Bringing a Studio 15 back to life
Bob S.
In the off-chance that there's still someone out there who's ISP
hasn't totally blocked newsgroup postings from rr.com.....
After the last round of discussions on the Marshall Studio 15 a
while back, I thought I'd get mine up and running again, and see
if I liked it any better than I did the first time around. I
bought it new back in '88 or '89, played it a little, then stuck
it in the closet and forgot about it. Kind of. Over the past
seven or eight years, it had become a rich source of replacement
parts for my gigging amps. Unfortunately, it now needed a few
things to make it playable - bass, treble, and gain pots,
complete set of tubes (I have _no_ idea where the original 6v6s
went), one output tube socket, and a full set of knobs.
Yesterday, my parts arrived. I started by replacing the stock
plastic output tube sockets with ceramic ones. They are
snap-ring style, which I'm really not thrilled with, but which
get the job done. (If anyone knows of any better Marshall
replacements, please let me know). Along with the rest of the
parts, I replaced a few of the stock ceramic disk caps in the
signal path with orange drops. Finally, I retubed with EH 6v6s @
24ma (370v on the plates) and JAN 12ax7wa's in the preamp and
phase splitter holes.
Ran it to a Laney 4x12 w/ Celestion G12M70s, fired it up, no
smoke. Good. Plugged in the only electric I own at the moment, an
Ibanez LP w/Duncan 59s and .01 tone caps, and it sounded OK. Not
bad, but I wasn't blown away either. The way this amp is voiced,
it really needs a single-coil to sound right - IMO, a Tele or
Strat would be a perfect fit with this thing. With the
humbuckers, there is a little too much bottom and low mids for my
taste. This could probably be rectified, at least partially, by
replacing the 22uf cathode bypass cap on the second gain stage
with a lower value, which I might try this morning. Before I do
anything though, I need to hear how it sounds at a healthy output
level. It was a little too late last night to really open it up.
Another very cool thing I tried was to run the 4x12 from the
headphone out jack, which is something I read about here
somewhere along the way. With all the controls dimed, the sound
was very thick and saturated, very Mesa Boogie sounding, at an
honest bedroom level. With the treble rolled off the bridge
pickup, I got a really nice, _very_ convincing Carlos Santana
lead tone. This will come in handy.
Gonna play with different speakers today to try and find a
replacement for the stock Marshall/Celestion Vintage thing.
-Bob
intifada
Well, if my short experience is anything to go by, I wish you all the
best in getting your Studio 15 back to life.
I got hold of one of these just yesterday. Payed a bit more than I
wanted to ($300) - and the amp had been converted into a head - but I
finally got my hands on it yesterday. Got home late last night so I
couldn't play for too long, but I fired it up and WOW! Did that baby
roar!!! With the gain and mids on full, bass and treble on half, and
volume on three quarters, I have to confess that I was amazed at the
sweetness of the raunch (if such a thing can be said). Lots of
compression and bounce too, which made me really happy. Bit louder
than I had hoped, but whaddya expect with 15W into 100db/W speakers?
Anyway, gonna pop some NOS 12AX7s into it over the weekend (cheapo
chinese-looking thangs inside, tho the 6V6s look like NOS) and expect
to get it sounding even better. I ran mine into a 4x12 Recto cab, so I
can see why Marshall coupled this with the V30s (or possibly even
designed the V30 for this amp. Bit too much high frequency stuff, but
then I always feel that. Maybe it's my ears, which certainly have
taken a battering recently and would really like me to stop.
Still, like a moth to a flame...
JC
intifada
pickup on an LP Studio. I think the baby was raised for humbuckers.
Your mileage has obviously varied.
JC
Bob S.
<ed29c079.01083...@posting.google.com>:
>I got hold of one of these just yesterday. Payed a bit more than
>I wanted to ($300) - and the amp had been converted into a head
IIRC, there may have been some solid-state combos produced that
used the same cabinet - could be a cheap source of a replacement.
>WOW! Did that baby roar!!! With the gain and mids on full, bass
>and treble on half, and volume on three quarters, I have to
>confess that I was amazed at the sweetness of the raunch.
Nice, isn't it? In true Marshall fashion, it doesn't start making
tone until you get the volume up. This was my mistake the other
night, posting an opinion based on a low-volume test. What sounds
best to me so far is to keep the master pretty much wide open,
and use the gain to adjust the volume. I've been playing this
thing for days now, and - contrary to my original post - have
absolutely fallen in love with it. Only took 12 years....
My only gripe at this point is how much effect the mid
control has on gain, but I think I'll live with it rather than
mess with the circuit.
>Bit louder than I had hoped, but
>whaddya expect with 15W into 100db/W speakers?
I've found it to be loud no matter what I run it through,
although "loud" is a relative term. Loud for the house, yes, but
it may be just right for your basic club gig. Have you tried the
headphone-out trick yet? It's pretty neat for low levels.
>Anyway, gonna pop some NOS 12AX7s into it over the weekend
How'd they work out?
>tho the 6V6s look like NOS
Black bottle by any chance? That's what came stock in mine. No
identification of any kind on them, but it's my understanding
that they may be Brimars. Using the new EH 6v6 now, and couldn't
be happier.
>and expect to get it sounding even better. I ran mine into
>a 4x12 Recto cab, so I can see why Marshall coupled this with
>the V30s (or possibly even designed the V30 for this amp. Bit
>too much high frequency stuff, but then I always feel that.
That's how I feel about mids, which is why I can't bring myself
to like the V30s. They are just too prominent with this speaker.
My hands-down favorites so far are the Celestion G12-65s. Run
through a pair of these in an open back 2x12 configuration, this
amp sounds perfect to me - bottom just tight enough, mids nice
and warm without being in your face, and highs that are crisp and
seem to roll of at just the right point. Nice.
I probably should add at this point that I _did_ make a small
change to the preamp. The schematic shows a 22uf bypass cap on
the cathode of v1b, but it actually came through with a 10uf. I
replaced that with a 1mfd to bring the mids - which I thought
sounded very "boxy" and dark originally - into line. This worked
beautifully, but I may go further still, to a .68uf and see how
it sounds.
I'm pretty much convinced that there are/were several variations
of this circuit that made it into production. From what I've
read, these amps can sound quite different from one
another. There were several discrepencies between the two
published schematics that I have (which are each a bit different
from each other) and my amp, as well as discrepencies on the
board itsself. There are spots marked for resistors that have
caps in them, and vice-versa, and a few spots that are marked for
certain components but are empty. One day when I have some time,
I may trace this board out and see what's really going on.
>Maybe it's my ears, which certainly have taken a battering
>recently and would really like me to stop.
>Still, like a moth to a flame...
I have _no_ idea what you're talking about.... :)
-Bob