Hello Tom!
On 27 Jan 98, Tom Scioscia wrote to Rich Lockyer:
 TS>        Well, I now have the amp. Apparently it's biased PERFECTLY. :) 
OW
 TS> is all I can say. After playing through it for a while, I seriously had 
to
 TS> go to the bathroom and drench myself in cold water. :)
Coolness.  Glad you like it.
 TS>        Well, maybe from an electrical design standpoint... They do work.
 TS> But from an audible standpoint... Ouch... I really haven't found a
 TS> Silverface that I like. They tend to have a shrill sound and no umph.
Yup... the high B+ and all of those caps they threw in to eliminate the 
parasitic oscillation that started happening when they rewired them.  
Parasitic oscillation is probably the #2 concern in building your own amp... 
if the lead length and component position isn't just right (or is "just 
wrong"), you'll get parasitic oscillations.  It started on Tom's Traynor when 
I modded it, but I fixed it by replacing the longer leads in the preamp with 
shielded cable, with one end of the shields all tied to one ground point.
 TS> from the Deluxe and unplugged it for safety). Wow... With that, I 
actually
 TS> could get it up loud enough that there was breakup. WOW!!!
And you can still hear? ~8-)
 RL>> Major retooling.  You want to spend $100/tube for a special like that?
 TS>        YEAH!!! I HAVE G.A.S.!!! MONEY IS NO OBJECT!!! :)
You've got it backwards... money is no object BEFORE you get G.A.S.
 TS>        Dunno... Don't feel like taking it apart... Yet. :) I'll have to
 TS> get a multimeter and check it out if I do. :)
I wouldn't worry about it.
 TS>        Ahhh... Gotcha... That 700Vs on an EL34 would explain why that
 TS> Marshall I played through that time was so damned clean!!!
You checked the plate voltage on the Marshall?
 TS> I think that
 TS> the voltage on the plate of the 6L6s is something like 460... I must be
 TS> hitting it with at least 46V by the time I hit 6 on the volume, then. :)
Get a signal generator, set it for 1v p-p at 1khz and apply it to the input. 
Now measure the voltage on the grid of one of the power tubes and advance the 
volume until you go deaf.
 TS>        Hmmm.... If GTs die like that, what would you suggest as a good
 TS> tube brand? I remember you saying something about liking the Rubies,
Oh no... they were in my Carvin when I bought it from Tom.  I liked them 
BETTER than the GTs that replaced them (seemed to have more gain before), but 
they are by far not the best.
 TS> but
 TS> if Rubies are Chinese, I wouldn't like them dying on me... Hell, I think 
I
 TS> have RCA 7025s in the preamp section of the DS. They're 35 years old and
 TS> still sound great!!! How are Svetlanas, Teslas, or EI's?
Fender OEM tubes are relabelled Sovtek.  They probably make the best NEW 
12AX7 available.  If you want to get into N.O.S., Telefunken is reputed to be 
the grail, if you can find them.  NOS RCA and Sylvanias are good and readily 
available from AES for maybe $5.00 more than a new GT.
C-ya! Rich
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