COLORSOUND: Hybrid Fuzz Box

The Colorsound Fuzz Box has to be one of my favourite fuzz circuits, due to its simplicity and reliable results.  It's very much a one trick pony, but if you just want a nice thick fuzz, this will to that trick quite nicely.

The layout is the same as the traditional all silicon version, with some component values changed - most notably Q2 is now a germanium NPN transistor and the bypass cap has jumped up from 10u to 22u.  

COLORSOUND HYBRID FUZZ BOX - 0.15" VERO LAYOUT

If you don't have the CV7112, try any low leakage NPN germanium transistor that you can get your hands on, and see how it sounds.  Maybe you will need to tweak the resistor values a little (the 2k2 and 82 ohm in particular), hopefully you have a breadboard that you can experiment on, rather than unsoldering and soldering resistors on the board.

I was testing it on the breadboard with a 10k pot in place of the 2k2 and found that about 4K was the sweet spot for the AC127 I was using.  I also increased the 82 ohm resistor to 120 for higher output.

I've not found reliable photos of the low value resistor paired with the 2k2 (the one on the far left). I've left what I consider the stock value of 82 ohms on the layout.  It might be a little different to this - who knows...  increasing the 82 ohm resistor increases output, which might be a good thing in some cases.  It doesn't need a substantial increase to see higher output - even taking up to 120 is noticeable.

LTSPICE RESULTS

Here's the difference between 10u and 22u on the bypass cap.  

And for the diagram below, this is what happens when the input cap is changed (retaining the 22uf bypass cap).  

In this circuit, the input cap, combined with the 150k resistor and the bypass cap largely control the frequency response.  The 220n cap is not contributing as much at all.  A lower value makes little difference.

No doubt there will be some colouration as a result of the germanium transistor, as it's not entirely unusual for some to sound tonally different to others.  i.e.  fatter or thinner at times.  LTspice is a handy guide, but it by no means replaces real world testing with a breadboard and a guitar plugged into an amplifier running at an obnoxious level.   

Changing the 82 ohm resistor has no effect on frequency response - the level increase is very obvious.

PETE CORNISH: P-1

I'd created a layout for the Pete Cornish P-1 about four years ago, based on best guesses as to what this said to be - a Rams Head Big Muff.   I was kind of close, but here's a layout from a very reliable Aion FX trace.  If you want to see where it sits in the spectrum of the Big Muff, check my BMP components table.

Interestingly, the circuit matches the 1976 Rams Head circuit #2, despite stories of it being based on a 74 model.  Who knows?  It's quite possible this was the case for the original P-1 with Pete changing values at a later date.

PETE CORNISH: P-1 VERO LAYOUT

Yes it's a very big layout for a Big Muff.  I included all of the buffers on the board, and left room on the corners for mounting.  I'm sure the multitude of standing resistors will throw a lot of people off too.  I clearly don't mind them.

I wasn't all that concerned about size, as I intend to drop this into an old big box BMP enclose, as beat up NYC ones seem to be going pretty cheap, and of course they already have cool graphics, pots and a hardware ready to go, so job done in that respect. 

DEATH BY AUDIO: Evil Fuzz

Thought I was overdue for a regular vero layout, as it has been a while - schematic available at PedalPCB.   

It has the usual DBA weirdness - upside down low-gain silicon transistors etc (reverse beta).  

DEATH BY AUDIO - EVIL FUZZ VERO LAYOUT

This humble little transformer is a favourite valve amp OT among some DIY folks in Australia, as it's cheap at only $27 and readily available from Altronics.   It's sold as a 20w 100v line transformer, but it also works really well as a 8k P-P output transformer.   Based on real world testing, it's thought to be closer to 15w, rather than 20w.

Here’s how you connect it: just follow the primary side and pick an output impedance that works for you (4, 8, or 16 ohms).

P: 1.25w 
CT:  5w
P: Common

These are perfect for replacing transformers in lower-power amps. I’ve even used one in an 8w push-pull PA head, and it sounds great.  Some old PA heads have output impedances that were meant for a bunch of 100v line speakers, not a single 8 or 16 ohm speaker. 

There's a few more versions available in the line with higher and lower wattages, but this one is probably the most commonly used.  The M1130 is larger, and with an impedance mismatch on the secondaries, it can be taken up to a 4k plate to plate load suitable for a pair of 6L6 not running too hot - they're used in the valve Heaven Lamington II.

Further reading:  Ozvalve amps

ALTRONICS M1120 OUTPUT TRANSFORMER

Frequency Response: 30Hz - 20kHz ±3dB
Secondary Taps: 4, 8 & 16 Ohm
Power taps: 1.25W, 2.5W, 5W, 10W, 15W, 20W
Frequency Response: 20Hz - 20kHz ±3dB

HOW IS THIS CALCULATED?

Note the transformer’s rated voltage (100v). Square this voltage: 100 squared is 10,000.

Divide 10,000 by the wattage on each tap. The smallest wattage has the largest P-P value.

10,000 divided by 1.25 equals 8,000. Repeat for the rest of the taps.

To calculate the centre tap (CT), divide 8,000 by 4 and match it to the relevant tap. In this case, the CT is the 5w tap.   

If for some reason 4K P-P was required, then connections would be as follows:  P 2.5W, CT 10W, P common.   

ALTRONICS M1120
PRIMARY	Watts	P-P Value	CT
6 (P)	1.25	8,000	2,000
5	2.5	4,000	1,000
4 (CT)	5	2,000	500
3	10	1,000	250
2	15	667
1	20	500
C (P)

Which is conveniently confirmed by the specs on the box.

and here's a youtube clip explaining the theory

 

100W KT88 PA Amplifier

Cause everyone needs a 100w valve powered PA head right?  Mainly for historical interest & I wanted to note the way the meter is set-up for later.