Re: [Harp-L] Re: the amazing VHT Special 6 amp

[Rick Davis <bluesharpamps@xxxxxxxxx>]

Splash-

I agree...  Great little amp!

A couple of things:

The Pull Boost doesn't activate an additional gain stage.  It lifts the
ground on some components in the tone stack, thereby increasing apparent
gain.

The harshness you heard in the amp may not have been from the 12AX7 tube.  I
heard the same reedy harshness, and in my case it was cured by a change in
the cathode bybass cap.  Running a low-gain tube like the 12AU7 may mask the
hashness, but it will be at the expense of much of the amp's gain.  With a
6-watt Class A amp you don't have a lot of power to waste, and a 12AU7 tube
has a different impedance than the tube you replaced, which affects
components downstream of the tube.

You're absolutely right about the line out.  The amp is not loud enough for
most gigs, and would get buried at your average blues jam.  But the tone is
glorious, so a line out is a must.  There is room on the back of the chassis
for the line out jack and a LO Level pot (both standard features on the
Mission Chicago 32-20 amp, btw).  Or, you could use the 4-ohm speaker tap as
the line out, it the amp owner does not anticipate the need to drive a 4-ohm
cab.

-- 
-Rick Davis
The Blues Harp Amps Blog
http://www.bluesharpamps.blogspot.com/

On Fri, Nov 26, 2010 at 9:03 AM, Splash! <celtiac@xxxxxxxxx> wrote:

> I got one (Thanks Mike) and agree with most of the good reviews.  It has a
> pull/volume knob which activates an additional gain stage.  The push/pull
> switch also can be used with a foot pedal.  I don't remember the tweed champ
> having THAT!  Also has diodes instead of the GZ3Y or 5AR4.
>
> Having not completely removed the eyelet board to draw out a schematic yet,
> I suppose the additional gain stage might be coming from the second half of
> the 12A*7.  Or a germanium transistor somewhere?  I did remove the chassis
> for a quick inspection.
>
> Also, swapping tubes for American Vintage 6V6GT  & 12A*7's is an adventure
> into warm creamy tones that boutique amp makers strive to achieve.  That
> russian 12AX7 is kinda harsh!  (Good for guitar)
>
> Currently running a metal 6V6GT from an old 1959 Cadillac car radio and
> aWWII US Navy JAN 12AU7.
>
> This amp absolutely LOVES the Shure 545SD.  Not too shabby either with
> vintage hot bullets, but there must be some kind of DNA match with the 545.
> I can dime the Special 6 with the high-gain stage on and it just honks like
> a cool horn. This is definitely the mic for this amp.
>
> On my list of things to do:  Create and install a line-out with adjustable
> line level pot.  It's really not loud enough to stand alone with a bunch of
> guitar stacks on stage =8^D.
>
> I repeat, "Thanks, Mike!"
>
> Splash!
>