Changing phase and powering 2 effects in one stompbox

[MrFrog]

Hi all,

I'm back with another question, well, two related questions.

I have recently built a bearhug compressor following these instructions:
https://tagboardeffects.blogspot.co.nz/2013/01/bearhug-fet-compressor.html

The compressor itself works fine but it appears to change the phase of the signal. My signal chain has a splitter and I recombine the two signals in my amp. When I turn the compressor on it all gets very quiet. If I turn down either input to the amp the volume comes back.

From what I have read the LPB1 reverses phase. I was thinking about using the layout here:
https://tagboardeffects.blogspot.co.nz/2013/01/electro-harmonix-lpb1-with-trimmer.html

By setting it to unity gain and putting in the same box as the bearhug (linking up beahug output to LPB input) I hope it will put the signal back to the original phase.

My two questions are:
1. The LPB1 is apparently not transaprent. Is there is simple (and small!) transparent phase change layout I can build instead?
2.  To have the LPB1 come on at the same time as the compressor do I just need to wire the LPB 9v and ground in parralell with the bearhug or is it more complex that that?

Thanks in advance!

[GibsonGM]

One opamp stage set up inverting would invert your signal for you, and should remain pretty clean provided you are not cranking the signal too much prior to its input.    You could place it before the compressor, invert, and then raise the signal level within the compressor if you like so as to avoid this...the way to "figure it out" is to try something like that before, and after, your compressor to see which sounds best.  It should be pretty clear if it clips!   

If you added a stage like that (or the LPB-1, but you are right, it's not clean), you'd just wire it in, yes, and it would always be "on".   Same power supply as the compressor and ground.   You'd only need one cap between the gain stage and the comp., so one of them would be omitted. 

[antonis]

1. Any inverting op-amp buffer will do the job - just search for something like: "inverting buffer layout".. or similar
(alternatively, a FET amp with unity gain should also work fine..)

2. It depends on the way you'll wire their individual IN jacks - if both have IN stereo jack with ring as GND switch it doesn't mater if they have separete power supplies or a common one..
If you'll use mono IN jack for the inverter you'll have to get its ground from compressor's PCB (or compressor's IN jack ring..) with common +9V..

edit: I give up, Sir - can't compete against your speed..

[MrFrog]

Thanks for the advice!

I tried google for various combinations of inverted, phase, stompbox, layout and buffer but could not find a vero/stripboard layout. I'm not confident enough to try designing my own layout from a schematic yet. Thats ok though, I'll give the LPB1 a try anyway and see how it sounds.

Funnily enough when thinking about this I was always putting the LPB1 after the compressor but putting it before might work alot better as it is a 'one knob' compressor and I might be able to make it kick in earlier if I boot the signal before it gets to the compressor part. The Bearhug has a volume control so I can always reduce the final output using that.

You'd only need one cap between the gain stage and the comp., so one of them would be omitted.

As I have already built the Bearhug would this mean removing the 100nF capacitor furthest to the right on the LPB1? If I leave it on would that cause any problems?

[GibsonGM]

But Antonis - speed cannot compete with wisdom 

LPB-1 is not clean, Frog...it may not 'wildly distort' your sound, but it WILL add a little bit of distortion.  That may be ok for your needs, but is not ideal.   Booting the compressor might overdrive it....

Caps in series follow the rule of "C1xC2 / C1 + C2" (product over sum)...so the output cap from LPB could limit the input bandwidth to the comp, as total C there would be less than .1u.   So yes, keep the larger cap (bearhug).   In layman's terms, "it will let more low end thru".

Have you tried building on perf board yet?  Then you can build anything you want!  You have to start somewhere, and a 1 opamp buffer is a nice place to begin...

A neat way to do this might be to install an inverter in the location where you blend, and place it on a switch.  Then it's there if you need it, no big deal.  Some splitter/blend circuits have this included. 

[MrFrog]

Hi GibsonGM,

I have a spare 1590A box so I figure if the LPB1 does not work out as my "inverter" I'll just add the knob, box it up and use it as a seperate stompbox :-)

I have not tried to build on a perf board yet, I do have one but at the moment I am happy getting used to soldering and making something 'cool' but little by little I am learning more about how some parts of the effects work and how to troubleshoot when things don't seem to be working.

My next planned project is to build a "Prince of Tone" but experiment with different diodes for the overdrive options.

If my LPB1 does not work out it might be enough to make me take the leap from stripboard layouts to working up from a perfboard. Especially as you are right that it would be a nice simple starter project for this.