Power of Tube Amp and Transistors Amp

[weiyan]

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.

 

[TheGimp]

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.

 

[Evenharmonics]

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

And destructive to speaker driver.

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.

 

[DF96]

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.

 

[Minx]

Thanks for the question and the answers. I'd often wondered the same thing. Oh boy, am I learning on this great site!

 

[weiyan]

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?

 

[chrish]

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.

 

[Evenharmonics]

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.

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.

 

[weiyan]

Learn a lot from this thread.

Thank you!

 

[Twobeers]

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.

 

[disco]

... 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.

OK but for OTL good point though.

 

[DF96]

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.

You seem to be confusing DC with a square wave of the same peak voltage. Very different effect on a speaker.

 

[Twobeers]

No I am not confusing DC with a square wave. Just trying to make a point to a newbie in regards at to what happens when you drive a transistor amp past its limits. Lets say we have a 10W speaker and a 10W amp, tube or transistor. If drive a tube amp to distortion, that's all that is going to happen, its going to distort (with a guitar that's a cool thing). Now if we take that little 10W transistor and drive it to distortion for too long, eventually something is going to give up besides the fact that it sounds like crap. Shall we get into dynamic head room?

 

[puginfo]

if we do not operate in clipping mode in either case, the 1W in tube amp still sounds much sweeter than a 1W SS amp. is that due to the fact of even harmonics domination in the tube amp?

 

[Evenharmonics]

if we do not operate in clipping mode in either case, the 1W in tube amp still sounds much sweeter than a 1W SS amp. is that due to the fact of even harmonics domination in the tube amp?

Try this link.

 

[DF96]

Now if we take that little 10W transistor and drive it to distortion for too long, eventually something is going to give up besides the fact that it sounds like crap. Shall we get into dynamic head room?

Unlikely that an amp will go from distortion to latch-up, but if it is prone to latch-up then the length of time it has been overdriven is probably irrelevant. I'm not sure dynamic head room is relevant.