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

[Jim Rossen <jimjimdr@xxxxxxxxx>]

Rick-  It would be great to hear the difference you describe between a
Copper Cap and tube recto in the Mission Chicago.  Can you do a video
of your playing to demonstrate this?

Jim


On Dec 10, 5:39 pm, Rick Davis <bluesharpa...@xxxxxxxxx> wrote:
> Jim, the sag circuit in the copper solid state rectos is (as I understand
> it) a power resistor.  It attempts to emulate the sound of real tube sag,
> but it does not sound the same.  Tube sag is a kind of living, breathing
> effect that varies with volume and attack and load on the amp.  It is one of
> those things that makes good tube harp amps seem to be alive.  Artificial
> sag (from a static resistor) sounds rigid, the same at low volume as as
> higher volumes.
>
> I've used the copper solid state recto in several amps, and I liked it in
> smaller class A amps like my Champ.  But small amps like the Champ don't
> really produce sag, since they are always cookin' on high anyway.  The solid
> state recto gave the Champ a crisper feel.  "Crisp" and "sag" are opposites
> of each other as far as rectifiers go.
>
> --
> -Rick Davis
> The Blues Harp Amps Bloghttp://www.bluesharpamps.blogspot.com/
>
> On Fri, Dec 10, 2010 at 3:37 PM, Jim Rossen <jimji...@xxxxxxxxx> wrote:
>
> > 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
> > cap)
>
> > 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