General question regarding power amp input voltage

[nosaj]

I've got a couple of poweramps I am working on. What I'd like to know is roughly what voltage signal should be going into a power amp. Example I have a Peavey gps2600 Chb is shorted out so I disconnected it and brought it up ChA I hooked an Ipod up to it. It passes music but not loud enough considering the amp.

I have the manual here peavey gps2600 gps2400 gps3500 user manual Download page :: Schematics Unlimited

It says the Input sensitivity is 1.54v for a 4ohm load. Does this mean my signal in should be roughly 1.5volts into the power amp?

Thanks,
nosaj

[Leo_Gnardo]

It says the Input sensitivity is 1.54v for a 4ohm load. Does this mean my signal in should be roughly 1.5volts into the power amp?

1.54v for full output into a 4 ohm load. IOW if you supply an input signal of 1.54v (RMS I guess?) with volume control all the way up you'll just barely clip. Probably wouldn't be too much different for 8 or any other load. Apparently your Ipod's output falls well below the 1.5 volt spec, that's why there are preamps. Most any hi fi preamp or small mixer will get you the gain you need, I'm guessing 20 to 30 dB if you're looking to get stage level volume.

[Jazz P Bass]

Or, if you are serious about repairing audio equipment, you should have a decent sine wave generator.

[J M Fahey]

Your IPod, like all Phones, MP3 players, pocket rdios, battery powerd Vs, etc. , usually has a headphone output, hence will provide output to comfortably drive them and not much else, why would it otherwise?

I always have these MP3 audio tone files loaded in mine, take little space and have saved my bacon 1000 times, but I have measured tons of devices and most provide up to 200 mV RMS through the headphone out, all reach at least 100mV RMS

Excellent for general purpose guitar amps, PA mixers (Line/Aux In) but definitely not enough to straight drive a power amp, which usually need between 1 V (0 dBV) and 1.4V (+4dBV)

If anything, because phones are fed from a 3.7V battery, some MP3 players even less, while for 1.5V RMS you need *at least* a 4.5V supply if very careful, or straight 6V.

Least you can do is to build a 9V powered preamp, gain 10X (so 100mV in give you 1 V out) , using a modern rail to rail Op Amp.

MP3 audio tone source:
Download Audio Tone Files
get the 30 second ones and set your player to Loop/Repeat so when they end they repeat for continuous sound.
YouŽll hear a small glitch every 30 seconds, no big deal.
Download and test them as is, so you measure how much does your phone actually put out, and post results.

Regular multimeters can be trusted up to 400Hz, a few will decently read 1kHz, anything above canŽt be trusted, cheap meters are meant to measure mains frequencies.

[nosaj]

Your IPod, like all Phones, MP3 players, pocket rdios, battery powerd Vs, etc. , usually has a headphone output, hence will provide output to comfortably drive them and not much else, why would it otherwise?

I always have these MP3 audio tone files loaded in mine, take little space and have saved my bacon 1000 times, but I have measured tons of devices and most provide up to 200 mV RMS through the headphone out, all reach at least 100mV RMS

Excellent for general purpose guitar amps, PA mixers (Line/Aux In) but definitely not enough to straight drive a power amp, which usually need between 1 V (0 dBV) and 1.4V (+4dBV)

If anything, because phones are fed from a 3.7V battery, some MP3 players even less, while for 1.5V RMS you need *at least* a 4.5V supply if very careful, or straight 6V.

Least you can do is to build a 9V powered preamp, gain 10X (so 100mV in give you 1 V out) , using a modern rail to rail Op Amp.

MP3 audio tone source:
Download Audio Tone Files
get the 30 second ones and set your player to Loop/Repeat so when they end they repeat for continuous sound.
YouŽll hear a small glitch every 30 seconds, no big deal.
Download and test them as is, so you measure how much does your phone actually put out, and post results.

Regular multimeters can be trusted up to 400Hz, a few will decently read 1kHz, anything above canŽt be trusted, cheap meters are meant to measure mains frequencies.

I have an HP 200cd I'd just hooked the ipod up to hear signal pass cause it was close by. Which then lead me to read the manual that prompted the original question about what voltage power amps look for at input. Which was in specs sheet just wasn't sure I understood it correctly.

Thanks,
nosaj