Bearhug Compressor - schematic, demo, layouts, & forthcoming 1776 PCB!

[rankot]

Changed R6 to 56k so Q1´s Gate voltage went up to 6,7V. I think it isn´t harmful to any component 
Also left R4 in 2k2 value.

How did those two changes affected the sound?

[blackieNYC]

thanks for the reply Jon.  I was very interested in the Bearhug and the Engineer's Thumb, just to avoid the idea of the OTA in the audio path (silly really. Love my MXR and the many other OTA things on the pedalboard). 
I've built the Madbean 4:1 - an optical with clean blend. (I reduced R10 to 6.9K just to have ridiculous distortion available. Less than that becomes very noisy.) I like the blend more than I expected.  I think Mark Hammer pointed out somewhere the value of the blend in giving you initial attack from the clean, which of course fades quickly, leaving you the compressed signal.  This yields lots of squish but with that country-ish initial snap if you wish. Or looking at it a bit differently, you can keep the highs from the clean (initially) for when you've dialed up so much compression that your highs seem reduced. I may even filter the lows out of the clean with a toggle.
As for the bearhug and the thumb, I assume I've got something wrong - I don't doubt the design or my parts. But I'm going to move on for now.  I'll bag up the parts and label it, and let it glower at me from the Drawer of Shame.
"if at first you don't succeed, try, try again. Then quit. No use being a damn fool about it." WC Fields

[Flaconsius]

Changed R6 to 56k so Q1´s Gate voltage went up to 6,7V. I think it isn´t harmful to any component 
Also left R4 in 2k2 value.

How did those two changes affected the sound?

Well, I didn´t note any big difference.

[soggybag]

I just built up a Bearhug from one of the 1776 boards. I think it's the first version of the board. It works as a boost I'm getting little to no compression? Any suggestions on how I might debug this?

here is a picture of my build. I used the mods from page 2 of this thread:

• Left out R12
• Si diodes

Here is a super gigantic image, how can you make these smaller?

[bloxstompboxes]

I just built up a Bearhug from one of the 1776 boards. I think it's the first version of the board. It works as a boost I'm getting little to no compression? Any suggestions on how I might debug this?

here is a picture of my build. I used the mods from page 2 of this thread:

• Left out R12
• Si diodes

Click quote to see how I edited your post to make the image smaller. As for the build, I am at work at the moment but someone on the forum should be able to assist!
Here is a super gigantic image, how can you make these smaller?

[midwayfair]

There are some general troubleshooting instructions for the rectifier and FET over the course of the thread. There are similar posts on the Madbean thread if you're still stuck after browsing through this one. The tests are relatively similar for each version.

I don't see anything immediately obvious on your build from the pictures but voltages will help.

[soggybag]

Thanks for the replies. Here are some voltages:

Q1

D - 4.93
S - 2.21
G - 2.25

Q2

E - 0
B - 8.41
C - 8.91

Q3

D - 0
S - 0
G - 0

[soggybag]

I measured the resistance across DS of Q3 and get about 260 ohms at idle and get only a small change when there is input. Seems like Q2 or the rectifier section might be the problem. Any suggestions on how I might trouble shoot this?

[midwayfair]

I measured the resistance across DS of Q3 and get about 260 ohms at idle and get only a small change when there is input. Seems like Q2 or the rectifier section might be the problem. Any suggestions on how I might trouble shoot this?

Find out where your signal is being lost -- you can audio probe the Q2 collector for instance to make sure Q2 is amplifying. Other things to check are to make sure your diodes and resistors aren't dead or mismarked. About the only other things that can happen there are maybe the hold capacitor is shorting or something like that. It's only a small number of parts to verify, so it wouldn't even be too tedious if you have to individually test them. But start with simple ways to check the signal strength, like an audio probe.

[soggybag]

The signal is strong at the Base of Q2 but weak and sputtery at the Collector.

[midwayfair]

The signal is strong at the Base of Q2 but weak and sputtery at the Collector.

What are your voltages?

And check the pinout.

[soggybag]

I'm guessing the signal should be a lot stronger the Collector of Q2?

[midwayfair]

I'm guessing the signal should be a lot stronger the Collector of Q2?

Yes, it's amplified between 2 and ... 2200/47 times.

[soggybag]

Turns out I out a 2N5087 in Q2 for some reason. Which I suppose might have worked if I had turned it around. I had an MPSA18 in the parts pin and now there is lots of compression. With Comp knob all the way up hit a chord hard the volume drops. Overall seems to be working well.

Thanks for the help!

[midwayfair]

Happy to help. Enjoy!

[jbr]

Happy to help. Enjoy!

Hi Jon, I've got a V2.1 PCB from 1779 effects and built the Bearhug according to the given specs but I'm having some distortion issues i hope maybe you or someone else could help me with...

