Orange Squeezer help plz???

[bortlett]

I just built an orange squeezer compressor, and I'm having some trouble with it. Here's the schematic that I used to lay the circuit out on strip board: http://www.geofex.com/FX_images/orgsqz.gif. I'm using a JRC4558 and swapped the N100 with a 1N34A.

There is a bunch more distortion than expected. My understanding is that this pedal does provide a boost if you want it, but it can be somewhat clean. I can get the distortion to roll off by dropping my guitar volume down to about 3/4, but at full guitar volume, it is present even when the pedal volume is down close to 0. I tried it with really hot pickups and some more mellow ones... same result. I read somewhere that grounding the unused half of the opamp should help. My circuit has pins 5, 6, and 7 going nowhere. Any chance that this could be part of my problem? This is my second build, so maybe I'm just reading the schematic wrong? I assumed that if pins 5-7 aren't mentioned in the schematic, they aren't supposed to go anywhere.

I swapped ICs just to see if there was a difference. I tried a couple other 4558s and a TL074 with the same result.

Pics would help, I know. I'll try to get some up tonight.

A second issue is that the bias trim doesn't seem to do anything. Maybe this is related, but I'm trying to troubleshoot the distortion first.

[selfdestroyer]

are you building it from this vero? http://tagboardeffects.blogspot.com/2012/02/orange-squeezer.html

I noticed that a person was getting distortion also in the comments. One person said they subbed a 1n914 for the 1n34a. Does your build have an internal trimmer?

Hope this helps some.

[bortlett]

I laid it out myself based on the schematic. I know that's like reinventing the wheel since there are plenty of layouts out there, but I wanted to lay it out myself as part of the learning process. I compared mine to verified layouts, but I obviously could have made mistakes as I was moving things around to save space.

I'll try to get an image together of how I did everything. I have a rough sketch of the layout in excel here at work, but I found some errors and made a couple of changes to tighten things up as I was actually putting the board together. The 'final' version is at home, so I can post it later for lolz.

Thanks for the link and the tip on the diode sub.

Edit: Trimmer... I have a b10k pot to adjust the bias. It's not internal, because I didn't have one handy. Adjusting it appears to do nothing or or VERY little at this point. That's next on my trouble-shoot list.

[Mike]

The 220k (feedback loop) / 10k (to ground) fix the OS gain at 23x. (220k+10k)/10k.

Double-check the values of these two resistors.

If, for example, you did 220k and 1k, you would have (220k+1k)/1k = 222x

I bet that would distort.

Mike

[bortlett]

Ok I think I missed something in the schematic. Looking again, I never noticed the jump that allows the signal to skip the 2nd transistor in the chain and the 2.4k resistor. That seems like it would explain the bias pot not working correctly. Hopefully that solves the distortion issue too.

[bortlett]

So that didn't fix it either, but I eventually figured out what was wrong. Just for the benefit of anyone who ever happens to run into the same problem, Here's what I checked/fixed and the results:

First I terminated the connections on the unused half of the op amp: jump pins 6 & 7 and send 5 to ground. That didn't fix my problem, but from what I read on teh tronz it is better than leaving it all open ended.

Second, I closed added the jump that I missed in my post above. That didn't really help my problem either, but it was definitely a mistake in the first place.

Third, I checked the pins on my 2N5457s. I should have looked here earlier. The ground and source were reversed on the second one. Fixing that cleared everything up and got the trim working correctly. Fuckyeah! Sounds sweet now.