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Re: Volume vs. watts

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12/18/1997 1:32 PM

Re: Volume vs. watts

The definitive paper on this is Russell O. Hamm's "Tubes Vs Transistors - Is There an Audible Difference?" as presented to the AES and published in the JAES.

The jist of the explanation is that this is an audible illusion. For the first 12db or so of overdrive, the distortion products of tube based amps sounds to the human ear as though it's getting louder, not more distorted. In solid state amps, the reverse is true. So tube based circuits have a built in illusion of having more headroom than they actually have, and "sound as loud" as solid state amps with more real power ability.

I have a link to this paper on my web page at http://www.eden.com/~keen/.

12/18/1997 7:07 PM

>The definitive paper on this is Russell
> O. Hamm's "Tubes Vs Transistors -
> Is There an Audible Difference?" as
> presented to the AES and published
> in the JAES.

It might have been definitive in the early 70s but soldi state materials technology and circuit design has advanced considerably since then. Its not really definitive of anything now a days.

> So tube based circuits have a built in
> illusion of having more headroom than
> they actually have, and "sound as loud"
> as solid state amps with more real power
> ability.

There has never been any hard evidence that this is in fact the case with musical instrument amps, which vary considerably from the sort of amps considered Hamm's paper.

"Sound" is a very subjective thing and the SPLs that would need to be created to account for the loudness difference that some claim to be able to "hear" between tube and solid state amps defy the laws of phsyics.

I dont want to start a tube vs SS argument, just point out that there is little hard evidence to support this commonly heard proposition.

Bill

12/18/1997 4:35 AM

Yes, I did mean 10x wattage = 2x the
volume; I DID NOT mean adding 10
(ie 30 to 40).

I have a 100 watt Marshall. I also
have a 15 watt Fender Pro Jr. Putting
both amps through my 4x12 cab yields
a supprisingly similar sound level --
Yes, the Marshall is louder, but the
Fender Pro "keeps up" pretty darn well!
And remember, Since the Fender accepts
and 8 ohm speaker, and the 4x12 cab,
is 16 ohms, I'm actually cutting some of
the wattage in the Fender Pro Jr, and it
still almost matches volume with the
Marshall.

I STILL say 15 watts is TOO gosh darn
loud.

And I STILL say people who claim they
NEED 100 watt amps (other than
professionals playing in Mega Auditoriums)
are wasting money replacing 4 tubes.

12/18/1997 7:12 AM
J Fletcher	Depends how clean you want it.If you play country music you need the headroom that 80 watts or so gives you.

12/18/1997 9:02 AM
dave	The desire for a particular sounding amp is a matter of taste based on personal opinion. It may be well worth the extra money to someone to achieve a particular sound/tone or loudness that can be achieved with a four tube amp.

12/18/1997 7:30 PM

The perceived loudness of an amp depends on its voicing. 100W of mega bass might be tolerable in a certain situation, but 100W of screaming top-boosted trebly distortion could shatter your eardrums in the same situation and sound many times louder, due to the ear's far greater sensitivity to treble than to bass.

Also, manufacturers have no standardised way of measuring power output so comparisons are not precisely valid. Marketing, however, says that people will buy <= 15W amps for practice or recording, and >= 100W amps for large gigs, so you can expect an amp with a certain wattage rating to be intended for a certain task. (This is certainly not a hard and fast rule but gives some indication of the expected sound levels).

Hamish

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