Gibson Maestro reverb echo?
Teemu_K
thinking of building this amp. I have schematics and everything but
the reverb section seems a bit weird. It uses a spring reverb but it
looks like that no signal from it comes to preamp tube. I read
somewhere that it needs an amp of its own and GA-1RT-1 just acts as
sort of an "effect box". Is that true? Does anyone have any
information concerning this amp or technical knowledge of how to add a
reverb to a clean channel without major operations or changes in
circuitry?
Miles O'Neal
> Does anyone know how the reverb in Gibson Maestro 1RT works? I am
> thinking of building this amp. I have schematics and everything but
> the reverb section seems a bit weird. It uses a spring reverb but it
> looks like that no signal from it comes to preamp tube. I read
> somewhere that it needs an amp of its own and GA-1RT-1 just acts as
> sort of an "effect box". Is that true?
Yes. That's an odd, little amp. I wish I knew what
they weer thinking (besides, Hey! it has reverb!)
> Does anyone have any
> information concerning this amp or technical knowledge of how to add a
> reverb to a clean channel without major operations or changes in
> circuitry?
You could build the reverb circuit from the GA-1RVT,
with the second gain stage after the one in the GA-R-1,
but sub in a low gain tube for the two gain stages in
the dry signal path. If that's too much, you just
need to pick a different amp to build.
John King
Hi,
Yes, these amps were intended as an extension to your "regular" amp.
I've examined the manuals of several models, and they did things
different on about every model (typical of Gibson amps). The GA-1RT-1
that you are asking about uses the speaker level of your "regular" amp
to drive the reverb tank of the "reverb" amp. Note the markings "red"
and "black" on the schematic at the reverb tank; those are the speaker
level connections. They actually had "clips" on a speaker wire that
the user clipped onto the speaker terminals in the back of their
"regular" amp.
This arrangement doesn't allow you to use the internal reverb with the
GA-1RT-1 when you use it as a stand alone amplifier. (A very limited/poor
design to say the least.)
A much better plan is the GA-1RVT. It DOES pre amp the reverb tank,
and you can use the reverb in it when operating as a stand alone amp.
It has a monitor out on the panel and that is where the "regular" amp
is fed from.
I use a similar setup to get reverb into my '53 tweed Deluxe or '55
GA-77. My '61 Epi EA-28RVT has that monitor out, and I plug my guitar
into its input, and then feed the other amp from it's monitor out.
A VERY SWEET SETUP!!!
I know the GA-1RVT looks more complicated on the schematic, and it is
(slightly), but the added versatility would be well worth the effort.
Also, it has been my experience that the Gibson amps that use the low noise
7199 reverb tube have a really plush reverb sound. Beware though a NOS 7199
is going for about $30 now, I've heard that imports are available, but I
don't know it they're good.
In case you aren't familiar with Gibson reverb circuits, they work like an
independent channel. You can turn up the reverb without the regular channel
volume and get 100% "wet" signal with NO dry signal!!! Surf City ;=].
Good luck,
John King
http://www.angelfire.com/blues/rockinjohn/rockinamps.html
Teemu_K
Gibson RVT schem and noticed the reverb was built different way. As I
was trying to get with a pretty simple setup (less tubes, less
transformers) i deserted it. Now it seems I have to continue my
project with different approach....
Still, if anyone has some information of how to insert reverb into
circuit without using the transformer I would appreciate it. Is it
even possible without solid state circuitry?
Luca R.
>Still, if anyone has some information of how to insert reverb into
>circuit without using the transformer I would appreciate it. Is it
>even possible without solid state circuitry?
Hi. I've saved some schematic during the last year, as I'm interested
in the same matter. So these are amps with reverb-without-tranny (at
top those who seems to be the best, at least at my sight):
1) Sjb ant rev head - 1 triode/pentode (6U8A) - even specified
Accutronics tank #
2) Traynor YGM3 & 4 - 3 triodes - even specified Accutronics tank #
3) Traynor YSR1 Custom Reverb - 4 triodes
4) Gretsch G6144 - 2 triodes
5) Gibson GA-15RVT - 3 triodes
6) Silvertone 1474
Contact me offlist if you need some or all the above.
Ciao
John King
As Luca pointed out, it is possible to have reverb without the
transformer.
He's correct in that a Gibson GA-15RVT doesn't use an impedance
matching transformer for the reverb, but then it uses a transformer
for phase splitting. 6-o-1, ˝ dozen t-other. In other words, there
are still three transformers in the amp.
The GA-1RVT could probably be modified my replacing the 7199 tube
with a 12AU7, removing the transformer and using a higher input
impedance tank.
You can, of course, chain another amp to it by jumping the inputs,
but you get no reverb in the other amp that way. To do that, you need
a post reverb monitor out like I described in my previous post.
See the schematic for a GA-19RVT for that. Look at the speaker area,
and you'll see a simple monitor out circuit that drops the speaker level
down to a line level. That gives you the benefit of the reverb AND the
power tube overdrive going into the second amp!!! Lower powered amp
crunching away, boosted by a same or higher powered amp. I'm telling
ya... SWEET SETUP!!!
John King
Giving away my own plans...
http://www.angelfire.com/blues/rockinjohn/rockinamps.html