I have been considering ways to reduce costs in meeting my
requirements for 5 channels of amplifications. Because I require about
250 watts a channel into 8 ohms for all 5 channels with loads
occasionally falling to 3 ohms it is pretty expensive to find an amp
that meets those requirements. I only know of two that do.

In a side bar email exchange Norm Strong made an interesting
suggestion that I consider amps made by QSC. It was just a suggestion,
Norm has no first hand experience with these amps. Many of these amps
seem pretty cheap when compared to name brand "high-end", even lower
high end amps.

Question. Are there any technical reasons why a "DJ" amp such as those
marketed by QSC, Numark, Crown and others don't produce high fidelity
sound on the par with Adcom, Bryston, Theta Digital, etc., etc. They
seem to "measure" the same. The class of operation is generally AB,
although I have occasionally seen class H. Are they "voiced" a certain
way. Do the requirements for high power, efficiency, and bullit proof
reliability compromise neutral sound?

On 4 Sep 2004 21:08:42 GMT, (Robert C. Lang)
wrote:

I have been considering ways to reduce costs in meeting my
requirements for 5 channels of amplifications. Because I require about
250 watts a channel into 8 ohms for all 5 channels with loads
occasionally falling to 3 ohms it is pretty expensive to find an amp
that meets those requirements. I only know of two that do.

In a side bar email exchange Norm Strong made an interesting
suggestion that I consider amps made by QSC. It was just a suggestion,
Norm has no first hand experience with these amps. Many of these amps
seem pretty cheap when compared to name brand "high-end", even lower
high end amps.

Question. Are there any technical reasons why a "DJ" amp such as those
marketed by QSC, Numark, Crown and others don't produce high fidelity
sound on the par with Adcom, Bryston, Theta Digital, etc., etc. They
seem to "measure" the same. The class of operation is generally AB,
although I have occasionally seen class H. Are they "voiced" a certain
way. Do the requirements for high power, efficiency, and bullit proof
reliability compromise neutral sound?

They produce a sound just as neutral as any other amplifier, and they
really have only one downside in the domestic environment. Because
they are 'pro-audio' units, size is a definite factor in the design
process, so most of them are compact units for their power, and use
forced air cooling over heatsinks that would otherwise be much too
small. If you can place your amps somewhere that fan noise won't be an
issue, then you're all set!
--

Stewart Pinkerton | Music is Art - Audio is Engineering

A lot of them do sound terrible by comparison. The QSC however is a
better sounding pro amp than most, but as you see, even the better pro
units are more expensive than the other pro amps. Bryston is also used
extensively in professional applications. There is really no way
around quality costing a bit more, but you will get that returned in
sound quality. Most "DJ" amps are designed to provide cheap power,
where loud is the biggest factor and cost the second as most users are
either kids or notoriously cheap restaurants/bars. Better
installations include better amps and speakers and of course get
better sound. Cheap can still be loud, so there is quite a market for
that sort of stuff. I would re-evaluate your "need" for 250+ watts. In
a nice power amp, that is a huge amount of power and only required for
speakers under 88db/w/m in very large rooms. You may be surprised to
learn that only 20wpc can produce some very loud sound from most
modern speakers. A lot of amps are overated in terms of power output
as they do not reference that to noise or frequency. You have to take
all of that into account and the best way to go about it is just to
listen to them for yourself. The paperwork can appear quite impressive
for some of the most marginal gear available.
-Bill
www.uptownaudio.com
Roanoke VA
(540) 343-1250

"Robert C. Lang" wrote in message
...
I have been considering ways to reduce costs in meeting my
requirements for 5 channels of amplifications. Because I require
about
250 watts a channel into 8 ohms for all 5 channels with loads
occasionally falling to 3 ohms it is pretty expensive to find an amp
that meets those requirements. I only know of two that do.

In a side bar email exchange Norm Strong made an interesting
suggestion that I consider amps made by QSC. It was just a
suggestion,
Norm has no first hand experience with these amps. Many of these
amps
seem pretty cheap when compared to name brand "high-end", even lower
high end amps.

Question. Are there any technical reasons why a "DJ" amp such as
those
marketed by QSC, Numark, Crown and others don't produce high
fidelity
sound on the par with Adcom, Bryston, Theta Digital, etc., etc. They
seem to "measure" the same. The class of operation is generally AB,
although I have occasionally seen class H. Are they "voiced" a
certain
way. Do the requirements for high power, efficiency, and bullit
proof
reliability compromise neutral sound?

"Stewart Pinkerton" wrote in message
...
They produce a sound just as neutral as any other amplifier, and they
really have only one downside in the domestic environment. Because
they are 'pro-audio' units, size is a definite factor in the design
process, so most of them are compact units for their power, and use
forced air cooling over heatsinks that would otherwise be much too small.
If you can place your amps somewhere that fan noise won't be an
issue, then you're all set!
--

Stewart Pinkerton | Music is Art - Audio is Engineering


Fan noise is less intrusive if you use a pro-amplifier with variable fan
speed control, where fan speed is automatically varied according to heatsink
temperature. The Yamaha P4500 (620W per channel into 4 ohms) has a low &
quiet fan speed set for 50 deg C increasing speed proportionally with heat
sink temperature to a max speed at 70 deg C. I'd expect the fan noise to be
generally unobtrusive in domestic use using a pro-amplifier like this unless
you are driving the amp hard into sub 4 ohm loads.
(I've heard recently of the new danger of standing too close to very loud
speakers may cause lung collapse).

