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[HateEvent]

5-watt tube amps are still as loud as a trumpet! 50 mW is needed for 1/8 the volume of 50 W

Basically:

5-watt tube amps are still as loud as a trumpet! 50 mW is needed for 1/8 the volume of 50 W
The sound of a blaring 5-watt amp is at least as loud as a trumpet!

I'll just take a Fender Champ and cheap guitar cable.


Those who hope a 5 watt tube amp will enable them to play at 2am in their apartment, the fact is, you will still have to use a power attenuator or speaker isolation cabinet, if you want cranked power tube tone at low room noise levels. Shout really loud -- that's how loud 5 watts is.

For most people, 5 watts is completely unacceptable at home, except perhaps during the middle of the day. The lxh2 ultra-low power tube amp is only about 20 mW. Thus the Champ is 5 / .002 = 2,500 times louder than the desired level, which is headphone level.

Relative to the standard amp power of 50 watts:

50 mW - thousandfold decrease in power (1/8 as loud) 3 orders of magnitude 0.5 W - hundredfold decrease in power (1/4 as loud) 2 orders of magnitude 5 W - tenfold decrease in power (1/2 as loud) 1 order of magnitude 15 W - threefold decrease in power (about 2/3 as loud) 50 W - unity 100 W - twofold increase in power (maybe 25% louder) 500 W - tenfold increase in power (twice as loud)

1/8 the volume of a 50 watt amp sounds like the level I want to hear. Everyone can agree, 1/8 the volume would be nice. But let's look at the amazing decrease of power that will give this result. A 1/8 decrease in volume amounts to 3 orders of magnitude of power, yielding just 50 mW -- a *thousandfold decrease* in power. *Three* orders of magnitude! A 50 watt amp is *a thousand times too powerful*.

X% louder = 2^log10(P2/P1) * 100%

40 watts is 94% as loud as 50 watts.
30 watts is 86% as loud as 50 watts.
25 watts is 81% as loud as 50 watts.
22 watts is 78% as loud as 50 watts.
20 watts is 76% as loud as 50 watts.
18 watts is 74% as loud as 50 watts.
15 watts is 70% as loud as 50 watts.
12 watts is 65% as loud as 50 watts.
10 watts is 62% as loud as 50 watts.
9 watts is 60% as loud as 50 watts.
8 watts is 56% as loud as 50 watts.
7 watts is 55% as loud as 50 watts.
6 watts is 53% as loud as 50 watts.
5 watts is 50% as loud as 50 watts.
4 watts is 47% as loud as 50 watts.
3 watts is 43% as loud as 50 watts.
2 watts is 38% as loud as 50 watts.
1 watt is 31% as loud as 50 watts.
3/4 watt is 28% as loud as 50 watts.
1/2 watt is 25% as loud as 50 watts.
1/4 watt is 20% as loud as 50 watts.
1/10 watt is 15% as loud as 50 watts.
50mW is 13% as loud as 50 watts
20mW is 10% as loud as 50 watts.
10mW is 8% as loud as 50 watts.
5mW is 6% as loud as 50 watts.
1mW is 4% as loud as 50 watts.
0.5mW is 3% as loud as 50 watts.
0.1mW is 2% as loud as 50 watts.
50uW is 1.6% as loud as 50 watts.
10uW is 1% as loud as 50 watts.

The formula and this usage of it is from knowledgeable, respected math/guitar people in this newsgroup thread: Calculating the power/volume relation for amp wattage?

There are only two tube power amps I've heard of that get down to the 10 mW level: the LXH2 project and the Studio amp by London Power. I have heard a cranked 5 watt tube amp but not driving a serious speaker cabinet. The 5 or 6 watt Fender Champ is far too loud for my needs, and so is the 5 watt Crate VC508. The Studio is particularly interesting as far as pointing the way for designers of truly low-power tube amps, because it can be adjusted instantly to any value from 0 to 10 watts, and was tested in the milliwatt range, while of course keeping the output transformer and speaker system constant. The enables easy testing of the above calculations about perceived volume vs. wattage. This amp is supposed to produce the same classic amp-breakup tone whether at 10mW or the wide-open 10 watts, so a brief test with this amp should be able to settle whether or not cranked-amp tone must necessarily involve driving speakers hard and pushing air hard. Let us hope that top-notch tone can be achieved at 10mW, as the LXH2 and Studio claim, and give it a try, in more designs.

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I knew alot of what was said in it but it is worded in a way that hopefully people questioning such a thing will understand clearly.

[Tubthumper]

I thought you said it was interesting?

[HateEvent]

Originally Posted by Tubthumper

I thought you said it was interesting?

Hopefully it makes it easier as some n00bs will have a background knowledge before coming into my work and asking me which 50W valve amp is best for using in their bedroom to get that sweet valve sound.

[Hogisbald]

You came across this article? Doesn't suprise me.

[HairyScaryMark]

I found it interesting and confirmed what I had always known/suspsected.

[scottyboy]

slightly concerning that a tiny amp is so loud... a person shouting very loud is enough to damage your ears isn't it? i still use a 10w solid state thing on low volume... getting sweet valve tone at 2am sounds like more money and hassle than it's worth

[Jeid]

I just built a 5w valve amp... it's pretty fuckin loud!

[The Byre]

Two things to bear in mind -

1. +10dB = double the perceived volume.

2. Valve amps create harmonic distortion, making them sound louder when driven.

If you want to read about the relationship between Watts, volume and decibels, you can download tthe complete book published by JBL here

http://www.jblpro.com/pub/manuals/pssdm_1.pdf

http://www.jblpro.com/pub/manuals/pssdm_2.pdf

[Pierre Von Mondragon]

I just read about Cornell amps that are switchable to 0.25 Watt, if that is too loud, then its time to get modelling.

[soundian]

Just thought I'd point out that the power-to-loudness ratio works for all amps not just valve amps, although a valve amp will sound louder than a solid state amp of equivalent rating (all other things being equal).