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K250 Actual power measurements [message #1708] Wed, 17 July 2002 21:28 Anonymous For what it's worth...I finally set up my K250 on the bench with a scope and audio generator, plugged into a 4 ohm power resistor. Just prior to clipping I measured about 64 volts peak to peak...works out to 22.6 volts RMS or 127 watts. This was typical all the way from 60 Hz up to 4K.... I have not replaced the filter caps yet, maybe in a month or two I'll get around to that and measure it again. I am curious how much droop I'm getting on power supply voltage, will measure across rails next time too. Report message to a moderator

Re: K250 Actual power measurements [message #1709 is a reply to message #1708] Thu, 18 July 2002 21:58 KustomBlues Messages: 490 Registered: June 2001 Location: Michigan Senior Member When our Kustom Brother Gary Hull rebuilt my 250-1 head, he measured it our at 131 watts RMS when done. He replaced all the resistors with metal film ones, and did other fantastic work in there. Just thought I'd share that. Deb Report message to a moderator

Re: K250 Actual power measurements [message #1710 is a reply to message #1709] Fri, 19 July 2002 12:53 ET Messages: 146 Registered: October 2000 Location: Charlotte NC Senior Member Dude...everybody knows by now that you can't measure wattage on the bench...its gotta be on the stage with its skin on...cause we all know that black kustoms are louder than the sparkledy ones ;) Play Loud! ET Report message to a moderator

Re: K250 Actual power measurements [message #1711 is a reply to message #1709] Fri, 19 July 2002 13:18 Anonymous Power measurements... RMS or otherwise have no meaning unless you specify a distortion content. Report message to a moderator

Re: K250 Actual power measurements [message #1712 is a reply to message #1711] Fri, 19 July 2002 17:55 Anonymous This was power at clipping. Sorry but I don't have a distortion analyzer. While I agree that distortion figures are very meaningful, it's the power when clipping is observed on the scope that's important to me. After all, distortion through a tube amp is well over 1 percent and nobody cares. Report message to a moderator

Re: K250 Actual power measurements [message #1714 is a reply to message #1712] Sat, 20 July 2002 12:51 Anonymous All good information, but at what voltage was the test done at? And again the amp will always vary with voltage from club to club. Peavey used to rate the CS-800 at 410 watts rms at .01 THD with 125V regulated power source at 1K. I don't ever remember seeing a club with 125V power source. Add a few more amps in equation and it is still sound that counts. Report message to a moderator

Re: K250 Actual power measurements [message #1715 is a reply to message #1714] Sat, 20 July 2002 14:11 Anonymous My house voltage runs around 125 volts, usually a little more though, it's pretty hot!! And I got the 127 watt figure at a frequency of 1k. It started dropping as I lowered f below 150 hz although ti didn't drop much. Above 1k it stayed fairly constant up to 3 or 4k, I didn't go past that. Report message to a moderator

Re: K250 Actual power measurements [message #1716 is a reply to message #1715] Tue, 23 July 2002 11:22 C4ster Messages: 686 Registered: June 2001 Location: Mukwonago, WI (Milwaukee... Senior Member The THD of an amp is only the ability of an amp to reproduce the input signal EXACTLY. That is totally different than what happens at clipping. The maximum RMS power is only good for a sine wave at 1 frequency. That is not what music is about. The actual power output can be much higher for the same amount of sound pressure at the speakers. That is because the true RMS value rises as the output waveform approaches a square wave. The more individual signal sources mixed into a power amp at different frequencies, especially octaves and harmonics, will tend to fill in the areas not filled by the fundimental frequency. That is why a 50 watt guitar amp, screaming, will cut through a 2000 watt PA mix and drive the sound man nuts. Report message to a moderator

