Merman Compression

[fair.child]

I just finished the Merman. Very interesting pedal and I have been in love with this pedal ever since. I was wondering how should I test the compression on Merman? I don't hear/feel much difference when I turn up/down the compression knob. How do I know if the compression working?

[Betty Wont]

Lol, that's why i don't mess with compressors. They are hiss increasers, if anything. I can't tell if they are working. Sorry i can't help.

[fair.child]

I can't even distinguish the hiss or noise by my ears when the compression goes up or down. I've built the Pale Horse and Alpha Dog. Those two also have compression sections on them. When I turn it up, I can feel the tone differences for Pale Horse and Alpha Dog. However, I don't hear the similar/close enough result with Merman. It uses the C10k. The VFE Projects compression pots that I've known so far commonly use that C10k. Though, the pedal is nice. I still would like to know how to test it if it's working.

[somnif]

The "comp" knob does something a bit different on the Merman compared to the Pale Horse. On the Pale Horse, its sort of fading between two clipping styles (1 diode or two). On the Merman its essentially deciding how much signal you let get clipped. Since its going through soft germanium diodes, Its not the most obvious clipping out there. Fully cranked Its open, as much can clip as wants to (over the fv of the diodes), 0'd its like a diode lift, no clipping at all.  (I may have those two extreme backwards, the schematic is hard to read on my phone).

To test compare playing softly to playing really aggressively at various knob settings, want those nice voltage spikes for the clippers to play with.

[Boba7]

The "comp" knob does something a bit different on the Merman compared to the Pale Horse.

Yes.

In every case though there's no compression circuitry involved, it's all about clipping. I find it a bit confusing. And I remember reading a review of the Merman on the gearpage where the guy could hear a big difference with the comp knob on clean to low gain settings... which doesn't make any sense, since the comp knob adjusts the clipping threshold...
Anyways. You won't hear compression as in a dedicated compression circuit, you'll hear less or more clipping, or in the case of the Pale Horse or Alpha dog, less or more and different clipping (soft, hard, led, silicon etc.) But it will never affect the cleaner, low gain settings.

[fair.child]

This is tough. I am still waiting for the answer how to test the compression knob. Voltage driven? Scope? Any thoughts?

[madbean]

This is tough. I am still waiting for the answer how to test the compression knob. Voltage driven? Scope? Any thoughts?

One important component here is that you are only going to notice this change when your drive level is turned up pretty high. You could put a scope on it if you are inclined. The signal should square off when the comp knob is turned up. But, your ears should be enough. When you turn the knob up, more signal gets clipped (gets dirtier) and the overall volume output goes down. If that's not what you are getting then the problem could be with the pot itself or the clipping diodes in your build. It's basically the same idea as a diode lift but using a pot for degrees instead of a switch for on/off.

Try it with the Warm knob down, drive all the way up and everything else set to midpoint. You should definitely here the comp knob doing what I described with those settings.

[fair.child]

I did the test like what Brian said. I tried to change the clipping diodes and the C10K as well.It wasn't very subtle compression. My ears just can feel that when the compression goes up, it doesn't get dirty. I didn't hook up to the scope yet. Not sure where to probe and start to take a look.

I guess I might need to hook the audio probe to debug this.

[bsoncini]

For the scope I would say put it on pin 2 of the comp pot. You should see the wave starting to square off as you turn it up.

[fair.child]

Alright, I'll test that up then. I've seen some Merman demo and I've noticed similar output like what I'm having right now. Sometimes it's very hard to test by ears.

[warriorpoet]

You might try socketing C18. I use a similar configuration in part of my commercial builds, and find that a cap in parallel not only softens treble frequencies, but makes clipping more difficult to hear. In my case, I leave the cap out altogether.

[fair.child]

I did socketing C18 and experienced no difference from 1nF to 33nF. I assume the C18 range is high and I tried to debug it for several hours, still, no clue why it doesn't sound right. Also, now I am experiencing another issue. The pedal starts whining when the Gain and Volume go up high with Bottom at 0, Compression 0, and Warm at 12 o'clock. I brought back the 1nF and the result was the same (the pedal whining/ starts oscillating)