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In Reply to: RE: Its all about the OPT posted by Ralph on September 08, 2021 at 15:04:29
SE amps need High-Power, low DCR power supplies.
Ordinary power supplies that use time-honored
power supplies that were historically designed
for push/pull amps were also used for SE amps,
which is a severe power mismatch for SE operation.
Properly designed SE amps don't have the
described distortions mentioned.
-Dennis-
Follow Ups:
Properly designed SE amps don't have the
described distortions mentioned.
Single-ended circuits have a quadratic non-linearity. That's a thing unaffected by the OPT. I'd be very interested to see a 'properly designed' SET that behaves as you describe.
I agree with the quadratic non-linearity.All topologies have some kind of problem(s).
Really good push/pull-- really good--- sounds
just like the best SE, but they're very different
animals as you point out.I would point out that the P/P or any balanced topology
is processing the signal (if it had started out as a SE signal--
there are some sound labs that use all SE topology-- ),
applying Common-Mode rejection to it-- the
distortions & noise are lowered.Just how much of what is filtered out was music? Is
perhaps the lack of this filtering why we love SE amps?Yet I have heard all balanced systems that sound exactly
like the best SE systems-- NO audible differences!It comes down to the designer-- what you get in your
listening room. It is very possible that the best
SE amps require certain speakers, and those speakers
may offer some sort of corrections---?.High power SE's have never interested me because of
the output trans limitations and the power required
to drive the large output device.It's an amp driving another amp, so why not just
listen to the stage before the output device?
You get fewer signal quality losses due to excessive parts,
better sound-- so why not just get a speaker that needs less power?As your top-notch work indicates, the two
examples are different anyhow-- the handling of
musical data will be different depending on how many
stages are used. I certainly agree with your work
on P/P amps-- different coupling methods, etc.,
will deliver different handling of waveforms.In the end, one may decide to change or even
compromise one topology in some way in order to
get a better overall result. For instance, one may
choose to drive a P/P output stage with a single triode
that is driving an interstage transformer-- using
the transformer as a phase inverter.You would see a flaw right there, and you would be
correct. Someone else, however, might look at it
differently-- see that it is very simple, has a truly
balanced phase inverter, and has
few signal losses in the circuitry even though
things look better if that amp is just balanced all
the way-- giving a far different handling of the signal.One could point out-- why not trash the transformer
phase inverter and just install two triodes-- that's
better, isn't it? SURE-- for about 10 minutes.One need only wait until the two tubes decide to
differ from each other. Then, the single-triode
driving the transformer/phase inverter will CREAM it.Now, which one is going to be the most fun for the
user? Especially if he keeps it for long time, and
puts many hours on it?Why wear-out tube sockets-- that's another signal
compromising problem for sure....Well, which one is going to sound the best?
That would depend on what the designer did with
the rest of the amp, and what he did to minimize the
effects of the flaw.Kudos to you and your fine work, Ralph!
-Dennis-
Edits: 10/04/21 10/04/21 10/04/21
Just how much of what is filtered out was music?
None, although if poorly executed you might wind up with a poor distortion signature (what most people call the amp's 'sonic signature').
Operating fully differential (and therefore balanced) there is nothing specifically acting as a filter unless you include the fact that all audio circuits are filters in that they have limited bandwidth.
Distortion cancellation won't remove actual musical information, just distortion. Its never perfect of course. But what that means isn't that some music got thrown out; it means that some distortion got left in the signal.
In the case were a transformer is used to convert from single-ended to balanced (which is one of the things they do really well), if you are using a single-ended circuit to drive it you'll still get some of that pesky 5th. So you'll want to drive it with a balanced circuit rather than single-ended.
The way I get around drift in the triode driver is done by using a triode differential cascode with a highly effective constant current source. With the extra gain possible and with the current in the circuit highly regulated, the drift is really minimal and tends to drift to a design center rather than away. That solves a number of problems at once- the only issue then is driving the power tubes. I use direct coupled cathode followers for that. Over a period of weeks and months the drift is surprisingly minimal- no adjustments needed in that time unless a tube failed.
