James, Tony, Dave and Patrick,

Many thanks for all of the input.

I'll keep you posted; it'll likely be a bit slow moving project because 
of other commitments.

Now does anyone know of any good references on tube guitar amps and 
audio circuitry?

Remarkably, this is one area where tubes do actually seem to produce 
superior sound.

I've been doing some research on the internet. I found out that in 
addition to their characteristic distortion, which many guitarists 
prize, it turns out that their response to transient input is can 
actually sound cleaner and brighter than transistors. They have a softer 
response to the transient and that tends to smooth out the response and 
avoids the introduction of clinky sounding even harmonics, or so I read. 
I would post the link for this, but I lost track of it. It had to do 
with an audio engineering firm tasked to improve the lousy sound of a 
large mixing board in a recording studio. Frustrated that nothing was 
working, they tried a tube preamp and incredibly the harsh sound of the 
board went away. After a bit of analysis they found it had to do with 
this initial transient response of the SS preamp in the board vs. the 
tube preamp.

I have verified this by placing a Fender HotRod Deluxe tube amp side by 
side with an older Fender Princeton Chorus and noted not only the 
greater richness of the sound but the sparkly quality in the tube amp. 
Compared side by side, the solid state amp really does sound harsh and 
grating on the attack.

Visiting some local music stores this last couple of weeks I have 
learned that not all tube amps are this good. For instance, I played 
some Epiphones that sound really muddy and "blatty." The Vox AC30 (class 
A) sounded particularly good to me.

There are push pull, class a, and class a/b models. all have their 
unique character. It will take some time to really figure out what I 
like out of what's available.

All of this has led me to become interested in tube guitar amps and to 
consider experimenting with some of my own designs. The first step will 
be to learn some more about tubes. It was a subject not broached in my 
classes at school.

I may start here; an open source tube amp design:

http://www.torresengineering.com/freplantomak.html

This seems to be the premier resource on tube guitar amps:

http://www.torresengineering.com/inbydantor.html

Mark

Dave King wrote:
> Mark
>
> Look around some of the online Amp shops. They will sell you a new old stock
> or reproduction plate for far less than you can do a one off.
>
> Dave
>
> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu]On Behalf
> Of Mark E. Skeels
> Sent: December 18, 2006 7:14 AM
> To: Microcontroller discussion list - Public.
> Subject: Re: [OT] Restoring vintage Gibson GA-9 guitar amp
>
>
> Actually, I took a little closer look and graphics on the chassis is
> just a silk screen. It's not stamped. So I guess unless I can find a new
> silk screen, I'm out of luck.......
>
> Mark
>
> Mark E. Skeels wrote:
>   
>> This old amp has a chrome plated steel control panel that is stamped and
>>
>> then some kind of ink is put into the depressions for letters, graphics
>> patterns, etc in the depressions.
>>
>> Most of the ink is worn away.
>>
>> Does anyone here know how that is done and what kind of ink to use to
>> restore the graphics to the front panel?
>>
>> Thanks,
>> Mark
>>
>>
>>
>>     
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