| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 2279.1 | Can you say "How much to fix this amp?" | LEDS::ORSI | Listen up now ya little booger machines | Tue Mar 06 1990 08:31 | 20 |
|
DANGER WILL ROBINSON!!!
Using the amp in that way may severely hamper its
operating lifetime. One channel is bucking the other,
and what you hear is the difference. Not much, huh?
You're clipping the hell out of the amp.
If you want to parallel the inputs, leave the switch
in the "Stereo" position, and use a short patch cord
between the r + l channel inputs.
The bridging switch does NOT parallel both inputs. It
inverts the signal to one amp. The amp then operates
as a mono amp ONLY when using the input and output jacks
specifically designated for bridging the amp.
Neal
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| 2279.2 | no smoke yet | PCOJCT::RYAN | | Wed Mar 07 1990 09:29 | 5 |
| thanks for the tip, while I did try it for a few seconds, i'm always
hesitant to run in any configuration thay I'm unsure of...
PS: any thoughts on the LED indicator confusion??
Gary
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| 2279.3 | Haven't figured out the LED thing yet | LEDS::ORSI | Listen up now ya little booger machines | Thu Mar 08 1990 08:44 | 35 |
|
Gary, is your amp the DECA 724? It's rated at 350W/ch
@ 4 ohms. I'm not familiar with the 700. You can write
to Peavey for an operating manual.
Re - LED problem.
I have a few questions.
When the switch was in the bridge position;
(A) which input channel did you plug into?
(B) how did you hook up the speaker(s)?
(C) spkr(s) 8 ohm?
(D) were LED's on BOTH channels in the red?
Here's some info on bridging an amp if it will help.
Bridging is most useful when using just one speaker
and you need a mono amp.
Flip the Stereo/Bridge switch to "bridge" position,
plug signal into channel A, then hook your spkr BETWEEN
the two RED banana jacks, with the channel A banana jack
being the + side when observing polarity.
DO NOT USE THE BLACK CONNECTOR OR GROUND.
Also, the speaker load should not be less than 8 ohms.
If you are using two spkrs, you can run the amp in "dual mono"
by leaving the switch in the "Stereo" position, plug into
channel A input, patch a cable from channel A input to channel
B input (if your amp has two paralleled input jacks on each
channel) then plug a speaker into each channel output using
the 1/4" jacks or the banana jacks
Neal
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| 2279.4 | more info,same ??'s | PCOJCT::RYAN | | Fri Mar 09 1990 14:34 | 33 |
| Neil, thanks for the info.... The 700 was one of the 1st of the DECA
series. It is older that the 724. I've see both in person and checked
out the published specs on both, I really can't see any difference.
I guess the need to push a newer, better model every year, exists in
the power amp world also.... I thought it was only midi stuff...
Anyway, My original question was actually 2 different questions.
I am cyurrently running the amp from a mono signal using a
Y cord to drive both inputs. I am using TOA cab's @ 8 ohms, each
plugged into one side or the other.
RE: My question on the LED's, I've never worked with a device that had
LED meters. It just seems to me that they pop up into the yellow and to
a lesser extent red areas at a relativly low output. There is no
audible distortion in fact, the DDT lights are not on. I guess I'm just
curious.
As for the bridge question, I had both speakers plugged in, I just
un-plugged one of the inputs, b, I think and switched into bridge.
Both speakers worked and sounded fine, onlu one set of LED did their
thing and the entire amp ran from 1 level control. It would simplify
my set-up not to need this Y cord, on the otherside of the coin,
I'd like to be able to adjust the level of each side indivigaly.
PS Excuse spelling errors..... it's been a long day...
I think I'll keep my trusty Y cord, everthing is currently working fine
and that's about the best I can expect.....
Now, about those LEDS....
Gary
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| 2279.5 | | LEDS::ORSI | Listen up now ya little booger machines | Mon Mar 12 1990 12:24 | 17 |
|
Gary, I can't figure out by your last reply that you are
indicating that you are going to continue to use it that
way because it "sounds" ok and that what you are really
worried about are the LEDs. If so, the LEDs are the least
of your problems. When you switch to the bridge position,
the amp become a "mono" amp, hence, only one set of LEDs
is needed. The fact that they extend into the yellow indi-
cates (again) that the amp is working twice as hard to put
out a relative sound pressure level because the output of
one speaker is out of phase with the other and they are
working against each other. This is not good for the amp OR
the speakers.
Neal
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| 2279.6 | | STROKR::DEHAHN | | Tue Mar 13 1990 08:32 | 33 |
|
I'll jump in and back Neal up on this...DO NOT CONTINUE to operate that
amp in bridge mode WITH SPEAKER WIRES ON THE BLACK TERMINALS or you
may soon have a smoking mass of melted silicon.
Most people don't understand what bridge mode means. What is happen-
ing is one OUTPUT channel is getting inverted and then is coupled in
PARALLEL with the other channel. The resultant OUTPUT LOAD is put across
the TWO RED (or + [plus]) JACKS. Like two resistors in parallel, the
output impedance of the amp is then cut in half, so your effective
output load must be double for the same power output. Thus if your amp
can drive at best a 4 ohm load per channel it will only drive an *8*
ohm load in bridge mode. Some of the larger pro amps will drive a 4 ohm
bridged load, but I don't think the DECA will.
Usually, only the channel '1' or 'A' or whatever input is used when in
bridge mode. The amp is effectively a single channel amp. If you have a
stereo signal you must sum them before the input jacks, although there
are a few amps which will sum internally if you hook up your inputs in
stereo. Check with Peavey.
If all you want to do is feed a mono signal to two channels and then
hook up two speakers, all you need to do is run it parallel mono (or as
Neal calls it, dual mono, same thing). Some amps have a switch for
this. Otherwise just jump a patch across the inputs.
The DECA 700 has a history of thermal runaway problems which were
corrected with the DECA 724. Be careful with this amp, it is not
bulletproof.
CdH
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