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

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/

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/

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

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?

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

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

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

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

"Martin Hardy" wrote in message
news
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