In article ,
Keith G wrote:
Anyway, the clarity I'm getting from this little bugger from any number
of different sources is quite exceptional and I'm wondering if the
'digital volume control' has anything to do with it?

No - a digital volume control might well make things worse.

Welcome to the 21st century where cheap SS amps beat the s**t out of most
valve amps at anything near an affordable price...

--
*(over a sketch of the titanic) "The boat sank - get over it

Dave Plowman London SW
To e-mail, change noise into sound.

Serge Auckland wrote

The DSP solution would appear to be preferable. However, presumably there are
rounding errors. That is, if I divide every word by a constant, each result
must be rounded to the nearest step, and this rounding error is not linear
wrt the audio signal. I assume there is a name for this kind of error? How
significant is it?

The DSP solutions I'm familiar with operate either floating point or 32 or 48
bit internal which means that when the output is finally reduced to 16 or 24
bit the errors from the DSP calculations are minimised.

The error would be reduced by the same ratio as the conversion I suppose.

I don't know of a specific name for the errors resulting from DSP operation.

Perhaps it is no different from the usual sampling error, and possibly makes sod
all difference to the total.

A digitally controlled attenuator chip contains not only a resistor ladder,
but also a heap of semiconductors to do the switching. I expect those who
object to them are wary of the SS junctions in, and perhaps also parallel to,
the signal path.

A motorised pot may be an expensive component, but it is easier to program
the control system. The pot remembers where it is, and only needs 2 bits to
control. OTOH, it is not convenient to use if you want a rotary control on
your remote.

The main problems with all pots, motorised or otherwise is tracking over a
stereo pair.

Yes, good point. I guess better matching is part of why better quality stereo
pots are better, but the problem is always there to some extent. I get the
impression these days that the best digital attenuator chips are at least as
good as anything else.

With 5.1 surround, there would have to be 6 tracking controls so some form of
electronic volume is almost essential.

I guess so...and much more than 6 times harder to match. Not into multichannel;
it's bad enough having to make everything twice.

I have never seen a remote with a rotary volume control. Why not? If the link
is reasonably error free, then it should be possible to put a rotary encoder
on the remote as well as on the system case. I hate push-button volume
controls.


I don't think I've ever seen one either. The closest was a rotary shuttle
control for a S-VHS VTR which would allow frame by frame forward or backwards
movement. Now that I think about it a bit more, didn't QUAD have one on their
66 and 77 series?

Looks like it in this pic

http://www.whats-new-at-totallywired.com/specials.html

Come to think of it, not easy to do with the usual remote coding systems. The
most reliable way would be to send the absolute position, rather than a string
of increments. That would require a different code for each position of the
attenuator. I guess Quad used their own coding scheme. DIY remotes tend to use
RC5 or Sony codes, so you don't need to make your own transmitter.

I have a remote output level control on this quirky Sony CD player that I can
compare quite easily with my Alps pot. I have never tried it because it defaults
to bypass on power-up. I'll give it a try and report back if I can hear any
difference. Don't wait up...

Oddly, and infuriatingly, this same machine uses a front panel pot for the
headphone output, with no control on the remote, AFAIK. I wonder how they make
these decisions.

cheers, Ian

"Jim Lesurf" wrote in message
...
In article , Keith G
wrote:




As Don Pearce mentioned, the provision of a "digital" volume control
is often done for reasons of cost. Digital volume controls track left
and right channels virtually perfectly (comfortably within 0.1dB)
from full output to extremely quiet, and don't generate any
significant noise when changing levels. Normal carbon pots can be
relatively quite noisy, and even conductive plastic pots will find it
difficult to track both channels to better than 2dB at high
attenuations.


Interesting.

FWIW some of the larger and more expensive 'pots' are stepped attenuators
with laser-trimmed resistances. One of the benefits of these can be much
closer tracking of the balance as you wind down the level. They may also
use 'landings' between the settings that are particularly good at not
deteriorating with age/use. However they have tended to cost far more than
simple pots...


Excellent answer Serge - thanks. Makes me think there's even less of a
good reason for manufacturers to avoid them if, as Don says, they are
'properly implemented...???

The problem is that the 'proper implimentation' involves processes which
the user can't directly check, and the makers may be lazy or trying to cut
corners...

I would have thought a standalone 'digital attenuator' (with remote?)
would be a good thing for some valve amp owners - I wonder if such a
thing is available??

The concerns may be:

1: such a unit would require its own power and ADC/DAC, buffers, etc.

2: Would valve/analog enthusiasts wish to have this digital/solidstate
device always in their signal chain? I'd have thought they'd fear it would
corrupt the 'purity' of their system. :-)

3: Good quality stepped attenuators and detented pots exist and can work
fine.

FWIW I have always used the ALP 40mm stepped detent volume controls. When
I bought them commercially in the past I got them with tight levels of
balance, etc, spec. If you can find a source for these, I'd recommend you
try them. You may find they give an active attenuator a run for its money.



