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Hi, I'm sorry, I forgot to write here that I solved the problem. I misunderstood the istructions and I soldered a wrong wire on the gain pot.
The pedal sounds really good. I just notice that the buffer, in bypass mode of course, cut a little bit of some treble.

I think the smd version and that mini pcb are the only one solution we have got. The J201 we used often until a few years ago are difficult to find. I never used the smd because I still have about three pieces in my stock, but soon I'll have to use the J201 smd.
I'm pretty sure that's ok and more accurate than the old (it's already vintage?) one.

Waiting for further opinions.

Meanwhile, I found this project:
http://byocelectronics.com/ampselectorinstructions.pdf
This has two input , but I have to find out if I can send the two inputs both in one amp, or if it's impossible to join the two sources.

I ordered a new LM13700 from Musikding. Waiting to test it.

I also ordered some stuff I usually order from Tayda.

Bump, I need some help, please.
I hope is clear enough what is the problem.

Thanks!

I really would like to solve changing the LM13700. That will be so easy!
By the way, I tried, just to be sure, the other LM13700 (Tayda) from the Snow White (without this issue, but with a not working Decay pot, as I said. Maybe there's a link?) and the result is the same.

To tell this issue with few words the effect (the LM13700?) work, but bad. Because I guess it boosts too much, so I got this very loud initial attack (at least three time the normal volume), and, I'm trying to guess, for the same reason I heard this high pitch click when I switch off the effect after the release time, and a bit when I turn on, It's not the usually bump when we got without the pulldown resistor. And I got a bit too much volume jump: louder when I play softly (because the too much boost) and less loud when I play harder (because the compression, perhaps the good working part).

This issue is absurd, the Engineer's Thumb has pro and cons, but I get an effect unusable, I don't think that nobody notice this, except me.

The funny thing is that the same loud initial attack I got in the Auto Wah DOD FX25 I dismessed, it was loud even in the decay, just with a bunch of low frequency, but that was the wah effect like in the heel position.

Midwayfair, how did you realize that Tayda had bad LM13700 chip? It doesn't work at all or you got a sort of issue like me?

By the way, I even more sure I'll never buy transistors or ICs from Tayda.

Voltage LM13700:
1 - 2.24v
2 - 0v
3 - 4.50v
4 - 4.49v
5 - 4.49v
6 - 0v
7 - 0v
8 - 0v
9 - 0v
10 - 0v
11 - 0v
12 - 0v
13 - 0v
14 - 8.99v
15 - 0v
16 - 0v

I measured it without the LM13700 and without cables.

Resistors value are correct, as well the orientation of the BC327 and the diodes. Caps orientation and value correct. Position of the components is right.

I prefer the chip is bad, because I didn't see anything wrong. But I'll check again.
I'll take out the chip for the measurement, too.

What I get is right a loud initial attack. When I play harder I get less volume than when I play softly, but this maybe depend from the settings, and this could be almost handle. But the loud attack is a bigger problem, especially when cause the loud snap when I turn off the effect. It's not the usually pop, but an high pitch click.

Later, I included even the two LEDs, but the problem was the same. Initially I didn't think this issue was a thing so bad. But now with the footswitch... I can't give this pedal to my friend.
He should engage the overdrive before to turn off the compressor. Not so cool.

Edit: I bought these two LM13700 from tayda, when the cost was 1,50 $. Now it's 2,02 $. Musikding has it at 1,75 €.

You can find the instructions to exclude the Release, Threshold and Attack pot on the Sabrotone page.
Anyway, I used 1M resistors for Threshold and Release, I guess it should be like if both was at max.

By the way, this kind of reaction I found it some years ago when I tried to build an auto wah DOD FX25, using an LM13700. Even this effect was sensitive to the picking (like the compressor). When I let it for a few seconds and then I hit the strings I got a quick loud bump of low frequency before the normal volume wah sound of the effect. The same things when I let the strings release by their self, the same loud bump of low frequency in the tail of the decay of the wah. Unusable, so I rejected.

Thinking this now I get the exact thing, though with a different effect: in this case I have a bump of volume.

Unfortunately, I have just another LM13700, even this bought from Tayda, it is right that LM13700 coming from the dismissed DOD FX255, now used for a Snow White Auto Wah, without this bad issue but with an unexplained not working Decay pot that I left anyway.

