Amp bias indicator add-on (moved from the "microprocessor bias" thread

[nickb]

I had considered was something like a mosfet

You considered......a sillicootie! I'm speechless. Chuck!

If you were to ramp in the current to both tube slowly to minimise the output, say over 25mS then the combination of speaker response and common mode rejection would get the the switch on noise into the acceptable region, I would think. Further, you don't want to switch the current to zero, just enough to make the tubes last longer. Also, careful choices in the design of the signal present detect logic means that normal current will be applied due to string / instrument handling noise in time to avoid the ramp on being a problem. Worst case, you learn to gently tap the strings to wake it up before you hit the first note.

On the power supply, aren't we are talking about a situation where there is a silence of maybe 30 seconds and then, suddenly, it is overdriven? In this case the B+ will have ramped up anyway. Any further increase due to a reduction in idle current will be small. I doubt it's a concern in practice.

OTOH, it's 99% marketing bull and I have a strong suspicion that failures due to the complexity may outweigh any actual cost savings.

[Justin Thomas]

You considered......a sillicootie! I'm speechless. Chuck!

I didn't want to be the first to say it... he blasphemes!

Justin

[Chuck H]

Aw c'mon guys!?! I'm not some kind of crank. I don't use silicooties and I don't participate much in silicootie threads because I've only worked with tubes. And I can't just crossover principals because I'm not schooled in electronics overall. I'll admit that I still think tubes sound better. And, for me, there's something aesthetically pleasing about an all tube amp. Amps that use silicone for the reverb and effects loops seem like a practical evolution in working class models. I'll happily use them too. But given the choice I probably wouldn't own one. Still... If I thought I could make my tubes last four times as long by adding a MOSFET!?! Sure, I'd do that. Hell, I've been a part of this forum for over twenty years and the only circuit I'm known for uses Zener diodes. It's not even mine, it's kg's. I just developed a system for using it a certain way in conjunction with another circuit (that also isn't mine, it's Paul Ruby's). IIRC diodes are silicone devices

[Justin Thomas]

Cone, or Con?
Okay, okay, sometimes I over-romanticize the whole debate. I've only used 3 sillicooties in 4 amps - and 1 was a recycled bridge recto; the others were for bias supplies. And I'm still debating using some of those tiny tube diodes for a bias supply.
What's the worst that could happen? I guess I know of only one other person here who is like me in saying, "fine, just DON'T GO DIGITAL!"

And Chuck, make it two circuits - your Spitfire-With-Cheese kicks some ass. I like it. And it makes a great PA, too.

Justin

[J M Fahey]

Aw c'mon guys!?! I'm not some kind of crank. I don't use silicooties and I don't participate much in silicootie threads because I've only worked with tubes.

Cīmon Chuck, nobody accused you of *that*.
We all know you want "bottles" in your amps:


To be more precise, I bet we will find "bottles" and even "cans" inside them


Somebody told me you even modified an SS Lead 12 amp with "bottles" , more precisely "glass" inside it, is that so or just another Internet myth?

[Chuck H]

Cone, or Con?

Haha! I'm a painter (by trade). I use a lot of caulking. Chalk it up to a reflex synapse typo Besides, That circuit is the breast. Er, uh, best. Also, leaky diodes don't work for the circuit so I only use the silicone models instead of silicon!

Funny that I have used silicone in amps for different purposes. You have to be sure it's the right stuff though because some common household types are slightly conductive. In fact I've probably used more silicone than silicon.

[Old Tele man]

What happened with the system that Fender (FMIC) was using back some years ago? Obviously wasn't a success or it'd STILL be around.