This Week on the Breadboard: The Golden F**k

Well I've been experimenting with this circuit. It's a great circuit stock of course. But through my amp it's possibly a bit more compressed than I'd like and I barely use the Normal channel at all - it's usually only just on, and anywhere above 9.00 it just adds a rumble and takes over. On its own it is actually a lot darker than the normal channel on any 4-hole Marshall I have played. I've built quite a few JTM45 and 1987 style Marshall amps and invariably mod the Normal channel to make it more useful. In fact what I often do is make it more like the Bright channel, just keeping it enough different to justify having two channels. This makes sense when you look at the history of Marshalls. They were built to the Fender 5F6-a Bassman schematic after all.

So at first I tried doing what I do to the amps but to the pedal. I reduced the 100µF C3 to 47, then 22, then 1µF - and that's still plenty bassy. I often add a 470pF bright cap at the mixers to the Normal channel too - that's like C8 on the Golden Falk only I would put another in parallel with R6 in the GF. But I wondered why I would bother - the channels are already very similar. So I tried removing the Normal channel altogether and adding a Bass pot to the Bright channel at C4. After all, that section is where the two channels differ in where the low end cuts off.

So I kept the 470nF cap at C4 of the Bright channel and tried a few different cap values for the lower extent of the bass and settled on 22µF with a B10K Bass pot. This saves a fair few parts and I actually like the sound better. And for some reason as a bonus it appears to have reduced the compression somehow - maybe having one less transistor pushing the clipping section has had an effect? I don't know but I like the sound. This is where I ended up:

Mongrel schem.png
I'm sure most of you will still prefer the stock Golden Falk but I thought this might interest some of you. It really works for me - It actually sounds and feels more like the old Marshalls I have played and the amps I like to make. The stock GF is kinda more hot-rodded Marshall; more Van Halen or Slash. Mine is more Malcolm Young. :)

Thanks for writing this up, Chuck. The Golden Falk is a great Marshallesque pedal! I hope I haven't hi-jacked your thread - let me know if I have.
 
Can I ask a more basic question about this circuit. I read the Fetzer Valve Revisited article on runoffgroove.com, and the first gain stage looks familiar. For the gain stage of both this and the Viceroy we have the mu-amp. What is the reason for that? Does that allow pushing the distortion harder than a straight f.v.r. style of gain stage?
 
BTW I had a C10K for Bass originally but it made the low end come on too quickly. I also tried a 100nF cap at C3 which gives a wider range obviously but figured that the original has 220nF as the effective lowest level for bass, so...
 
Can I ask a more basic question about this circuit. I read the Fetzer Valve Revisited article on runoffgroove.com, and the first gain stage looks familiar. For the gain stage of both this and the Viceroy we have the mu-amp. What is the reason for that? Does that allow pushing the distortion harder than a straight f.v.r. style of gain stage?
The Mu Amp does two beneficial things for us, compared to a simple one-transistor amplification stage.
1. More Gain! *
2. Nearly symmetric clipping.

* HamishR increased R6 in his Mongrel pedal to moderate the 2nd stage gain.
 
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