Ego driver trouble, clipping section doesn't seem to be clipping

[Guitarmatt]

I just soldered up an ego driver board and attempted to rock it before I box it, and got an odd result. The circuit works and all three knobs plus the hp/lp switch do what they're expected to do. But then I noticed that the clip mod switch made absolutely no difference in the sound. Plus the LEDs didn't light at all with the switch in that position. Using my audio probe I can hear that sound is getting to the clipping section just fine, and the switch is working correctly, routing the signal to only one clipping section at a time. 

I saw a similar thread on the forum where the problem was that the particular leds used for clipping sounded too much like the mosfet clipping.  That builder fixed their problem by switching out 5mm red diffused (same as i am using) for 3mm.  To see if this was my problem, I disconnected the wire leading to the led section, so my switch would switch between MOSFET clipping and no clipping. I figured I should really be able to tell a difference between those 2, but once again I could hear no difference. Now I'm at a loss for what to do.

Here are my measured voltageswith the circuit idling and input and output disconnected:
Opamp
Pin 1 and 2: 4.5v
Pin3: 4.25v
Pin 4: 0v
Pin 5: 4.4v
Pin 6: 4.5v
Pin 7: 4.6v
Pin 8: 8.94v

Center pad of clip switch (set to MOSFET): 4.44v
Vb measured off r3 pad towards middle of board:4.44v


Now I don't know a whole lot here, but shouldn't the measurement at the input of the clipping section be higher than vb if it's supposed to clip to vb? Do I actually have everything right and the effect of the clipping section in this pedal is just not very noticeable? I doubt that, since the ocd's clipping to vb instead of ground is one of its most touted features...of course, like I said, I don't know much, so someone please enlighten me!

Btw, I didn't include a pic of the solder side of my board since it's obscured by the pcb mounted pots. I'll of course take those off and resolder them later of needed for a fix.

[oldhousescott]

Your voltages look correct. Pin 3 reads a little low because the meter loads the circuit at that point. The center pin of the clip switch should read Vb. It's the excursions of the signal around Vb (plus and minus) that cause the clipping.

You say the pots all work, are you getting any overdrive sound? More as you turn up the gain? Have you confirmed your clip switch does in fact short center to left, and center to right as it's switched? I would expect you to hear some difference (maybe not huge) between the MOSFETs and the LEDs. Make sure you don't have a solder bridge on your board at the clip switch between the MOSFET pad the center pad.

[GermanCdn]

Is this the latest version Ego board, or the previous version?  Reason I ask is if memory serves, there was an issue with the LED clipping for the old Ego boards, and a workaround had been posted in the old documents.

[Guitarmatt]

Your voltages look correct. Pin 3 reads a little low because the meter loads the circuit at that point. The center pin of the clip switch should read Vb. It's the excursions of the signal around Vb (plus and minus) that cause the clipping.

You say the pots all work, are you getting any overdrive sound? More as you turn up the gain? Have you confirmed your clip switch does in fact short center to left, and center to right as it's switched? I would expect you to hear some difference (maybe not huge) between the MOSFETs and the LEDs. Make sure you don't have a solder bridge on your board at the clip switch between the MOSFET pad the center pad.

Thanks for the confirmation on the voltages. I do get drive, it does increase with the gain knob, switch soldering is confirmed with both dmm continuity tester and signal probe. No solder bridges.

Is this the latest version Ego board, or the previous version?  Reason I ask is if memory serves, there was an issue with the LED clipping for the old Ego boards, and a workaround had been posted in the old documents.

It's the new one, picked it up a few days ago in the sale.

The circuit does work in that good sounds come out.  I guess I just expected the clipping section to make a bit more of a difference. Perhaps it'll show more through a better amp and guitar. I was testing with a cheapo old squier with lace sensors through an old Marshall dsl401 with vintage 30. My main rig is an ibanez js100 with JB/Jazz pups through a Bogner Alchemist. I'll bring my test rig to the studio and try it out there.

[Guitarmatt]

I'm calling this one solved, on account of there was never a problem to begin with. Listening closer it seems that the clipping section just takes a bit off the edge of the opamp distortion, as opposed to adding distortion in its own right.  I'm going to box this one w/o the clip mod switch as a standard OCD. Thanks to those who responded and helped me learn a bit more about this whole pedal building thing.

[oldhousescott]

If you remove the switch, you still have to jumper one of the sets of pads to engage one or the other clipping options, either middle and left, or middle and right. With the component side up, and the HP/LP switch at the top, the middle and right pads of the clipping switch will select the standard OCD clipping.