On Sat, 31 Jul 2010 09:18:11 +0100, "David Looser"
wrote:



I hadn't heard that; FWIW the Sony 'PCM-on-Betamax-cassettes' system was
14-bit.

It was 16 bit switchable to 14 bit. (I've still got a PCMF1.)

Philips started the development of CD as a 14 bit system with a
smaller disc than they ended up using. At some later stage they
started cooperating with Sony. It was Sony who wanted the higher bit
depth and they also wanted the playing time increased, so the disc
diameter increased. The story is that Akio Morita wanted to be able to
play Beethovens 9th without interuption.

At the time Sony had been developing digital audio systems for some
time and had the capability to make 16 bit converters. Philips could
only manufacture 14 bit converters, and the oversampling that they
ended up using was a way in which they could keep up with a 16 bit
spec, but using the 14 bit converters that they had.

At the time (late 70s) this was difficult technology to mass produce
and Philips original 14 bit system was much potentially much better
than LP anyway. Sony improved it and future proofed it well.

Bill

Jim Lesurf wrote:


Any reason you did not build an emitter follower instead as a buffer?
Or is that just a bit too complex for your aims above?

Chose this approach my aim was to make it as 'simple as possible' for
people who had not previously built anything. So a 'minimal' design. Must
confess that having thought of using transformers I became curious to see
how well the cheap 'CPC' ones might work. :-)

I see your point there. I made a simple head phone amp years back. Gain
via common emitter stage forllowed by an emitter follower for current gain.
I did not get around to the Mk2 as I found myself using headphones less. It
had two significant problems:

* Appaling power on / off thump - basically 4.5V step into headphones.
* A lot of crosstalk, presumably via the bias cct on the voltage gain stage.

The latter was inelegently partly solved by a large electolytic across the
power rails.

Lession - a usable circuit would be more complex to solve the above issues.


Of course, there is no reason I or someone else can't now suggest
'improved' versions - like better transformers or using buffers.
Similarly, adding crosstalk bleed networks which some may prefer for
headphone
listening. :-)

But surely transformers are expensive and have hysterisis losses?

But they do kill earth loops!


And I'd expect that others might prefer a physically 'tidier' construction
that I am using. Never been much of a 'mechanical engineer'. ;-

But having listened to the unit with Sennheiser EH350 phones my main
reaction is that the results sound more enjoyable than I'd expected. The
only tweak I plan at present is to to add a limited-range balance control.

I liked mine but I don't know how objective I was!

FWIW later tests and all listening have been with 4 x NiMH AA (1700mAh)
cells as the power supply. These have so far lasted a couple of hours but
I've no idea how much longer they will manage before needing a recharge.

A PP9 seems to run mine for a reasonable time, even though the output was
class A - but I suspect that I could buy a PSU for cheaper than the battery
if I looked carefully.

--
http://www.petezilla.co.uk

In article , Peter Chant
wrote:
Jim Lesurf wrote:


Any reason you did not build an emitter follower instead as a
buffer? Or is that just a bit too complex for your aims above?

Chose this approach my aim was to make it as 'simple as possible' for
people who had not previously built anything. So a 'minimal' design.
Must confess that having thought of using transformers I became
curious to see how well the cheap 'CPC' ones might work. :-)

I see your point there. I made a simple head phone amp years back.
Gain via common emitter stage forllowed by an emitter follower for
current gain. I did not get around to the Mk2 as I found myself using
headphones less. It had two significant problems:

* Appaling power on / off thump - basically 4.5V step into headphones.
* A lot of crosstalk, presumably via the bias cct on the voltage gain
stage.

Yes, that was one of the things I had in mind. The modern 'solution' tends
to be dual rails ... thus making the setup more complex.

The latter was inelegently partly solved by a large electolytic across
the power rails.

That can reduce the thump (and reduce crosstalk if the psu is poor) but
then means a series resistance in the rail as well - unless you decide just
to poke the psu hard at every turn-on. 8-]

An alternative is ye olde 'volume pot with the on-switch at the 'off' end
of the travel'. But does anyone still make these with decent specs?

Lession - a usable circuit would be more complex to solve the above
issues.

