SD-1 to Crunch Box/Guv with TRUE BYPASS (w/PICS)

[11 Gauge]

Well, here's another "let's see if we can do it simply because why not?" kinda projects for a semi droll day.

First, the objectives/parameters:

-Use a Boss enclosure, reusing as much as possible, w/o altering it permanently in any way.

-Install a DPDT E Switch in place of the stock momentary.

-Use the stock indicator LED as 1/2 of the clipping diodes.

-Aside from the 100K Gain pot in the Guv'nor, use whatever is handy for the (singular) Tone and Level controls.

-Repurpose a really beat up and otherwise left for dead V1 Bluesbreaker PCB.

...There were other sorts of indifferent choices made along the way. The Crunch Box uses an op amp that's more in the JRC4XXX family, so I went with a JRC4580. But a 1458 sounded a little better, but that chip is now residing in some other pedal. It's kind of a modgepodge of V1 Guv, CB, and of course V1 BB. The biggest deviations from the first two are that the tone and output section of the BB shunt to Vbias/Vref instead of ground. So I did the same with my diode clippers and Rat Filter type tone control. I didn't like the CB's tone network at the tail end (is a mix of fixed and adjustable).

Descriptions will accompany the pics...

[11 Gauge]

In these pics you can see the E Switch installed. Small Bear carries them, but you can get similar switches from elsewhere.

I will typically use a little perfboard to solder the wires to the pins together more quickly, but in this instance I wanted to see if I had the chops to solder the wires straight to the super tiny pins. The "bypass" pins are simply connected with a piece of wire that's formed into 3 right angles.

Not shown in the pics is the hunk of plastic spacer that I hot glue inside the treadle plate underside. It's roughly 3/8" thick and is centered on the raised circular portion, more or less.

[11 Gauge]

Here's a shot or two of the clipping LED arrangement. It basically replaces the "first" .01uF tone cap on the BB board, with a pair of jumper wires that are run down to the stock status LED daughterboard, with another LED piggybacked onto it. The stock red LED's work great - pretty low voltages that they turn on at - around 1.6VDC (I like smaller clipping thresholds).

The one side shot with the board in the picture shows that it's seen better days. Bear in mind that this was mainly a curiosity project. If it's a keeper, I'll go back in and tidy up wiring, and probably etch a brand new board (without the need for all of the reverse engineering).

[11 Gauge]

Here are random shots that will hopefully show some of the reverse engineering that was necessary to convert a V1 BB into the Guv hard clipper, but keep the single tone control. It required running some components in series, bypassing a resistor or two with a cap, and jumpering some stuff around. There's also quite a few things that are simply left open on the board.

The circuit has been gained up a bit more like a Crunch Box, for insane amounts of crunch. The singular tone control is a 20K linear pot after the clipping diodes, with a .01uF cap to ground. There's also a 100 ohm resistor in series with the tone pot. It's a low cap value, but IMO the thing sounds best with lots of top end slice, especially at low gain settings (it allows it to clean up really well). If you go smaller on the pot, you typically want to go bigger on the tone cap.

I used a 50K log pot for the Level control. It works fine, IMO.

[11 Gauge]

So how does it sound? I really like it. Of course, I really have always liked the V1 Guv'nor, anyways.

Some of the Crunch Box touches are nice (a little pre gain filtering, some bigger caps in the neg FB loops, etc.) - the extra gain is a judgement call, especially with the lossy T/M/B tone stack replaced with a singular unit.

Having the clippers and tone circuit run to Vref instead of ground seems to add a touch more "life" to the tones, as well. Or it's probably just my ears playing tricks on me.

I know that the pics don't show everything clearly, so I'll elaborate where possible when requested. I don't want to either post the GGG BB schematic with my mods OR a stock Marshall schematic either. The first is using someone else's property, and the second doesn't have component numbers, so it would be potentially very confusing for those that are newer to modding. Just ask about any part of the circuit that you think or know has been modified, and I'll elaborate.

Enjoy!

[JohnnyCrash]

That board does look like it's seen better days! HAHA

I have the feeling your suggestion on using the E-Switch for old dead BOSS pedals will come in handy for me to re-appropriate some dead pedals. Maybe a CraigsList want ad is in order...

I can't wait for sound clips. *cough* <hint>

[11 Gauge]

Originally Posted by JohnnyCrash

That board does look like it's seen better days! HAHA

I have the feeling your suggestion on using the E-Switch for old dead BOSS pedals will come in handy for me to re-appropriate some dead pedals. Maybe a CraigsList want ad is in order...

I can't wait for sound clips. *cough* <hint>

Yeah - this following BB board is in just a tad better shape. I just need a box to stuff it in...

Clips will probably happen tomorrow, along with some Big Muff clips - I just modded one for .01uF caps before and after the Sustain pot - that is what is the first of the two "Cornish" switches in the Dice Works Muff Diver. Really cool distortion tones after swapping those two caps.

[JohnnyCrash]

Originally Posted by 11 Gauge

Yeah - this following BB board is in just a tad better shape. I just need a box to stuff it in...

Clips will probably happen tomorrow, along with some Big Muff clips - I just modded one for .01uF caps before and after the Sustain pot - that is what is the first of the two "Cornish" switches in the Dice Works Muff Diver. Really cool distortion tones after swapping those two caps.

I'd be curious about the cap switch as well... I love the Big Muff, but I'm always up for more flexibility - especailly with such a spacious box to add switches to

[Rbuzz]

Originally Posted by 11 Gauge

I just modded one for .01uF caps before and after the Sustain pot - that is what is the first of the two "Cornish" switches in the Dice Works Muff Diver. Really cool distortion tones after swapping those two caps.

Might I inquire about the second "Cornish" switch and how it effects the circuit and values?
My first post here BTW. Love the great info.