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Old 23rd July 2012, 11:36 AM   #1
weiyan is offline weiyan  Hong Kong
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Question Power of Tube Amp and Transistors Amp

Sorry for a naive question.

I read many power suggestion of speakers, most of them suggest different power for Tube amp transistors amp. For transistors amps usually needs double the power of tube amp.

Is the electrical characteristic of transistors amp not the same as tube amp?

Thank you.
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Old 23rd July 2012, 12:39 PM   #2
TheGimp is offline TheGimp  United States
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One big factor is the clipping characteristics of the two amps.

Solid state amps clip hard, producing displeasing odd harmonic distortion.

Tube amps tend to clip much softer producing a combination of even and odd harmonic distortion which is much less displeasing.

For this reason, it is possible to use a tube amp with a lower power out rating, and drive it slightly into clipping without it being annoying.

A higher power rating SS amp is needed to insure no clipping takes place.
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Old 23rd July 2012, 02:39 PM   #3
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Quote:
Originally Posted by TheGimp View Post
Solid state amps clip hard, producing displeasing odd harmonic distortion.
And destructive to speaker driver.

Quote:
Tube amps tend to clip much softer producing a combination of even and odd harmonic distortion which is much less displeasing.
Odd harmonics are usually described by listeners as displeasing.
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Old 23rd July 2012, 04:18 PM   #4
DF96 is online now DF96  England
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Symmetric clipping produces odd-order for valve and SS. The difference is that valve typically has smaller high-order products, so sounds better.

This assumes PP. For SE both valve and SS will produce mainly even-order but again valve will be lower order.
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Old 23rd July 2012, 10:12 PM   #5
Minx is offline Minx  United Kingdom
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Thanks for the question and the answers. I'd often wondered the same thing. Oh boy, am I learning on this great site!
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Old 24th July 2012, 02:46 AM   #6
weiyan is offline weiyan  Hong Kong
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Thank you for the great answers. I had this question for tens years.

From the above answers, if both valve and solid state amps are distortion free, no power difference required.

For distortion, there seems two view points.

1. Solid state distortion is less tolerable.
2. Valve has fewer high order harmonics, this lead to valve has better sound in distortion zone.

Is my understanding correct?
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Old 24th July 2012, 06:35 AM   #7
chrish is online now chrish  Australia
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When the solid state amp clips it will be giving power at the rail voltage of the amp with nasty HF hash that can fry your tweeters.

Generally speaking, when the tube amp clips it will still sound bad, but probably not as destructive to your speakers.

So, generally speaking, you want extra head room for the solid state amp to keep you away from clipping as it is dangerous to speakers. Solid state power is cheap, so generally it is easy to get the head room you require.
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Old 24th July 2012, 02:25 PM   #8
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Quote:
Originally Posted by weiyan View Post
2. Valve has fewer high order harmonics
If it's designed to be, then yes. I've seen valve amp (P-P) with as much of high order harmonics as some transistor amp (P-P). I've also seen transistor amp with very little of high order harmonics. They sounded close.

Quote:
this lead to valve has better sound in distortion zone.
What you may find pleasing is the sound of single ended amp which uses no feedback. It produces relatively high second order harmonic compared to the third and beyond. It has a masking effect of odd harmonics that follow which the listeners commonly describe as pleasing sound or "tube" sound.
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Old 26th July 2012, 04:43 AM   #9
weiyan is offline weiyan  Hong Kong
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Learn a lot from this thread.

Thank you!
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Old 29th July 2012, 05:36 AM   #10
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Let me clear this up a little bit. 1W is 1W tube or transistor. If you drive a transistor amp to distortion on the output stage its going to start putting out a square wave, meaning that its going to start pumping out DC like voltages, now throw the fact that transistor amps are directly coupled to the speakers. Speakers don't like DC, the voice coil in the speaker tends to destroy itself. Neither do the transistors they'll overheat and burn out. Now a tube amp on the other hand is always coupled to the speakers from the amp thru what they call the output transformer. The transformer cannot pass DC (direct current) to the speakers.
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