Mike Gilmour

Stewart Pinkerton wrote in message ...
On 4 Sep 2004 21:08:42 GMT,

They produce a sound just as neutral as any other amplifier, and they
really have only one downside in the domestic environment. Because
they are 'pro-audio' units, size is a definite factor in the design
process, so most of them are compact units for their power, and use
forced air cooling over heatsinks that would otherwise be much too
small. If you can place your amps somewhere that fan noise won't be an
issue, then you're all set!

Oh yeah, I remember those. Many years ago I owned a behemoth SAE 2500
amplifier as well as a Phase Linear 500. They both (the Phase Linear
for sure) had fans that caused me to move my electronics to a closet.
When I moved I didn't have the luxury of having the electronics in a
different room. The fan drove me crazy. I sold the SAE to a friend
(who, by the way says the amp is still going strong). I sit fairly
close to my amp so a fan, even a quiet fan would be a big minus.

Robert C. Lang

Uptown Audio wrote in message ...
A lot of them do sound terrible by comparison. The QSC however is a
better sounding pro amp than most, but as you see, even the better pro
units are more expensive than the other pro amps.

Yeah. I have the last Audio Annual Equipment Directory from October
1999. Even back then QSC list prices were fairly expensive, including
amps, albeit very high powered ones, in the $6000 to $7000 range. Most
of them were in the $2000 range back then.

I would re-evaluate your "need" for 250+ watts. In
a nice power amp, that is a huge amount of power and only required for
speakers under 88db/w/m in very large rooms. You may be surprised to
learn that only 20wpc can produce some very loud sound from most
modern speakers.

Over the past 10+ years I have owned 3 generations of my current
speaker, the Nestorovic System 16A. I have used them with several
amps. You are correct. Not a huge amount of power is required to make
them perform adequately. I first used an Electron Kenetics Eagle 2A
with 120 watts, followed by a 200 watt Bedini 803, then a 400 watt
Eagle 400 and currently a 300 watt Musical Fidelity Nuvista 300. The
Bedini at 200 watts sounded pretty good. But the Nuvista is a much
better match. At most sound levels there is not much to distinguish
the two amps. But at climaxes of large orchestral and organ works the
Nuvista clearly shows its superiority in my system due, I believe, to
the extra power and head room. The 400 watt Eagle 400 also out
performed the Bedini in these situations.

The manufacturer says a minimum of 50 watts can be used for adequate
performance, but that 200 watts is strongly recommended for moderate
sized rooms. My room at 30x 24.5x 10 (in excess of 7000 cubic feet)
requires a bit more. Like I said the Nuvista has proven to be an ideal
match. The system is safe with amps of about 650+ watts.

But among multi-channel amplifiers there seem to be ample choices to
about 125 watts per channel. Then it gets slim with almost nothing
between 125 and 200 watts. I have found two 5 channel amps in the 200
watt range, the B&K Reference.5, an amp in Anthem MCA line, and the
Theta Digital Dreadnaught 11. All three amps, aside from being on the
low end of the power scale, are otherwise not acceptable for my
system. The B&K and Anthem MCA suffer a power reduction when all 5
channels are driven simultaneously. While this is anticipated in their
designs, I consider this to be a design weakness. The Dreadnaught, in
addition to being much more expensive then the competition has an
input sensitivity of a whopping 2.8 volts. This is unacceptable for a
system centered around a passive line stage. So among multi-channel
amps, the acceptable ones I have found are the Bryston 6B SST and the
Anthem Statement P5. They are both in the magical (for my system) 300
watt per channel range, measurably more than the B&K and Theta Digital
and they are $2000+ cheaper.

So that brings me to "DJ" amps in one last attempt to potentially save
costs.

Robert C. lang


-Bill
www.uptownaudio.com
Roanoke VA
(540) 343-1250

"Robert C. Lang" wrote in message
...
I have been considering ways to reduce costs in meeting my
requirements for 5 channels of amplifications. Because I require
about
250 watts a channel into 8 ohms for all 5 channels with loads
occasionally falling to 3 ohms it is pretty expensive to find an amp
that meets those requirements. I only know of two that do.

In a side bar email exchange Norm Strong made an interesting
suggestion that I consider amps made by QSC. It was just a
suggestion,
Norm has no first hand experience with these amps. Many of these
amps
seem pretty cheap when compared to name brand "high-end", even lower
high end amps.

Question. Are there any technical reasons why a "DJ" amp such as
those
marketed by QSC, Numark, Crown and others don't produce high
fidelity
sound on the par with Adcom, Bryston, Theta Digital, etc., etc. They
seem to "measure" the same. The class of operation is generally AB,
although I have occasionally seen class H. Are they "voiced" a
certain
way. Do the requirements for high power, efficiency, and bullit
proof
reliability compromise neutral sound?