Re: K250 Actual power measurements [message #1717 is a reply to message #1716] Tue, 23 July 2002 23:07 Anonymous That's why I prefaced my first post with "For what it's worth" or words to that effect. Ideally we would be able to generate measurements of THD at given power levels, and given frequencies, with a host of other measures as well. But unfortunately most of us don't have the test equipment sitting in our shop to make these detailed measurements, and even if we did, most music equipment manufacturers do not publish test measurements on their products, or if they do they are so vague they are almost meaningless. The RMS power calculated when clipping has been observed on the scope, however,at least gives us SOMETHING that we can use to make a comparison with another amp. The test might not be exactly the same as an actual music program source, but music DOES consist of sine waves, granted with harmonics and overtones that are superimposed on one another. A sound man probably will have trouble dealing with a guitarist that has his little 50 watt amp up to 10, but we can still say with certainty that the 1000 watt PA has more power--a lot more power-- than the guitar amp. It's just being applied differently. (And no, tube amp watts AREN'T somehow much more powerful than solid state watts, but that's another debate) Report message to a moderator

Re: K250 Actual power measurements [message #1719 is a reply to message #1717] Thu, 25 July 2002 11:25 C4ster Messages: 686 Registered: June 2001 Location: Mukwonago, WI (Milwaukee... Senior Member Just one little request. Please log in so we all know the source of this fine knowledge. So far I totally agree with everything you have written. Anon just doesn't have the same ring as KustomBlues or Pleat. Report message to a moderator

Re: K250 Actual power measurements [message #1720 is a reply to message #1719] Thu, 25 July 2002 18:06 Anonymous I've entered name for several posts but they didn't get entered, kept coming up as Anon. I don't mean to be anonymous on purpose, I just got tired of entering name for nothing.... Bill Campbell Report message to a moderator

Re: K250 Actual power measurements [message #1722 is a reply to message #1720] Sun, 28 July 2002 02:19 Anonymous Bill, I have found if I type the message first and then put my name in very last it appears to work everytime, I had the same problem if I started with my name and email, by the time I was ready to send it appeared anon. Don Report message to a moderator

Re: K250 Actual power measurements [message #1723 is a reply to message #1722] Sun, 28 July 2002 02:21 Anonymous So it used to work every time. Don Report message to a moderator

Re: K250 Actual power measurements [message #1725 is a reply to message #1723] Mon, 29 July 2002 09:59 C4ster Messages: 686 Registered: June 2001 Location: Mukwonago, WI (Milwaukee... Senior Member I find if you login, all of the relevant information is already in the proper fields. All you need is a password that you can remember. My computer logs me in automatically. I'm not sure how or when I did that, but it works. Conrad Report message to a moderator

Re: K250 Actual power measurements [message #1730 is a reply to message #1710] Mon, 29 July 2002 21:28 KustomBlues Messages: 490 Registered: June 2001 Location: Michigan Senior Member ET, I have to disagree. This head that Gary rebuilt first lived in a black skin. Then I put it in my blue skin so it would seriously thump the walls in 500 blue SPARKLE set. I am here to tell you that it did not start to come alive until it was in the blue sparkle skin!!!!!! :-) I love black, but sparkle makes 'em "thumpier". They don't call me the Low Frequency Goddess for nothing!!! :-) Report message to a moderator

Re: K250 Actual power measurements [message #1732 is a reply to message #1719] Mon, 29 July 2002 21:37 KustomBlues Messages: 490 Registered: June 2001 Location: Michigan Senior Member Yes, please log in so I can ask you questions using your name. :-) Report message to a moderator

Re: K250 Actual power measurements [message #1734 is a reply to message #1732] Tue, 30 July 2002 17:56 WildBill Messages: 4 Registered: July 2002 Junior Member There! I finally registered and logged in (although under a different nickname, I have seen several Bill C's throughout the forum) Deb, you might remember mailing me schematics for my K250 a while back. Thanks. Bill Campbell Report message to a moderator

Re: K250 Actual power measurements [message #1736 is a reply to message #1734] Tue, 30 July 2002 20:42 KustomBlues Messages: 490 Registered: June 2001 Location: Michigan Senior Member Sure Do, Bill! Glad to see you now are a registered user!!! Report message to a moderator

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