Digital volume control question....
 

A week or two ago I bought a little cheapo ss amplifier from Argos for
fun/summer/curiosity/all day long radio, MP3s &c. and wuz so taken with it I
bought a couple more (similarly cheap) components from the same range to go
with it:

http://www.apah69.dsl.pipex.com/show/outbreak.JPG


(OK, I admit it - I was driven by the 3-way, multi-purpose remote control!!
:-)

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?

I know the speakers (firewood horns - Pinkies) are 'on song' now and will be
contributing mostly to the sound quality and I am convinced that normal
(carbon wiper) volume pots do the sound no favours whatsoever, but is there
any reason the 'digital volume' (much like a computer soundcard, I guess) is
likely to be helping in a significant way?

(If it is, I wonder why more manufacturers don't use them?)

Digital volume control question....
 

On Fri, 19 May 2006 12:28:48 +0100, "Keith G"
wrote:

A week or two ago I bought a little cheapo ss amplifier from Argos for
fun/summer/curiosity/all day long radio, MP3s &c. and wuz so taken with it I
bought a couple more (similarly cheap) components from the same range to go
with it:

http://www.apah69.dsl.pipex.com/show/outbreak.JPG


(OK, I admit it - I was driven by the 3-way, multi-purpose remote control!!
:-)

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?

I know the speakers (firewood horns - Pinkies) are 'on song' now and will be
contributing mostly to the sound quality and I am convinced that normal
(carbon wiper) volume pots do the sound no favours whatsoever, but is there
any reason the 'digital volume' (much like a computer soundcard, I guess) is
likely to be helping in a significant way?

(If it is, I wonder why more manufacturers don't use them?)




No - in fact there is more chance that a poorly implemented digital
control will damage the sound. But the real reason why your amp has a
digital volume control is the usual one - cost. Pots cost money, they
need mechanical fixings to support them and people have to bolt them
in and wire them up. That is all bad news for a high-volume
manufacturer. People are still resistant to digital volume controls in
much of the market, though. I have a couple of amps with motorized
volume pots.

The reason why it all sounds so clear is that it is a normal SS amp
and it isn't broken. These days it really doesn't have a lot of choice
in the matter - you need to exert special efforts to make a bad amp
these days, particularly if, as I suspect, this one uses chips for the
PA stage.

d

--
Pearce Consulting
http://www.pearce.uk.com

Digital volume control question....
 

"Don Pearce" wrote in message
...
On Fri, 19 May 2006 12:28:48 +0100, "Keith G"
wrote:

I know the speakers (firewood horns - Pinkies) are 'on song' now and will
be
contributing mostly to the sound quality and I am convinced that normal
(carbon wiper) volume pots do the sound no favours whatsoever, but is
there
any reason the 'digital volume' (much like a computer soundcard, I guess)
is
likely to be helping in a significant way?

(If it is, I wonder why more manufacturers don't use them?)




No - in fact there is more chance that a poorly implemented digital
control will damage the sound. But the real reason why your amp has a
digital volume control is the usual one - cost.


Sure, the amp only cost 60 quid brand new (with warranty)!!


Pots cost money, they
need mechanical fixings to support them and people have to bolt them
in and wire them up.


Yep.


That is all bad news for a high-volume
manufacturer. People are still resistant to digital volume controls in
much of the market, though.


Hmm....


I have a couple of amps with motorized
volume pots.


Nothing 'motorized' here - the *Control* knob (multifunctional) doesn't turn
when the zapper's up and down buttons are being used and it rotates
endlessly when being turned by hand....

(Bit like the manual focussing on my digital camera - OK on the amp, but
pretty irritating on the camera!!)



The reason why it all sounds so clear is that it is a normal SS amp
and it isn't broken. These days it really doesn't have a lot of choice
in the matter - you need to exert special efforts to make a bad amp
these days,


Yes, my suspicion also and why I bought the amp in the first place, to check
it out. (See below...)


particularly if, as I suspect, this one uses chips for the
PA stage.


PA stage?? (Preamplification?)

I believe it's pretty hard to buy a bad *anything* much these days. I can
understand stuff costing a lot of money if it uses a lot of expensive
material or is hand-built (in a one-off kinda way) but I generally think the
VFM factor is pretty high for what these things cost! As to the the volume
control, I would consider that anything that took a carbon pot out of the
occasion would be a good thing? (I don't know about 'poorly implemented' -
why should it be poor? Is this one area where it would be particularly
difficult to do the thing well?)

