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Tube Replacement

2/1/1997 7:39 PM
Charlie Graves
Tube Replacement
My tube ignorance I'm sure will be obvious, but I have to ask anyway. I have a Carvin X100B 100W Tube head. It has some good tones, but it doesn'd sound like a Marshall. It has 12AX7 pre amp tubes (3) and EL34 Power Tubes. The distortion is a little nasal sounding for my tastes. Does anyone know of any tube changes or other modifications that I could make to closer approximate my desired tone ?  
Charlie Graves.  
2/1/1997 9:01 PM
I am not familiar with the Carvin schematic,  
and it doesnt sound like you want to go inside  
your amp and make drastic changes with a  
soldering iron. It's also not safe for you or  
your amp without some experience. There are no  
tubes I know of to change the tone that much.  
Without having to cut your loses and trade it  
in for little or nothing to buy a Marshall  
that won't do a good high high gain tone anyway,  
I have a goto for you. Call Torres Engineering  
in San Mateo (information 415 555 1212, don't  
know the number). He is the only guy I know  
that does Carvin mods. Tell him what you want,  
(to sound like a good high gain Marshall) and  
he can hook you up. He is really cool the first  
time you meet him but ends up a dickhead by the  
third or fourth time. He is very busy and has  
no tolerance for support talk. But he's the  
only guy I know that does Carvins, and he has  
some cool sounding stuff. Ask for Dan.  
Don't tell him about the dickhead part.  
2/2/1997 6:26 PM
Charlie Graves

Thanks a bunch for the Reply and the goto. I'll be sure to check it out. While I'm on the subject, can you recommend a good reference/tutorial on Tube amp circuitry ? I have a EE background and am comfortable with Solid State electronic design, but tubes were not part of my ciriculum (nor was spelling).  
. I'd be happy to arrange faxing the schematic to you if you think you have time too mess with looking at it. But if not, that's cool to. Thanks again for the reply. Have a good one.  
Charlie Graves
2/2/1997 11:15 PM
I'd love to see a schematic of your amp.  
I have a couple of complete rewirings under  
my belt and the results have been stunning.  
Not just rebuilding but changing almost  
every thing the amp does. My pet project  
is a '91 plexi reissue that I have built to  
sound like a vintage Fender in one jack, and  
an overdrive Marshall in the other. This amp  
kills every thing else I own. Except my Fender  
Prosonic which is only equal at best. I don't  
have any formal training in electronics, but  
after 4 years of tinkering and looking over  
alot of schematics along with getting some  
very basic theory, it's all pretty simple stuff.  
I cant guarantee anything, but if you fax me a  
schematic for your amp I may be able to fax you  
back some good circuit changes. If I only have  
a schematic to work with, you will have to be  
able to trace a curcuit to make the changes on  
the actual layout of your board. It sounds  
like you can do that. My fax number is (408)  
297-4422. Please no vagabond faxes (this is  
my work). Send :attn:Chuck, and include your  
fax nuber on your cover sheet. This is gonna  
be great fun.  
Anyone who wants a schematic of the changes I  
made to my amp can fax also. This mod should  
work on all Super Lead, JMP, and Plexi(reissue  
or other) Marshalls.  
I modified mine to use 2 of the input jacks as  
a line in/out (not an FX loop, but it works  
with most effects). If you don't have 4 inputs  
(JMP) you will have to drill holes in your amp  
to do this.  
Again, please be kind with this fax number.  
2/3/1997 6:35 PM
OOOooops...I gave the wrong phone number.  
The one in my other post is a voice number.  
The fax number is (408)297-4992...Sorry.  
2/7/1997 3:46 PM
Charlie Graves

No Problem. I figured it out when I dialed and then asked someone at your place. I faxed it to that number yesterday (2-6-97). Did you get it ?  
2/7/1997 6:44 PM
Yes I got it. I have what should be a killer sounding  
preamp mod, but you have to change the values on about  
20 componants to do it. It fools the amp into thinking  
its a Super Lead Marshall with a tube overdrive plugged  
in. I can see now why it sounded the way you say. I'll  
fax the changes to you (real easy stuff) but I make no  
guarantee on tone. This circuit design has worked in  
other amps I've done, but that doesn't mean for certain  
it will work with your Carvin. Nothing will burn up,  
but it may not be as great sounding as other amps with  
this mod. If it does, I can tell you, it'll blow your  
head right off. Save your parts in case you want to  
change it back. Sight unseen it's hard to say what kind  
of working conditions your dealing with. Are the preamp  
tubes on the board or on chassis mounted sockets? Are  
the pots pc mount type or do they have wires running to  
them? Is your circuit board a 1 or 2 side laminate? All  
this will effect the ease of the operation, or even the  
plausability. Still, if this works, your amp should have  
more thunder, grit, and most of all attitude. Please  
respond to the above questions. I'd like to know.  
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