DC-10 volume drops with GEQ

Space_cowboy · Aug 24, 2009

I own a 2nd hand DC-10 that sounds great.
However, everytime i toggle in the Graphic EQ, my overall volume drops. A lot. I've tried setting all the sliders to max, it still drops.
Also, it seems as if sliding the knobs over the 0db mark, (boosting the signal at given frequencies), won't boost but filter the signal as if I was sliding the knobs under the 0db mark (cutting the signal)

Has anyone had a similar experience? I'm thinking maybe there's something wrong with the EQ driver tube or something in the preamp, or maybe there is something broken in the circuit. However, I don't want to pick my amp into small pieces if I don't have to...

Any help is gladly appreciated!

Monsta-Tone · Aug 25, 2009

The driver circuit for the EQ is not tube. Your amp may need a checkup. It sounds like the LDR that switches it in and out is not opening up enough and choking the signal.

Or, it could be a bad solder connection or resistor.

Space_cowboy · Aug 26, 2009

Thanks for the reply. I have no idea what a LDR is, but I will do the serial fx loop mod soon so I'll have a chance to check the soldering

If the LDR is choking (whatever that means!), how do I fix that problem?

Cheers

Monsta-Tone · Aug 26, 2009

Light Dependant Resistor. It's a switching mechanism in your amp.

Basically, when the EQ is sellected, the LDR has current flowing through it, which lowers it's resistance and lets signal flow through it. If there is not enough voltage or if the LDR is damaged, it will not let enough signal pass through it.

Space_cowboy · Aug 27, 2009

Nothing I can fix myself in other words. I have no experience in draining the amps caps so I'll have to take it to a tech?

Thanks

Space_cowboy · Nov 30, 2010

Sorry to bring back this old topic, but I just fixed the problem with the broken GEQ. So I thought I'd share some information in case anyone should experience the same problems.

After studying the DC-10 schematic, I figured that probably one of the transistors in the EQ circuit was broken. To make a long story short, Q4, an MPSA20 transistor had blown. I couldn't find any MPSA20s where I live, but I replaced the old transistor with an NTE123AP, which has similar specs. My GEQ now works perfectly again