"Trevor Wilson" wrote in message
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"Arfa Daily" wrote in message
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"Trevor Wilson" wrote in message
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"N_Cook" wrote in message
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Before wrapping up a Mackie SRM450 powered speaker I took some
representative DC voltages on the complementary pair power devices of
the
bass driver amp, for me and all else, future reference.
-42, -88, -42.8
41.2, 88, 42
What would the circuit type/ class name be, for this sort of biasing?
in comparison for horn side amp, same devices
0, -43, -.55
.55 , 43, 0
**There are only Class A, Class A/B, Class B and Class D amplifiers used
in audio. Anything else is just marketing bull****. What you have is a
Class A/B amp, with a switched rail power supply. Class H, Class G, et
al are just marketing terms.
--
Trevor Wilson
www.rageaudio.com.au
Well, you could say that about almost anything.
**Wrong. Classes of amplifiers are clearly and explicityly stated.
There are many manufacturers
that would disagree with you that it is just marketing bull****.
**Of course.
In fact I
can't remember ever seeing anywhere that a piece of regular Joe hifi has
ever been marketed as class G - or even class A/B.
**Here's where I get to say: COMPLETE bull****. Technics, Yamaha and
others have claimed Class A & Class A/B operation for their consumer (as
opposed to audiophile) grade components.
I see nothing wrong at
all with giving a derivative of an existing class, a new letter.
**Me either. Trouble is, it is POWER SUPPLY switching. The fundamental
Class of the amplifier's operation remains Class A, Class A/B or Class B
in all such cases. Rail shifting schemes are not alterations of amplifier
Class of operation.
Whilst
class G is indeed a switched rail class A/B amp, it never-the-less is
different from a fixed rail class A/B amp.
**No, it is not. The amplifier is STILL a Class A/B (or whatever)
amplifier, with a rail switching scheme attached. Of course, that does not
suit marketers, who dreamt up fancy new terms.
Based on what you're saying, you
might as well say that class D is an invalid term,
**Fair comment.
as class A and class B
and class A/B (and for that matter class C at RF as well) refer to the
point that the output devices are biased to in normal operation, whereas
class D refers to an entirely different concept of waveform
reconstruction by power device switching i.e. the fully digital output
stage.
**Indeed. The term: Class D has always troubled me. It does not fit with
the accepted Class of operation of an amplifier.
--
Trevor Wilson
www.rageaudio.com.au
I hear what you're saying, Trevor, but it seems to me that we are basically
just dancing around semantics. Granted, it is still a basic class AB or
whatever amplifier, but power supply switching or not, there is still
additional circuitry to detect when the higher rails are required, and it
could be argued that this circuitry is part of the power amp and its overall
design concept.
Given that you accept class D, but are not easy with it, what other
designation would you use to identify the switched rail concept as something
which 'broadly fitted in with the scheme' and allowed engineers to at least
know what it was that they were looking at ? As soon as you start giving
design concepts fancy names, every manufacturer will pick his own, and no
one will know quite where they are at ...
For sure, it's not ideal, and it does fly in the face a little, of what the
original concept of the class lettering system was about, but times move on,
and I think that for clarity, issuing this concept with a new letter, is
acceptable in practice, if not in theory, for the clarity it brings with it.
Arfa