Vibroluxish build

[überfuzz]

Yeah, I've been messing around with the components. You caught me red handed. Also, I guess I was to preoccupied by the simulation and the gnarls in it. I didn't see the simple fact you pointed out. :-)

[überfuzz]

Is it possible to estimate the level attenuation of a signal going through a tank? (I don't gear at home so I can't measure it)

[Chuck H]

Not really. The tone stack and volume control (as well as the actual guitar output) are all variable before the signal gets to the dwell pot. Also, you would need to figure, fairly precisely, attenuation due to coupling cap frequency as it relates to circuit impedances, peripheral loads like tube impedance @ frequency and any FB issues due to smaller than fully bypassed cathode resistors, etc. More math than I would trouble with to find anything like even a nominal setting voltage at the reverb driver grid. If your simulation shows more than adequate reverb that's good. The way your circuit is arranged there are many ways to manage both the input to the pan and the output of the recovery triode. Just build it and adjust from there once you have actual voltages at favored settings to measure and evaluate.

[überfuzz]

That's the plan, but I'm waiting for some hardware and components. And, on top of that I'm a nervous tinkerer, like to have a fair idea of what I'm doing.

[Chuck H]

like to have a fair idea of what I'm doing.

Why should you be so privileged compared to the rest of us?

[überfuzz]

Why should you be so privileged compared to the rest of us?

HAHA! Is it ok if I quote you on that one, next time my boss harass me.

[überfuzz]

Eureka! I found a way of simulating the reverb tank is my simulation software. The reverb circuit seems to be quite sturdy. I guess I'll keep tinkering with the values etc until I get all part going into the build. ;-)

[überfuzz]

This might sound funky but there's one kind of break up that really sets me off. Break up in reverb stages. Anyone care to suggest some neat way of adding a pot or so in a clever place to achieve this in the reverb section?

Edit. Eyy, the Dwell pot. Maybe I can achieve the level of break up by tinkering with it.

[Chuck H]

BUILD IT!!!!

Your reverb driving coupling cap looks to be 82p, is that right! not too much voltage passing there. If you need more you're pretty safe increasing it in size. There's nothing unusual about your reverb driver input impedance, so you'd still be within a useful pass frequency for reverb up to around 10X that value! You could use a push/pull pot to select between your stock cap and a larger one, say 220p, for more oomph or just a different tonal effect. Or maybe you'll find that two other values like 220p/680p work or sound better to you. Between that and the dwell pot you should have a lot of adjustability. YOU CAN"T KNOW UNTIL YOU'RE LISTENING TO IT!

[überfuzz]

Thanks for the input. I will build it! Just have to get the part for it. :-)

The simulations I do while waiting gives me, actually, a fair idea of how it will sound. And now there are still reverb stuff I like to fiddle around with, in the simulation.

[überfuzz]

I'm tinkering with the bias circuit at the moment. I've got a question regarding the negative voltage. How big span do I need to be able to bias different power tubes? With the bias pot at 'center' the negative bias is -45 V. Plate going to the power tubes is 365 V. With the attached circuit the negative bias is roughly -45 ± 5 V. Is this span good, should be wider or narrower?

[Chuck H]

365Vp and -45V bias should be pretty forgiving. It depends on how particular you are about a specific current for a given tube, but it would probably work for any clean tones with any tube. At the extreme ends you have, say, a soft 6L6 type or a 6V6 that doesn't like being pushed around that might sound best at -52V bias (hypothetical) Or an EL34 that really wants to be pushed that may be happier at -38V bias. IMHE different brand tubes even of the same designation can all bias very differently. Certain to be more when dealing with different brands AND different designations. 20V bias range should still compensate and keep any tube from blowing up on startup and would give you more flexibility in case you need it. Maybe you'll want to try some 6K6's some time.?.

[überfuzz]

Thanks Chunk!

I'll opt for a 20 V range instead. I believe I have a 20 kOhm pot that would give me a wider range, probably somewhere around 20 V.

[überfuzz]

I've never fiddled around with variable negative feed back. Well, now I figured, why not install a 1M potentiometer in series with the NFB resistor I all ready have see and if something nice happens. Is it worth it?

[überfuzz]

I've added some stuff to the circuit. And in addition to that changed some values to components I found in my own stash. As I wrote in the previous post, I've tried to model some variable NFB or something (on this particular version there's a presence thingy) but it doesn't seem to do anything. I know it's only a simulation, but still. Short story, all other pots, TREMOLO, REVERB, TONESTACK, are most likely in the final version. I am however intrigued by the idea of having some control over the break up, lets call it a gain pot. Finally, I also like the have some tone pot that affect the reverb stage.

Are there any suggestion on these two additions to this build? Feel free to comment other stuff too, any gnarls found and pointed out would be appreciated. Oh, sorry about the layout:ish schematic. When I started to plan how everything would go into the amplifier I switched to this layout style.



Cheers!