"Robert C. Lang" wrote in message
...
Uptown Audio wrote in message
...
A lot of them do sound terrible by comparison. The QSC however is a
better sounding pro amp than most, but as you see, even the better pro
units are more expensive than the other pro amps.

Yeah. I have the last Audio Annual Equipment Directory from October
1999. Even back then QSC list prices were fairly expensive, including
amps, albeit very high powered ones, in the $6000 to $7000 range. Most
of them were in the $2000 range back then.

I would re-evaluate your "need" for 250+ watts. In
a nice power amp, that is a huge amount of power and only required for
speakers under 88db/w/m in very large rooms. You may be surprised to
learn that only 20wpc can produce some very loud sound from most
modern speakers.

Over the past 10+ years I have owned 3 generations of my current
speaker, the Nestorovic System 16A. I have used them with several
amps. You are correct. Not a huge amount of power is required to make
them perform adequately. I first used an Electron Kenetics Eagle 2A
with 120 watts, followed by a 200 watt Bedini 803, then a 400 watt
Eagle 400 and currently a 300 watt Musical Fidelity Nuvista 300. The
Bedini at 200 watts sounded pretty good. But the Nuvista is a much
better match. At most sound levels there is not much to distinguish
the two amps. But at climaxes of large orchestral and organ works the
Nuvista clearly shows its superiority in my system due, I believe, to
the extra power and head room. The 400 watt Eagle 400 also out
performed the Bedini in these situations.

The manufacturer says a minimum of 50 watts can be used for adequate
performance, but that 200 watts is strongly recommended for moderate
sized rooms. My room at 30x 24.5x 10 (in excess of 7000 cubic feet)
requires a bit more. Like I said the Nuvista has proven to be an ideal
match. The system is safe with amps of about 650+ watts.

But among multi-channel amplifiers there seem to be ample choices to
about 125 watts per channel. Then it gets slim with almost nothing
between 125 and 200 watts. I have found two 5 channel amps in the 200
watt range, the B&K Reference.5, an amp in Anthem MCA line, and the
Theta Digital Dreadnaught 11. All three amps, aside from being on the
low end of the power scale, are otherwise not acceptable for my
system. The B&K and Anthem MCA suffer a power reduction when all 5
channels are driven simultaneously. While this is anticipated in their
designs, I consider this to be a design weakness. The Dreadnaught, in
addition to being much more expensive then the competition has an
input sensitivity of a whopping 2.8 volts. This is unacceptable for a
system centered around a passive line stage. So among multi-channel
amps, the acceptable ones I have found are the Bryston 6B SST and the
Anthem Statement P5. They are both in the magical (for my system) 300
watt per channel range, measurably more than the B&K and Theta Digital
and they are $2000+ cheaper.

So that brings me to "DJ" amps in one last attempt to potentially save
costs.

Robert C. lang

Have you looked at the 200 watt per channel amp from Outlaw?

"Robert C. Lang" wrote in message
...
Uptown Audio wrote in message

But among multi-channel amplifiers there seem to be ample choices to
about 125 watts per channel. Then it gets slim with almost nothing
between 125 and 200 watts. I have found two 5 channel amps in the
200
watt range, the B&K Reference.5, an amp in Anthem MCA line, and the
Theta Digital Dreadnaught 11. All three amps, aside from being on
the
low end of the power scale, are otherwise not acceptable for my
system. The B&K and Anthem MCA suffer a power reduction when all 5
channels are driven simultaneously. While this is anticipated in
their
designs, I consider this to be a design weakness. The Dreadnaught,
in
addition to being much more expensive then the competition has an
input sensitivity of a whopping 2.8 volts. This is unacceptable for
a
system centered around a passive line stage. So among multi-channel
amps, the acceptable ones I have found are the Bryston 6B SST and
the
Anthem Statement P5. They are both in the magical (for my system)
300
watt per channel range, measurably more than the B&K and Theta
Digital
and they are $2000+ cheaper.

So that brings me to "DJ" amps in one last attempt to potentially
save
costs.

If you're down to the last desperate attempt to save money, I'd first
consider not requiring your 5 channels to put out their maximum power
simultaneously. The chance of this happening in practice is
negligible, and the amount of money that can be saved by using a
smaller power supply is considerable. Grit your teeth and accept
this "design weakness."

Norm

"Robert C. Lang" wrote in message
...
I have been considering ways to reduce costs in meeting my
requirements for 5 channels of amplifications. Because I require about
250 watts a channel into 8 ohms for all 5 channels with loads
occasionally falling to 3 ohms it is pretty expensive to find an amp
that meets those requirements. I only know of two that do.

In a side bar email exchange Norm Strong made an interesting
suggestion that I consider amps made by QSC. It was just a suggestion,
Norm has no first hand experience with these amps. Many of these amps
seem pretty cheap when compared to name brand "high-end", even lower
high end amps.

