1/2 rack space amps
Kevin Tully
I am looking for a 1/2 rack space amplifier. So far I have found a product
from Stewart Electronics that is 100 watts per side stereo. Any info would
be appreciated. Thanks!
--
Kevin Tully - ktu...@insync.net
Scott Dorsey
In article <ktully-0602...@dialup-164-150.insync.net> ktu...@insync.net (Kevin Tully) writes:
>I am looking for a 1/2 rack space amplifier. So far I have found a product
>from Stewart Electronics that is 100 watts per side stereo. Any info would
>be appreciated. Thanks!
That's pretty much your only alternative if you want four channels in a
single rack space. I don't like the way the small Stewarts sound, and they
have switching power supplies. I don't like switching supplies because they
feel like they just have too much to go wrong, and I don't trust my ability
to do repair work on them in the middle of the night in the back of a
VW bus at a folk festival without a manual. They're really glorified car
stereo amps from the power supply perspective.
But, they don't have any competition here, and if you can't spare the rack
space, they're the only way to go.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Tom Loredo
Hi-
I have a Stewart PA200, which is probably the one you're
talking about. I'm using it for live (PA) work, amplifying
acoustic instruments & voice, so it's not exactly getting
pushed hard. It does the job fine, though it does get warm.
Some threads here in rap have mentioned it shutting down
due to overheating when it's pushed hard and mounted in a rack;
they had to install a fan in the rack to deal with this.
I don't have it in a rack; I only use one and just put it
on stage or on the floor near the speakers, so there's been
no problem as far as an enclosed space....
Good luck,
-Tom Loredo
David L. Rick
In article <ktully-0602...@dialup-164-150.insync.net>,
ktu...@insync.net (Kevin Tully) says...
>
>I am looking for a 1/2 rack space amplifier. So far I have found a product
>from Stewart Electronics that is 100 watts per side stereo. Any info would
>be appreciated. Thanks!
I've got one of these. Actually, it's the PA 100B, which is 50W/ch.
It has been a decent performer for driving nearfields and small floor
monitors in acoustic situations. There are a few things you should
know about it, though.
1) Be *very* careful about how you mount it. Stewart, in their
infinite wisdom, has put the mounting holes in the sides, not the
bottom. This means you need to buy a more expensive rack shelf
for it, but the real problem is that the circuit board revision
that I got had an AC filter capacitor behind one of the holes!
As a result, the first one I got lasted exactly 1.5 seconds in
the rack before being shipped back to the manufacturer with an
irate note. (That's why I *never* lift my grounds, folks.) I
put some epoxy in that particular hole on the second one. I
imagine Stewart has changed the circuit board layout by now,
but you can't be too careful.
2) The speaker leads connect via a small, removable terminal
block. Save yourself some grief, spend $5 to get a spare
from the manufacturer now. You will _never_ find one of these
at the local parts jobber. I recommend you strain-relieve the
speaker leads to the mounting shelf to keep them from pulling
the terminal block loose.
3) The unit makes a "pop" in the speakers whenever you cycle power.
No room inside for relays, I guess. Maybe not a good match for
Alesis nearfields, unless you keep plenty of spare tweeters around.
4) These amps put the rectifier and filter cap _ahead_ of the
power switch. (You can see the wall plug spark when you plug
it into the outlet.) So don't open 'em up when they are
plugged in.
5) As with most switching power amps, you should be careful
about using them in an installation with wireless mics.
Also, don't plan on touring abroad with them -- no way would
these pass the European harmonic content rules.
6) These are convection cooled amplifiers. If you put stuff
near them that is heat sensitive (e.g. Lexicon LXP-5), you
could be in for trouble. I've used them next to Symetrix
half-rack pieces without any difficulties, though.
7) If you run the amp in bridged mode, you _must_ use balanced
inputs. At least on the PA 100B, bridged mode doesn't work
with unbalanced inputs.
Hope this helps,
David L. Rick
Seventh String Recording
dr...@hach.com
TNT
In <kludgeE5...@netcom.com>, klu...@netcom.com (Scott Dorsey) writes:
>That's pretty much your only alternative if you want four channels in a
>single rack space. I don't like the way the small Stewarts sound, and they
>have switching power supplies. I don't like switching supplies because they
>feel like they just have too much to go wrong, and I don't trust my ability
>to do repair work on them in the middle of the night in the back of a
>VW bus at a folk festival without a manual. "
Are you still doing the WoodStock festivals Scott???
