Boost my Ultrastoner?

[AntKnee]

It wouldn't take much to do it. If the caps you have in there are rated at 25V or more, they'll all be OK. If you had any 16V caps in, especially in the power section, they'd need to be changed.

If the circuit you are using has a power filtering resistor in it, you need to make sure that it can handle the power across it, but the current draw is small enough that it shouldn't be a problem with any of the circuits I've seen.

The first gain stage is probably going to be a bit cleaner, but that shouldn't really be a problem. The middle two clipping stages aren't going to need any changes really since everything there is pretty much limited by the diodes. If you've got a mod in place to toggle out any of the diode sets, then it could get cleaner and louder here because the clipping from the transistor will be reduced.

The only real modification needed is in the output amplifier, and even here it'll work without any mods. But, you would want to mod this section because the whole point would be to allow this section to have more clean gain. The tone control section attenuates the volume quite a bit, so the final amplifier is where you get most of the volume. At 18V, you can get a bunch of gain out of this amplifier. The only changes needed are in the resistor values. What you want to use depends on how much gain you need. It isn't hard to figure out though.

I just put 18V on a couple of my Big Muff builds. It works fine. One of them has settings that can remove both sets of clipping diodes. This gets loud at 18V! I've been wanting to test a tone control mod, so I might have a go at putting this on the breadboard and take a look at what happens with the 18V mod while I'm at it. I'll let you know if I get a chance to do it any time soon.

I'd like about the same amount of gain available from my Kingslayer. So, its basically just a matter of raising the values of the resistors in the output section and squeezing a Road Rage in there?

[RobA]

That's basically the idea, although you can alter the gain of the amplifier stage by either raising the collector resistor or lowering the emitter resistor or both. You may need to alter the bias resistors depending on what happens with the other two resistors. You may not need to move to 18V at all. It depends on how much extra gain you need.

I don't have a Kingslayer or an Ultrastoner build of a Big Muff, so I can't compare directly. I can make a pretty good guess of where the volume level of the Ultrastoner should be based on the muffs I do have and comparing the output stage values.

Maybe we can figure out how much more gain you need from the final amplifier stage this way -- where do you set the volume level of the Kingslayer normally and how far do you have to turn it down to bring it down to the level of the Ultrastoner?

[Muadzin]

The Musket Fuzz puts a LPB booster before a Big Muff. Maybe that's what you're looking for?

[AntKnee]

The Musket Fuzz puts a LPB booster before a Big Muff. Maybe that's what you're looking for?

Part of the problem is that any boost in front of the Ultrastoner in the chain gets compressed down such that it does no good.
I am going to try the US into my SHO tonight and if it works I will do a dual box build with the SHO. I have a couple extra Ultrastoners anyway.

[RobA]

I finally got a chance to put this on the breadboard and test it out. I had simulated it in LTSpice to do some quick testing and get an idea of how far it could be pushed first, and the bread board results are pretty consistent with the simulation.

The first thing to note is that if you are using 1n4148 type diodes for the clippers, then whatever version of the Big Muff circuit you are using is close to irrelevant for this test because the clippers alone pretty much set the level going into the final amplifier stage. If you were to do different diodes, then you could end up overdriving the output stage depending on what you did use. Given that, I put what's close to a Violet Ram's Head version on the breadboard. I had a slightly modded first gain stage but not by a whole lot.  I used BC550C transistors for this test. With the VRH values in the final amplifier (resistors of 100k, 390k, 2.7k, and 10k) at 9V I get about a 2V peak-to-peak swing on the output of the amplifier (before the volume pot). If I move that to 18V with the same values for the resistors, it'll move up to about 2.2V peak-to-peak on the output swing. There is a slight change in tone probably from increased headroom in the initial amplifier stage.

I then changed the output amplifier to use 68k, 680k, 2.2k, and 30k resistors. This should be a big increase in the output level. At 9V, the output level is about a 4V peak-to-peak swing with maybe a touch of distortion added in the output amplifier. With the same resistors at 18V, it gets a bit more than a 6V peak-to-peak swing on the output with no added distortion in the output wave shape.

If you were to move the collector resistor down to 27k from the 30k, you could probably do it at 9V without much change in the tone of the pedal and still get a good boost in volume. If that's not enough, pushing it to 18V with the 30k and the 2.2k does give a pretty good increase in output level

[AntKnee]

Sorry for the late reply.
Thanks for the research! I'll give it a try.