That's all very interesting but a little way wide of the point - forget
expensive, 'laser cut' options, my curiosity here is that in an amp costing
only 60 quid (and which includes 6 inputs, headphone socket, phono stage as
well as all the necessary ADC/DAC circuitry, power supply &c.) there is a
very useful *digital* (ie cheap) way of controlling
volume/treble/bass/balance/muting/'loudness' with some of the major
functions (not all) available on the (included) remote control.

I reckon this could be of interest to some (if not many) valve amp users,
as none of these functions are normally available outside of arm's length
with valve amps and some are not usually available at all! I know there are
times when I wouldn't mind being able to make various adjustments without
having to get up - volume being the obvious choice, but being able to zap to
a tuner after a record has finished (and the deck switched itself off) and
then change stations (when the volume control would be *essential*) would be
neat!!

If 'properly implemented' means that any artifacts, digital 'rounding off'
or whatever are *inaudible* there might be the possibility of an inexpensive
digital 'front end' which offers the convenience of remote control on the
main functions as well the additional capability to adjust
tone/balance/loudness/muting &c. (An amusing concept on a valve amp!!)

Or, as the price of the whole amp is peanuts, I would even go as far as to
suggest that someone with more expertise than me could butcher one of these
amps to create a very interesting 'digital pre' with all the afore-mentioned
functionality!

;-)

"Stewart Pinkerton" wrote in message
...
On Fri, 19 May 2006 19:02:31 +0100, "Keith G"
wrote:

Well, I reckon a 30 wpc amp will work out at about 2 to 4 quid per watt,
but
the trouble is you *need* 100+ watts these days (ludicrous) and then I
reckon you are looking at 5 times that sort of money *at least* for
similar
(construction/appearance/appointments) 'assembly line' amps....??

Untrue for subs, Keith. You can buy a 500 watt 'plate' amp with active
crossover and all necessary connections and controls, for less then
three hundred quid. Just the job for getting deep, clean bass down to
20Hz at decent SPLs from an 18" cube. Also one of the last remaining
areas where the home builder can beat the commercial stuff.


The thing with home builders is that just about all of them think they are
beating the commercial stuff or I guess they wouldn't bother??

But it's not all about the money - many DIYers are looking to beat
commercial stuff in terms of ultimate performance/specification and are well
aware they would definitely *not* be beating commercial producers on a cost
basis if their own labour was priced into the equation....!!??

"Dave Plowman (News)" wrote in message
...
In article ,
Keith G wrote:
Anyway, the clarity I'm getting from this little bugger from any number
of different sources is quite exceptional and I'm wondering if the
'digital volume control' has anything to do with it?

No - a digital volume control might well make things worse.

Welcome to the 21st century where cheap SS amps beat the s**t out of most
valve amps at anything near an affordable price...



I'm afraid I don't share your view - much as I like the various/numerous ss
gadgets I use (and enjoy) here, when it comes to amplifiers and playing
*music* none of them beat the various valve amps I've got. (Quite simply,
you either *get that* or you don't....)

Try to get past this 'mutual exclusivity' thing - you don't have to make
*final* choices forever, you can drink both Coca Cola and Pepsi Cola if you
want to....

Keith G wrote:
The thing with home builders is that just about all of them think they are
beating the commercial stuff or I guess they wouldn't bother??

But it's not all about the money - many DIYers are looking to beat
commercial stuff in terms of ultimate performance/specification and are well
aware they would definitely *not* be beating commercial producers on a cost
basis if their own labour was priced into the equation....!!??


Some people want to climb a mountain because it is there. The people
that put a wall around that idea don't understand the enjoyment one gets
in making the journey - no matter how ill looking the end looks (or not!)

I take my hat off to this person and many like her.
http://en.wikipedia.org/wiki/Jeri_Ellsworth

DIY electronics rules forever!

--
Adrian C

Adrian C wrote:
Keith G wrote:
The thing with home builders is that just about all of them think they
are beating the commercial stuff or I guess they wouldn't bother??

But it's not all about the money - many DIYers are looking to beat
commercial stuff in terms of ultimate performance/specification and
are well aware they would definitely *not* be beating commercial
producers on a cost basis if their own labour was priced into the
equation....!!??

Some people want to climb a mountain because it is there. The people
that put a wall around that idea don't understand the enjoyment one gets
in making the journey - no matter how ill looking the end looks (or not!)

I take my hat off to this person and many like her.
http://en.wikipedia.org/wiki/Jeri_Ellsworth

DIY electronics rules forever!

Absolutely!

Like many of my generation I got into electronics through the DIY route,
trailing round the component shops in Lisle St in London, falling over
the ladies of the night in our search for some particular component!
Sadly, now, just buying components is a trial in itself. It has to be
mail-order or forget it. One notable exception is the wonderful emporium
of Gee's in Cambridge. A real old-fashioned component shop staffed by a
great guy who's been there since Schottky was a lad.

