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Author Topic: Stated watts vs real watts  (Read 5136 times)

gwEm

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Stated watts vs real watts
« on: April 10, 2017, 08:45:36 PM »
I measured these RMS values using a 1kHz sine wave into an 8ohm dummy load at the point the sine wave started to audibly distort:

H&K CF100 - stated 100w, actual 94w
JCM1H - stated 1w, actual 0.6w
Mini Rectifier - stated 25w, actual 13.7w (measured again)
JMP50 - stated 50w, actual 34w
Magnum44 - stated 25w, actual 31w

The valve amps didn't do very well here(!)
« Last Edit: April 11, 2017, 08:13:03 AM by gwEm »
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you wouldn't use the meat knife on crusty bread but, equally, the serrated knife and straight edge knife aren't going to go through raw meat as quickly

Dave Sloven

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Re: Stated watts vs real watts
« Reply #1 on: April 11, 2017, 02:36:14 AM »
I wonder how this would go with Peaveys.  I've always found them to sound quite a bit louder than you'd expect for their ratings, especially the old solid-state bass amps.
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gwEm

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Re: Stated watts vs real watts
« Reply #2 on: April 11, 2017, 07:33:14 AM »
Quote from: Dave Sloven on April 11, 2017, 02:36:14 AM
I wonder how this would go with Peaveys.  I've always found them to sound quite a bit louder than you'd expect for their ratings, especially the old solid-state bass amps.

I'd really love to test some Peaveys.

On reflection, I'm quite disappointed by the performance of my Mini Rectifier.
(Actually I woke up early this morning to remeasure it and got slightly better power). Even fully cranked I only got 18watts out of it.

The JMP50 I biased myself deliberately a bit cool. I may try to rebias it tonight and see what effect that has.

I expected the manufacturers of the solid state amps to be overstating the RMS power, but actually the solid state amps are the closest and it is the valve amps which are optimisticly rated.
« Last Edit: April 11, 2017, 08:23:21 AM by gwEm »
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Quote from: AndyR
you wouldn't use the meat knife on crusty bread but, equally, the serrated knife and straight edge knife aren't going to go through raw meat as quickly

gwEm

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Re: Stated watts vs real watts
« Reply #3 on: April 11, 2017, 08:52:04 PM »
Rebiased the JMP50 and got 40 watts dead. It's not clipping symmetrically though, so I need to look at it more.

Edit: there's a resistor in the phase inverter which is out of spec. Might get 50watts out of the old girl yet.
« Last Edit: April 11, 2017, 09:15:34 PM by gwEm »
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Quote from: AndyR
you wouldn't use the meat knife on crusty bread but, equally, the serrated knife and straight edge knife aren't going to go through raw meat as quickly

gwEm

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Re: Stated watts vs real watts
« Reply #4 on: April 21, 2017, 03:53:44 PM »
Received a highly detail reply from Mesa Boogie on why the mini-rectifier doesn't generate 25 watts. Seems it was designed this way. The 25 watts is only delivered briefly during transients.

I'll be having a go at the JMP50 this weekend.

edit: In fact - the email from Mesa was from Randy Smith himself!!
« Last Edit: April 21, 2017, 04:00:10 PM by gwEm »
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Quote from: AndyR
you wouldn't use the meat knife on crusty bread but, equally, the serrated knife and straight edge knife aren't going to go through raw meat as quickly

one

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Re: Stated watts vs real watts
« Reply #5 on: April 22, 2017, 10:21:24 AM »
Interested thread, I'd like to know about my 5153 50w
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gwEm

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Re: Stated watts vs real watts
« Reply #6 on: April 22, 2017, 03:28:22 PM »
Replaced some bits in the JMP50. Got 47.9watts out of it. Sounds a bit nicer cranked too
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Quote from: AndyR
you wouldn't use the meat knife on crusty bread but, equally, the serrated knife and straight edge knife aren't going to go through raw meat as quickly

Plenum n Heather

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Re: Stated watts vs real watts
« Reply #7 on: April 22, 2017, 05:28:04 PM »
Quote from: gwEm on April 22, 2017, 03:28:22 PM
Replaced some bits in the JMP50. Got 47.9watts out of it. Sounds a bit nicer cranked too
Goal!  :cool:
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