Question. Are there any technical reasons why a "DJ" amp such as those
marketed by QSC, Numark, Crown and others don't produce high fidelity
sound on the par with Adcom, Bryston, Theta Digital, etc., etc. They
seem to "measure" the same. The class of operation is generally AB,
although I have occasionally seen class H. Are they "voiced" a certain
way. Do the requirements for high power, efficiency, and bullit proof
reliability compromise neutral sound?

I've heard QSC amps and they sound like other solid state amps, IOW they
have no sound of their own. They make models with fan cooling and without.

To meet your need you could get some stereo amps that are bridgeable and run
them as monoblocks, which triples the power output. As an example
http://www.overstock.com/cgi-bin/d2....PROD_ID=822794

Check around some pro audio sources and see what's available.

They don't pay the kind of advertising rates that high end stuff has deal
with so they can sell for less.

(Robert C. Lang) wrote in message ...

Question. Are there any technical reasons why a "DJ" amp such as those
marketed by QSC, Numark, Crown and others don't produce high fidelity
sound on the par with Adcom, Bryston, Theta Digital, etc., etc. They
seem to "measure" the same. The class of operation is generally AB,
although I have occasionally seen class H. Are they "voiced" a certain
way. Do the requirements for high power, efficiency, and bullit proof
reliability compromise neutral sound?

In my view, a DJ amp should sound just fine -- they are typically
faithful to their specs -- the "wire with gain" ideal. As others have
noted, fan noise would be an annoyance. Variable speed fan is a good
idea.

A lot of these amps have built-in compressor limiter, which may or may
not be what you want for hi-fi, but you can usually disable it. One
nice thing about these products is that they are sold by mainstream
dealers -- it should be easy to return something you don't like, or
even sell it quickly on eBay.

Check out two vendors: www.musiciansfriend.com and www.wwandbw.com

For a non-mobile application, you might actually be able to get away
with the less expensive (hence probably less rugged) brands such as
Nady. But these hardly qualify for discussion on a "high end"
newsgroup ;-) Nonetheless it is useful to discuss systems that combine
elements from various ends: Low, high, sound reinforcement, and so
forth, in pursuit of superb sound.

"normanstrong" wrote in message ...
"Robert C. Lang" wrote in message
...
Uptown Audio wrote in message

But among multi-channel amplifiers there seem to be ample choices to
about 125 watts per channel. Then it gets slim with almost nothing
between 125 and 200 watts. I have found two 5 channel amps in the
200
watt range, the B&K Reference.5, an amp in Anthem MCA line, and the
Theta Digital Dreadnaught 11. All three amps, aside from being on
the
low end of the power scale, are otherwise not acceptable for my
system. The B&K and Anthem MCA suffer a power reduction when all 5
channels are driven simultaneously. While this is anticipated in
their
designs, I consider this to be a design weakness. The Dreadnaught,
in
addition to being much more expensive then the competition has an
input sensitivity of a whopping 2.8 volts. This is unacceptable for
a
system centered around a passive line stage. So among multi-channel
amps, the acceptable ones I have found are the Bryston 6B SST and
the
Anthem Statement P5. They are both in the magical (for my system)
300
watt per channel range, measurably more than the B&K and Theta
Digital
and they are $2000+ cheaper.

So that brings me to "DJ" amps in one last attempt to potentially
save
costs.

If you're down to the last desperate attempt to save money, I'd first
consider not requiring your 5 channels to put out their maximum power
simultaneously. The chance of this happening in practice is
negligible, and the amount of money that can be saved by using a
smaller power supply is considerable. Grit your teeth and accept
this "design weakness."

Norm

It's better characterized as a good faith effort to save money on
amplification and still meet the *demonstrated* minimum power
requirements for my system. It may be a final attempt but it is no
where close to being desperate. Talk about griting your teeth, what
would be desperate and foolish (and cost more money in the long run)
is buying an underpowered amp to save a few bucks.

If I meet my minimum power requirements I should *never* reach maximum
power because I estimate my peak needs to fall safely below the amps
clipping level. As I explained since I moved up from a 200 watt amp to
a 300 watt amp (with a 2 db headroom) I have not come close to
clipping as far as I can tell.

True, in a surround system all channels are not called upon equally
with respect to power usage. In SACD multi-channel mixes I understand
the rear channels are at about -3db of the front channels, so
considerably less power is required for the rear channels. But this
power reduction requirement for the rear channels in no way makes,
otherwise competent amps like the B&K or Anthem MCA series, but that
have an acute power reduction when all 5 channels are driven
simultaneously, acceptable for *my* requirements.

Let me explain. With all channels active those amps are not capable of
delivering the full rated power to any single channel that may need
it. On the contrary with all 5 channels being driven *all* channels
are limited, by design, to no more that 80% output no matter how small
the power requirements might be in any of the other channels. So, for
example, with all channels being driven in the Anthem MCA (maximum 225
watts for one channel), even though the rear channels may require only
10 watts the amp is limited to no more than 180 watts to any of the
other channels no matter what the power requirement. Since it is
likely that all 5 channels in a surround system would be active
simultaneously the amp is not really a 225 watt per channel amp; it is
more realistically a 180 watt per channel amp. This falls below the
200 watt per channel *demonstrated* minimum required for my system.

