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From: Mark Beckles Willson
Date: Tue, 13 Apr 1999 21:22:41 +0100
Subject: Re: Bassman modifications, yet again

Bill

I have answered some of your points below but I think that maybe you
should try a different approach. You could spend a fortune having your
amp tweaked and still end up dissatisfied. I have tried most of the
things which you mention and more but in the end came to the conclusion
that it is more sensible to buy a smaller amp. There are loads of small
and medium sized amps which would suit you and would give you a great
sound at a reasonable volume.



At 18:46 12/04/99 -0400, you wrote:

>>>>

Hi gang,



A while ago, someone wrote:



>I modified my Bassman RI and my Bassman blackface to run in class A.

>That cuts the output power by about a half.




I dunno who wrote it, but it got me curious.

<<<<<<<<


Steven Rousseau I suspect.


>>>>





How is this done? It sounds like something altogether different from
changing out 12AX7's to lower value tubes. But, I have no clue what
"Class A" means, so someone please clue me in?



<<<<<<<<


I don't know exactly what SR has done but I have modified amps to cathode
bias, to sort of fake class A by adding cathode resistance and to run in
various sorts of almost triode mode. The second two of these tend to
reduce power - I don't like cathode bias for high powered amps.


>>>>



My Bassman RI is simply too loud. It really sounds nice when jacked up
loud, but I play mostly in small clubs, and I'm whomping the hell out of
the rest of the band when we play hard. I need to get that tone at lower
volumes.



I'm considering the following mods/additions to my rig:



- -- making the amp's input jack 5meg, like my mic's volume pot.

I dunno how it works, but someone mentioned it a while back.



<<<<<<<<


Changing the input impedence will match the amp's input better to a high
impedence mic and should give you more control with the volume pot.


>>>>



- -- trying a power brake (like the THD hotplate).

<<<<<<<<


This will allow you to run the amp flat out at lower volume but don't
forget that tubes will were out quicker when used like this. I have
heard mixed reports of the reliability of amps running into power
attenuators but have no personal experience.


>>>>





- -- trying those Black Jack tube converters

<<<<<<<<


Again, I have never tried these.


>>>>





- -- having the Hoffman board kit put in with the "gain channel" mod.

<<<<<<<<


In my experience, high gain channels and mods are bad news for harp
players.....


>>>>





- -- having the Kinder "Rod Mod" done.

<<<<<<<<


I have read good reports but can only guess at what KInder actually does.
One day I shall find a modified amp and pull it apart to confirm (or
otherwise) my guesses.


>>>>



- -- slaving the amp with a Fender champ (still gotta build the slave box,
though)

<<<<<<<<


I have done this, or something similar, and had unsatisfactory
experiences with feedback. Basically there were just too many controls
to tweak with the two amps running together for a simple guy like me!


>>>>





- -- changing the power tubes (is this possible or advisable?)

<<<<<<<<


Yes, you can put high quality 6V6 tubes in a tweed Bassman but I should
advise dropping the B+ voltage (a tube rectifier will help in a reissue)
and you must rebias. I should also suggest increasing the value of the
screen grid resistor to 1Kohm. I used think that this sounded fantastic
but good 6V6s are becoming scarce and I am now much more purist about old
amps and prefer to leave them stock.


>>>>





- -- what is "sag"???

<<<<<<<<


Sag usually means the power supply voltage dropping when the amp draws a
lot of current. This happens in all amps to a greater or lesser extent,
depending on the impedence of the power supply and the extent of filter
capicitance. This is generally considered desirably up to a point in
guitar amps where it contributes to compression etc at high volume. It's
bad news in hi-fi amps on the other hand.


>>>>





- --Is there a way to install a master volume and is it a decent idea or
pure folly?

<<<<<<<<


Yes, you can put all sorts of master volume controls in a Bassman but I
think that they are inventions of the devil and wouldn't put one in any
of my amps!


>>>>



I guess the tone I'm looking for could best be described as a combination
of Kim Wilson's "Tiger Man" tone with Magic Dick's "Full Court Press"
tone.




Back in August 96 Tom Ellis reported the following about Kim Wilson's
Tigerman amps:-


>On Tigerman Kim Wilson used a compliment of Gibsons--4X8, 6X8, 8X10,
etc. with

>Crystal and Ceramic mics; many of these amps were very rare and owned
by a

>collector in Wisconsin.


I can get very close to the sound with an old Silvertone with one 8"
speaker........



Mark