Re: Vacuum Tubes - Are They Warmer Sounding?

"JANA" <jana@[EMAIL PROTECTED]
> wrote in message
news:DqKdnRmPVODntt_VnZ2dnUVZ_qzinZ2d@[EMAIL PROTECTED]
> In actual fact a good vacuum tube amplifier does not add
> to the sound. They are accurate,

Then we impose basic logic - all accurate amplifiers sound the same.

> but there is a
> difference in the way the sound is heard for a number of
> reasons.

The differences come when the amplifiers are not accurate. This is borne
out 
by the discussion below:

> The tube amplifier uses an output transformer. Some tube
> amplifiers also use a driver transformer.

Some solid state amps used driver transformers. Interestingly enough, the 
solid state amps that used driver transformers did not suffer many of the 
faults of tubed amps that use output transformers.

Some solid state amps used output autotransformers, and again they did not

suffer many of the faults of tubed amps that use output transformers.

> Because of this, there is a lower slew rate.

It appears that slew rate and rise time are being confused here. Output 
transformers can impose a rise time limitation due to lack of high
frequency 
response. But this is not the same as a slew rate limitation. Slew rate 
limiting imposes a lack of high frequency response that increases with 
increasing signal level. A normal treble roll-off is independent of power 
level. Treble roll-offs due to transformers are usually independent of
power 
level.

> Very high end output
> transformers will still have some effect on the sound.

It appears that tubed amplifiers with very good parts and designs can be 
sonically accurate, similar to how good SS amps are. Therefore none of
their 
components will be having an effect on the sound. Either this statement 
about output transformers still having some effect on the sound is 
incorrect, or the author's opening statement that "...a good vacuum tube 
amplifier does not add to the sound." is incorrect. I think he started out

right and went wrong.

> The tube amplifier is higher in THD, but at odd
> harmonics.

Just plain wrong. The balance of odd and even harmonics in an amplifier
are 
up to the designer. An amplifier with an unbalanced or single-ended design

will ultimately tend strongly towards producing even harmonics.  An 
amplifier with an balanced or push-pull design will ultimately tend
strongly 
towards producing odd harmonics because its basic design tends to cancel
out 
even harmonics. Tubes, transistors or whatever active device you might
have, 
these are very strong effects.

> When the tube amplifier is over driven, the
> clipping is not as harsh as on a tube amplifier.

Again, just plain wrong. The clipping behavior of an amplifier has a lot
to 
do with inverse feedback. The more inverse feedback, the sharper the 
clipping. Back in the days when tubes were all we had, we could make very 
nicely clipped square waves whenever we wanted to, using amplifiers that
had 
lots of inverse feedback.

A tubed amp with lots of inverse feedback will clip very nice and sharply.

And in fact, sharp clean clipping is the best alternative in most cases. 
This is because sharp clipping yields the cleanest sound as long as you 
don't clip the amp. With SS the ready alternative to sharp clipping is to 
simply get a more power amplifier, or turn the volume down a little.

With gradual clipping, you have an amp that is a little dirty well below 
maximum power. With sharp clipping you have an amp that is easier to get 
clean sound out of - just turn it down a little.

> These are the main reasons why musicians like tube amplifier
> and say they sound better.

Musical instrument amps and high fidelity amps are two vastly different
sets 
of requirements. Anybody who tries to apply musical instrument technology
to 
high fidelity amps is badly confused.

> Solid state amplifiers
> generally have slightly less internal phase delay than
> tube amplifiers.

Generally not true. When you look at solid state maps with no output 
transformers and compare them to tubed amps with output transformers which

is the usual case, the SS amp's high frequency advantage comes primarily 
from the absence of an output transformer. So its not the absence of tubes

that gives the SS amp its great potential for good high frequency
response, 
it is the absence of an output transformer. Most SS audio amps have high 
frequency response that is intentionally rolled-off to avoid problems with

EMI, etc.

> Solid state amplifiers generally have no output
> transformers or driver transformers.

Agreed, and the major benefit comes from getting rid of the OPT. However, 
tubed amps that lack OPTs have been built and other than parts count and 
attendant reliability problems, they can be very good, but at a high
price.

> Transistors and
> especially IC's in general have a faster response than
> tubes.

That's why UHF TV stations have tubed RF amplifiers. In the audio range,
the 
best estimate is that either tubes or transistors as devices have more
than 
enough high frequency response and are fast enough.

> The slew rate on the solid state amplifier is much
> faster, and it is possible to achieve lower distortion.

Two irrelevant clauses tied together to make up a misconception.  Slew
rate 
isn't a problem with tubes, after all we had tubed oscilloscopes that 
produced very nice square waves up into the MHz. In power amps the limit
to 
high frequency response is the OPT. But even with OPTs, a very good OPT
does 
not limit the HF response of the amp in a way that is necessarily audible.

SS amps are easier to build with low distortion because of the well-known 
trade-off between gain and distortion. The usual methodology for building
a 
low distortion amplifier, whether tubed or SS, is to build a very good low

distortion, high gain amplifier, and trade off the gain for low distortion

with loop feedback. It's simply cheaper and easier to build good high gain

amplifiers with SS than tubes. Thus, SS amps more commonly have very low 
distortion.

> Because of this, the solid state amplifier is said to
> have a harsher sound.

What sort of bass-ackwards logic equates harsher sound with low
distortion? 
This is just plain nuts.

> In actual fact, a good solid state
> amplifier is very accurate compared to a tube amplifier.

Both tubed and SS amplifiers can be built that are sonically accurate.
IOW, 
you have a SS amp and a tubed amp that are each very accurate and 
good-sounding, and impossible to distinguish based on their Sonics. Thing 
is, the good-sounding  SS amp can easily to be a very practical thing, and

readily available. The tubed amp is going to be larger, heavier, less 
reliable, and far more expensive.

The silliness is obsessing over amplifiers. Amplifiers are a solved
problem. 
The problem is speakers and rooms. The best use of amplifier technology is

to trade it off for better sounding speakers and rooms.