TNT
Tom Loredo
Howdy folks-
David wrote the following comments about the PA 100B. The
half-rack space PA 200 is different in the following respects:
David L. Rick wrote:
> 2) The speaker leads connect via a small, removable terminal
> block. Save yourself some grief, spend $5 to get a spare
> from the manufacturer now. You will _never_ find one of these
> at the local parts jobber. I recommend you strain-relieve the
> speaker leads to the mounting shelf to keep them from pulling
> the terminal block loose.
The PA 200 uses 1/4" phone jacks for the speaker connections.
> 3) The unit makes a "pop" in the speakers whenever you cycle power.
> No room inside for relays, I guess. Maybe not a good match for
> Alesis nearfields, unless you keep plenty of spare tweeters around.
The PA 200 does this, too, but it is a very low volume pop.
> 5) As with most switching power amps, you should be careful
> about using them in an installation with wireless mics.
> Also, don't plan on touring abroad with them -- no way would
> these pass the European harmonic content rules.
It's nice to know this! I share David's and Scott's misgivings
about using switching power supplies in an audio application.
However, if you want a power amp in a small space, I don't think
present technology offers any alternatives at this range of power
and price. It's a tradeoff for the convenience of the PA series.
> 7) If you run the amp in bridged mode, you _must_ use balanced
> inputs. At least on the PA 100B, bridged mode doesn't work
> with unbalanced inputs.
Not true of the PA200. I use it all the time in bridged mode,
with an unbalanced input. A handy feature is that if you plug
in only one input and one speaker, it automatically switches to
bridge mode.
>
> Hope this helps,
I certainly found it helpful info; thanks David!
By the way, I note the following: *Recording* had an interesting
review of power amps for studio monitors a few years ago. What
was interesting about it was that they found essentially no
discernable difference between various brands, as long as the
damping was above a certain number. I don't recall the numbers,
but I do recall checking the PA 200 spec, and its damping was
rather low by the *Recording* standard. This may have something
to do with the power supply technology, but I don't know enough
about power amp design to say.
Peace,
-Tom Loredo
Rick Auricchio
> 1) Be *very* careful about how you mount it. Stewart, in their
> infinite wisdom, has put the mounting holes in the sides, not the
> bottom. This means you need to buy a more expensive rack shelf
> for it...
I used their rack ears for two PA-200s; no problem at all. Perhaps this is
a 100 problem only.
> 2) The speaker leads connect via a small, removable terminal
> block.
The 200 uses quarter-inch jacks for inputs and outputs.
> 4) These amps put the rectifier and filter cap _ahead_ of the
> power switch. (You can see the wall plug spark when you plug
> it into the outlet.)
I'll have to check this on my 200s, which are usually powered off in the
studio but remain plugged in.
> 7) If you run the amp in bridged mode, you _must_ use balanced
> inputs. At least on the PA 100B, bridged mode doesn't work
> with unbalanced inputs.
On the 200, if you simply plug a speaker into one channel (it's marked
which one to use) you get bridged operation. I'm curious whether both
inputs mix in this case; another thing to try.
- rick http://www.cfcl.com/~rick/
- ----------------------------------------------------------------- -
Rick Auricchio ri...@apple.com 408-974-9742 voice, 408-446-3376 FAX
Apple Computer, Inc.1 Infinite Loop 301-2FM, Cupertino, CA 95014 USA
My opinion---not an Apple strategy, no matter what Management says!
Tom Loredo
Rick Auricchio wrote:
> > 7) If you run the amp in bridged mode, you _must_ use balanced
> > inputs. At least on the PA 100B, bridged mode doesn't work
> > with unbalanced inputs.
>
> On the 200, if you simply plug a speaker into one channel (it's marked
> which one to use) you get bridged operation. I'm curious whether both
> inputs mix in this case; another thing to try.
Rick, check the manual first. They are rather emphatic about
making the proper connections when using bridge mode, and as I
remember they insist there be only one input and imply damage can
be done if you screw this up. But I don't know for sure.
-Tom Loredo