Using the transformers also meant I could avoid needing a bit of veroboard
or some other board. In turn meaning no need for attachments for the
internals. With the tiny transformers I just let them rattle about in the
box. If that is a bother, I'd have just padded out with some foam. As the
French (nearly) say, "Not magnificent, just the railway station" :-)


Of course, there is no reason I or someone else can't now suggest
'improved' versions - like better transformers or using buffers.
Similarly, adding crosstalk bleed networks which some may prefer for
headphone listening. :-)

But surely transformers are expensive and have hysterisis losses?

In the case of the prototype I made I'm not sure all told if the
transformers are much more expensive than a nice amp and psu that had
minimal distortion, no thump, etc. And the output seems OK to me. But I'd
agree better transformers might be desirable, and more costly. One of the
things that did surprise me about the transformers I used was that the
winding resistances were higher than I'd expected. Also I suppose that does
help protect the DAC from an unintentionally shorted output. 8-]

[snip]


FWIW later tests and all listening have been with 4 x NiMH AA
(1700mAh) cells as the power supply. These have so far lasted a couple
of hours but I've no idea how much longer they will manage before
needing a recharge.

A PP9 seems to run mine for a reasonable time, even though the output
was class A - but I suspect that I could buy a PSU for cheaper than the
battery if I looked carefully.

Yes. I chose batteries because I wanted it to be portable and for use with
my laptop. Only after I made it, I decided it was decent enough to use with
my AV/audio items as well! FWIW The NiMH cells I'm using are still running
on the first charge so I don't know how long they will last. I'm also
hoping to find some 'better' transformers sometime I can try out. Now
curious to see if something along those lines is available and worthwhile.

And the AU-D3 seems to be designed for 5V rail. So a PP9 would be risky due
to the higher voltage. FWIW I've asked the makers for more info on the
AU-D3 so may know more later. If so, I'll report anything useful.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

"Bill Taylor" wrote in message
...
On Sat, 31 Jul 2010 09:18:11 +0100, "David Looser"
wrote:



I hadn't heard that; FWIW the Sony 'PCM-on-Betamax-cassettes' system was
14-bit.

It was 16 bit switchable to 14 bit. (I've still got a PCMF1.)

Yes, but the older PCM100 unit used with mains Betamax VCRs was only 14 bit.
Presumably the 14-bit switchable facility on the PCMF1 was to provide
compatablity with them.

At the time Sony had been developing digital audio systems for some
time and had the capability to make 16 bit converters.

I'm not convinced that anybody at the time had the capability to make
monolithic converters that actually delivered 16-bit performance. Certainly
none of the ones I measured at the time (inc. Burr-Brown which were supposed
to be the best) did so. If you wanted true 16-bit performance you needed to
go to hybrid DACs which were too expensive for consumer use.

David.

"Jim Lesurf" wrote in message
...
In article , David Looser
wrote:
"Jim Lesurf" wrote in message
...


What I actually said was "you seem to want to present the choices
Philips made as being simply cost-driven"; please note the presence of
"simply".

Then it seems to me that you are reading into what I have said things
which
I didn't say.

Well I guess we both were!

Also not clear to me what you mean by "simply".

Definition 2 of "simply" from the on-line OED: "merely; just:"

If a design decision is "simply" cost-driven then cost is the only
consideration, performance, reliabilty etc. do not figure.

So you'd need to explain what you mean here by "best" if it is
something else,

Lets go back to where this started: "fed up lurker" asserts that taking
the digital filters out of oversampling CD players makes them sound
"better". The actual word he used was "magical" which implies "much
better". I dispute that.

Then your argument wrt that is with him, not me.

Yes of course my argument is with him, it always was. But you seemed keen to
take it on :-)

You seem to be chasing me because of an opinion someone else has asserted.
:-)

Odd, I thought you were the one doing the chasing ;-)

David.

Jim Lesurf wrote:

* Appaling power on / off thump - basically 4.5V step into headphones.
* A lot of crosstalk, presumably via the bias cct on the voltage gain
stage.


Yes, that was one of the things I had in mind. The modern 'solution' tends
to be dual rails ... thus making the setup more complex.


Especially as 3 rail batteries or off shelf psu's are rare....

The latter was inelegently partly solved by a large electolytic across
the power rails.

