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From cmiy56–(at)–pcf.cc.utexas.edu Sun May 19 13:45:25 CDT 1996
Article: 15399 of alt.guitar.amps
Path: geraldo.cc.utexas.edu!not-for-mail
From: cmiy56–(at)–pcf.cc.utexas.edu (Clancy)
Newsgroups: alt.guitar.amps
Subject: Re: Ampeg V-4 users
Date: 19 May 1996 13:32:19 -0500
Organization: The University of Texas at Austin, Computation Center
Lines: 56
Message-ID: <4nnpfj$rm--(at)--pica.cc.utexas.edu>
References: <4nnmjb$ns--(at)--lterdial.UU.NET>
NNTP-Posting-Host: spica.cc.utexas.edu

>I’m curious about a few things with this amp if you can help. First
>what’s the current price like on one of these heads. I have a chance to
>pick one up in vg condition–(at)–$250. Also I wondering what tube
>alternatives may I consider for the head and what exactly does each
>preamp tube do. Any common ailments with this head, and could anyone
>explain exactly how I’d go about biasing a V-4.
>
>
>Tube Listing For V-4
>
>4 – 7027A Output Tubes
>
>Preamp Section
>
> 12AX7 6CG7 6K11
>12AU7 12DW7 12AX7 12AX7

I got one in working condition ( a ’77 model) for $99. It sat in a
pawnshop for over a year. Somebody else here mentioned they got a
V-4B which is about the same thing w/o reverb for $75.

I don’t know of any common ailments, but you can’t get 7027A’s anymore.
(which is a great bargaining angle if you ask me.) This amp uses
a hefty amount of filter capacitance in the power supply. It uses
the twist mount kind. Maybe the ones in that amp are ok,
I replaced mine with axial electrolytics mounted on wafer boards set on
standoffs.

Each preamp channel uses a 12ax7. The 6k11 is stage which basically
controls the midrange tone shaping circuit. The 6cg7 drives the
transducer in the reverb pan. half of a 12ax7 amplifies the signal
coming out of the reverb pan. The 12dw7 (you can directly replace
w/ a 12ax7 in this circuit) is the final gain stage before going
into the phase invertor 12au7.

signal path:

12ax7 -> 6k11 -> 12dw7-> 12au7-> 4-7027A -> ot-> speakers
12ax7 —-^
===============================================================
somewhere in the circuit the signal is sent out and returned for rev.
=============================================================
| ^
—>6cg7-> reverbpan — 1/2-12ax7

Sovtek 5881wxt’s work for power tubes, &el34’s. it’s been recommended that
the screen resistors be changed to 1k/5w. There’s no bias pot so
you have to insert a pot in the bias supply circuit in place of the
resistor and then later solder one in of the appropriate value.
There’s a number for this resistor, but I can’t remember it. Mine
had a schematic glued onto the chassis.

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