Other the other hand, multi "mono" amps like those from Bryston, or
the Anthem Statement P5 have separate power supplies for each channel
and can deliver up to their rated power to all or any channel if the
need arises.

Also, this makes the amp far more flexible. For example, my main
speakers are bi-amped, both woofers (bass modules) presently have
their own mono amplifier. With the P5 it would be possible to use two
channels each to drive the upper and lower frequencies of the left and
right channel speakers and employ the 5th amplifier channel to drive
the center speaker. In that case you would want (require) the
amplifier to be capable of delivering it rated power when all channels
were being driven.

"Michael McKelvy" wrote in message
To meet your need you could get some stereo amps that are bridgeable and run
them as monoblocks, which triples the power output. As an example
http://www.overstock.com/cgi-bin/d2....PROD_ID=822794

Check around some pro audio sources and see what's available.

They don't pay the kind of advertising rates that high end stuff has deal
with so they can sell for less.


Thanks for the lead. There are defintely some solutions worth checking
out at the site. Bridging stereo amps is also something I considered
and have done in the past. I currently employ a pair to drive my bass
modules.

Robert C. Lang

"Harry Lavo" wrote in message

Have you looked at the 200 watt per channel amp from Outlaw?

Thanks again Harry. I had not considered Outlaw. But I did check out
all the glowing user reviews at audioreview.com as well as the Outlaw
website. This seems to be a well built amp worthy of consideration.

I had mentioned that I previously had a 200 watt amp (like the
Outlaw), the Bedini 803, connected to my system and that it *did*
perform well. About 4 years ago I took the Bedini out and did a 30
trial run with the 300 watt Musical Fidelity Nu Vista 300. Initially,
as far as I could hear, the 10 year (now 14) old Bedini sounded the
same as the Nu Vista (that subsequently got rave reviews from all over
the place). In fact, after a few days I notified Musical Fidelity that
I was sending the Nu Vista back. But it soon became clear that the Nu
Vista was a better match, not because it sounded better; I don't
believe it does. But because it handled the most demanding (loudest)
passages in, for example, Mahler and organ works. I assumed (and still
believe) that it's because the Nuvista has more power not that it
inherently sounds better. I believe because the Bedini was
occasionally asked to operate outside of it power range it did not
compare as well to the NuVista.

But at $1300 for 5 channels at 200 watts (a third or quarter of some
of the other choices) the Outlaw must be considered. I still have the
200 watt Bedini.
I will reconnected it to my main speakers again and make another
determination as to whether it will be adequate. If it works then its
a good bet that the Outlaw would work as well.

Robert C. Lang

"Robert C. Lang" wrote in message
...
"Michael McKelvy" wrote in message
To meet your need you could get some stereo amps that are bridgeable and
run
them as monoblocks, which triples the power output. As an example
http://www.overstock.com/cgi-bin/d2....PROD_ID=822794

Check around some pro audio sources and see what's available.

They don't pay the kind of advertising rates that high end stuff has deal
with so they can sell for less.


Thanks for the lead. There are defintely some solutions worth checking
out at the site. Bridging stereo amps is also something I considered
and have done in the past. I currently employ a pair to drive my bass
modules.

My current subwoofer is driven by a Hypex plate amp I secured through
www.adireaudio .com.

I'm wondering now, since I plan on another DIY sub after the first of the
year, if it might be a better idea to drive it with a full range amp, since
it wouldn't be high passed.

Perhaps Tom or Stewart have some input here. Will a high passed amp keep
one of the Adire woofers from meeting it's full potential?

Leaving the high pass stuff out of the equation, a good bridged amp can
apparently be had for less than one of the plate amps.

Robert C. Lang wrote:


True, in a surround system all channels are not called upon equally
with respect to power usage. In SACD multi-channel mixes I understand
the rear channels are at about -3db of the front channels, so
considerably less power is required for the rear channels. But this
power reduction requirement for the rear channels in no way makes,
otherwise competent amps like the B&K or Anthem MCA series, but that
have an acute power reduction when all 5 channels are driven
simultaneously, acceptable for *my* requirements.

Let me explain. With all channels active those amps are not capable of
delivering the full rated power to any single channel that may need
it. On the contrary with all 5 channels being driven *all* channels
are limited, by design, to no more that 80% output no matter how small
the power requirements might be in any of the other channels. So, for
example, with all channels being driven in the Anthem MCA (maximum 225
watts for one channel), even though the rear channels may require only
10 watts the amp is limited to no more than 180 watts to any of the
other channels no matter what the power requirement. Since it is
likely that all 5 channels in a surround system would be active
simultaneously the amp is not really a 225 watt per channel amp; it is
more realistically a 180 watt per channel amp. This falls below the
200 watt per channel *demonstrated* minimum required for my system.


