Bearhug Version question- attn Jon Patton

[Eddododo]

Hey there all,
I have been playing around with the bearhug, and there are so many versions all over the place, referencing parts no.s from incorrect schematics, layouts of older versions edited only with footnotes, etc.

Jon has been great about keeping the discussions up to date, but it certainly takes some digging, several firefox tabs, and a clear head;
This project deserves a 1-step project noob-friendly stripboard layout. I'd be happy to do one, my only question: 'IS the schematic https://dl.dropboxusercontent.com/u/9878279/Jon%20Patton%27s%20layouts/Bearhug%20compressor%20schematic.pdf correct with all revisions (excepting things like tone controls or the 3-way release option etc]

This appears to be the case, and this version behaves optimally, to me. just want to make sure that i didnt miss anything big

[bluebunny]

Not sure if you're volunteering to do a stripboard layout, or you just want to use one.  If the latter, then I did one here.  Corresponds with the v1 schematic, btw.

[Eddododo]

thats what i meant, I want to, myself, MAKE a NEW one, corresponding to V.2

[midwayfair]

Sorry for the confusion. This forum doesn't allow post editing, and I overwrite old files when they are out of date.

The links on my page for the schematic and layout correspond to each other. My schematic doesn't really correspond to anything else at the moment, since it was a minor change but it can be built on the PCB as follows:

http://1776effects.com/wp-content/uploads/2014/02/Bear-Hug-Fab-Updated-2-15-14.pdf

Omit R13
Jumper C10
You can jumper or leave R11, it's just a limit on the comp control. (I actually forgot to leave this in on my layout and schematic, so I'll go ahead and put them in)

Follow the bill of materials otherwise.

If Josh does another run of boards, they will correspond to those changes.

I don't do vero, so you'll have to back track on the traces to find where the corresponding components are. The topology isn't different, it's just fewer parts and a couple different values.

[Eddododo]

Right on thanks jon

[heidensieck]

Hi,

I just finished my second bearhug, and love it overall. My builds do distort a little with hard strumming, though. Do the changes above (omitting R13 and jumpering C10) by any chance reduce the chance of distortion? Both my builds are on josh's PCB, one with a 47pF for C4 and and one with a 100pF. Exactly as BOM otherwise.

[heidensieck]

I'll try it anyway, since Jon recommends the mods.

[midwayfair]

Hi,

I just finished my second bearhug, and love it overall. My builds do distort a little with hard strumming, though. Do the changes above (omitting R13 and jumpering C10) by any chance reduce the chance of distortion? Both my builds are on josh's PCB, one with a 47pF for C4 and and one with a 100pF. Exactly as BOM otherwise.

No, those changes are only in the rectifier circuit. They are just to use fewer parts with the same functionality.

If you're getting distortion, first check that your voltages are correct (should be above 5V on the drain of Q1), then check that you're getting compression (should be audible when you turn the comp knob up).

Assuming everything's correct -- one suggestion I'd have is to measure the resistance from your JFET's source and drain. If it's less than 300Ohms, try a different FET. You don't really want anything higher than about 500Ohms, though, or there won't be as much compression. This really only affects the maximum gain when not compressing. If it's distorting even while compressing, this won't really do any good.

The gain is quite small when there's a lot of compression (as low as 2x), but if you have really hot pickups, playing a chord can put out a signal above a couple volts, which would distort it no matter what you do. So if everything's right and you're just using really hot pickups, you might need to go up to 18V (which might require rebiasing).

[heidensieck]

Hi Jon,
thank you so much for these tips! I measured the drain voltage of Q1, it's 5.5v. The 2N5457's source-drain resistance is 259 ohms, though. However, distortion does occur a bit with mild compression (not with heavier settings). I would've tried a different JFET, but I seem to only have ones that measure below 300 ohms.. Could I use a J201? Would the source-drain resistance need to be the same as for a 2N5457?

