6-knob compressor (LM13700 version)

[MAO]

03/07/2017 Update - Posted a smaller layout here

11/19/2016 Update - Added a 6 1/2 knob layout (Jangle Switch option)
11/29/2016 - Added Sound Sample

This one started out as mirosol's 5-knob Compressor then I added the the BYOC 5-knob Compressor Tone Control and also converted the 3080 to a 13700.  

The Tone control wires attach in the center of the board, there is space to route the wires through the board as shown on the layout. Between 10 & 11 o'clock is the Keeley 4-knob "preset" tone. Further CW cuts bass adding sparkle to the compressed sound.  

I used matched MPSA18 for Q1 and Q2, matched 2n3904 for Q3 and Q4 and a 2n5089 for Q5. (Mark Hammer suggestion way back when) Unmatched 2n5088s could certainly be used for all 5 transistors. To me, these matched sets do sound better.  

These selected transistors probably changed the gain for the straight signal as well as the pedals overall volume compared to mirosol's 5-knob version (2n5088s). So I changed the original 130k to 300k to bump the straight signal and lowered the 56k to 27k as mine seemed to have to much available output volume.  

With the transistors I used and the resistor changes, having the Sustain nearly maxed, the volumes of both the straight signal and compressed signals are about even with the blend control at noon. There was a slight boost available to the straight signal with the Blend control full CCW.    

Sounds great and super quiet (even without the "Keeley" tantalums)

Verified by me

[notnews]

Amazing work, MAO! Right on.

Re: the transistors you chose.. is there a reason you chose matched MPSA18's for the first pair, matched 2N3904s for the second pair, and 2N5089 for the fifth Q? Like you mentioned, I've read that it's possible to use 2N5088s for all five, even unmatched. Is there an advantage using these specific different matched pairs over using 5 matched 2N5088s, for example? The MPSA18s have the largest hfe of all the transistors mentioned here, right?.. does that have something to do with it?

Btw, which caps are the ones keeley uses tants for? I assume the multilayer ceramic 150pf cap by the input is one.. and I'd think that the caps working with supply voltage could possibly benefit from being tant, though I could be off-base.

thanks again for the time, MAO.. can't wait to build this up! this is great.

I'd love to add a side-chain input.. I'm gonna look into that. That would make this the ultimate comp for my board. The Diamond comp has always been my dream comp for that reason (along with the LED-array display, and the other features and general sound of the effect).

[MAO]

I started using the matched sets thinking they were helpful in both noise reduction and signal strength.

Years ago I had read much on the Ross and Keeley compressors on another forum where both R'G Keen and Mark Hammer regularly contribute. I believe it was Mark who had made that exact suggestion. I'll see if I can find the thread I based my choices on.

Anyway, I liked the way the sounded and have used them ever since. May not be necessary, but I've stuck with them because they work well.  

I also believe the LM13700 is quieter than the original CA3080. Will probably never purchase  another CA3080 :0)

I recently tried 5 random 2n5088s in the 5-knob compressor and the matched sets sounded better to me, more clarity and punch. I'm not sure if the matched sets play a part in that or just the transistor types...If I get some down time I will swap in a few randoms and report back.  

Yes, the MPSA18 have a higher hfe than the others.

I believe it was shown that Keeley used tantalums for all the electrolytics except the 1u coming off the emitter of Q1 (MPSA18 on layout). I have built it both ways and could not hear a difference, although I'm only playing at bedroom volumes these days...I usually do use tantalums when building for someone else just because.  

Good luck, BTW since this needs a 1590BB, you may want to consider adding a "jangle" switch (an additional preset tone control) I used a 100k internal trimmer on a daughter board. I have the internal trimmer nearly maxed out and leave the external Tone control set between 10 & 11 0'clock (Keeley specs) Of course, you could just simply turn up the tone control when wanted rather than add the additional parts, but I like the look of 2 stomp switches :0)

 

[Senor Avocado]

I had a quick question Mao, What gauge wire and what size drill bit do you use to drill the stress relief holes for the offboard wires? I love how tidy it looks. I tried searching around the forum to see if you had mentioned it before and didn't see anything. Thanks again!

[MAO]

Thank you, I actually got the idea from JohnK's builds.

I mostly use Tayda AWG24 solid wire and a 1/16 drill bit. (Just don't buy the yellow wire as the casing melts like butter. All the other colors do well)

Occasionally I'll also use AWG22 wire and a 5/64 drill bit, but I much prefer the AWG24.  

On a side note, if you were planning on building this one, I just tweaked the layout a bit to accommodate an onboard trimmer for use as a "jangle" switch.  I'll post the updated layout sometime this weekend.  

[MAO]

6 1/2 knob compressor: updated layout to accommodate an internal trimmer for use as a 'jangle' switch.



Preset the trimmer for desired jangle (bass cut), use a toggle or stomp switch to select either the external mounted tone control or internal preset trimmer.

Or if you don't want an external tone control, use a switch to select either the internal trimmer or a jumper across the yellow wire connections. In this case, I would increase the 7k5 resistor to 15k.

 

[MAO]

Sound Sample

[Mark SL]

Is the second layout verified? I built it and everything sounds great other than the blend pot. It is acting like a volume pot rather than a blend pot. Turning it down kills the volume.

[MAO]

Hi Mark,

Yes, I have built that exact layout.

Let me look it over again tonight and I'll see if I can offer some advice.  

[MAO]

Mark, does the sound go completely quiet with the blend control maxed CCW, or just get a little less loud?

Assuming it goes completely silent and the compression side is working, tone control, attack, clip and compress then the clean signal is either grounded or broken.

Can you post the voltages on the TL072?

Make sure Blend-2 is not shorted to ground. If so, the cut under the TL072 near pin 4 may be the culprit.

You can also start checking the circled component values, placements and for shorts. This is where the clean signal flows to Blend-3

[Mark SL]

The blend turns the volume down to zero as you roll it back. With the blend all the way up, everything works perfectly. I'll check out the spots you suggested and get back to you.

Mark

On Dec 13, 2016, at 7:33 PM, MAO Pedals [via Guitar FX Layouts] <[hidden email]> wrote:

Mark, does the sound go completely quiet with the blend control maxed, or just get a little less loud?

Assuming it goes completely silent and the compression side is working, tone control, attack, clip and compress then the clean signal is either grounded or broken.

Can you post the voltages on the TL072?

Make sure Blend-2 is not shorted to ground. If so, the cut under the TL072 near pin 4 may be the culprit.

You can also start checking these values, placements and for shorts.

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[Mark SL]

The layout is good now.  I had a bad resistor on the top rail.

[MAO]

Cool!

Of course we need to thank mirosol for the 5 knob original version.

How do you like the blend and added tone controls?

[tentomushi]

Hey mao, nice work, i made the layout that mirosol posted with with a few tweeks that you pointed out. im also having problems with the ratio pot, fall clockwise is silent and ccw is the comp which is working well, dead quiet for this type too. I will be most grateful if you had any pointers, i have checked the areas you pointed out to the chap before, I'm a bit stumped.. everything looks how it should and i can't find any bridges, maybe its a resistor like the other chap?

[MAO]

Hi, hope I can help.

Sounds like you built miro's layout on the main site? If so, please post you issue there so when I post some suggestions it doesn't conflit with this layout here.

I'll check it out tonight and see what I can do.

[MAO]

Hi tentomushi

I just realized I can't post pictures on the main site, so I posted some suggestions here

Hope it helps.