freestompboxes.org

Got an request to check this out in a bit more throrough manner. So here we go. Photos may not be much, but i think the bill of materials is complete. I'm not putting this back together just yet, in case someone wants more info on it...

C1 223 cer
C2 220µ/16V
C3 22µ/10V
C10 154 metal poly
C11 473 cer
C13 221 cer
C14 0,47µ/50V
C15 39
C16 0,22µ/50V
C17 0,22µ/50V
C18 0,47µ/50V
C19 0,47µ/50V
C20 4µ7/25V
C21 4µ7/25V
C22 10µ/16V
C25 10µ/16V
C26 682 cer
C27 473 cer
C28 473 cer
C29 10µ/16V
C30 0,47µ/50V
C31 821 cer
C32 0,15µ/50V
C33 0,68µ/50V
C34 182 cer
C35 333 cer
C36 4µ7/25V
C37 4µ7/25V
C38 10µ/16V
C39 10µ/16V
C40 10µ/16V
C41 102 cer
C42 102 cer
C43 471 cer
C44 417 cer
C45 103 cer
C50 223 cer
C51 223 cer
C52 104 metal poly

R1 10k
R2 12k
R10 10k
R11 1M
R13 47k
R14 47k
R15 22k
R16 680k
R17 10k
R18 10k
R19 47k
R20 22k
R21 1M
R22 100k
R23 ??? 270k/orange-orange-black-gold in green component (refer to photos)
R24 100k
R25 ??? 1M/orange-orange-black-gold in green component (refer to photos)
R26 27k
R27 5k6
R28 1M
R29 5k6
R30 33k
R31 4k7
R32 2k7
R33 33k
R34 470r
R35 2k7
R36 18k
R37 1M
R38 1M
R39 1M
R40 4k7
R41 82k
R42 82k
R43 22k
R44 22k
R45 150k
R46 150k
R47 100r
R48 1M
R49 1M
R50 10k
+extra resistor (33K) from C36 positive side to R29

D1 Si blue stripe
D2 1N4003
71 Si blue stripe
D10 Si blue stripe
D11 Si blue stripe
D12 Si blue stripe
D13 ? Zener
D14 red LED

IC1 JRC4558SD
IC2 NE571N
IC3 JRC NJU4069UBD
IC4 HD14016BP
IC10 JRC4558SD
IC11 JRC4558SD

Q1 C1740

Potentiometers Alps Japan, values unmarked, tapers unknown.
Measured values:
VR1 Low EQ - 25k (possibly rev. log.)
VR2 Out Level - 100k (possibly lin.)
VR3 Over Drive - 500k (possibly rev. log.)
VR4 High EQ - 25k (possibly rev. log.)

Thank you very much, I'm really curious about this one. Looks like a lot is happening inside, much more than the average distortion.

I started the tracing by entering all the parts in Eagle. After I can get no more info from your gutshots, I'll make a map with the unknown parts for you to (pretty please) fill in the blanks.

That's why i didn't put it back together just yet :) Some of the comoponent labels are partly under the parts, so the amount of photos to show them all would have been huge. Keep us posted!
+m

hi guys, FWIW I uploaded pictures of one (with which I tried to take so the parts values could be read, sometimes bending caps over so they could be read more easily) some while back:

viewtopic.php?f=7&t=10288

also, (just curious) what do you think of the sound? Do you like it? (I didn't but things like this can be quite subjective.)

Thanks for additional gutshots, dai h. It's a pity that the originals are no longer available, still I could get good info from your topic.

After I arranged the parts in Eagle as good as I could, I started the identification of the parts. This is where I am now: The green parts are the ones I think I know which is which.

At this stage I could use the color codes for further identification, but right now my head hurts from looking at the gutshots . BTW, mirosol, maybe you could take them at higher resolution.

Regarding the manufacturing, I noticed some weird/interesting things:
- the traces look like they used some CAD software, still the holes are not aligned or they are aligned in a weird way
- they used some resistors in parallel around the 4069 chip, which quite labour intensive

I had to resize the images down to attach them. I've uploaded the original sized ones on my temp folder here: http://mirosol.kapsi.fi/varasto/tmp/COD100/ These will most likely be gone from this location at some point. Possibly sooner than later.

I've added labels to the photo above. "jmpr" stands for a jumper.

