What does specification mean?
 

In the specifications of my AV Amp it says the following.

90 W + 90 W (8 ohms, 20 Hz - 20 kHz, 0.08 % THD)

125 W + 125 W (6 ohms, 1 kHz, 0.7 % THD)


What does the 1kHz bit mean? I'm assuming that it means the measurement has
been taken at 1kHz, is this correct?

thanks

Gav

What does specification mean?
 

Gav wrote:

125 W + 125 W (6 ohms, 1 kHz, 0.7 % THD)

What does the 1kHz bit mean? I'm assuming that it means the measurement has
been taken at 1kHz, is this correct?

Yes.

--
Mark.
http://tranchant.plus.com/

What does specification mean?
 

HI Mark,
I agree... it means the test to obtain 125 W was performed with a signal
of 1000Hz.

regards,
Tony

"Mark Tranchant" wrote in message
...
Gav wrote:

125 W + 125 W (6 ohms, 1 kHz, 0.7 % THD)

What does the 1kHz bit mean? I'm assuming that it means the measurement
has
been taken at 1kHz, is this correct?

Yes.

--
Mark.
http://tranchant.plus.com/

What does specification mean?
 

On Mon, 9 Jan 2006 11:31:59 -0000, "Gav"
wrote:

In the specifications of my AV Amp it says the following.

90 W + 90 W (8 ohms, 20 Hz - 20 kHz, 0.08 % THD)

125 W + 125 W (6 ohms, 1 kHz, 0.7 % THD)


What does the 1kHz bit mean? I'm assuming that it means the measurement has
been taken at 1kHz, is this correct?

Yes, and that spec also means that the amp will be well down on power
into 4 ohms, i.e. into many good-quality modern speakers, as it's
obviously been optimised for a 6-ohm load.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

What does specification mean?
 

How can you tell that the power will be low into 4 ohms? I don't know much
about this subject, but I would have thought that if you get 90W into 8
ohms, 125W into 6 ohms, then reducing the impedence further to 4 ohms would
have meant the power would go up again- not fall. How does this work?

What does specification mean?
 

In message , Martin
Hardy writes
How can you tell that the power will be low into 4 ohms? I don't know much
about this subject, but I would have thought that if you get 90W into 8
ohms, 125W into 6 ohms, then reducing the impedence further to 4 ohms would
have meant the power would go up again- not fall. How does this work?



Usually because the PSU or the output transistors have run out of
current capacity when feeding low impedances.

I'm not sure there's that many speaker (except car ones) that are really
4 Ohm over the whole frequency range though. Certainly there's a lot of
speakers that don't have impedance compensation on the drive units and
so they have some very reactive regions in the input impedance to the
crossover where the Z does fall to this level (or even below) for
certain frequency ranges.
--
Chris Morriss

What does specification mean?
 

There are plenty of nominally 4 ohm 'speakers around, which means that under
IEC rating, the impedance can go down to 3.2 ohms. You may recall the KEF
104.2 which was 4 ohms almost exactly at all frequencies, the Linn Isobarics
were 4 ohms, and several European 'speakers are 4 ohm rated.

The specification of 90w into 8 ohms, 125W into 6 ohms actually seems
inconsistent in that into 8 ohms, the amp will generate a voltage of 26.8v
rms, whilst into 6 ohms it will generate a voltage of 27.4v. Normally, the
voltage generated into lower impedance loads is equal to or lower than into
a higher load. If the specs are true, then that implies a negative output
impedance, not normally found on modern amplifiers, although was once used
by Pye amongst others in the valve era.

S.









"Chris Morriss" wrote in message
...
In message , Martin
Hardy writes
How can you tell that the power will be low into 4 ohms? I don't know much
about this subject, but I would have thought that if you get 90W into 8
ohms, 125W into 6 ohms, then reducing the impedence further to 4 ohms
would
have meant the power would go up again- not fall. How does this work?



Usually because the PSU or the output transistors have run out of current
capacity when feeding low impedances.

I'm not sure there's that many speaker (except car ones) that are really 4
Ohm over the whole frequency range though. Certainly there's a lot of
speakers that don't have impedance compensation on the drive units and so
they have some very reactive regions in the input impedance to the
crossover where the Z does fall to this level (or even below) for certain
frequency ranges.
--
Chris Morriss

What does specification mean?
 

