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Yes no issues, with no compression (and even with) I get a nice boost out of the volume control

Hug, Destitute!
Let's suppose, that yout PCB desk for BearHug V2-1 is connected ok :@)

1 - Control Q1 and D2. If they are still alive. Those details are sensitive for overheating while mounting, especially diode. Let there slightly longer "legs" for it. And that MOS-FET (and J-FET too) are sensitive for static electricity while handling and soldering. Learn about handling with it (if not yet).

2 - If they are good, play around TRIM 100k to get cca 4V at Drain (output signal) electrode of Q1. It's cca a half of fuell after D1. If it is ok, you have set basic DC setting for audiopath. Otherwise Q1 or D2 is "fired".

3 - Now you must set proper gain for it, not to have distorted signal. Disconnect C8 100nF from common point with diodes D3 D4. Now your J-FET Q3 has no signal and it's Gate is grounded by R7-R9. So, it's D-S pass is maximally opened, as can be for this schema. If this Q3 is good (again controll), then Q1 has now max. gain.

4 - Put sinus cca 2V/1kHz to input and measure (best by osciloscope) output. Or simply hear if signal is ok, without distortion, for maximal guitar signal. If there is problem, you must lower gain for this Q1 - serially with C7 47uF connect trimmer cca 10kOhm and try set clear signal, cca 2x stronger than original. If you are succesfull, you have finished basic audiopath setting. If even bigger value of trimmer doesn't give clear signal, try to play again with Q1 bias with 100k TRIM. When it is ok, change that serial trimmer for gain with resistor with closest higher value. If distortion is still here, Q1 or D2 are "fired". Especially, when you can hear noise. Axchange it and try set all again. If still noise or distortion is here, try to connect C7 straight at ground, bypassing Q3. If distortion or noise are away after we play with gain or TRIM trimmer, Q3 is bad - doesn't work as resistor. Exchange it.

5 - Now we must set Q2 - comp driver stage. At Collector of Q2 must be cca half of fuell voltage, which is cca 8V. Play around Basis resistor 10M. By me, is it too big to open it properly! I suggest 3M9, maximally 4M3, to get there cca 4V DC. Set it by trimmer at first and again exchange with similar resistor. Pot COMP 1kOhm set at minimal value while setting, so that resistor R10 47 Ohm is practically at ground. If it's ok, you have now strong enough signal for driving compressor branch. If signal is weak, you can change value of R3 2k2 to 4k7, as described in manual. But for the best range of setting this driver stage, change pot COMP too, at 2k5. And again set those 4V at Collector. If you can't set this voltage 4V DC, Q2 is probably bad.

6 - Now, connect C8 100 nF again with diodes. If you play some signals at the input now, at Gate of Q3 you will measure some negative voltage changes. Use digital meter, with high impedancy here. This minus jump will close D-S pass for Q3 and so lower gain of Q1. If negative jumps are ok, but signal is bad or without change, Q3 is probably bad for this work - try another.

Thats all.

Hi Zerro,

Thank you for the walkthrough of troubleshooting steps. I've actually been meaning to write a quick follow-up to this post here because I managed to fix the problem.

It turns out the THT JFETs I bought were no good, at least for this use. Despite me testing them and thinking they were in spec some parameter must have been out.

I bought some SMD 5457s and use one of those and oh boy I could tell instantly that it had fixed the problem, the compressor works and sounds great now. It's perfect for my use. 

Using my component tester I thought I'd compare the old THT to the new SMD JFET and I found the Id@Vg was considerably different. 0mA@0.35V for the THT vs 0mA@1.1V for the SMD

If you're getting a slow swell of volume of your guitar noise when you stop playing, it sounds like the compression is working.

Do this:

Pull Q3.

Is your signal amplified? (It should be quite a bit louder.) If not, your problem lies in Q1.

Put Q3 back in.

Put your probe on the gate of Q3 on DC and play a chord on the guitar. Do you see a jump in voltage?

Measure the resistance across Q3. It should be a few hundred Ohms (it's usually ~300 for me). Play a chord -- it should jump up to a few thousand.

There are other threads here where I've made similar suggestions, you might see what other peoples' results are. Nothing about your voltages jumps out at me, but I also am not familiar with the layout you're using, and I don't backtrace vero because I value my sanity

Thanks for the response, I appreciate it!

I did your steps in reverse order because I'm a dummy and didn't socket these transistors.

I saw no jump in voltage on Q3's gate but there was a negative jump on the source when I played a chord.

I couldn't see a few hundred ohms across Q3 no matter which leads I poked with my probes.

I desoldered Q3 and played and there was still no boost happening, my signal is quieter than bypass.

I'll search for the previous threads and see if anything there solves my issues. But before that, I'll revert back to the "stock" Tagboard layout to double check that the mods in this layout aren't to blame.

I'm sure I've messed something up somewhere, I measured the voltages and got these
Q1
D: 4.43V
S: 2.75V
G: 3.24V

Q2
C: 5.89V
B: 0.58V
E: 0.00V

Q3
D: 0.00V
S: 0.00V
G: 0.00V

The voltages of the source and gate for Q1 kept changing so I held my probe on them until they stabilised.

There are some mods down in the comment section on tag board effects that Jon suggest. They essentially make it V2 and are worth doing.

As for the noise, have you checked all the grounds? That is where I would start.

Photos of the solder side of the board are way more helpful.

And make sure to read the sticky thread about asking for help. If you follow those instructions it's much easier for people to help you.

Photo of the solder side attached, I've run down the tracks with a knife to make sure there are no unintended bridges.

I believe the layout I followed incorporates all of the V2 changes.

As far as I can tell all my grounds are good. When I'm playing the noise dies down then slowly comes back up as the compressor releases.

Photos of the front

As per the title I've made this compressor after getting some recommendations however the volume is less than unity when the knob is at it's max and the compression knob doesn't appear to change a whole lot through it's travel. I can tell the release time switch is working least.

My biggest issue is that it's amplifying some kind of noise. If I stop playing my guitar I can hear a hiss where it's raising the level of, what I assume is, the noise floor.

I've attached the layout I followed I believe it's a slightly modified V2. The only things I've changed are making the middle bottom 100k resistor a trimmer and I swapped a resistor out for a larger value for low output pickups.

Are there some transistor voltages or something I can check to quickly find the issue?