That can reduce the thump (and reduce crosstalk if the psu is poor) but
then means a series resistance in the rail as well - unless you decide
just
to poke the psu hard at every turn-on. 8-]


I don't think the battery minded. I do note, on one of my early attempts at
a pre-amp - which used two batteries for 3 rails, it was still bad as + and
- switch contacts made at slightly different times.



And the AU-D3 seems to be designed for 5V rail. So a PP9 would be risky
due to the higher voltage. FWIW I've asked the makers for more info on the
AU-D3 so may know more later. If so, I'll report anything useful.

You could stick a voltage regulator in there for the DAC.

--
http://www.petezilla.co.uk

In article , David Looser
wrote:
"Jim Lesurf" wrote in message
...
In article , David Looser
wrote:
"Jim Lesurf" wrote in message
...


What I actually said was "you seem to want to present the choices
Philips made as being simply cost-driven"; please note the presence
of "simply".

Then it seems to me that you are reading into what I have said things
which I didn't say.

Well I guess we both were!

Also not clear to me what you mean by "simply".

Definition 2 of "simply" from the on-line OED: "merely; just:"

If a design decision is "simply" cost-driven then cost is the only
consideration, performance, reliabilty etc. do not figure.

In that case "simply" seems to me to be meaninglessly strict. Making
nothing would have cost nothing. Making something that was unreliable would
have been cheap, etc. But they wanted to choose something that they could
make reliably, meet the nominal specs for the 16 bit CDDA, *and* be as
cheap to make as they could arrange.


So you'd need to explain what you mean here by "best" if it is
something else,

Lets go back to where this started: "fed up lurker" asserts that
taking the digital filters out of oversampling CD players makes them
sound "better". The actual word he used was "magical" which implies
"much better". I dispute that.

Then your argument wrt that is with him, not me.

Yes of course my argument is with him, it always was. But you seemed
keen to take it on :-)

Again I'm not clear what you mean by "take it on" here.

FWIW I think the idea of using non-oversampling is an interesting one. And
as I've pointed out there is no reason in principle why that can't work
fine. The devil is then in the details when it comes to assessing one
implimentation versus others and the nominal spec for CDDA. I can think of
potential advantages and snags of either approach. But they all depend
entirely on the details of what you do in practice.

I've been happy enough with oversampling DACs like the Meridian (and now
the DACMagic) for some years. Still enjoy the results they give. Before
that I enjoyed the ancient Marantz with the 1st gen Philips chipset -
albeit having added extra analogue filtering. But if anything that is why I
am interested in alternatives. To explore how they work and what they might
have pro or anti in practice, or if others like/dislike them, etc.

To me this is simply a matter of being curious, open minded, and willing to
consider things. I am also interested in things that might encourage hifi
users to 'get their hands dirty' and try things for themselves. Even if the
end results are no better than what they can buy in a technical sense I
suspect some people will enjoy the results more because of the added
pleasure from knowing they made/modded something and have some added
understanding or involvement. Provided people learn and are open minded
that seems fine to me. They can then decide for themselves what they prefer
or if something is good/bad. Better that way than for me or reviewers to
tell them.

You seem to be chasing me because of an opinion someone else has
asserted.
:-)

Odd, I thought you were the one doing the chasing ;-)

Your opinion, not mine. :-)

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

In article , Peter Chant
wrote:
Jim Lesurf wrote:



And the AU-D3 seems to be designed for 5V rail. So a PP9 would be
risky due to the higher voltage. FWIW I've asked the makers for more
info on the AU-D3 so may know more later. If so, I'll report anything
useful.

You could stick a voltage regulator in there for the DAC.

Yes. But for the prototype that would have added components/complications,
and in my experience the 'one chip' regulators tend to cause problems -
more details required to then prevent that. And it would be wasteful to
drop 9V to 5V when 4 x AA NiMH gives about 5V anyway.

Used the HeadDAC this afternoon to listen to a DVD I made of last nught's
AYO Prom. Another hour and the batteries still seem fine on their first
charge. The PSU that came with the AU-D3 says "0.3 to 0.5A" for its dc
output so I'd wondered if the AU-D3 was current hungry. The AAs I'm using
are rated as 1700mAh which implies from that somewhere in the 3 to 6 hour
range between recharges. Not been keeping notes, but I'd think I'm now well
over 3 hours of use.

