[Boatanchors] various rectifiers

[mikea]

On Thu, Jul 06, 2006 at 04:16:23PM -0400, Troglodite at aol.com wrote:
> In a message dated 7/6/2006 2:24:16 PM Central Standard Time,  
> mikea at mikea.ath.cx writes:
> 
> > I'll risk asking a question that may start some controversy,  because
> > I genuinely am interested in the answer as the owner of a Fender  
> > Bassman and some old tube-type stereo amps. 
> 
> > How would  going from tube rectifiers to SS rectifiers change the tome
> > of an amp?  It's all DC at the filter output, isn't it?
>  
> Mike,
>  
> You'll get all kinds of answers on this, some informed, some snake oil. :-)  
> Generally, there's not too much snake oil in this group, but you never know.  
> Anyway, here's mine:
>  
> The Fender Bassman with the four 10" speakers is one of those classic  
> designs like the DC-3 airplane. It is nearly perfect just as it stands. If you  want 
> different sounds, buy another amp, don't mess with a classic. Put in new  
> output tubes, change the electrolytics and wax/paper capacitors if necessary,  
> but don't change the basic circuitry.
>  
> If you put in silicon diodes, the voltage will go up just enough to stress  
> the output tubes. The sound will be "harder" due to the lack of voltage droop 
> in  the vacuum rectifier. The electrolytic capacitors will be under more 
> stress.  (These tend to dry out in the Fender amps due to their "upside down"  
> construction with the heat from the tubes heating the chassis.)
>  
> In other words, "If it ain't broke, don't fix it."

Oh, I wouldn't change it for the world. It was my dad's, and that 
makes it precious. I put thousands of hours on it, playing bass with 
a rock band around Houston in the mid-60s, and the only maintenance I
ever had to do was replacing the class-B 6L6 tubes. The output xfmr
died once, and I had to get another off-the-shelf at a parts house 
downtown (can't remember the name to save my life, but it had anything
and everything a 17-year-old ham could want). They had about a dozen 
in a bin, which may tell you something about the penetration of SS 
gear into the economy back then. 

And, of course, it's a boatanchor.

-- 
Mike Andrews, W5EGO
mikea at mikea.ath.cx
Tired old sysadmin