Often the power output specs are a bit obscure, some reference to 1kHz only,
which gives 10-20% better figures, because the low frequency output is
limited by the size of the smoothing capacitors and transformers. Others
will give the values with one channel only, or with a pulsed load current,
all of which will give erroneous results.
If you look at analog amps (in contrast to digital or PWM amps), the maximum
efficiency is limited to 35 to 49%, with 2/3power having the hardest
thermic impact, because the remainig percents are being dissipated as heat.
If the thermic mass is high, the amp may be able to dissipate around 3 times
more momentary power (but only for a short time measured in seconds), and
that is what is the figure in the data sheet. If the amp is not fan cooled
it simply cannot dissipate the heat continously.

So it is good to observe these two limitations: 1.) the maximum output
current 2.) max heat dissipation ability.
BTW professional amps are also *not* called DJ-amps, they are stated for
continuous RMS output power and have a maximum output current capability.
The power can only be obtained with the proper load resistance, for example
4 ohms. In professional installations we hardly find passive crossovers, but
active ones and multiple amplifiers.
This may differ for HiEnd, as the xovers are often so badly "designed" that
at certain frequencies the impedance can go really low, driving the amp into
current limiting without delivering even 1/4 or 1/10 of the stated power.
Infinity is infamous for that


Other the other hand, multi "mono" amps like those from Bryston, or
the Anthem Statement P5 have separate power supplies for each channel
and can deliver up to their rated power to all or any channel if the
need arises.

Also, this makes the amp far more flexible. For example, my main
speakers are bi-amped, both woofers (bass modules) presently have
their own mono amplifier. With the P5 it would be possible to use two
channels each to drive the upper and lower frequencies of the left and
right channel speakers and employ the 5th amplifier channel to drive
the center speaker. In that case you would want (require) the
amplifier to be capable of delivering it rated power when all channels
were being driven.

As you can see we are not too far from the car HiFi with overstated output
powers or the ghettoblasters with PMPO rating of 800W in a 1/4 shoebox
included speakers!
But "professional amps" do deliver the stated power for infinite time and
for this reason they need fans and heavy mains transformers.
--
ciao Ban
Bordighera, Italy

Hi Robert. I am joining the "conversation" late, so maybe I missed it.
Your room dimensions and speakers that will be driven? Also, what other
equipment do you own? Thanks.
BTW... still using your Amiga? I have my "toasted" Amiga still. Just
can't get rid of it.

TonyP wrote in message ...
Hi Robert. I am joining the "conversation" late, so maybe I missed it.
Your room dimensions and speakers that will be driven? Also, what other
equipment do you own? Thanks.
BTW... still using your Amiga? I have my "toasted" Amiga still. Just
can't get rid of it.


Hi Tony. I retired my Amiga 4000 a couple of years ago. I still have a
2000 in the basement. I use the Toaster 3 editing system for the PC.

A description of my system including room dimensions can be found at:

http://cgi.audioasylum.com/systems/1748.html

Not reflected in the description is my hope to have a surround system
(music emphasis) in place by the end of the year. It has been a real
slow and agonizing process. I'm trying to learn as much as possible
before I get the final pieces. I have all the speakers which match my
mains. Placette Audio is building my multi-channel passive line stage.
I now looking for a 5 channel amp that based on previous experience
should be capable of more than 200 watt but probably closer to 300
watts. My current two channel amp is rated at 300 watts and has proven
to be an excellent match for my mains.

Since most of my listening will continue to be two channel my new amp
must be as capable in the two channel mode as my current amp. It seems
that the performance of most multi-channel amps falter in performance
the more channels that are driven. A few claim the same performance in
when all channels are being driven. But they are huge and more
expensive, although less than 1/2 the cost of comparable mono boxes
from the same manufacturers. I am open to other alternatives but I
would prefer to have a one box solution instead of several amps to
power the surround system.

Robert C. Lang

On 10 Sep 2004 20:21:54 GMT, "Michael McKelvy"
wrote:

"Robert C. Lang" wrote in message
...
"Michael McKelvy" wrote in message
To meet your need you could get some stereo amps that are bridgeable and
run
them as monoblocks, which triples the power output. As an example
http://www.overstock.com/cgi-bin/d2....PROD_ID=822794

Check around some pro audio sources and see what's available.

They don't pay the kind of advertising rates that high end stuff has deal
with so they can sell for less.


Thanks for the lead. There are defintely some solutions worth checking
out at the site. Bridging stereo amps is also something I considered
and have done in the past. I currently employ a pair to drive my bass
modules.

My current subwoofer is driven by a Hypex plate amp I secured through
www.adireaudio .com.

I'm wondering now, since I plan on another DIY sub after the first of the
year, if it might be a better idea to drive it with a full range amp, since
it wouldn't be high passed.

Perhaps Tom or Stewart have some input here. Will a high passed amp keep
one of the Adire woofers from meeting it's full potential?

Since the high pass is at 10Hz, I doubt that this is a problem! It's
all a matter of whether you really want to privde output much below
20Hz. Note that doing this at a reasonable level, i.e. 100dB SPL,
will require *massive* volume displacement. You're talking in terms of
a dozen Shivas or 4 Tempests if you want anything even perceptible at
15 Hz!