My exploration into all this has been a staggering success AFAIAC - I have
proved (to myself, if no other) that the *speakers* drive the whole 'hifi'
thing *bigtime*! I would/will put this sound I'm getting off a cheap POS amp
against anything I've heard to date!! In fact, I'll go as far as to say I
don't much care about sources and amplification, the speakers can (and do)
make or break it all!!

I shudder to think how much money people are throwing at the game, trying to
get a pair of iffy speakers to sound good. I swapped the Pinkies for a pair
of very respectable JM-Labs the other day and the sound (from the exact same
kit) slumped like punctured tyre!! I've got turntables/tuners/CDPs here that
cost nowt and they all sound superb on the firewood horns, irrrespective of
the amplifiers used!!

Its revised my views completely, my advice to anyone looking for good sound
on the cheap would/will be 'build a pair of speakers and then chuck any old
kit at them' - I reckon you could get a superb tuner/CDP system going for
less than 200 quid!!

If me little mic weren't bust I'd post a track or two!!

(Off to check out the mic anyway..... :-)

Digital volume control question....
 

Keith G wrote:
A week or two ago I bought a little cheapo ss amplifier from Argos for
fun/summer/curiosity/all day long radio, MP3s &c. and wuz so taken with it I
bought a couple more (similarly cheap) components from the same range to go
with it:

http://www.apah69.dsl.pipex.com/show/outbreak.JPG


(OK, I admit it - I was driven by the 3-way, multi-purpose remote control!!
:-)

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?

I know the speakers (firewood horns - Pinkies) are 'on song' now and will be
contributing mostly to the sound quality and I am convinced that normal
(carbon wiper) volume pots do the sound no favours whatsoever, but is there
any reason the 'digital volume' (much like a computer soundcard, I guess) is
likely to be helping in a significant way?

(If it is, I wonder why more manufacturers don't use them?)

As far as I know there are two sorts of "digital" volume control. One is
a digitally controlled analogue attenuator, that changes its attenuation
according to the numeric code it is given. This can be linked to a
physical rotating control, driven from up-down counters etc. The second
sort is a DSP function that multiplies the digital audio signal by
varying co-efficients and outputs a digital signal who's values are an
attenuated (or can be amplified) version of the input. I would imagine
that the volume control of your amplifier is the former as it takes in
and gives out analogue. The latter would require A-D and D-A
conversions. Your Marantz CD player with the variable output could be of
either sort but I suspect more the latter, as changing the digits before
the D-A conversion would mean that the variable output would work on
both the digital and analogue outputs simultaneously.

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. Carbon pots can be as
much as 6dB out at low levels. This will move the stereo image around as
you change volume settings. An electronic attenuator chip is a lot
cheaper than a conductive plastic pot, and the actual mechanical control
can be a cheap device, as all one is sensing is position.

As to audio quality, a conductive plastic pot will have zero effect on
audio quality. It is virtually pure resistance, and that doesn't have
non-linearities or generate noise (other than Johnson noise, which is
not terribly relevant.) A digital attenuator will have a finite level
before overloading, and will generate some noise and distortion.
However, that can be so low that it is essentially swamped by the
inherent noise and distortion of the rest of the amplifier circuit. The
only disadvantage of a "digital" volume control I can think of is that
volume changes can only be made in discrete steps, typically 1dB at low
volumes, perhaps 2 or even 3dB at high volumes.

S.

Digital volume control question....
 

On Fri, 19 May 2006 13:33:54 +0100, "Keith G"
wrote:


"Don Pearce" wrote in message
...
On Fri, 19 May 2006 12:28:48 +0100, "Keith G"
wrote:

I know the speakers (firewood horns - Pinkies) are 'on song' now and will
be
contributing mostly to the sound quality and I am convinced that normal
(carbon wiper) volume pots do the sound no favours whatsoever, but is
there
any reason the 'digital volume' (much like a computer soundcard, I guess)
is
likely to be helping in a significant way?

(If it is, I wonder why more manufacturers don't use them?)




No - in fact there is more chance that a poorly implemented digital
control will damage the sound. But the real reason why your amp has a
digital volume control is the usual one - cost.


Sure, the amp only cost 60 quid brand new (with warranty)!!


Pots cost money, they
need mechanical fixings to support them and people have to bolt them
in and wire them up.


Yep.


That is all bad news for a high-volume
manufacturer. People are still resistant to digital volume controls in
much of the market, though.


Hmm....


I have a couple of amps with motorized
volume pots.