On the other subject.. It doesn't sound bad at all. Glassy and powerful tone.
+m

Wow, you're fast. Thanks.

OK, first try: Expect a fair share of mistakes, as I'm pretty tired (it's 03:30 at my place). It looks like this:
- CMOS switching with input buffer, but no output buffer
- I suspect that NE571 is used as compander to fight the noise, which in this case is augmented by the intrinsic CMOS noise. I have yet to check the NE571 datasheet to see if I'm right.
- the clipping part contains 3 CMOS inverters with no capacitor in the feedback loops.
- the tone control is based on gyrators.
- the switching is using 4016 CMOS switches for the flip-flop circuit.

As I said, there's a lot going in this pedal. I'll check the schematic again and when it'll appear to be right (and when I'll have some spare time) I'll breadboard the NE571 + 4069 stage.

Now, you're fast :)
Seems legit. This is complex enough to be less tempting subject for cloning, but the schematic will sure help on repairs if needed. You got everything from the control board? I still have the unit open on my desk...

Doesn't IC11A act as an output buffer for the effect? The input buffer takes care of the bypass as well, so it might not be that bad of a design decision to not send the bypass signal thtrough two buffer stages. Let us know how the breadboard tests on the compander go. I'd be interested to understand how that works in this circuit.

Anyway. Amazing job, as always! (and as lways, keep an eye on my collection if you want to reverse any others in there:))
+m

I think I got everything. At the start, I entered all the parts from your first post, then I just connected them until none remained. Actually, I still have the diode denominated as 71, but I think it was a typo.

About the buffer, I gues I'm being pedantic. I'm used to buffer the output of the electronic switching and COD-100 has only a 4k7 resistor to separate the output from whatever is going next. While this is important fo JFET switching, it's less important for CMOS switching.

Can you check R14? I don't get the role of IC1A, as it's just an unity gain inverter with a bit of filtering.

It certainly stretched my Eagle skills, as I didn't have NE571N or JRC4558SD (SIL-9 package) in my libraries.

There are some manufacturing aspects that left me not too impressed:
- the traces are very long and (to me) unnecessarily complicated
- D1 is on the negative side of the power supply. If you daisy chain the pedal there's a risk this protection will be simply shunted.

But it is a grand project. Easily one of the most complicated distortions ever seen by me, except the digital ones.

Oh, and I will keep checking your collection .

I don't understand why everybody always uses the inverters with those überhigh impedances. It's not like those chips would have problems driving 10k... But then use a compander to deal with the unnecessary noise they just produced . Also, there are a couple of inverters doing nothing. Put them in parallel, cut the noise in half, and decrease the resistors even more because you have double the driving power.

Next time i'll be on my desk is on sunday, so sorry, no checking anything until then :( But for R14, it would make a bit more sense if it was 470k.

It is a rather complex design indeed. Those two 4558s on the control board did surprise me.
+m

marshmellow wrote:I don't understand why everybody always uses the inverters with those überhigh impedances. It's not like those chips would have problems driving 10k... But then use a compander to deal with the unnecessary noise they just produced . Also, there are a couple of inverters doing nothing. Put them in parallel, cut the noise in half, and decrease the resistors even more because you have double the driving power.

Sadly, it doesn't work like this. There's a nice explanation by PRR on DIYSB from which I quote:

Resistor hiss-noise is a non-issue: the MOS transistor self-noise is several/many microVolts, more than a 1Meg resistance.

Input impedance is often an issue. If you want gain of 30 and a 10K feedback resistor, you want a 330 ohm input resistor and have a nearly 330 ohm input impedance. That's awful low. In fact a CMOS amp won't drive 300 ohms well.

(Although, at 10V-15V supply, you hardly have open-loop gain of 30 so you can't really NFB-define a gain of 30 without cascading.)

OTOH with 1Meg feedback we get 33K input resistance, managable in many audio systems. For guitar we like over 100K, and 150K is popular. If we wanted gain of 30 (in this case maybe not) then the NFB computes to 4.5Meg. There's no realistic upper limit on the NFB resistor: CMOS gate current is VERY low, and in this case there's some gate current cancellation.

So, it's not the output impedance that's causing the resistor choice, it's the input impedance.

