Hi, I'm looking to put a compressor near the beginning of my signal chain. I already own a Diamond compressor and I've built the two knob Engineer's Thumb. I might be able to get away with mods to one of these guys or I might need a new build.

What I'd like:
1. to be able to have the option to keep some dynamics in the initial pick attack and have the compression kick in late enough so that it is primarily increasing sustain. (more of an issue because I have an Escobedo PWM fuzz that tends to sputter out abruptly if input goes too low).
2. to be able to get a "janglebox" type sound, as well as a more transparent sound.

I am guessing 1. involves an attack time switch or pot and 2. involves a treble switch or tone pot.

Would it make sense to mod my Engineer's thumb for this? I used Merlin's vero layout and am not sure how to adapt for 5 knob version.

Alternatively, I could build the deep six compressor
http://effectslayouts.blogspot.com/2016/07/walrus-audio-deep-six-compressor.html

Or the four knob compressor
http://effectslayouts.blogspot.com/2016/06/keeley-4-knob-compressor.html

or another depending on your recommendations. Thanks for your advice.

Engineer's thumb is probably your best reference design to start with.

I am doing a lot with DSP these days and it gives me quite a bit of insight into what does what.

Attack will help preserve the initial pick attack, but at high compression ratios (where you get good sustain) your gain is usually such that it gets clipped and then it makes the initial transient sound "soft".  I helped this behavior with a 2-stage compressor which allows me to set a faster-attack compression to occur about 6 dB above the main compressor threshold.

In the engineer's thumb this would equate to a split in the sidechain.  You would have one side off the rectifier work with a fast attack rate and then set your (slower) attack control on the other split.  The side with the fast attack rate would have a ratio before its output starts responding.  The final transistor that drives the OTA would be driven by the sum of 2 level detectors.  This description doesn't tell you how to do it like a finished schematic, but it opens discussion of this possibility.

The second thing I have observed helps preserve pick attack transients is the use of parallel compression (basically wet/dry mix between compressed and un-compressed signal).  You could expand on this by putting two compressors into a mixer and set one for a low ratio compression with a slow attack and the other for a high ratio compression with fast attack.

To bring out the highs/jangle can be helped by putting some pre-emphasis into the side chain.  This would be done by putting a capacitor and resistor feeding into the rectifier U1b in this schematic.

You might be able to do this simply by changing the input 10n capacitor to a 220pF to 1 nF, which would also affect the signal directly.  Combining this with parallel compression (dry mix) could help restore some of the low end.

These suggestions are all "alternatives" to the mods shown on the schematic, which already look pretty useful.  Implementing those mods can be done easily with any layout but it may not be pretty on some if you have to do floating resistors/flying leads to squish things in there.

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The Deep Six compressor actually looks like it handles the main cases I brought up.  Its "Ratio" control is really a wet/dry mix, so it gives you actually what looks like what could be some really useful settings.  That might not be a bad build that could address your wishes with a little knob-twisting -- give it a try I say!

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The Keeley 4-knob looks good, but the Deep-Six has the main bases covered and adds the wet/dry mix.  If you decide to build a new compressor then I would suggest the Deep Six over the Keeley based on what effect you're trying for.

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Something to keep in mind with these feedback compressor designs is that attack time decreases with increasing compression.  The extra gain in the feedback loop speeds up the capacitor charge times.  The fact that the op amps will saturate is what will slow this down.  I had to emulate op amp saturation in my DSP feedback compressor for this reason:  my attack control wasn't actually making an audible difference at a ratio where it would have been useful.  Once I made the side-chain saturate then I could get the attack to do something .  This is  a hint that an adjustable clipping threshold in the side-chain might do something.

Hexe Tadek

Quote from: roseblood11 on August 07, 2017, 07:25:06 PM
Hexe Tadek

Connect LEVEL "VB" side to the output of IC1A and you have the parallel compression option.  "LEVEL" then would act as a wet/dry mix knob.

Thanks @Transmogrifox, this is really helpful!

After you recommended the Deep Six, I found the BYOC 5 knob, which looks like the same thing running at 9V instead of 18V:
http://byocelectronics.com/5knobcompschematic.pdf ...so based on your tips about the wet/dry mix, I ordered a PCB and will build that.

RE: wet/dry mix--I can see how you recover the pick attack, but do you lose the sustain benefit in that case? Or do you compensate by maxxing out the compression ratio on the wet side? Also why not just set the attack time to be very slow? Just curious.

Sorry one more, somewhat off-topic question:
I want to run the output to two separate output jacks. Do I need to make any modifications to the circuit or add an output buffer, or is it fine to just hook up to two output jacks?

Why not tranforming your Engineers Thumb into a five-knobber?


--
Scarlett Johansson uses a Burst Box with her Telecaster.

