Build Your Own Clone Message Board

Hi all

I have built the Crown Jewel, and I think it works as it is supposed to. However, I have one problem/question: Even if I do not engage any of the clipping circuits (both clipping switches in mid position), I still easily get a lot of distortion - probably from op-amp saturation. I do not have to hit the strings very hard for it to clip. It happens even if I turn the Drive and Presence controls all the way down - and turning them up will increase the (not very pleasing) distortion. Is this supposed to be so, or have I done something wrong? I would like to be able to use the nice EQ and the separate boost with very little distortion - maybe only the tiniest grit

My guitar does not have extremely hot pickups like active pickups or the like - it is an ordinary Les Paul Studio, so I don't think that it should saturate the Crown Jewel this easily.

Looking at the schematics, Q5, IC4a, IC5a and IC5b should be at unity gain when the tone controls are neutral, which leaves the clipping-circuit driving IC4b as the likely culprit, but with Drive and Presence down, it should only amplify by 2, which shouldn't cause it to distort. Am I reading the schematic wrong?

If the distortion is not the expected behaviour, what measurements would you suggest I did to locate the problem? Measure the signal level out of each of the op-amps?
If the distortion is to be expected, how should I mod the circuit to get the possibility of setting the gain low enough to have no distortion?

Regards,

Morten J

Oh and by the way: I have the blend board installed, and I just found an old post where it is explained that the distortion could be coming from the blend. I'll have a look at that.

I took a look at the dry blend board, the schematics and the crown jewel PCB. I guees i understand now

The dry bland board takes the dry signal just after the buffer transistor and the distorted signal just before the coupling capacitor between clipping and EQ. The cap is remove and the signal from the blaend is sent to EQ just after the removed cap - like this, right:



The dry blend will divide the dry and distorted signals with R1, R2 and VR1. With VR1 in middle position, dry is reduced to a half and the distorted to a third. The there is an inverting summing op-amp (IC1a) with a gain set by R3/R4 and R5. The gain is quite high - 15 times or 23.5 dB. So I guess the clipping is happening here or in the EQ opamps. Is there a reason that the gain should be so high in the blend board? Would replacing R5 with a 68k resistor create just about unity gain for the distorted signal when the blend pot is in the middle position? And would that solve my clipping issue?

Do you have it in 18v mode? Does it clip when you have the blend 100% dry?

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

Hi

Yes, I tried 18V mode, and it helped but did not solve the problem. I do not remember if there was any distortion when running 100% dry, but I'll check later. Yesterday i lowered the gain of the summing op-amp to 9dB and for me it made a nice difference - and made the level control much more useful. I have a boost installed in the Crown Jewel, so if I want more boost, I can get it there.

Regards

Morten Jøhnk