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

[MARK BURNESS <markwjburness@xxxxxxxxxxxxxx>]

Hi Joe,

I'm sure that you will eventually find somone to do the work, but I fear that 
you will have to settle for a hobbyist. The reason being that guys who are 
building 5F1 already have the chassis, transformers, boards.....etc. It's easier 
to build from the ground up than re-hash your amp's design & layout. A generic 
"5F1" board will not sit in your amp an work right, it needs a custom layout.

The "best stuff" is a relative term, for anyone to replace the parts in your amp 
for the most desirable parts would mean completely dispensing with your amp.

However, I don't mean for this to sound completely negative, my point is that 
you need to just have reasonable expectations. Many of the components in your 
amp are perfectly adequate (you say the amp sounds OK, I assume that there is no 
objectional hum?).

I would also query the validity of rewiring the circuit as a 5F1, with no tone 
control (unless you have played the 2 side by side & prefer the 5F1, which has a 
tube rectifier - 600  doesn't). What you essentially have is a BF champ with 
fixed tone controls that you cannot adjust. The BF/SF champ is a pretty cool amp 
for harp, the fixed values in your amp can be tweaked for a more harp friendly 
response (reset for a little less treble, tune mids to taste, bump up the 
bass)...it might just take a bit of sucking & seeing. You might also consider 
experimenting with removal of the 2nd stage cathode bypass cap, rewiring the NFB 
as per a tweed (it's a very high NFB ratio on the BF/Champion 600). I'd look to 
reduce voltage on the 12AX7 a little, maybe down to 150-175v-ish either 
with/without a 2.2K cathode resistor at V1 pin 3.

If you don't find a harp specific tech to do the work, take these suggestions to 
a good amp tech, they are not rocket science. Or if you have a friend who is 
competant with working on tube amps (technically & safety-wise) you are welcome 
to e-mail me directly for guidance via e-mail.

Regards, Mark.




________________________________
From: joe hagins <joe_hagins@xxxxxxxxx>
To: Harp L <harp-l@xxxxxxxxxx>
Sent: Wednesday, 27 October, 2010 4:15:58
Subject: [Harp-L] Who to mod my Champ 600

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