On Mon, 09 Jan 2006 19:45:24 GMT, "Martin Hardy"
wrote:

How can you tell that the power will be low into 4 ohms? I don't know much
about this subject, but I would have thought that if you get 90W into 8
ohms, 125W into 6 ohms, then reducing the impedence further to 4 ohms would
have meant the power would go up again- not fall. How does this work?


If you look at the two sets of figures, even for the modest power rise
into 6 ohms, they had to accept a hugely increased distortion figure.
That effectively means that the amplifier has already gone past its
comfort zone at 6 ohms so 4 would be asking too much.

d

Pearce Consulting
http://www.pearce.uk.com

What does specification mean?
 

Yes, I missed the distortion spec, that would certainly account for the
apparantly higher voltage into 6 ohms. Odd way of quoting a spec though.
It does mean however, that the presumption that the amplifier is running out
of current into 6 ohms may not be the case.

S.


"Don Pearce" wrote in message
...
On Mon, 09 Jan 2006 19:45:24 GMT, "Martin Hardy"
wrote:

How can you tell that the power will be low into 4 ohms? I don't know much
about this subject, but I would have thought that if you get 90W into 8
ohms, 125W into 6 ohms, then reducing the impedence further to 4 ohms
would
have meant the power would go up again- not fall. How does this work?


If you look at the two sets of figures, even for the modest power rise
into 6 ohms, they had to accept a hugely increased distortion figure.
That effectively means that the amplifier has already gone past its
comfort zone at 6 ohms so 4 would be asking too much.

d

Pearce Consulting
http://www.pearce.uk.com

What does specification mean?
 

"Martin Hardy" wrote in message
.uk...
How can you tell that the power will be low into 4 ohms?

**He cannot. He is, howeaver, making an educated guess, based on available
data.

I don't know much
about this subject, but I would have thought that if you get 90W into 8
ohms, 125W into 6 ohms, then reducing the impedence further to 4 ohms
would have meant the power would go up again- not fall.

**In the best of all possible worlds, that is true. In reality, this may not
be the case.

How does this work?

**It's about Dollars (Squid), power supplies and output stages.


--
Trevor Wilson
www.rageaudio.com.au

What does specification mean?
 

On Mon, 09 Jan 2006 19:45:24 GMT, "Martin Hardy"
wrote:

How can you tell that the power will be low into 4 ohms? I don't know much
about this subject, but I would have thought that if you get 90W into 8
ohms, 125W into 6 ohms, then reducing the impedence further to 4 ohms would
have meant the power would go up again- not fall. How does this work?

Power is a factor of voltage and current. An amplifier with zero
open-loop output impedance and infinite current capability will
maintain full voltage into any load, i.e. it will double power input
as the load impedance is halved.

This amplifier can deliver 26.8V rms into an 8 ohm load at low
distortion, requiring 3.35A. It can deliver 30V rms into 6 ohms at
just below clipping, requiring 5A. We can therefore take it that 5A is
the maximum available current. Into 4 ohms, this gives 100 watts,
which is less than 125.

In other words, the voltage at clipping into a 4 ohm load is 20 volts,
the equivalent of 50 watts into 8 ohms.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

What does specification mean?
 

Gav wrote:
In the specifications of my AV Amp it says the following.

90 W + 90 W (8 ohms, 20 Hz - 20 kHz, 0.08 % THD)

125 W + 125 W (6 ohms, 1 kHz, 0.7 % THD)


What does the 1kHz bit mean? I'm assuming that it means the measurement has
been taken at 1kHz, is this correct?

thanks

Gav



Don't worry about specifications, mate. Just be comfortable with the
knowledge that if you would set up an abx or a dbt with your AV amp and
the most expensive and powerfull krell, for instance, your amp would
just sound the same. Level match, bias adjust the suckers, fast switch
between them, a or b , or X and wham! all the sound the same! Now you
can sit back, switch on your favorite sine wave and be smug and
comfortable with the scientific knowledge that the guy that paid 4000
bucks to the plinius amp is listening to exactly the same sound as you,
if he would listen to sine waves that is... At any rate, happy listening! :)

What does specification mean?
 

