mkistler

Hi guys,

I recently purchased a used jvm410c over ebay and I am having issues with sound quality. The clean channels are great, but the crunch, OD1 and OD2 channels all sound muddy and dull. I tried this amp out in the store and got awesome metal tones, plus I listened to a ton of youtube videos of the various settings and they all sound great. So what am I doing wrong?

I am suspecting the tubes are going bad, but I am not sure how to test that. When the amp was shipped the tubes were pulled out and I had to plug them back in. Could that have changed the bias?

Also, I am running a bit of a low-fi guitar, but the tones are way to muddy. The guitar sounds great in other amps and gets great alt-rock or modern metal tones.

Any advice on things to check or what might be wrong?

Thanks!

Procter2812

yeah.. id check the bias... may be a bit low.

also how old is the amp/ tubes?

also try changing around the pre-amp tubes. I have a friend who plays metal and went through one of those chinese pre-amp tubes within 3 months! it wasnt broken.. just sounded muddy and flat.

SGed

Check tubes first. Then ask the original owner if the amp was modified. From your description, it almost sounds like the "C83" mod was done.

mkistler

What is the C83 mod?

With the tubes, how do I go about testing them? Is there a method for this?

Thanks for the input so far.

SGed

The easiest way would be to replace them. If it's not the tubes, having an extra set is always a good thing. The C83 mod is simply the removal of capacitor C83 from the circuit board. It reduces a lot of the high end of the amp. Some people like it. Others think it kills too much.

axeslinger

Were you playing through a tubescreamer/overdrive pedal into the amp at the store?
The lead channels can naturally sound muddy(ish) without an overdrive to tighten them up.
This isn't meant to be condescending or anything...just a bit of good ol outside the box thinking cause sometimes it's the littlest of things that cause the biggest issues!