For split rails from one set of cells it occurred to me that the trick QUAD
used for the PSU in their 34 preamp might avoid switchon thumps/clicks.
That uses an op-amp to center the ground about the polarities of a single
psu potential difference. Means 'both rails come on together' as soon as
that op amp wakes up. :-)

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

"Jim Lesurf" wrote

In that case "simply" seems to me to be meaninglessly strict. Making
nothing would have cost nothing. Making something that was unreliable
would
have been cheap, etc. But they wanted to choose something that they could
make reliably, meet the nominal specs for the 16 bit CDDA, *and* be as
cheap to make as they could arrange.


You really do seem to want to pick that particular point to pieces and look
at the entrails, well don't let me stop you!


Again I'm not clear what you mean by "take it on" here.

See below:-

FWIW I think the idea of using non-oversampling is an interesting one.

Do you? Oh well it takes all sorts I suppose :-)

And
as I've pointed out there is no reason in principle why that can't work
fine.

In theory it can work fine, but a high-performance analogue filter for a
non-oversampling converter is neither simple nor cheap.

The devil is then in the details when it comes to assessing one
implimentation versus others and the nominal spec for CDDA. I can think of
potential advantages and snags of either approach.

And your potential advantages for the non-oversampling approach are?

I've been happy enough with oversampling DACs like the Meridian (and now
the DACMagic) for some years. Still enjoy the results they give.

Are they multi-bit oversampling designs, or, like the majority of audio DACs
these days, of the 1-bit variety?

But if anything that is why I
am interested in alternatives. To explore how they work and what they
might
have pro or anti in practice, or if others like/dislike them, etc.

Been there, done that - got the T-shirt. :-)


David.

"David Looser" wrote in message
...

Dave
There are a number of *marketed* non oversampling DAC's,
apart from those previously listed in threads such as the
Project or Moonlab:
http://www.tnt-audio.com/sorgenti/audionote11kit_e.html
http://www.scott-nixon.com/dac.htm
http://www.positive-feedback.com/Issue27/monica_dac.htm

http://www.head-case.org/forums/home...pressions.html

http://www.head-fi.org/products/mood...ersampling-dac
http://www.enjoythemusic.com/magazin...abs_havana.htm

Then there are DIY'ers who so enthralled attempt to market their handiwork:
http://www.ecp.cc/NOS-USB-DAC.html
http://www.audioxsell.com/classified...H-Modified.htm

And ebay is cluttered up with NOS'd cd players, from the likes of me
who mod a bargain basement £5 1980's Philips or Marantz and flog
it for an easy profit (only joking...)

Plus there is plenty of waffle about the subject:
http://www.sakurasystems.com/articles/Kusunoki.html
http://www.youtube.com/watch?v=vgi-r_z1cS4

You Dave won't get the gist of this one (yet) but briefy in email
to Jim I touched on "piggy-backed" TDA1543's NOS'd:
http://home.comcast.net/~omaille/aud.../valabdac.html
http://avprime.co.uk/Project-DAC-Box-FL

But they all got it from DIY'ers, this is just one noted (notorious?) site
there are many, many more out the
http://www.lampizator.eu/Nonoversampling/NOS.html
http://www.lampizator.eu:80/LAMPIZAT...r/TDA1541.html

Dispite how marketeers bundle it up with all sorts of add-on tweaks
so as to justify the cost of a pre-packaged/marketed NONOS dac,
the essense of how it works and why is sounds as it does is simply
bypassing the filter. And it can be a very simple and effective 20 minute
modification by a complete novice - but one with steady hand and good
eyesight!

So Dave, because you never heard of it dosen't mean it never existed.
Arny is going to give it a try, and obviously Jim is beguiled by the whole
concept. Unfortunately this group is too narrow so any more info will
be on a need-to-know basis.

I don't think Jim is talking to me anymore, I think he finds me too
annoying and maybe strings have been pulled? So I'm leaving him to
his experiments with NONOS. He'll figure it out.
The "trend" appears to be to mention the Dacmagic as often as possible,
so I just have, for the last time ever..........