The inherent noise level of the CMOS inverters is really high. Sadly again, to make them clip/distort nice (and they can distort really nice) you have to starve them somewhat. The Bias control in a Emma Reezafratzitz will give you a good image of that. I fantasized since quite a lot ago about a "current compressor" to feed the inverters, so they have all they can eat at low levels (so lower noise), then when the signal goes large the inverters would be starved more and more, for the nice distortion they can make. Didn't find the time to do it yet, but who knows?
Also, in linear mode, the inverters eat gobbles of power. I can imagine using all six inverters leading to the overloading the smaller 9V/150mA wall-warts.

Bottom line, I think that the designer knew what he was doing and he played well enough within the constraints.

I didn't say anything about output impedance. The output of the inverter has to drive its feedback resistor which is in parallel to the following input impedance. The input impedance per se is a non-issue, since the inverter doesn't interface to the outside. You simply scale the input resistor down so it is still a couple of kiloohms. Decrease the feedback resistor by the same ratio, increase the coupling cap. Also, resistor noise of 1M or more is well within the same order of magnitude as the inverter.

Re parallel devices: the supply current is absolutely negligible, and it will be drawn whether the part of the IC is used in the circuit or not. The only thing you would add is the signal current, which is of course also totally negligible. You get a 3dB improvement for almost free. Almost, because you have to duplicate the resistors as well plus put a small output resistor in to isolate the parallel outputs from each other.

Doing both, I found the noise difference noticeable on the Blackstone overdrive, give it a try.

Hmm. I have to disagree. I quoted PRR (which is an authority for me) hoping that I would not have to debate this subject. This is my hand-on experience: CMOS inverters are far more noisy than most other parts, because of their 1/f (flicker) noise, which is inherent to their manufacturing process and has a specific "waterfall" timbre.
I should specify that the sound of low-gain CMOS inverter distortion circuits does not appeal to me. High-gain distortions as Emma Reezafratzitz, on the other hand, are very high on my tone reference list (heck, I can even write its name from memory). In this circuits, because of the gain stages count and the gain of each stage, noise builds up really fast. For reference, this is the clipping part of the Reeza:

Also, resistor noise of 1M or more is well within the same order of magnitude as the inverter.

I searched lots of interwebz for CMOS inverter noise measurements or calculus methods. I would be very interested to know how did you arrive at this conclusion.
One experiment I can think of would be to chain 4 1M resistors into a low-noise high input impedance op amp inverter and to compare the resulting noise to that of a chain of 4 CMOS unity inverters with 10k resistors. I might do this, although I'm not that motivated, given the information I have and the results of testing another claim you've made - power consumption.

This one was easy to check, as all that it needs is a DMM. This is the circuit: The IC is actually a HCF4069UBE. R8 is there to lower the load to COD-100 comparable values. The results are these:
1. when powered with 9V the circuit eats 14.9mA with 3 inverters (the other 3 being tied to the negative rail as in COD-100) and 39.1mA with the other 3 inverters connected in parallel
2. when powered with 15V the circuit eats 28.5mA with 3 inverters and 69.2mA with the other 3 inverters connected in parallel
As expected, the circuit use maximum power when has no input signal and the inverters stay all the time at half-supply voltage.

So, my statement about the wall-wart overloading was clearly exaggerated. However, I wouldn't call this power consumption "absolutely negligible".

About the sound: without help from the surrounding circuit, it is not an extreme distortion. And as I said, I don't really care for the not-extreme gain sound of the inverters. To me, it sounds buzzy with single inverters and farty with inverters in parallel. The sound I liked most was that of a D tuned guitar into the single inverters circuit supplied with 15V. I reckon it would make a really tasty bass overdrive.
Looking at the values, the maximum gain of the inverters section is less than the minimum gain of the inverters section from the Reeza (see first circuit snippet). R14 could help with some gain if it proves to be more than 47k, and so can the compander, so I have to breadboard it all.
I still have to test the inverters-in-parallel theory in a Reeza type circuit, to find if it is more than audiophile lore or if gives usable sounds worthy of several tens of milliamperes.

That being said, I found a mistake in the first schematic, around IC2A. I can confirm now that NE571 works as a textbook compander, IC2A being the compressor and IC2B the expander:

I thought I saw something like this using a NE571N. Not the same but I think it may help.... ETI Sustain Fuzz...

viewtopic.php?f=70&t=20527 ...gets into the way the circuit works a bit.