Anyway, one part of this is due to the fact that I rely on a (cheap) mic tube pre-amp to make my (cheap) solid-state combo amp sounds like an (expensive) tube guitar amp.
The problem with this is that to get the nice tone coloration out of a tube, you have to drive it hot, and it ends up being driven so hot that the signal level would be unsafe. So I just keep the volume as low as possible. I just nudge it up from zero until it sounds at all--and that's still usually too loud. I feel like if I turned it up any higher than that I'd blow my power amp or speaker for sure.
The combo I'm using is a Peavey Transtube Studio Pro 112, and the mic pre is an ART Tube MP Studio. Based on the specs, the amp nominally sends and receives -10dBV through the effect loop. The Tube MP has a maximum gain of 44dB, and a maximum output of about 20dBV. While it looks like I'd need a 30dB attenuator, I'd rather it be adjustable, so I'll probably end up testing several levels before committing to one.
Unlike a guitar amp preamp, the Tube MP also lacks any tone controls. I've been wanting to implement an idea for a new passive tone stack anyway, so I've decided to use it here. It consists of two Big Muff tone stacks, each with flat mids, but who have different cutoff frequencies. This would allow a wide range of mid cut and mid boost options in addition to regular Big Muff tone operation.
Both the attenuator and tone controls can be 100% passive, and since they're intended for the same device, I'm going to consider them the same project and put them in the same box, which with the ART TubeMP I'll hopefully be able to velcro somewhere on my amp.
Here's a diagram of how it would be.
Without the FX loop, the signal goes straight from the internal preamp to the power amp.
Next post I'll record a video of what it sounds like without the attenuator and tone stack (although I think I've done that before, but without really talking about it), and show what would have to hook up to what.