Re: Testing Amplifier Capability

"PDI Dave" <david@xxxxxxxxxxxxx> wrote in message
news:1166751760.416587.162150@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

** Groper Alert !


Please Help Me! I have a few amplifiers that i am having problems with
and i need to determine if the amplifiers are bad or if the speaker
circuits are bad. each has upwards of 100 speakers on them (70.7 volt
system) and they keep shutting down (internal circuit breaker
tripping). they only seem to do it when all/most speakers are hooked
up, but i can't yet figure out why. I've checked the AC current with a
Fluke DMM wired in series, but it only shows what i calc to be around
70 watts (.7 amps to .98 amps) but i should be able to pull close to
120 watts. everyone i talk to tells me this is a bad way to test this
system, but nobody can tell me how to. any help will be greatly
appreciated.

120 Watt Amps
70 Volt System
Lots of Speakers...



** Have any idea how to calculate the load presented by all the speakers
together ?

Was your amperage test done with a sine wave signal or speech / music ?

The minimum load impedance for a 120 watt 70 volt amp is 41 ohms.

If there are 100 similar speakers, each must be have 4100 ohms load
impedance.

Also - beware the existence of low audio frequencies, a big NO-NO with
70volt systems.




........ Phil





.

Relevant Pages

  • Re: valve amp power output
    ... drive my existing speakers. ... Many amps are only 8W per channel! ... My main reason for the post was to find what power range I ... or lower 32 watts of power at lower thd. ...
    (rec.audio.tubes)
  • Re: Distortion in amplifiers.
    ... and has very similar graphs of the NFB effects on THD spectra as Mr ... His methods for EL84 amps are just as valid now as they were in 1957. ... He was right about carts and speakers, and this is still valid today. ... High levels of bass were rude and tasteless in 1957. ...
    (rec.audio.tubes)
  • Re: amp and ohm question
    ... There's a good chance that I would not have read the fine print as carefully as i did and made the assumption that one manufacturer would use the same ohm load to rate their amps. ... While watts and loudness are related, the relationship depends on may things: the efficiency of the speaker driver and the design of the cabinet being two important factors. ... The primary advantage of more power is something called headroom. ... The average may be 5 or 10 watts, but if the transient peaks hit 100 or 200 watts, the music won't sound right if the amp and speakers don't have enough reserve power to handle those peaks. ...
    (alt.guitar)
  • Re: Testing Amplifier Capability
    ... circuits are bad. ... they only seem to do it when all/most speakers are hooked ... 70 watts (.7 amps to .98 amps) but i should be able to pull close to ...
    (sci.electronics.design)
  • Re: 2000 Corolla new stereo getting engine (alternator?) noise
    ... The noise is present through all the speakers. ... You'll have to connect the speakers to the head unit, ... Then add the amps back in and see if it ...
    (alt.autos.toyota)