Sadly building one's own stuff from scratch is a lot more expensive than
buying it built. Stewart mentioned buying plate amplifiers for
sub-woofers, which is fine, but if you want to make your own amplifiers
you end up spending a lot more than buying one. Keith's own experience
with the POS amplifiers shows this up well. There's no way you can even
buy the box for the price of the complete unit from Comet, Argos or whoever.

I hope there will always be a DIY sector interested in building stiff
not because it's cheaper but because it's a lot more satisfying.

More power to your soldering iron.

S.

Hi,

"Serge Auckland" wrote in message
...

This reminds of the ludicrous situation that was common in the mid eighties
when Linn in particular suggested a Linn-Ittok-Asak combination for use with
a little Nytech or NAIM amp and Linn Kan 'speakers. The results were truly
horrible entirely due to the appalling 'speakers. I really felt for people
who had wasted their money in that way but what could a layman do when every
mag recommended such folly.

Hi-Fi Answers perchance? I remember their long, drawn out arguments
on why "garbage in meant garbage out", and being young and naive
I almost fell for it. Fortunately the old boy at the local electrical shop
(no 'proper' hi-fi shop nearby then or now) put me straight and
made me sit down and listen to some systems. I came out with a
good one, and I've been a major sceptic about all 'hobby' magazine
recommendations ever since.

When I was in retail at the time I tried to fight against it, putting
'speakers first, then decent amplification and a CD player, but went bust
for my pains. Ah well.....

Good man. At least you were on the right side. Sometimes it's better
to be right than to win the argument. Sorry it meant you going bust
though...

Regards,

Glenn.

In article , Keith G
wrote:

"Jim Lesurf" wrote in message
...
[big snip]


That's all very interesting but a little way wide of the point - forget
expensive, 'laser cut' options, my curiosity here is that in an amp
costing only 60 quid (and which includes 6 inputs, headphone socket,
phono stage as well as all the necessary ADC/DAC circuitry, power
supply &c.) there is a very useful *digital* (ie cheap) way of
controlling volume/treble/bass/balance/muting/'loudness' with some of
the major functions (not all) available on the (included) remote
control.

Yes, I'd agree. I was just pointing out that some people have an aversion
to anything 'digital', and that a 'digital attenuator' may have flaws, so
should assessed with due care. But the silicon for one is cheap, and should
be able to give good results if well done.

Note also that applying tonal changes (treble, bass, etc) is slightly more
complex, so again should be fine if well implimented, but...


If 'properly implemented' means that any artifacts, digital 'rounding
off' or whatever are *inaudible* there might be the possibility of an
inexpensive digital 'front end' which offers the convenience of remote
control on the main functions as well the additional capability to
adjust tone/balance/loudness/muting &c. (An amusing concept on a valve
amp!!)

Yes. However the above comment should be applied with caution in practice
since it starts by assuming that the imperfections *are* "inaudible". The
snag is that they may not be. For example, a digital volume control will
have a clipping level in a way that an analogue one does not. This may not
matter for some applications, but be vital in others. Hence "inaudible"
will depend both on the volume control and the specific use.

I don't have any real objection in principle to 'digital' controls. Indeed,
I tend to prefer processing signals in digital form when the process needs
flexibility, etc. However the reality is that an ADC-process-DAC-psu-clock
combination is electrically more complex than a pair of resistors. Hence it
gives the poor designer/maker more options for making errors. :-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

"Serge Auckland" wrote


Sadly building one's own stuff from scratch is a lot more expensive than
buying it built. Stewart mentioned buying plate amplifiers for
sub-woofers, which is fine, but if you want to make your own amplifiers
you end up spending a lot more than buying one. Keith's own experience
with the POS amplifiers shows this up well. There's no way you can even
buy the box for the price of the complete unit from Comet, Argos or
whoever.


I would just like to point out that my recent excursion into the cheap 'n'
cheerful Argos kit is just another of my 'investigative/curiosity' trips and
I wouldn't claim that this sort of kit (almost toys, if you go by price)
would satisfy many people - the price/POQ alone will prevent many from
taking it seriously or being content with it on a long-term basis, I would
guess. Take it from me that the sound quality is well up snuff compared with
what cheaper 'mid-fi' kit I've heard (including the Roksan Kandy mentioned
elsewhere) and the build quality is not far (if at all) behind, although
only time will tell in respect of durability....??

(At the end of the day *cheap* never really does anybody any favours -
factor life, but if the cheap stuff is at least OK/usable, gets people
*into* decent sound and possibly starts them off on an upgrade path (groan)
it possibly isn't completely bad news for the industry....??)



I hope there will always be a DIY sector interested in building stiff not
because it's cheaper but because it's a lot more satisfying.


Well, the diyaudio.com forum:

http://www.diyaudio.com/index.php?s=...857351d6501ec0

claims 54,824 members and there are *countless* other such forums (fori?
fora?) on the Net these days, so I guess it's not looking too bad! (Plus it
seems that there's plenty of people ready to *tweak* just about any bit of
electronics kit you can get these days - audio, AV, TV and computer!!)



More power to your soldering iron.


Ooh, er!! Steady on, old bean!! :-)