I'll poo-poo at the other suggestions and instead suggest merely doing the Hollis flatliner with an added clean blend. Parallel compression is a great way to get some squish while maintaining a nice feeling attack

Addendum- I'm a bassist so I'll admit I don't exactly 'get' what jangle box tone is to guitarists, but if you want a little harmonic sweetness you can play with the above suggestion of the flatliner in combination with a fetzer 2.0 input stage or something.. or even build a discrete flatliner.
Maybe I'm not helping

Quote from: Hatredman on August 09, 2017, 05:47:17 PM
Why not tranforming your Engineers Thumb into a five-knobber?

I'm reluctant because (1) with Merlin's vero layout, it's not obvious which components need to be changed, and (2) I am really reluctant to change a working pedal. This usually ends up badly for me  and it might be faster to just build a new board from scratch from the Sabrotone vero layout.

Quote from: Transmogrifox on August 08, 2017, 07:08:20 PM

Quote from: roseblood11 on August 07, 2017, 07:25:06 PM
Hexe Tadek

Connect LEVEL "VB" side to the output of IC1A and you have the parallel compression option.  "LEVEL" then would act as a wet/dry mix knob.

Have you tried that?

I have to say that IMO, the escobedo pwm does not need a compressor.  just hit it harder.  It's one of those deals that gates.  If you hit it harder, with a simple boost, the sputtering end to your notes will be pushed back in time.  A long time.  You can hit it with just about anything - a fuzz pedal - and it will still sound like a escobedo pwm.  Some thing with an uglyface.

why not just orange squeeze?

I think TC sustainer has the longest ... sustain.
Not a build for beginners, though...

I linked schematic on the other site

I will build the Engineer Thumb using this veroboard layout http://www.sabrotone.com/?p=2901
There are even the instructions to left out the "advanced" control pots.
Maybe somebody can tell something about that layout.

Sorry I never followed up on this. I was going to try the Deep Six but then I found out about the BYOC 5 knob compressor:
https://buildyourownclone.com/collections/compression/products/5-knob-compressor

I got the PCB for that and it was an easy build (aside from some weirdness in the switch wiring). It sounds fantastic, very transparent, and super sustain. I now have the source of infinite feedback that I have been searching for after all these years!

Looks like a great choice.  Glad you like it.

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QuoteQuote from: Transmogrifox on August 08, 2017, 04:08:20 PM

    Quote from: roseblood11 on August 07, 2017, 04:25:06 PM

        Hexe Tadek

Connect LEVEL "VB" side to the output of IC1A and you have the parallel compression option.  "LEVEL" then would act as a wet/dry mix knob.

Have you tried that?

I have to admit I have not tried it on the Hexe Tadek.  I have a DSP feedback compressor running in my Bela in which I do the digital equivalent of this.  It adds a whole new dimension of flexibility for balancing attack dynamics and sustain.  The BYOC 5-knob compressor does what I had in mind and calls this knob "ratio".

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RE: wet/dry mix--I can see how you recover the pick attack, but do you lose the sustain benefit in that case? Or do you compensate by maxxing out the compression ratio on the wet side? Also why not just set the attack time to be very slow? Just curious.

Just for posterity of this thread, I will answer:
I would take a both/and approach to this.  Play with both mix AND attack time.

The main reason is at high compression ratios (best for sustain) your gain is really high.  Anything on a slow attack gets clipped and you still lose some of the attack transient.  If your compression ratio is high, then the tail-end of the note (sustain) is going to be held up for a long, long time.  So even if your sustain is mixed down at -6 to -10 dB, it's still very present.  For example, if you mix 50%/50% compressed and dry, then you get the original attack, which dominates during the time the compressor is squishing the compressed part of the mix.  Then as the note naturally decays, the compressor keeps holding it up and the compressor's sustain dominates in the mix.

The BYOC 5-knob compressor "ratio" knob is a wet/dry mix control, and not strictly a ratio control in the context of "compression ratio".  The "sustain" control is more of a ratio control, but it also serves to lower the threshold at the same time.  It's definitely not going to behave in the same way as a rack-mount pro compressor, but it doesn't need to do so in order to be a good guitar effect.  The labels on the control I think are reasonably descriptive from an end-user point of view.

The wet/dry mix adds another dimension of flexibility to how you balance these things. 

Here's a really good write-up about the concept:
https://www.soundonsound.com/techniques/parallel-compression

A very nice clean compressor is the dod 280 compressor. When used with the LED/LDR combo that you like (use a socket, try a few), I had best luck with very bright red leds and small ldr shrink wrapped.
http://tonepad.com/project.asp?id=21

If I were to build one now it would be a Ross clone with level, sustain, blend and input trim, maybe a switch for attack. I can take or leave anything else.

Do you prefer chip type comps or opto's