THE ENGINEER'S THUMB... At last, a better compressor!

[tpoolan]

Deleted for stupidity...  

All fixed - apparently I have difficulty distinguishing red from brown...

[PRR]

> stupidity...  I have difficulty distinguishing red from brown...

NOT stupid!!

There is color-blindness, though you'd probably have a clue by now. (There's online tests which can say "No" or "maybe".)

Mostly some reds and some browns are not much different.

Especially in crappy light.

I have to be very fussy about the light at my resistor bench. When I had skylights, that was great. A good 100W *incandescent* is tolerable. Some fluorescents (including compacts) have such a narrow peak of "red" that all the colors near there look alike.

And part of our self-education includes learning our "favorite mistakes", so when we go "? ? ?" they come to the front of the list of things-to-check.

[psychedelicfish]

Deleted for stupidity... 

All fixed - apparently I have difficulty distinguishing red from brown...

Personally, I never use the colour codes on resistors, I just measure them with my MM. Then again, I have been diagnosed with colour blindness by an optometrist.

Mostly some reds and some browns are not much different.

That's another reason why I don't bother reading the colour codes. I find that the colours are never consistent, even between different batches from the same manufacturer. Another thing that bugs me is that the bands are never a consistent width, packets I get have good, thick bands, while others are almost unreadably thin.

[tpoolan]

It's a sign of age when I've got more magnifiers than I have screwdrivers...

As I said before, fab compressor - this is the first time I've tried board mounted pots (I adapted some standard alphas) never mind a big LED so I'm pleased I got everything to line up. 

Here's a couple of pics:

[Roger Martin]

A neat job, man.
My next project.
I read a few posts and they recommend me to pair a compressor with a big muff, is it really worth a try ?
I used the other compressor and came up with an unimpressive sound result.

[merlinb]

Here's a couple of pics:

Beautiful!

[gritz]

It's a sign of age when I've got more magnifiers than I have screwdrivers...

Me too bro, me too...

Sweet build btw!

[tpoolan]

I read a few posts and they recommend me to pair a compressor with a big muff, is it really worth a try ?
I used the other compressor and came up with an unimpressive sound result.

Most fuzz boxes have a 'compressing' effect in that they naturally squeeze the attack portion of the guitar signal. You can use the attack control on the compressor to put back some bite while adding sustain - it's a good combination (fuzz first). Add some treble back with the tone control for even more bite.

I was using the ET tonight with a fuzz face and pow! - instant Gilmour solo on 'Money' (if played by a chimpanzee...). A big muff should work well too.

By the way Merlin, if I push the input of the ET from the FF while bypassed I can get the LEDs to light up. Should this happen?

[merlinb]

By the way Merlin, if I push the input of the ET from the FF while bypassed I can get the LEDs to light up. Should this happen?

Assuming you have wired the ET bypass switch in the usual way (true bypass), then when bypassed there is absolutely no signal connection to the ET, so no, nothing should light up! Sounds like you have a wiring error...

[Jdansti]

>That's another reason why I don't bother reading the colour codes. I find that the colours are never consistent, even between different batches from the same manufacturer. Another thing that bugs me is that the bands are never a consistent width, packets I get have good, thick bands, while others are almost unreadably thin.

If I use color codes, I have to shine a bright light on the resistor (usually my iPhone light) and sometimes use a magnifier. Same for reading diode markings. 

[tpoolan]

By the way Merlin, if I push the input of the ET from the FF while bypassed I can get the LEDs to light up. Should this happen?

Assuming you have wired the ET bypass switch in the usual way (true bypass), then when bypassed there is absolutely no signal connection to the ET, so no, nothing should light up! Sounds like you have a wiring error...

A wiring error wouldn't surprise me. Can you see anything wrong in the pic? I'll have another look...

[tpoolan]

I can't see anything wrong with the wiring and it checks out with a meter. There is no physical signal connection between the input or output jacks and the circuit when bypassed. The only connection is between the circuit output and the switching FET. The switch is wired exactly as in the picture from the original ET docs.

Might it be to do with the positive ground FF?

I can also do this (FF flat out, ET bypassed):

[merlinb]

I can also do this (FF flat out, ET bypassed):

Interesting... in that case I suppose it could be picking up the higher frequencies that are coupled across the switch capacitance, or possibly something is coupling into the ground. The VU is very sensitive after all. Not sure what, if anything, can be done about this. Maybe add a few picofards from the input of the ET to ground (right at the opamp input), to shunt the switch capacitance...

[tpoolan]

Thanks Merlin, I'll try that. It's not a big deal, to be honest, but I get a bit OCD about these things. 

[musiclikscreams]

Any smaller 5 knob pcbs out there?

[waltk]

Any smaller 5 knob pcbs out there?

You can take about 20% off the top of Merlin's latest 5-knob layout.  The only things up there are the power connector and the protection diode.  That's what I did here - and substituted a series Schottky diode for the power protection.

[waltk]

Two questions for Merlin...

How can I reduce the brightness of the 3916 leds?

How can I adjust the low-end sensitivity of the leds (the lowest one is always on - even with no input)?

I guess it would be some adjustments to R26, R27, and/or R28.

[merlinb]

How can I reduce the brightness of the 3916 leds?

Increase R26- it controls the internal current source.

How can I adjust the low-end sensitivity of the leds (the lowest one is always on - even with no input)?

Reduce R28 and/or increase R27. There are actually two resistors (R11+R28) to make it easier to adjust the total resistance to pin 6.

[waltk]

Thanks Merlin - for the quick answer, and also for sharing this fantastic design!  I only box up about 1 out of every 20 circuits I build, and this one is a keeper.  Sounds great!

[KazooMan]

I liked the original version of The Engineer's Thumb so much that I had to build the 5-knob version.  I guess you could say I am "all Thumbs" now

Here are the pedals.  Thanks to Merlin for the artwork concept that I unabashedly copied.  Both pedals have my homebrewed adapter to allow using a surface mounted LM13700 as I described in a previous post in this thread.  The LM13700 performs better in my opinion.