Leaving the high pass stuff out of the equation, a good bridged amp can
apparently be had for less than one of the plate amps.

Possibly, but will it be as convenient or as well tailored to driving
a subwoofer? You don't say how your system is configured, but if it's
a sealed enclosure, then the plate amp EQ should be very useful.

--

Stewart Pinkerton | Music is Art - Audio is Engineering

Robert C. Lang wrote:

Hi Tony. I retired my Amiga 4000 a couple of years ago. I still have a
2000 in the basement. I use the Toaster 3 editing system for the PC.

My 2000 is sitting next to me. I turn it on once in a while. Those were
the fun days of video editing. Pioneering days.

A description of my system including room dimensions can be found at:

http://cgi.audioasylum.com/systems/1748.html

Thanks. Very nice system.

Not reflected in the description is my hope to have a surround system
(music emphasis) in place by the end of the year. It has been a real
slow and agonizing process. I'm trying to learn as much as possible
before I get the final pieces. I have all the speakers which match my
mains. Placette Audio is building my multi-channel passive line stage.
I now looking for a 5 channel amp that based on previous experience
should be capable of more than 200 watt but probably closer to 300
watts. My current two channel amp is rated at 300 watts and has proven
to be an excellent match for my mains.

My system is very modest compared to yours. I have had for many years, a
Counterpoint SA220 poweramp. I loved it. It powered my Acoustat 1+1's
faithfully (difficult speakers to drive) to levels that were
uncomfortably loud (for me) in my smallish 20x12x8' room. Then, I
replaced the Acoustats with Von Schweikert VR4's. Easier load to drive,
and better sounding in a lot of areas than the Acoustats. One of the
channels went out, so I took it to my high repairman. He said about
3weeks. Not wanting to be without music, I searched Audigon for a "used"
piece of something to listen to while the Counterpoint was being
repaired. I picked up a Parasound HCA 2200 Mk II. A very favorably
reviewed amp by the press. I listened to it. It sounded "different". The
more I listened the more I heard from the music. I got the Counterpoint
back (all biased, spec'ed and shiny), listened for a week. Went back to
the Parasound, and, kept it in the system. The Counterpoint has been
replaced. I say all this to point you to this link....
http://www.parasound.com/halonew/A51details.asp
Specs look great. They might even come close to what you are looking for.

As for price..... http://tinyurl.com/3r4rn

The Halo's have gotten excellent reviews. And if they are an
"improvement" over the Parasound that I have (once considered John
Curl's best ever), I don't see how you can go wrong.

Happy listening!

On Sat, 04 Sep 2004 21:08:42 +0000, Robert C. Lang wrote:

I have been considering ways to reduce costs in meeting my
requirements for 5 channels of amplifications. Because I require about
250 watts a channel into 8 ohms for all 5 channels with loads
occasionally falling to 3 ohms it is pretty expensive to find an amp
that meets those requirements. I only know of two that do.

In a side bar email exchange Norm Strong made an interesting
suggestion that I consider amps made by QSC. It was just a suggestion,
Norm has no first hand experience with these amps. Many of these amps
seem pretty cheap when compared to name brand "high-end", even lower
high end amps.

Question. Are there any technical reasons why a "DJ" amp such as those
marketed by QSC, Numark, Crown and others don't produce high fidelity
sound on the par with Adcom, Bryston, Theta Digital, etc., etc. They
seem to "measure" the same. The class of operation is generally AB,
although I have occasionally seen class H. Are they "voiced" a certain
way. Do the requirements for high power, efficiency, and bullit proof
reliability compromise neutral sound?

This is the route I decided to go, as I am a blue collar guy who simply
cannot afford spending multiple thousands of dollars on an amplifier.
I purchased three of the QSC RMX 850 amps from a local Guitar Center for
the princely sum of $870, and they threw in the 1/4" to RCA interconnects.
Specs are available on the QSC website, and they came with a six year
warranty, which I promptly voided...the amps are cooled with a 24 volt
80mm fan, and they are really obnoxiously loud. I replaced them with
Panaflo low speed fans, which is an immense improvement. They are barely
audible with the mute on, and are not audible at all with music playing.

I am not able to hear any significant difference between these amps and
a high end multi-channel amp, and neither could a friend who brought over
his Krell Theater Standard amp to do an A/B comparison. I'm sure that the
"golden ear" audiophile would be able to nitpick the QSC's to death, but I
am extremely happy with these amps, and would recommend them to anyone on
a budget.

Related link: http://www.qscaudio.com/products/amps/rmx/rmx.htm

feroce

"Michael McKelvy" wrote:

"Robert C. Lang" wrote in message
...
"Michael McKelvy" wrote in message
To meet your need you could get some stereo amps that are bridgeable and
run
them as monoblocks, which triples the power output. As an example
http://www.overstock.com/cgi-bin/d2....PROD_ID=822794

Check around some pro audio sources and see what's available.

