"Robert Morein" wrote in message
wrote in message
oups.com...
Arny Krueger wrote: snip
It is true that cheap-ass tubed equipment is far more technically
deficient than some of the expensive stuff. There's no reason why a
price-is-no-object tubed amp can't sound good and accurate when that
high
price is invested in a technically sophisticated way.
That's exactly what I said. If you are willing to spend money either
tubes or solid state may be used to build good amplifiers. Good solid
state ones IMO aren't cheap either. They need (IMO) big heat sinks
and quiet low impedance power supplies.
Partly true.
A price-no-object tubed amp can sound as good in many ways. That does
not mean they are equivalent.
In his sad quest for the false appearance of technical competence, the
Morein grotesquely distorts what I said and then tries to make a big show
out of *correcting* his own statements as if they were mine.
Obviously I never said that tubed amps and SS amps could be equivalent. I
said
"There's no reason why a price-is-no-object tubed amp can't sound good and
accurate when that high
price is invested in a technically sophisticated way."
But output transformer saturation leads to an inherent high-pass
filter that cannot be eliminated, unless on goes with something like
the Futerman OTL design.
Regrettibly, the Morein confuses two common output transformer failings.
(1) Core saturation, which causes nonlinear distortion (e.g., THD and IM).
(2) Leakage capacitance, which causes loss of high frequency response.
There are also third and fourth common transformer failings:
(3) Leakage inductance, which also causes a loss of response.
(4) Resonance, which causes rough response and ultimately additional high
frequency losses.
Morein's incorrect statement would look like this:
Core saturation, which causes loss of high frequency response.
Morein mentions saturation, but he lines it up with the wrong amplifier
performance fault.
Here is confirmation of my claims from a independent source:
http://www.allaboutcircuits.com/vol_2/chpt_9/11.html
"When a transformer's primary winding is overloaded from excessive applied
voltage, the core flux may reach saturation levels during peak moments of
the AC sinewave cycle. If this happens, the voltage induced in the secondary
winding will no longer match the wave-shape as the voltage powering the
primary coil. In other words, the overloaded transformer will distort the
waveshape from primary to secondary windings, creating harmonics in the
secondary winding's output. As we discussed before, harmonic content in AC
power systems typically causes problems.
You can see that the independent authority essentially says that
Core saturation causes nonlinear distortion.
The three other common transformer failings are also described by the
reference:
http://www.allaboutcircuits.com/vol_2/chpt_9/10.html
"Like their simpler counterparts -- inductors -- transformers exhibit
capacitance due to the insulation dielectric between conductors: from
winding to winding, turn to turn (in a single winding), and winding to core.
Usually this capacitance is of no concern in a power application, but small
signal applications (especially those of high frequency) may not tolerate
this quirk well. Also, the effect of having capacitance along with the
windings' designed inductance gives transformers the ability to resonate at
a particular frequency, definitely a design concern in signal applications
where the applied frequency may reach this point (usually the resonant
frequency of a power transformer is well beyond the frequency of the AC
power it was designed to operate on).
....
"Closely related to the issue of flux containment is leakage inductance.
We've already seen the detrimental effects of leakage inductance on voltage
regulation with SPICE simulations early in this chapter. Because leakage
inductance is equivalent to an inductance connected in series with the
transformer's winding, it manifests itself as a series impedance with the
load. Thus, the more current drawn by the load, the less voltage available
at the secondary winding terminals.
It is not possible, with a practical level of effort, to equal the
amperage and damping factor of an excellent solid state design.
Agreed, which is why I said that a price-is-no-object tubed amp can't sound
good and accurate when that
high price is invested in a technically sophisticated way. However, I would
probably cut to the chase and elmiinate the output transformer all together.
Eliminating the output transformer and yet providing ample ability to drive
difficult speaker loads would require a large number of output tubes, which
would drive up the expense quite *effectively*
That said, I have seen a Krohn-Hite vacuum tube laboratory amplifier that
was flat from about 1 Hz to 10 mHz.
Probably didn't have an output transformer, and probably couldn't drive a
speaker load to appreciably power levels. Krohn-Hite still provides wideband
amplifiers, but they are designed to work with loads in the 200-600 ohm
range. They'll drive lower impedance loads, but with a tremendous loss of
rated power output.
The caveat is that the Krohn-Hite was this flat only at the 1 watt
level. At higher levels, the inherent storage capacity of the output
transformer constricted the bandwidth. All tube amplifiers suffer
from this at more than low power levels.
I question whether there was an output transformer.
Solid state amplifiers slow down a little when driven toward the
supply rails, but the corresponding bandwidth reduction is fractional
compared to tube amplifiers.
Agreed.
Tubes are high impedance devices. Speakers are low impedance devices.
Making the two work together requires the output transformer, which
introduces artifacts from the hysteresis of the iron core. Some
people regard this as beneficial to the sound. There is no point in
arguing with a personal preference. However, I, personally, have not
heard a tube amplifier as pleasing to my ear as the best solid state
equipment.
I don't find the sound from really good tubed amplifiers disturbing or
substandard. I just question working so hard and spending so much money to
obtain a result that can be obtained easily and inexpensively from
well-designed SS equipment.
I would not dispute that some tube equipment sounds better than some
solid state equipment.
Or, vice versa which is the more common situation.