Extremely wierd DC-10 problem!

[Monsta-Tone]

I haven't really played my DC-10 in the last few months, since I put the SLO mod in my Heartbreaker.

I fired it up today because I just found a drummer and plan on using the amp at least once a week for practice.
I put a set of JJ High Gains in it from Eurotubes just before I stopped playing it. They sounded great!
It also had an older set of Winged 'C' 6L6's in it that were about a year old.


When I fired it up today, I noticed that the lead channel made a horrible feedback sound if the gain was over 7.
It's never done this before, so I automatically assume (yeah, I know what they say) it's a tube issue.
I swap out each preamp tube 1 at a time and the sound is still there.

It only happens when the guitar's volume is up all the way.

I'm scratching my head like you wouldn't believe.....

I took the opportunity to change out the power tubes and re-bias it right in the middle.
:mrgreen: Now it has a quad of KT-66's in it, which sound freakishly phenomenal! :mrgreen:


Still has the sound.

I start removing preamp tubes to see where the feedback is coming from. Traced it all the way back to before V1!
So, I open it up. Nothing out of the ordinary.

I decide to change the wires from the input jack to a shielded cable and the noise magically disappears.
I've been messing with it for over an hour and still no noise???????


What the hell? I've never seen this before. I can understand that the wires should be shielded, but why, after 15 years of use has this occured????


Everyday is a new mystery! :lol:

 

[edward]

Interesting. Anything new in the house/studio? Lights, dimmers, high-draw appliances? New neighbors enriching uranium??

Edward

 

[Monsta-Tone]

:lol: :lol: :lol: You would think I would have noticed my new neighbors making bombs! :lol: :lol: :lol:


Nothing new. I'm an electrical contractor, so everything in the house has been done by me. Had the same appliances for years.

It's not really a hum like you would get with fluorescent lights, and all the lights that are fluorescent are electronic ballast, so they don't have transformers in them.


It's feedback like a microphonic preamp tube. I got rid of most of it with the shielded wiring. Might have to re-visit it a little more since it hasn't completely gone away!

Kind of strange that a high gain amp doesn't have a shielded wire for the input jack. I looked through all of my old pictures and didn't find any Mesa amps that do. Says a lot for proper wire placement!

 

[Monsta-Tone]

I called Mesa today about it. They walked me through the usual, tubes, LDR's, all the stuff I already tried.

Might be a filter cap, since I haven't changed those yet. I'm out though, so I won't know until they arrive.

They couldn't believe that I run the gain at 10 as a standard distortion level and I've never had any problems.
I don't always run it there, but maybe 30% of the time. :mrgreen:

Time for the More Gain mod I guess!

 

[injected]

hm, anything over 6 i find muddy on my dc-5. But yes, I have this same problem. If i run the gain past 6-7, (on LOUD volumes only,) i get terrible screeching noise.


But i normally use my gain on 3-4 and let me playing talk the heavy

 

[Monsta-Tone]

I've always run the gain really high at lower volumes and back it off to 7 or so at higher volumes with no problems at all.

The new caps should show up tomorrow. Guess it's a good thing if I'm out of them, means I've been busy!

 

[MJ Slaughter]

I never experienced that with mine. Usually I run the gain around 6-7 but have pegged it out of curiosity but never any problems with bad feedback if all the tubes are in good working order. Hope the new caps take care of it for you.

 

[Monsta-Tone]

I repeatedly peg it just for pegging sake! Unfortunately, I have the same curiousity streak that my 5 year old son has.
:lol: Father and son mad scientists! :lol: Drives the wife crazy!

The caps didn't show up yesterday, so I'm hoping today. I have a pile of other stuff to get to as soon as I get this off the bench!

 

[scottcrud]

With the SLO mod does the Heartbreaker have anywhere near the gain of the DC10's lead channel?

 

[Monsta-Tone]

It definitely does! It's mids are voiced lower though, so it sounds extremely beefy.

I can play them side by side for you if you like.

 

[scottcrud]

Yea, do it, would it do the high gain tones my band does? Guitars are all MKIII's and .50Cal+...Always been intrigued by the Heartbreaker but was always told there was only MKI type gain, and I hate using a $40 od pedal on a $700-up amp.

 

[Monsta-Tone]

Oh hell yeah. I PM'd you with my phone #. I don't have any way to post things on the web just yet.