Your jocular post ignores the fact that we *do* only listen to sine waves.
All music is composed of sinewaves at different frequencies, amplitudes and
phases. Therefore, the sine-wave behaviour of an amplifier defines what it
will do on music, which is a band-limited signal.

Square-wave or impulse testing with signal bandwidths in excess of the audio
band serve to indicate how well the amplifier handles these signals, and
therefore, if out-of-band signals are handled correctly, there should be no
problems in-band.

It is not sufficient just to gain-match the AV amp and the Krell reference,
if no account is taken of the load being driven or the maximum power
required. If the AV amp runs out of current because of an excessively severe
load, or the amplifier is allowed to clip, then of course the Krell or
whatever will sound better. However, if the gains are matched, both
amplifiers are operated withing their clipping capability and the load is
within their current capabilities, then you are right, they will sound the
same. This of course assumes that both have flat audio responses and low
distortion. What this says to me, and I think to most engineers, is that if
the amplifiers measure the same and are operated within their design
parameters, then they will sound the same.



S.






"Forwarder" wrote in message
...
Gav wrote:
In the specifications of my AV Amp it says the following.

90 W + 90 W (8 ohms, 20 Hz - 20 kHz, 0.08 % THD)

125 W + 125 W (6 ohms, 1 kHz, 0.7 % THD)


What does the 1kHz bit mean? I'm assuming that it means the measurement
has been taken at 1kHz, is this correct?

thanks

Gav



Don't worry about specifications, mate. Just be comfortable with the
knowledge that if you would set up an abx or a dbt with your AV amp and
the most expensive and powerfull krell, for instance, your amp would just
sound the same. Level match, bias adjust the suckers, fast switch between
them, a or b , or X and wham! all the sound the same! Now you can sit
back, switch on your favorite sine wave and be smug and comfortable with
the scientific knowledge that the guy that paid 4000 bucks to the plinius
amp is listening to exactly the same sound as you, if he would listen to
sine waves that is... At any rate, happy listening! :)

What does specification mean?
 

Serge Auckland wrote:

Your jocular post ignores the fact that we *do* only listen to sine waves.

Don't top post, please.

All music is composed of sinewaves at different frequencies, amplitudes and
phases.

I'll go tell that to Ibrahim Ferrer. Oh wait, .. nevermind.


Therefore, the sine-wave behaviour of an amplifier defines what it
will do on music, which is a band-limited signal.

Ok, sure, no contest. :)

if the gains are matched, both
amplifiers are operated withing their clipping capability and the load is
within their current capabilities, then you are right, they will sound the
same.


Ok so no problems here also, that's exactly what I was saying. I know
because I tried. I put up an av amp, some cheap 250 euro yamaha in
stereo mode against a densen beat b 100 integrated, on it's own an
elegant sounding machine, but that's because you are not supposed to see
it when it is performing, or know that it is *it* that is performing. At
any rate, we went to a lab, hooked both up, put level matching and abx
gear connected to a pc in between, adjusted the volume level that was
comfortable for both (the yamaha is rated 90 watts into 8 ohms, while
the densen is 60) and they sounded almost exactly the same. ALmost so
that it was almost impossible to "reliably" tell which was which when
"x" was at it. In fact, the same lab had as "reference" an accuphase
unit. And the yamaha managed to sound the same with that also.

I was in shock and disbelief! :) And I started mumbling audiophool mumbo
jumbo as "soundstage" and "tight bass", etc.. :)

So I *continued* the test, being an audiophool, by employing the yamaha,
over a longer period of time as my main amp for listening to music,
driving my sonus faber speakers. The result of *that* test was that I
stopped listening to music after about two weeks, since the sound of the
natural and metallic yamaha started bugging me after about 15 minutes of
listening each and every time.

The next pahse should be that I will acquire a spare yamaha or a densen,
have the guts of one of the other fit in to it, and not knowing which is
which listen to a "unit" like that, see what happens. :)


if
the amplifiers measure the same and are operated within their design
parameters, then they will sound the same.

Agreed. Just set it up right and even the stereo amp section of one of
those LG home theater in a box appliances will sound the same as a
halcro dm58 monoblock, provided that those slimy audiophool con men
produced monoblocks are up to spec. :)

What does specification mean?
 

very informative everybody- thankyou very much!