at low volumes but clamped with a big signal, hopefully enough to keep you out of trouble
Note I've never had to do this sort of thing & proposed solution is my best "back of the envelope" attempt. At least it's cheap and fast. Tack a couple of diodes on, give 'er a go and let us know how/if it works.
down technical blind alleys . . .
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Stevem
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Re: Diode Limiters?
What is that signal level difference?
Are you clipping the Verb driver stage also with the tone stack bypassed?
I would think that the root of your issue is something along the lines of where the Verb driver OT is located / mounted in regards to the preamp tubes and or wiring layout, and or you may need to shield the primary and or secondary wires on the driver OT?
Are the cables feeding the Verb pan good shielded wire like with a full aluminum shield, as many times rca type HI Fi cables suffer from a non full shield wrap!
Also note that if you are making use of a old reverb pan the RCAs on them since they are aluminum tarnish up badly and will make for much higher resistance which will in turn make the pan act like a antenna to signals!
I have had SS amps sing away like a bird due to this poor connection taking place!
Are you clipping the Verb driver stage also with the tone stack bypassed?
I would think that the root of your issue is something along the lines of where the Verb driver OT is located / mounted in regards to the preamp tubes and or wiring layout, and or you may need to shield the primary and or secondary wires on the driver OT?
Are the cables feeding the Verb pan good shielded wire like with a full aluminum shield, as many times rca type HI Fi cables suffer from a non full shield wrap!
Also note that if you are making use of a old reverb pan the RCAs on them since they are aluminum tarnish up badly and will make for much higher resistance which will in turn make the pan act like a antenna to signals!
I have had SS amps sing away like a bird due to this poor connection taking place!
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Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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bruce egnater
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Re: Diode Limiters?
What Jana said. The diodes will limit the signal into the reverb but will also distort it. Since the amp is already distorted in that scenario, it may be OK. Let us know what works for you. Assuming you are using a switch to bypass the tone controls, could you use a switch with additional poles and attenuate the input to the reverb drive at the same time?