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

[bean]

Update on my post - all 5 boards are spoken for.

[DrAlx]

Im looking to build one of these on stripboard.

The layout is on 20 row, can this be built on 19 row?

I got my vero build down to 18x18 but that involved cutting gaps between holes with a sharp blade instead of drilling out entire holes.  I also tack adjacent tracks together with solder on the bottom of the board.
Following layout includes the millennium bypass and treble boost mod.  Both can be easily omitted.
Bottom pic is view from the bottom of the board showing where to make breaks in tracks (done before anything is soldered in place) and where to blob tracks together (done after everything soldered in place). 

[digi2t]

[quote/]

Dang son! That looks like what used to be on TV at 3:30 in the morning

[jfrabat]

Update on my post - all 5 boards are spoken for.

Already got started on mine!  I am missing some resistors and diodes, which I plan to get on Monday, but what I have is already in the board!

[merlinb]

I now have PCBs available too. Three knob version (Attack, Ratio, Level).
http://valvewizard.co.uk/shop.html
Don't PM me here, use the email address on my website above.

[kuzieem]

I have  built two stripboard 2knob versions, the lm13700 and CA3080. Both have the same problem with my  bass guitar - comp knob works as distortion (in unpleasant way). Everything double-checked, been building a dozen effects successfully so far.
How can I decrease the gain of compressed signal?

[merlinb]

comp knob works as distortion (in unpleasant way).

This indicates there is a fault with your build. Time to post photos?

[Mark Abbott]

I have built the compressor Merlin designed, I built it using the JMT board. I like it much more than Ross/MXR types as it doesn't colour the sound of the guitar and it isn't noisy.

My interest in the compressor is to have a "crunchy" rhythm sound and use the compressor to boost the guitar's output and provide more sustain. I'm finding that I could use more output.

Is there any thing in the circuit that could be changed that would provide more volume?

Thanks for your assistance.

Mark

[merlinb]

Is there any thing in the circuit that could be changed that would provide more volume?

I *think* if you change R8 from 220R to 100R you will get a 6dB boost.

[auden100]

I was just fooling around this morning with the intention of finding a volume boost. I have not tried the 100R you suggested. I did have success with a 47k substitute for the 10k going from #3 on the LM13700 to the op amp output. I got just the boost I was looking for.

I have precious little electronics knowledge. Is one of these methods preferable to the other?

P.S. Thanks for all the time you put into this circuit and sharing it, Merlin.

[merlinb]

I did have success with a 47k substitute for the 10k going from #3 on the LM13700 to the op amp output. I got just the boost I was looking for.

That accomplishes the same thing, yes. Reducing the 220R is a lower noise, lower-offset solution than increasing the 10k, but not by much!

[Mark Abbott]

Thanks Merlin, that should be the sort of boost I'm after. I'll give it a try and report findings.

Regards

Mark

[jfrabat]

Hope this isn't too much of a derail: I have a version of the Thumb I made for myself which uses an LM13700 and has external pots for attack, release and threshold. Build is verified with a couple minor caveats. Anyway, I have 5 extra boards I don't need and I'm happy to just give them away. If anyone wants one lemme know.

Build doc is here: http://madbeanpedals.com/projects/Thumb/Thumb.zip

Bean,

Quick question; what do G and L stand for in the bottom of the board?  I would have thought Ground and LED+, but the L seems to be connected to the - of the LED...  Not to mention that there is LED + and - already there...  The board is all done, and I was installing everything into the case (I had to get a bit creative to fit it in, but at then end, the battery was dropped because there was no way to fit it in).  Case is painted, switch and jacks are all wired, just need to connect everything to the board...

[PRR]

> what do G and L stand for

Probably go to the switch. Did you hunt MadBean's page for switch wiring info?

[jfrabat]

> what do G and L stand for

Probably go to the switch. Did you hunt MadBean's page for switch wiring info?

Good idea... I looked in the 1590G build tutorial.  It seems that the LED connects wot he LED + and -.  But that leaves the circuit open, and the L is the - of the LED, which goes to the stomp switch.  G is ground to the stomp switch.

[jfrabat]

Just wanted to report the pedal is finished and working...  Thanks, Bean!!!

[POTL]

.

[POTL]

.

[antonis]

Just finished a 4 knob version (Attack, Release, Compress & Level) incorporated in a multi-effect pedal and it simply sounds fantastic in front of either a Fender Blender, a (modified) Mig Muff or a Wampler Triple Wreck..!!   

@Merlin, you rock, man..!!! 

[Mark Abbott]

Antonis, thanks for the feedback on your compressor build. I experimented with the attack knob but found there was a sweet spot I liked and I'd just put a fixed resistor in, basically I wanted some delay so the attack of the note is preserved somewhat so the compressor still allows the guitar to sound natural. What is the release control like?

Regards

Mark