When i strum hard, i get a "splat" sort of distortion. Not a pleasing soft distortion. I'm using humbuckers, but i don't believe they aren't particularly high output. The distortion does reduce when i turn the volume on my guitar down. With a 2n5457, the distortion is nearly constant, completely unusable. I put a J201 in and it is significantly better, but still gets distorted on hard strums. It gets worse the higher the compression is turned up.

If i pull Q3 (J201), i get just less than unity volume and the distortion nearly entirely goes away. Only the hardest strum still causes distortion. If i remove Q2 (MPSA18) as well, there is no longer any distortion. I've swapped the MPSA18 for a 2n5089 and I get the same distortion. Below are my voltages:

BS170
D 5.2
G 2.46
S 2.99


MPSA18
E 18.4 - 364.5mv
B 0.9
C 7.36

J201 (390ohm D-S Resistance at idle, 15-20k on hard strum)
D 0
S 0
G 0

with 2n5457 (309ohm D-S at idle, 15-25 mega ohms on hard strum??)
D 0
S 0
G 0

Does anything look wrong here? Any idea why a 2n5457 would be distorted most of the time, but the J201 would be better, but still distorting?

Thanks so much.

[midwayfair]

When i strum hard, i get a "splat" sort of distortion. Not a pleasing soft distortion. I'm using humbuckers, but i don't believe they aren't particularly high output. The distortion does reduce when i turn the volume on my guitar down. With a 2n5457, the distortion is nearly constant, completely unusable. I put a J201 in and it is significantly better, but still gets distorted on hard strums. It gets worse the higher the compression is turned up.

If i pull Q3 (J201), i get just less than unity volume and the distortion nearly entirely goes away. Only the hardest strum still causes distortion. If i remove Q2 (MPSA18) as well, there is no longer any distortion. I've swapped the MPSA18 for a 2n5089 and I get the same distortion.

The J201 has a higher idle resistance (you can measure them). It's about 1K, which means that the gain of Q1 in that situation is only 2.7x max (with your ratio being accordingly much lower).

There are a LOT of posts throughout the thread about distortion problems with humbuckers. There really aren't any particularly great solutions to the problem as designed, but I did have some success in cutting some bass at the input.

BUT it's kind of interesting that pulling Q2 removes the distortion -- once you've pulled Q3, the sidechain no longer affects the gain of Q1. It would also be extraordinary if you were able to clip Q1 when it's at unity gain, since that would require a signal from your guitar that's 9V, which is gigantic for pickups by themselves.

This leads me to believe that maybe Q2 is acting like a diode and clipping the signal, and the problem only really manifests with louder pickups. Try this: Lift one leg of C5, and put a 33k resistor between the lifted leg and the now-empty pad on the PCB. Put Q2 and Q3 back in.

I'll try it myself too when I get a chance.

[jbr]

The J201 has a higher idle resistance (you can measure them). It's about 1K, which means that the gain of Q1 in that situation is only 2.7x max (with your ratio being accordingly much lower).

There are a LOT of posts throughout the thread about distortion problems with humbuckers. There really aren't any particularly great solutions to the problem as designed, but I did have some success in cutting some bass at the input.

BUT it's kind of interesting that pulling Q2 removes the distortion -- once you've pulled Q3, the sidechain no longer affects the gain of Q1. It would also be extraordinary if you were able to clip Q1 when it's at unity gain, since that would require a signal from your guitar that's 9V, which is gigantic for pickups by themselves.

This leads me to believe that maybe Q2 is acting like a diode and clipping the signal, and the problem only really manifests with louder pickups. Try this: Lift one leg of C5, and put a 33k resistor between the lifted leg and the now-empty pad on the PCB. Put Q2 and Q3 back in.

I'll try it myself too when I get a chance.

Thanks for the quick response.

I haven't had a chance to try your suggestion with C5 yet, but I did try placing an EQ in front of the bearhug and rolling off the bass after you said you had some success with cutting bass. Unfortunately it still seems to give the splat distortion on hard strums or picks regardless of the bass.

I'll try the resistor with C5 soon.

[midwayfair]

I forgot that the input impedance of Q2 will drop as the comp pot is turned up. I tried a 33K and it doesn't seem to hurt the sidechain. Can't comment much on whether it improves the distortion, though, since I don't seem to have a guitar that noticeably distorts it. Even my Sheraton is pretty clean sounding in the room (though I can hear some distortion on a recording when using that guitar).

[solderfumes]

Hi Jon, could I trouble you for a link to the schematic you're referring to in your most recent posts?  I have the one in the 1776 Effects build document, and based on the part numbers being mentioned I'm not sure it's the same one.  I too am having some problems with distortion that go away when I turn down the guitar a little bit.