Apogee mini dac or Benchmark DAC1
 

"Eeyore" wrote in
message ...


Andy Evans wrote:

You've snipped all the previous content so it's impossible to know what
exactly
you're replying to.

Please use 'inline posting'.
http://en.wikipedia.org/wiki/Bottom_...nline_replying

You currently have all the hallmark signs of an arrogant opinionated
self-obsessed jerk !


And you don't....??

Apogee mini dac or Benchmark DAC1
 

"Eeyore" wrote in
message ...


Andy Evans wrote:

What they are confusing this with is their preference for an
intentionally flawed but
entirely pleasnt and relatively benign form of distortion. Nothing
wrong with their
listening preference but the presentation of this as inherently
superior is utterly
bogus.

The idea that valves are simply "added distortion" and nothing else
could only be made by somebody with a) very little knowledge of modern
valve circuits and how they sound or b) somebody with cloth ears.

There is precious litle 'modern' about any valve circuit. I learnt on them
btw.


Nahh, I doubt that - you post like you've learnt nothing at all.....

Apogee mini dac or Benchmark DAC1
 

"Andy Evans" wrote in message
oups.com...
There is precious litle 'modern' about any valve circuit. I learnt on
them btw.

I've no doubt you know valves from ( ?50s, 60s?, 70s?), but you'd be
very surprised at how much things have changed. Not the function of the
triode itself, which is well known, but the support circuitry is now
quite complex - cascode active loads, constant current sinks etc. - a
whole cuisine of modern ss devices and traditional stuff like glow
tubes. It really is "nouvelle cuisine" if you pardon the expression.
We're not talking Mullard circuits with EF86s and ECC83s any more.



You've got more faith with some of these 'hot under the collar' types than I
have Andy - I take a lot of what they say with a pinch of salt (large one).
Most of 'em have never heard a valve amp and some of the others have only
heard some old *legacy* struggler at best and seem to forget what some of
the transistor equipment from the 70s could sound like.....

Apogee mini dac or Benchmark DAC1
 

On 2006-09-09, Andy Evans wrote:
If the DAC isn't (sufficiently) transparent then putting a valve (tube)
in series with it cannot make the combination transparent. Yet
sometimes I see the T word used to describe
"better" in this context.

Isn't a DAC by definition something with an analogue output stage? ...

No, it's a device with an analogue output (not necessarily an analogue
output *stage*). For example, in the case of current summing DACs the
summing point is sometimes connected directly to a pin on the DAC and you
are expected to supply your own virtual-earth transimpedance amplifier
(valve or SS) if you want a voltage instead of a current output.

So
something must be on the end of it, whether ss circuit,
transformer,capacitor or tube stage. ...

Well, in the audio context a DAC will not (usually) drive a loudspeaker
so you need amplification and/or impedance conversion and/or current
to voltage conversion after the DAC itself. However I can't see the
relevance of this. There is still a very real DAC in the reproduction
chain.

The advantage of a tube stage is
that the output with DC on it can be fed directly into the grid of the
tube, and the DC included in the biasing.

That may be an advantage in certain cases but you still have a DAC
feeding the tube stage (if I have interpreted you correctly) which can
then (as you say) feed the grid of the tube amplifier with DC as well
as the analogue signal.

However that DC is only needed in the case of feeding a tube grid
- it is not usually necessary if feeding other amplifying devices.
Indeed a DAC driving a tube output stage that fed a lot of DC as well
to the output socket would be a dangerous device. (I think I must be
mis-reading something here.)

You can't talk about a DAC as
if there's "nothing" on the end of it.

Of course you can. What do you call the device whose output you connect
directly to the tube output stage?

I am totally puzzled (sorry - I *have* tried to think what the agument
and point is, but I've failed).

--
John Phillips

Apogee mini dac or Benchmark DAC1
 

you still have a DAC feeding the tube stage (if I have interpreted you
correctly) which can then (as you say) feed the grid of the tube
amplifier with DC as well
as the analogue signal.

I think you've misunderstood this. The DAC - or my DAC to be precise -
outputs an analogue signal of about 1.3v AC with about 2v DC
superimposed on it. To eliminate the DC one could put a capacitor at
this point (i.e. "something" on the end of it) But what I'm saying -
and what my setup does - is to put the analogue signal (both AC signal
and DC) directly into the grid of the triode of what we should call the
"line stage". At the output of this line stage, which has some gain, we
have the usual coupling cap and volume control. You can't put the
volume control in front of the grid because of the DC on the signal,
but the tube stage rather neatly incorporates the 2v DC into the bias
requirements of the stage. To be precise, my DAC has a balanced output
into the grids of a diff pair with a CCS under it, so the CCS
determines the current through the stage.

Apogee mini dac or Benchmark DAC1
 

The advantage of a tube stage is that the output with DC on it can be fed
directly into the grid of the tube, and the DC included in the biasing.


Are you claiming this is impossible for non-tube stages? JLS

Bad choice of words - I can see what you mean. Let me rephrase "it's
convenient to go directly into the grid because you don't need a
coupling cap at this point". You're the expert at ss, and I'd be
delighted to see a schematic for a ss solution with no coupling cap.

Apogee mini dac or Benchmark DAC1
 

Jim Lesurf wrote:

In article .com,
Andy Evans wrote:
Precisision and linearity can be measured scientifically and
objectively. The remainder are in the ear and brain of the listener.

So? The purpose of the DAC is to listen to it.

The purpose of the DAC is to reconstruct an analogue waveform as defined by
the series of sample values.

Unforunately due to Mr Evans half-assed method of quoting you mixed his comments
with mine.

I did indeed say " Precisision and linearity can be measured scientifically and

objectively. The remainder are in the ear and brain of the listener ".

And he said " So? The purpose of the DAC is to listen to it. "

Graham

Apogee mini dac or Benchmark DAC1
 

But of course, some DACs may be made so as to alter the results in
specific ways. Hence someone might then prefer this to a result
indistinguishable from the original prior to ADC conversion. :-)

I see all the signs of you being rather sly here, and if I can rephrase
this it looks like "some people prefer colourations to accurate sound",
which we know from a litany of posts about valve equipment. No, I'm
speaking about instrumental timbre which appears to be more faithful
rather than less. I can only ask people posting on this subject to hear
this for themselves, since neither scientific method nor adjectives
will substitute for the actual sound itself.

Apogee mini dac or Benchmark DAC1
 

Jim Lesurf wrote:

In article . com,
Andy
Evans wrote:

The advantage of a tube stage is that the output with DC on it can be fed
directly into the grid of the tube, and the DC included in the biasing.

Are you claiming this is impossible for non-tube stages?

Mr Evans omits to mention that the output on the tube anodes cannot be directly
coupled to the load.

Selective criticism applies as ever with this kind of tortured thinking.

In comparison, an op-amp or discrete transistor 'DAC follower' can indeed be
100% DC coupled.

Graham

Apogee mini dac or Benchmark DAC1
 

Andy Evans wrote:

There is precious litle 'modern' about any valve circuit. I learnt on
them btw.

I've no doubt you know valves from ( ?50s, 60s?, 70s?), but you'd be
very surprised at how much things have changed.

There has been no change whatever. Tube technology peaked in the early 50s.

Not the function of the
triode itself, which is well known, but the support circuitry is now
quite complex - cascode active loads, constant current sinks etc. - a
whole cuisine of modern ss devices and traditional stuff like glow
tubes. It really is "nouvelle cuisine" if you pardon the expression.
We're not talking Mullard circuits with EF86s and ECC83s any more.

Indeed, toobists now use semiconductors to help cure the inherent flaws of
thermionic devices.

Graham