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? Peak to Peak volts to Peak Pwr output @ 8ohm

Mearle

Mearle

Active Member
Peak power calculation
Just rejuvenated my Marantz 2325, load tested it and got 92.6 V peak to peak across each 8ohm load.
What does that calculate out to in Peak output Wattage?
I'm thinking its 134 W? but don't know for sure on the calculation.

What is the formula for Watts with PP Voltage & Ohms?
 
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Yes ok, maybe I am confusing the issue here but I was twisting it around to know what level of Clean ie; NON Clipped peak power I can demand from the amp before it passes to the speakers before clipping, would that be then 92.6VPP/2 = (41.3 Vpk x 41.3) / 8 Ohms = 213W peak before clipping? (I mean instantaneous bursts)

Maybe my theory is messed up, just trying to understand how hard I can drive the amp without clipping it and burning the voice coils (with a clipped signal = DC).

Please correct me if I am wrong, I know that RMS represents constant power, but I am not sure if it represents the MAX instantaneous power before clipping the amp, Am I messed up on this approach???? I think I want to make or buy a clip detector or power meter that is active while playing.

Thanks, Mearle...
 
Mearle said:
Peak power calculation
Just rejuvenated my Marantz 2325, load tested it and got 92.6 V peak to peak across each 8ohm load.
What does that calculate out to in Peak output Wattage?
I'm thinking its 134 W? but don't know for sure on the calculation.

What is the formula for Watts with PP Voltage & Ohms?
Click to expand...
You have 92.6V peak to peak which means you have 46.3V peak voltage. To find peak power you square the voltage and divide by the load resistance: 46.3^2/8 = 2143.69/8 = 267.96 peak Watts.
 
tcdriver said:
You have 92.6V peak to peak which means you have 46.3V peak voltage. To find peak power you square the voltage and divide by the load resistance: 46.3^2/8 = 2143.69/8 = 267.96 peak Watts.
Click to expand...

TC thats great, thank you, Your calc makes total sense for my thinking.
So spec is:
-133 WPS RMS 8 Ohms
-267 WPS Peak (at clip level) 8 Ohms

Do you feel my thinking make sense to know the peak Watts for the Bursts, to avoid sending a clipped signal to the speakers? This assumes the speakers can take the peak of course.... Just really looking at my "head room". I think I will stick a Watt meter in the system and calibrate it to touch red at the clip VPeak while on the scope, that way I will know the peaks, when I am playing.
 
Here's how it looks to me...

Marantz 2325 rated power output is 125 watts per channel into 8Ω, distortion: 0.1%.

Rated power is average voltage output before exceeding the distortion specification. The amp does not have an intrinsic power or distortion... the manufacturer chooses a distortion level and measures the power there. If the marketing research at that time indicated that the competition was using a 0.5% distortion specification and that was what the public expected, they could have rated the amp at a higher power. If the popular expected distortion spec had been 0.02% they would have rated it at a lower power.

W = (V^2)/R
V = SQRT(WxR)
V = SQRT(125x8)
v = SQRT(1000) = 31.5V average volts

(V peak to peak) / 2 x 0.707 = average volts

Your measured 92.6V is 92.6V / 2 x 0.707 = 32.7V average volts 133 watts

There is some variability in manufacturing, and fine manufacturers' equipment typically bests their specifications in order that they all meet or exceed them. Measuring 133W on a 125W spec'ed amp is an indication of high quality, especially for an almost 50 year old amp!

When test rating amps, test signals are used rather than music - there is no consideration for additional headroom requirements under the clipping level. As far as how much power you have for music before clipping the amp, there are three levels to consider.

Average level - about 12dB below the fast peak level, a bit lower for classical
Fast Peak level - what SPL meters, VU meters, and watt power meters measure - they can't resolve the transients
Instantaneous transient level - about 13dB above the fast peaks

So, if you allow about 25dB headroom over your average level, that should be good for all but a few recordings from some specialty studios and test records.

Power reduced -25dB from 125W is close to 1/2 watt providing clean average listening level with clean fast peaks to about 8 watts and clean transients above that (if the speaker is capable).

1/2 watt will be reached at about 2 volts output
8 watts at about 8 volts
transient peaks up about 30 volts
 
Pauln said:
Here's how it looks to me...

Marantz 2325 rated power output is 125 watts per channel into 8Ω, distortion: 0.1%.

Rated power is average voltage output before exceeding the distortion specification. The amp does not have an intrinsic power or distortion... the manufacturer chooses a distortion level and measures the power there. If the marketing research at that time indicated that the competition was using a 0.5% distortion specification and that was what the public expected, they could have rated the amp at a higher power. If the popular expected distortion spec had been 0.02% they would have rated it at a lower power.

W = (V^2)/R
V = SQRT(WxR)
V = SQRT(125x8)
v = SQRT(1000) = 31.5V average volts

(V peak to peak) / 2 x 0.707 = average volts

Your measured 92.6V is 92.6V / 2 x 0.707 = 32.7V average volts 133 watts

There is some variability in manufacturing, and fine manufacturers' equipment typically bests their specifications in order that they all meet or exceed them. Measuring 133W on a 125W spec'ed amp is an indication of high quality, especially for an almost 50 year old amp!

When test rating amps, test signals are used rather than music - there is no consideration for additional headroom requirements under the clipping level. As far as how much power you have for music before clipping the amp, there are three levels to consider.

Average level - about 12dB below the fast peak level, a bit lower for classical
Fast Peak level - what SPL meters, VU meters, and watt power meters measure - they can't resolve the transients
Instantaneous transient level - about 13dB above the fast peaks

So, if you allow about 25dB headroom over your average level, that should be good for all but a few recordings from some specialty studios and test records.

Power reduced -25dB from 125W is close to 1/2 watt providing clean average listening level with clean fast peaks to about 8 watts and clean transients above that (if the speaker is capable).

1/2 watt will be reached at about 2 volts output
8 watts at about 8 volts
transient peaks up about 30 volts
Click to expand...

That makes sense from the standpoint of doubling power requirement for every 3db increase, @ 1/2 watt & 25 Db range I need 8 power doublings = 128 watts RMS... now that I am getting down to the understanding that will apply to most or all Power Amp scenarios, I thought it would be prudent to look for the clip level on the scope while testing under the worst condition with an actual Music signal through the dummy loads, I say this because I am not sure if the music wave form with all mixed in transients become more than a simple sine wave...

I guess I will just figure it out from here, my skills maybe weren't that good back in the day, so I may not be dealing with a full deck of cards here... All I know is that low power blows more speaker coils than clean unclipped power. Thank you for your post.
 
Sounds like a full deck to me... Just keep in mind that with music, what you see on the scope may likely be only the fast peaks. Maybe modern scopes can capture and hold the transients.

Also, transients are just a couple of milliseconds duration, critical in the recording studio, more forgiving in home playback... you can squeeze through with less headroom if your amp recovers gracefully (does not "rail hang") after clipping the occasional highest transients... :)
 
Pauln said:
Sounds like a full deck to me... Just keep in mind that with music, what you see on the scope may likely be only the fast peaks. Maybe modern scopes can capture and hold the transients.

Also, transients are just a couple of milliseconds duration, critical in the recording studio, more forgiving in home playback... you can squeeze through with less headroom if your amp recovers gracefully (does not "rail hang") after clipping the occasional highest transients... :)
Click to expand...
Thank you...., dont know what rail hang is, but it hasnt killed me so far... :-)
 
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