[Harp-L] Re: The Mission Chicago 32-20 harp amp

I disagree with this analysis of Weber Copper Cap rectifiers. Copper
Caps are actually a line of rectifiers that have different b+ (power
supply) voltage and sag (the fall in b+ when the amp is presented with
a strong input signal) characteristics- from none to lots depending on
the model chosen.  This is similar to tube rectifiers, for example-  a
GZ34 tube recto provides higher voltage and less sag than 5U4 which
provides higher voltage and less sag than a 5R4.  So... a Copper Cap
can provide less, more or about the same sag as a particular tube
recto, depending on the one chosen.  The exception to this is with a
solid state recto with no sag circuitry- which will provide high b+
and no sag compared to about any tube recto setup (but perhaps
parallel GZ34s).

The trade-off of characteristics associated with different b+ voltage
and sag characteristics (loud/crisp/tight vs warm) occurs with
different tube rectos AND Copper Cap rectos.  (BTW- b+ with lower
voltage and more sag can be produced without changing the recto by
inserting a power resistor between the b+ source and the first filter

Was the message below directed at Gary O's recent posts regarding the
use of Copper Cap rectos in the Cruncher?  Does a 1961 Fender Concert
solid state rectified amp lack tone?  I am pretty sure the Harp King
is SS rectified.

Jim R

> When the amp was being designed, special attention was paid to the
> rectifier. The copper solid state rectifiers were tried but discarded in
> favor of real tube rectifiers. The copper solid state rectos deliver
> slightly more B+ voltage with less sag, which is why they give the
> impression of “tightening up” the sound, or making an amp sound more
> “crisp.” But that is at the expense of real tube sag and the warmth it
> provides. It would have compromised the true vintage tone of the amp. The
> rectifier tube is one of the tone generating components in a vintage tube
> harp amp, and solid state just doesn’t cut it.
> http://www.missionharpamps.com/
> --
> -Rick Davis
> The Blues Harp Amps Bloghttp://www.bluesharpamps.blogspot.com/

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