Thanks so much for the help !

best
Chris

[heidensieck]

So, in the meantime I've tinkered a bit. Socketed the transistor, and found a 2N5457 that measured 320 ohms. Still distortion on hard strums. Tried an mpf102, for fun. No distortion, alright sounding compression, but an unstable decay. Tried a J201, since I had it socketed, but no compression :-)

Silly ideas, probably, but I felt like tinkering a bit. Will probably need to try one really good 2N5457. Or it could still be something else.
I read somewhere that changing the diodes might make a difference. There are 1N914's in there. Is that worth a tinker ?

thanks!
good night,
Chris

[midwayfair]

So, in the meantime I've tinkered a bit. Socketed the transistor, and found a 2N5457 that measured 320 ohms. Still distortion on hard strums. Tried an mpf102, for fun. No distortion, alright sounding compression, but an unstable decay. Tried a J201, since I had it socketed, but no compression :-)

Silly ideas, probably, but I felt like tinkering a bit. Will probably need to try one really good 2N5457. Or it could still be something else.
I read somewhere that changing the diodes might make a difference. There are 1N914's in there. Is that worth a tinker ?

thanks!
good night,
Chris

It sounds like it's not distorting when it compresses. And your JFETs aren't out of line with what I'd expect. I wouldn't worry about them further. And yeah, J201s have quite a bit more resistance -- more like 1K! At idle they don't really offer that much gain or wiggle room when the source resistor is only 2.7K.

The only thing changing the diodes will do is change the compression level, so unless you want it to compress more, there's nothing to change there.

A useful way of thinking about this is that the JFET is the gain pot in Jack Orman's MOSFET booster, and it starts out around 75% of the way up and the compression turns the knob down as low as 0. So if your guitar would distort the booster at that level, it's going to distort the compressor until the compression is hard enough to turn down the knob far enough. Does that make sense? But the circuit should turn down the gain automatically after the first split second, so really it shouldn't matter too much how loud your pickups can get. A feedback circuit is self-correcting.

Also, the pedal as designed will have a certain amount of gain when not compressing. Honestly, there's only so much headroom you can squeeze out of 9V. You're stuck either lowering the gain (make it boost less) or lowering the input signal.

If you need to make it boost less, you could lower the drain resistance on Q1 (e.g. 3.3K or 3.6K, or way down to 2.7K) to lower the idle gain, but there won't be nearly as much output (which you might be okay with) and you'll also lose a bit of compression (which again you might be okay with). If you do the drain resistor change and you're not getting enough compression, the there are other places in the circuit to start looking before you should ever have to change the diodes.

To lower the size of of the input signal (so that the signal is smaller before it gets amplified, there really isn't a great way to do that without adding more circuitry or using your guitar's volume knob. The output level should be high enough to let you cut the input signal by about half and still get above unity volume. Although you could probably put a 500K or 250K pot on the input of the circuit before the input cap like a gain control in a lot of fuzzes, that would really lower your input impedance, and you'd probably lose a bunch of treble. Putting a buffer with a volume control after it in front of the Bearhug wouldn't be many components at all and would let you add the pre-gain control without the tone loss, but if you're trying to fit it in a 1590A, that could prove very challenging! Although you could take advantage of the addition of the buffer and make it buffered bypass. Worth a thought, at least.

Another way to lower the gain would be to add a small value potentiometer or trimpot -- like another 1KC pot -- and hook it up in series with the 47uF on the source of Q1. You'd remove the 47uF and use the  It'll sorta be a ratio control. Like this:

+pad of C7 on the PCB -> new potentiometer lug 2 ... New potentiometer lug 3 -> +side of C7 (which will be floating in space ... ) -> -side of C7 goes to the -pad of C7 on the PCB. If you use a trimpot, it could go on a little daughter

That is, you're making a new gain control that's EXACTLY the way the compression pot is shown for Q2 in the old schematic, before you removed R13 and replaced C10 and R11 with jumpers.

A lot of this changes the way the circuit works. Unfortunately, not every compressor works for every application or guitar, but the good news is that if you can build your own, you can find one that might fit what you need better if you can't get this one to clean up enough. And again, there's always the option of trying the circuit on 18V to see if it's really just a headroom issue.

[heidensieck]

Jon, thanks for this fantastic reply. Sorry for not replying earlier, the forum seemed to have some database error trouble. I will start with trying to lower the boost level in the circuit. I built a previous version with a tillman buffer with volume control in front of it, and lowering the signal going to the bearhug with that one seems to help. Strange thing is that my guitars are not all that high output. I also built the tillman into a telecaster, so I can use that with the volume turned down. Again, THANKS! I will experiment and report back.

Best
Chris

[Groovenut]

Necro hit here but it might be useful

I was having similar issues and came up with this fix

http://www.diystompboxes.com/smfforum/index.php?topic=113507.0