Re: [Harp-L] Watts Up With That?



I doubt if you will get a "standard" for amp watts. I went through this in the 60's and 70's with guitar amps. For example, 70 watts RMS(ROOT MEAN SQUARE) is the same as 100 watts, PEAK and is the same as 200 watts PEP (PEAK ENVELOPE POWER ). Then someone came up with a standard called Peak Music Power (w.t.f. is that??) Then you have to figure out if that's watts at how much distortion, because a square wave has more power than a sine wave. But if you list the wattage of a clean signal, how does many harp players use the amp, .... at full power, with lots of distortion, no where near a clean signal. What you probably want for a standard is peak watts before clipping, that's where the rating of watts with distortion comes in handy with "stereo amps". But since harp amps are used for sound "production" rather than reproduction, the idea of attaching a distortion number could be misleading. I do not see a simple answer.

So Rick. What "standard" would you propose to use?

Jim Rumbaugh
----- Original Message ----- From: "Rick Davis" <bluesharpamps@xxxxxxxxx>
To: "Greg Heumann" <greg@xxxxxxxxxxx>; "Harp- L" <Harp-L@xxxxxxxxxx>
Sent: Friday, December 04, 2009 10:47 AM
Subject: Re: [Harp-L] Watts Up With That?



Au contraire, Greg!  Amp buyers often let wattage claims influence their
purchasing decisions.  A visit to some of the popular harp forums will
convince you of that. That is precisely why amp makers might be prone to
inflate the numbers.

Some time ago I bought an amp from a "well established, respected amp
builder" who claimed a rather impressive wattage number. When I scoped it,
it was delivering less than half of his claim. I contacted the engineer who
had done the original design work and found the claimed number was BS. The
amp was working properly when I got it.


The amp builder/seller was evidently using the rule of thumb I wrote about
in my post: A tube from the X family automatically gets a claim of Y watts
per tube. In this case, it was misleading and dishonest.


There is nothing wrong with demanding that amp builders tell the truth about
the amount of power their amps generate. I contacted several amp builders
when I was doing research for this article and found that most of them
were using a valid method to measure watts. The methods differed enough to
make the numbers unsuitable for direct comparisons, but they were derived in
a logical fashion.


Greg, all the amp makers on harp-L may indeed build amps "that are loud
enough for just about any situation," but that is not the point. The point
is clarity and honesty in the marketplace. For example, automaker's claims
are tested by the EPA and by others. As a result, claims of mileage and
performance are valid enough for worthwhile comparisons. There is no reason
we cannot have that kind of transparency with harp amps.



-Rick Davis The Blues Harp Amps Blog http://www.bluesharpamps.blogspot.com/




On Fri, Dec 4, 2009 at 12:48 AM, Greg Heumann <greg@xxxxxxxxxxx> wrote:


Rick - it is a fair question and you did a good job of explaining the
issue. Expecting that all amp manufacturers are suddenly going to begin
publishing power specs based upon a standard you propose on HARP-L (even if
we all demand it) however, is pretty unrealistic. If you want to make it
happen you need to form an amplifier industry association, encourage all the
amp makers to join it, succeed at getting them to, and put this on the
agenda. Examples of such organizations are IEEE (engineering), the RIAA
(recording), CTIA (cell phones.) In a previous career I had to work with
CTIA. Getting anything done is like pushing on a rope. Get yourself a staff,
a large budget and plenty of time to spend.


In the mean time, we have among us on this list a handful of well
established, respected amp builders. And they all make amps that are loud
enough for just about any situation. At which point, who cares about watts?
It is, as you point out, not a very good way to compare amps anyway. The
present "typical" ranges (5W, 15W, 30W, 50W) are close enough to know
whether two amps are in the same ball park.


/Greg

http://www.blowsmeaway.com
http://www.bluestateband.net
http://cdbaby.com/cd/bluestate



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