They don't pay the kind of advertising rates that high end stuff has deal
with so they can sell for less.


Thanks for the lead. There are defintely some solutions worth checking
out at the site. Bridging stereo amps is also something I considered
and have done in the past. I currently employ a pair to drive my bass
modules.

My current subwoofer is driven by a Hypex plate amp I secured through
www.adireaudio .com.

I'm wondering now, since I plan on another DIY sub after the first of the
year, if it might be a better idea to drive it with a full range amp, since
it wouldn't be high passed.

Perhaps Tom or Stewart have some input here. Will a high passed amp keep
one of the Adire woofers from meeting it's full potential?

Leaving the high pass stuff out of the equation, a good bridged amp can
apparently be had for less than one of the plate amps.

Practially every competent ampliifer has a built-in high pass function. My
Crown Macro-Tech 5000VZ has a -3 dB specification of 6 Hz. Most of the larger
power amplifiers have a similar specification which is perfectly in alignment
with modern recordings.

The hi-pass function should be aligned with the displacement capability of the
subwoofer driver/amp system. With a vented system its practically required to
high-pass the system below system resonance. With another system
sealed/infinite baffle its a good idea to high-pass the "system" at the point
where the "system" runs out of displacement (typically a function of the
drivers' linear capability.)

For example my current system is effectively "high-passed" by the amplifier at
6 Hz because the cab/driver system has a displacement the equivalent of 5 small
block chevy gasoline engines (8 15" TC Sounds woofers) and will produce 120 dB
@ 2 meters 10% THD so the normal amplifer function high-passes the system
without a separate filter.

My suggestion is that you measure/listen to your system and use a high-pass
filter that keeps distortion/noise in check according to the programs you
employ and in alignment with the driver/amp displacement capability.

"Robert C. Lang" wrote in message
...
"Harry Lavo" wrote in message

Have you looked at the 200 watt per channel amp from Outlaw?

Thanks again Harry. I had not considered Outlaw. But I did check out
all the glowing user reviews at audioreview.com as well as the Outlaw
website. This seems to be a well built amp worthy of consideration.

I had mentioned that I previously had a 200 watt amp (like the
Outlaw), the Bedini 803, connected to my system and that it *did*
perform well. About 4 years ago I took the Bedini out and did a 30
trial run with the 300 watt Musical Fidelity Nu Vista 300. Initially,
as far as I could hear, the 10 year (now 14) old Bedini sounded the
same as the Nu Vista (that subsequently got rave reviews from all over
the place). In fact, after a few days I notified Musical Fidelity that
I was sending the Nu Vista back. But it soon became clear that the Nu
Vista was a better match, not because it sounded better; I don't
believe it does. But because it handled the most demanding (loudest)
passages in, for example, Mahler and organ works. I assumed (and still
believe) that it's because the Nuvista has more power not that it
inherently sounds better. I believe because the Bedini was
occasionally asked to operate outside of it power range it did not
compare as well to the NuVista.

But at $1300 for 5 channels at 200 watts (a third or quarter of some
of the other choices) the Outlaw must be considered. I still have the
200 watt Bedini.
I will reconnected it to my main speakers again and make another
determination as to whether it will be adequate. If it works then its
a good bet that the Outlaw would work as well.

Robert C. Lang

I think you are on the right track. Two points:

*If you can use your Bedini's for the rear channel, and your speakers are
biampable, you might be able to use the five channel as two biamp channels
and a single amp center.

* Even if using just five 200wpc amps, keep in mind that acoustic power in
the room (particularly in the bass) is raised substantially by five full
range speakers and you don't necessarily need as much power in the front
channels as when trying to achieve the same sound level via two speakers.

"Harry Lavo" wrote in message ...
"Robert C. Lang" wrote in message

But at $1300 for 5 channels at 200 watts (a third or quarter of some
of the other choices) the Outlaw must be considered. I still have the
200 watt Bedini.
I will reconnected it to my main speakers again and make another
determination as to whether it will be adequate. If it works then its
a good bet that the Outlaw would work as well.

Robert C. Lang

I think you are on the right track. Two points:

*If you can use your Bedini's for the rear channel, and your speakers are
biampable, you might be able to use the five channel as two biamp channels
and a single amp center.

Absolutely, that is one of the ways that I have considered using the
resources. I could use the Bedini in the rear (I would have to wrestle
it away from my son who is using it for strictly low fi applications).
Or I could use the The Electron Kenetics Eagle 400 monos in the rear
and sale the Nuvista to defray costs. (It is not unusual for me to get
inquiries about the Nuvista; it may be fairly easy to sell).

* Even if using just five 200wpc amps, keep in mind that acoustic power in
the room (particularly in the bass) is raised substantially by five full
range speakers and you don't necessarily need as much power in the front
channels as when trying to achieve the same sound level via two speakers.

I have definitely considered that. BUT one of my *main* objectives in
this entire process is to ensure that my two-channel listening
experience is not compromised or minimally so. That is why it is
critical that my L+R speakers have on tap all the juice they need to
handle the two-channel workload as before.


Robert C. Lang