[Harp-L] Re: Who to mod my Champ 600

[Joe <abcdeasy@xxxxxxxxx>]

I just got done modding my Champ 600.  I gotta say these are very nice
sounding amps when tweaked.  I did all the work myself since I'm a
techie. The amp is practically hum and noise free now.  The amp is
much louder.  Tone is very smooth and crunchy.  Nice breakup at lower
volumes.  Much better low end. Some of the mods are from
Alnicomagnet's mods.  He sells mod kits on ebay.  See this for an idea
of what it can sound like. http://www.youtube.com/watch?v=M9tgW5IdHek

1. Added larger filter caps in power supply to reduce hum.
2. Moved output transformer away from power transformer to further
reduce hum and noise.
3. Used shielded cable between input jacks and first preamp stage.
Aided in noise reduction.
4. Removed fixed tone stack.  Greatly effects tone in a good way. This
increases gain.  Steps must be taken to counter this change.
5. Added large value (.2mfd) coupling caps for increased low frequency
response.
6. Removed bypass caps in preamp.  Reduce gain/feedback control.
7. Reduced plate voltage to preamp stage.  Now at 140VDC. Reduce
feedback/effects tone and breakup.
8. Remove negative feedback loop. I really don't hear much difference?
9. Change bias on preamp sections with 2.2K cathode resistors. Reduce
gain/feedback control.
9. Installed Weber Sig8s alnico speaker. Requires new baffle board and
moving speaker to the right to avoid power tube.
10. Change grill cloth to something more acoustically transparent.
11. Add high cut switch.  Gives a little tone control.  Helps reduce
feedback. Used .047mfd cap.
12. Use 12AY7 preamp tube.  Reduce gain. Feedback reduction.




On Oct 27, 2:16 pm, Rick Davis <bluesharpa...@xxxxxxxxx> wrote:
> Last Sunday at the blues jam we host at Ziggies in Denver, AC Blue brought
> in a Champion 600 amp that Bruce Collins had modified for harp a few days
> ago.  It was not a 5F1 retro-fit;  he simply replaced some components to
> voice the amp better for harp and added a line out jack.
>
> AC lined the little amp out to his big keyboard amp (AC is a killer keys
> player, too) and played harp using his EV RE-10 mic.  I gotta tell ya....
> the tone was impressive.  This was late in the jam and it was quite loud (as
> it often is when guitar players and drummers get drunk.)  AC's harp cut
> through like a hacksaw.  Nice rip and grunt in the tone.
>
> I kick myself for not getting video of it.  I think you'd be impressed.  The
> Champion 600 amp was used pretty much as a pedal; no way you could hear it.
> Pretty cool.
> --
> -Rick Davis
> The Blues Harp Amps Bloghttp://www.bluesharpamps.blogspot.com/
>
> On Tue, Oct 26, 2010 at 9:15 PM, joe hagins <joe_hag...@xxxxxxxxx> wrote:
> > Hi guys,
> >       Well I have a stock Champ 600 that I have been using is it sounds ok,
> > and I know these are cheap amps. I love the compact size, but would like
> > tohave all the guts ripped out and have a Harp amp builder rebuild this to a
> > 5F1 spec using all of the best stuff for us harp players, and shoe horn my
> > Weber Vintage Series 8A125 8" speaker. I emailed Mission amps a while ago
> > and they never got back to me.. does any of yous know who else might be
> > interested in doing this for me?
>
> > ~Joseph