"Distortion cancellation won't remove actual musical information, just distortion. Its never perfect of course. But what that means isn't that some music got thrown out; it means that some distortion got left in the signal. "
I just wanted to add to that for clarity. The distortion cancelled by a differential circuit is just the distortion that would otherwise have been created by the circuit, not distortion present in the signal from the source. On a related topic, the hum/noise picked up by the cable is the only thing "rejected" by a balanced connection between units, not any hum/noise present in the signal on the recording. Either way, none of the music is being filtered out by these methods.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
TRE and Ralph:Thank you BOTH for the excellent discussions.
You've given readers a good grip on how the
circuits you describe are supposed to work.I agree with you both, but I DO hear ANYTHING
that complicates a circuit, adding and subtracting
it's own artifacts, no matter what it is.For instance, CCS. Lots of people use them in many
ways and swear by them-- no argument there.Trouble is, I and others can hear the extra circuit
operating on the music. With the best circuits, and
speakers, it's subtle, but obvious. I really hate CCS circuits
because I can spot one operating anytime I hear it--
in anyone's amp-- two sounds for every one that's really
there. It's very small, and it's subtle. But over months of
use, CCS circuits eventually become musically boring.Another most excellent performing Band-Aid. BUT,
you can HEAR the thing doing it's thing....A super simple amp with a huge power supply can feed
the load without a CCS circuit better, and not color
the musical timing cues.So------- a few of us break a few rules now and then.
And why do we do that, when everybody knows we're WRONG?It's only because that's how we get really good
performance.I've been doing this all my life. When racing Motocross bikes,
I always had more usable power than the other guys in the same class.
They ran more RPM's= more horsepower.BUT-- I had more low-end torque AND decent hi-rev power, but
not as much as theirs.. TRE would call my engine linear and point
out that my amp isn't truly linear, only my Motocross engine is!
(the engine was putting better power to the ground, sooner).Most people today listen to a lot of single-taste music,
and build amps for their tastes, which is fine with me.I don't like that because I want to play anything I want
and have IT sound right-- no matter what it is.So----ooooo---- what is necessary gets done, trying to
keep it all simple, transparent, and honestly dynamic.It is perfect? No, it's not perfect. But it is reliable,
and you never want to replace it with something else you've
heard somewhere else.Overall, not to any particular taste. It's still not
perfect, it's still not absolutely linear, it's still
got some forms of distortions-- like everything else.It does do one thing right: it plays music like it really
sounds. With your kind understandings, it could make some
sense to you. The reviewers and the guys who play with it
agree-- even if you don't, and I am sometimes at a loss
to explain it all in engineering terms because I don't
groove-out on bringing-up online data-- I figure people
can easily already have that..After all, when a tube is operated in the lower 3/4 of
it's linear curve, why would it sound good? It might not--
unless the system is transparent enough to convey what's
taking place-- the sound of unstressed physics playing
through minimal interference circuitry..Anything-- everything-- that you do to force a vacuum
tube to comply with YOUR demands for some coveted thing--
linearity, loading perfection, etc., is audible as
something or somebody tampering with music if the audio
system playing it is sensitive enough so you can tell.Vacuum tubes-- above all-- operate best when as little
as possible is attached to them, and their operating
temperatures don't stress them in any way.-Dennis-
Edits: 10/04/21
I don't use a CCS in single-ended circuits so I can't comment, but I use them in differential amps all the time and I do have this to say:
Most CCS circuits I've seen are detrimental, because they leave performance on the table and often have linearity problems. I solved that issue about 25 years ago by implementing a 2-stage CCS in our circuits. By having 2 stages it could be referenced to ground at one end- so it knew what 'quiet' was supposed to be; at the other end it was referenced to the power supply, so it could suppress noise from the power supply as well. You really do need a 2-stage CCS to get the job done.
In our amps the power supplies were not regulated. So the performance was affected by line voltage. With the CCS installed as described, the performance of the voltage amplifier circuit was unmeasurable with the line voltage variable from 105VAC up to 130VAC. The CCS over that range varied in performance by 17 parts per million. That's pretty sweet- works really well to reduce noise and distortion while increasing gain.
I can't speak to use in single-ended circuits.
GOOD STUFF. Wonder how many DIY guys are NOT paying attention to what you typed here. Thank You, Ralph.
The Mind has No Firewall~ U.S. Army War College.
Thanks, Ralph. I like that it "sees"-- both sides--
that's an excellent idea, and a good implementation of it.
A two-sided CCS. Better-- much more so,
it's a far more stable circuit.
-Dennis-
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