Or both this LM13700s bought with at least three years of distance are defeated, or all the LM13700s coming from Tayda are defeated. Or all this behaviour is normal and I don't know what mess I did.
Anyway, my Engineer's Thumb sounds too weird to be normal and usable with no worries.

This building is enough urgent.
Thanks for the help.

I'm using just three pots. Ratio and Volume and Attack. I followed the instruction to exclude, or better to keep the fix value for the other pots.

The compression sounds clean and nice (not distorted), but I get this thing really strange to me, that make this compressor a bit hard to play without the right touch. And I get this loud volume after the release time. This cause the loud attack of the first hit, and probably the loud snap when I switch off.
I guess that the overdrive effect after the Engineer's Thumb attenuates the snap becuase it attenuates even the compression.

Edit: The LM13700 come from Tayda. Some bad experience with this chip from Tayda?

Hello, I have a problem with the Engineer's Thumb using Sabrotone layout.
https://www.sabrotone.com/?p=2901
All the informations about it, here:
http://www.valvewizard.co.uk/engineersthumb.html

The effect seems work, a sort of, indeed I get the compression, but with some weird issues.
When I don't hit the strings I can hear the hiss and the volume rise up, and when I hit the strings I get a loud attack, then the compression act and I can play normally, though I got another strange thing: depends by the settings, but if I hit the strings harder the compression low the volume more than when I play softly.
I think this depends from the volume that rise up too much, it cause the loud attack and the loud volume when I play softly.
This issue cause a third problem. When I wired it into the box with footswitch and all the rest, this loud attack cause a high pitch snap when I switch off the effect, especially after I waited 6-7 seconds the release time.
This snap is barely audible when I engage the Vemuram Jan Ray (in the same box).
I tried anyway to use a pulldown resistor input or output, but the problem is in that big boost of the compressor.

I really need help, the pedal is for a friend.

Thanks!

Then should be something wrong. Try to check the wiring of the pots, eventually faulty connections or mismatched wires. Probabyl it has nothing to do with it, but I was building a Vemuram JanRay, and I misunderstood a wire connection, so the circuit sounds, but even if all the pots worked fine the sound was puttering and compressed.

Do you suspect that with in the low resistor mode it sounds ok or weird? Did you try to low Sustain and also the volume pot of the guitar and emulate the low mode?

Else, check again the usual things: orientation of transistor and polarity capacitors (did you use the tantalum?), resistors value...

[Original schematic by R.G Keen and layout by Matt Rabe.]

Thanks, I'll search some info for my own and I'll try to understand how it works.
Perhaps, I could need some help for the final project, I hope I can count on you in case, guys.

Update: Ok, I just found something useful, like this layout:

Original schematic by R.G Keen and layout by Matt Rabe.

This seems really good for my purpose, but I have just a problem. Now start the hard part, so pay attention, please. I'l try to explain.

This one schematic includes just one input, the Morley ABY Mix has two input but they joined, indeed I guess the two input convey both, after their own boost, through the switches and go out in the two output, (following the switching method we can use Output A or Output B or both or none.)

So, looking at the Morley the mod is that my friend get two signals, clean and distorted, and want to keep them separated. So I thought I can simply let the tow signals separated:
Clean -> [ Input A -> Boost A -> Output A ] Amp 1
Distortion -> [ Input B - > Boost B -> Output B ] Amp 2
There is the case when my friend have to use just the Amp 1, I tought to include a toggle switch to join the distortion signal from the Output B tip to the Output A tip, and get both the signals, clean and distorted, in the Amp 1.

But, with the Hume Free that receive just one input I don't know how keep the two signal separated.

Thanks for the help!

I don't know anything about this, it's the first time I hear. Can somebody show me something more?

Hello. I want to build a ABY looper for a friend. He wanted a Morley ABY Mix, but he would to do a thing that the Morley can't do, sometime to send both the input in one of the output, I guess I can do it.

But my fear is the ground loop that the looper can get using two amps. Also the original has this problem.
I didn't know it but this problem can be solved with an accessory, a sort of plug.

I wonder, what I can do to avoid this problem with this looper I'm going to build?

Thanks!