0.9V

The last time I did this was a couple of yrs back - music was Classical with a full-fledged orchestra, Tutti Orcherstal Sampler of Reference Recordings, Track 1 Dance of the Tumblers. At the heaviest cresendos, I was getting readings of 8-9V while soft passages were typically 200-700mV (0.2-0.7V).

Neutral schrieb:

I measured the output voltage of my amplifier when playing classical music and was shocked at the findings. I found the voltage at each terminal was varying between 0.1V and 0.9V only. (I had expected to see a voltage of around 20V at the peak.) It seems that a tiny dry-cell battery produces a higher voltage than a stereo amp All my readings were taken with a borrowed digital multimeter. If anyone has done their own research, please let me know the findings.

music is a time-varying signal. the multimeter cannot measure a varying signal - it was not designed to. Thus, you are reading off the average output signal voltage.
attach an oscilloscope to the output & take a look @ the signal.
see any difference?

Bombaywalla is PERFECTLY correct.

It seems that a tiny dry-cell battery produces a higher voltage than a stereo amp

Nah !

Connect a 1.5Volt Dry Cell Across the speaker terminal ( It WONT Harm the speakers... they can handle WAY more than that ) repeatedly, and check out the sound level from yr speakers

Cheers

P.S: Which Meter are you using ? Is it set to AC Voltage ( Not DC voltage ? Most low cost meters are made for 50 Hz measurements, and their response rolls off rapidly, at higher freqs. Ofcourse the dynamic nature of the music signal is the main cause of the lower reading.

PPS: If you have a Laptop, there are freeware programs that can enable it as an O'scope, signal generator, FFT analyser etc, without the need for any external hardware. Same software can ofcourse be loaded on a desktop, but its impractical to use it around...

Hi ..
please check if the voltage is DC or Ac..
if it is DC then its good that the output is low..
though in actuality the DC output has to be less than 20mV...or 0.02V
A high DC is enough to melt the voice coil and blow ur speakers to hell..
That is waht happpens when amplifiers blow..full DC is deliverd to the load..aka ur speakers..
But since u guys mostly use passive speakers(not to mention commeercial amps with adequate protection) the capacitors in the crossover should prevent the DC from reaching the spekaers and give u enough time to turn it off..

Amp_Nut schrieb:

Bombaywalla is PERFECTLY correct. It seems that a tiny dry-cell battery produces a higher voltage than a stereo amp Nah ! Connect a 1.5Volt Dry Cell Across the speaker terminal ( It WONT Harm the speakers... they can handle WAY more than that ) repeatedly, and check out the sound level from yr speakers

i would advise that u rather not do that..though as i have explained u have proper circuitry for DC protection(relays that turn off when DC is detected above a certain limit) and the caps in series with the drivers..why try it..

as bombaywalla says, use a scope if u want to check the output of the amp.

Hello,

as a rule of thump, the AVERAGE power at normal listening levels is only 0.1 Watt, that's about 1 Volt ac into an 8 Ohms speaker. Only for very short peaks (bass drum beat) an amplifier will send pulses up to 40 Volt ac to the speaker.
You can't measure those short pulses with a digital voltmeter, it reacts much to slow. Better is a (peak reading) VU-meter or an oszilloscope.

Gruß, Helmut

Hm.....the VU meter is not a bad idea.

manek.

I used the AC voltage function of a digital multimeter. Those who have access to oscilloscopes can post their findings. I don't have access to those equipments. Maybe, as you folks say, the digital multimeter is measuring the average signal rather than the instantaneous signal.

Re making a computer into an oscilloscope, is that done with Cool Edit, sound forge, etc? But how can you tap a voltage from an amp? Wouldn't it be dangerous?

Hello,

But how can you tap a voltage from an amp? Wouldn't it be dangerous?

You won't hurt yourself, but you could easily ruin your amp or speakers. To make measurements that make sense you need a basic electronics background and some equipment like function generator, load resistors,o-scope....
What is your intention anyway?

Helmut

Re making a computer into an oscilloscope, is that done with Cool Edit, sound forge, etc?

There are small software available on the net which will run on a Win platform. It uses the sound card inputs as the O'scope input and the sound card o/p as the Waveform / signal generator outputs.

Hence measurements are restricted to freqs that the sound card will support.

Most of such software is freeware. Google and see.

A laptop ( on battery power ) is a better option to use, since besides the portability, it is not referenced to ground, or worse still to the local mains supply neutral or ( God Forbid) the Mains live.... I have experienced many PCs, where the chasis is live....

ruesselschorf schrieb:

Hello, as a rule of thump, the AVERAGE power at normal listening levels is only 0.1 Watt, that's about 1 Volt ac into an 8 Ohms speaker. Only for very short peaks (bass drum beat) an amplifier will send pulses up to 40 Volt ac to the speaker. You can't measure those short pulses with a digital voltmeter, it reacts much to slow. Better is a (peak reading) VU-meter or an oszilloscope. Gruß, Helmut

Hi Ruesselschorf,
Nice to have you on the English forum too. I guess you're German? What you say ties in with my readings. Average signal strength varying between 0.1 to 0.9V of AC at a speaker avg impedance of 6 ohms.
At peak of avg signal, P= V * V/R = .9 * .9/6

Amp_Nut schrieb:

Re making a computer into an oscilloscope, is that done with Cool Edit, sound forge, etc? There are small software available on the net which will run on a Win platform. It uses the sound card inputs as the O'scope input and the sound card o/p as the Waveform / signal generator outputs. Hence measurements are restricted to freqs that the sound card will support. Most of such software is freeware. Google and see. A laptop ( on battery power ) is a better option to use, since besides the portability, it is not referenced to ground, or worse still to the local mains supply neutral or ( God Forbid) the Mains live.... I have experienced many PCs, where the chasis is live.... :(

Hi Amp Nut,
I will check out the software. I unfortunately never checked my desktop PC for live chassis etc. And now the multimeter is back in the US

I have noticed that software like Win ISD pro have signal generators. I guess they could also be used for testing of room modes at various frequencies. My room should have a peak around 57 Hz (though I never got down to measuring it). It's a 10h x 10b x 12l room.

I unfortunately never checked my desktop PC for live chassis etc. And now the multimeter is back in the US

1. Crudest tester .... Use your finger !

2. You can also use a Mains tester scrwedriver.

3. Incidentally, El Cpeapo Digital Multimeters ( From China ofcourse ! ) are available at Lamington Road, Mumbai for abouit Rs 100.

Amp_Nut schrieb:

I unfortunately never checked my desktop PC for live chassis etc. And now the multimeter is back in the US 1. Crudest tester .... Use your finger ! 2. You can also use a Mains tester scrwedriver. 3. Incidentally, El Cpeapo Digital Multimeters ( From China ofcourse ! ) are available at Lamington Road, Mumbai for abouit Rs 100.

1.If I used my finger and it was live, I would have died long ago. My comp is fine that way.

2. No way a tester will measure a tiny voltage.

3. The multimeter I used was US and cost around 60$. A very accurate meter. No clue about Chinese stuff being good enough for finicky audio folks like us.