Re: [Harp-L] Re-tube Baseman 100 top

["Rick Davis" <bluesharpamps@xxxxxxxxx>]

Well, there are lots of options and I think you will get lots of good advice
on this.

To keep it simple and inexpensive I'd start by concentrating on the Phase
Inverter tube in socket V3, the input tube closest to the bigger power
tubes.  The amps comes with a 12AT7 tube in that socket, which is designed
to give miles of clean headroom, something we don't necessarily want in a
harp amp.

I have two suggestions:  Try any good 12AX7 or 5751 tube in the PI socket
and see how it sounds.  An alternative is to try a 12DW7, a peculiar tube
that drives your power tube pairs at unbalanced levels.  It gives a slightly
coarser tone.  I tried this in a silverface Twin and liked it for harp.  I
also use it in my project Fender Pro Junior harp amp.  JJ sells a 12DW7 tube
(ECC832) for only about 10 bucks, so it won't break the bank to try
it.  This should ease up on the Fender "Sparkly Clean" tone a bit.

The tweed Bassman amps came with a 12AY7 tube in V1, so you might try that
as well.  And lastly, disconnecting the Negative Feedback Circuit will give
a grittier tone.  The NFB is a wire that runs to the speaker tap from the
preamp section of the circuit board, not from the power transformer.  You
might need a tech to help you with this one.  Be careful whenever messing
around inside a tube amp.  ZAP!!!

These simple mods should make the amp sound a lot better for harp, without
breaking out the soldering iron and schematics.  If you try this, please let
me know how it works out.

-Rick Davis

On Thu, Dec 11, 2008 at 4:10 PM, <MundHarp@xxxxxxx> wrote:

>  Apologies!
> My mistake.
> the amplifier is a Fender Bassman *100* top...
> It is 100% tube.
> Mea Culpa!
> John Walden
> London
> England
>
>  In a message dated 11/12/2008 22:13:32 GMT Standard Time,
> bluesharpamps@xxxxxxxxx writes:
>
> Fender Bassman 120 head?  The tube Bassman heads that I'm familiar with are
> the 50, 70, 100, and 135.  The only Bassman 120 I know of is a solid state
> combo amp.  Is this an odd-duck tube amp?
>
> -Rick Davis
> The Blues Harp Amps Blog
> http://www.bluesharpamps.blogspot.com/
>
>
>
> On Thu, Dec 11, 2008 at 2:51 PM, <MundHarp@xxxxxxx> wrote:
>
> > HELP!
> > Anyone know what valves/tubes to fit to a Fender Bassman 120  silver
> face
> > to
> > make that piggy-back amp more harp friendly? It is simply too powerful!
> I
> > used it for about 5 years, and got reasonable harmonica sounds out of it.
> > However, it was simply like playing through the PA... No "built in" tube
> > distortion at all.
> > I just can't get enough volume to get a good distorted tone out of  it...
> > Of
> > course I can add a "pedal"... But that reduces the "tube appeal"
> harmonica
> > wise! It is a great "direct wired" amp... The later "circuit board"  amps
> > simply
> > are not as good. If no one knows directly, please point me to a good
> >  Fender
> > Amp Tec!
> > Best wishes...
> > John Walden
> > London
> > England
> > _______________________________________________
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> >
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>


-- 
-Rick Davis
The Blues Harp Amps Blog
http://www.bluesharpamps.blogspot.com/