Nothing 'motorized' here - the *Control* knob (multifunctional) doesn't turn
when the zapper's up and down buttons are being used and it rotates
endlessly when being turned by hand....

(Bit like the manual focussing on my digital camera - OK on the amp, but
pretty irritating on the camera!!)



The reason why it all sounds so clear is that it is a normal SS amp
and it isn't broken. These days it really doesn't have a lot of choice
in the matter - you need to exert special efforts to make a bad amp
these days,


Yes, my suspicion also and why I bought the amp in the first place, to check
it out. (See below...)


particularly if, as I suspect, this one uses chips for the
PA stage.


PA stage?? (Preamplification?)

I believe it's pretty hard to buy a bad *anything* much these days. I can
understand stuff costing a lot of money if it uses a lot of expensive
material or is hand-built (in a one-off kinda way) but I generally think the
VFM factor is pretty high for what these things cost! As to the the volume
control, I would consider that anything that took a carbon pot out of the
occasion would be a good thing? (I don't know about 'poorly implemented' -
why should it be poor? Is this one area where it would be particularly
difficult to do the thing well?)

My exploration into all this has been a staggering success AFAIAC - I have
proved (to myself, if no other) that the *speakers* drive the whole 'hifi'
thing *bigtime*! I would/will put this sound I'm getting off a cheap POS amp
against anything I've heard to date!! In fact, I'll go as far as to say I
don't much care about sources and amplification, the speakers can (and do)
make or break it all!!

I shudder to think how much money people are throwing at the game, trying to
get a pair of iffy speakers to sound good. I swapped the Pinkies for a pair
of very respectable JM-Labs the other day and the sound (from the exact same
kit) slumped like punctured tyre!! I've got turntables/tuners/CDPs here that
cost nowt and they all sound superb on the firewood horns, irrrespective of
the amplifiers used!!

Its revised my views completely, my advice to anyone looking for good sound
on the cheap would/will be 'build a pair of speakers and then chuck any old
kit at them' - I reckon you could get a superb tuner/CDP system going for
less than 200 quid!!

If me little mic weren't bust I'd post a track or two!!

(Off to check out the mic anyway..... :-)


OK - we can stop calling you Grasshopper now; you've graduated.

Oh, and PA is power amplifier.

d

--
Pearce Consulting
http://www.pearce.uk.com

Digital volume control question....
 

"Serge Auckland" wrote


(If it is, I wonder why more manufacturers don't use them?)

As far as I know there are two sorts of "digital" volume control. One is a
digitally controlled analogue attenuator, that changes its attenuation
according to the numeric code it is given. This can be linked to a
physical rotating control, driven from up-down counters etc. The second
sort is a DSP function that multiplies the digital audio signal by varying
co-efficients and outputs a digital signal who's values are an attenuated
(or can be amplified) version of the input. I would imagine that the
volume control of your amplifier is the former as it takes in and gives
out analogue. The latter would require A-D and D-A conversions.


OK. Makes sense.


Your Marantz CD player with the variable output could be of
either sort but I suspect more the latter, as changing the digits before
the D-A conversion would mean that the variable output would work on both
the digital and analogue outputs simultaneously.


And again.



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.


Carbon pots can be as
much as 6dB out at low levels.


Even more interesting (but not surprising).....


This will move the stereo image around as
you change volume settings. An electronic attenuator chip is a lot cheaper
than a conductive plastic pot, and the actual mechanical control can be a
cheap device, as all one is sensing is position.

As to audio quality, a conductive plastic pot will have zero effect on
audio quality. It is virtually pure resistance, and that doesn't have
non-linearities or generate noise (other than Johnson noise, which is not
terribly relevant.)


Oh I don't know - I would have thought a noisy Johnson could be a bit
embarrassing at times!! ;-)


A digital attenuator will have a finite level
before overloading, and will generate some noise and distortion. However,
that can be so low that it is essentially swamped by the inherent noise
and distortion of the rest of the amplifier circuit. The only disadvantage
of a "digital" volume control I can think of is that volume changes can
only be made in discrete steps, typically 1dB at low volumes, perhaps 2 or
even 3dB at high volumes.


-1.25 dB steps across the range on this amp it appears....

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...???

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??

Digital volume control question....
 

"Don Pearce" wrote in message
...
On Fri, 19 May 2006 13:33:54 +0100, "Keith G"
wrote:


Its revised my views completely, my advice to anyone looking for good
sound
on the cheap would/will be 'build a pair of speakers and then chuck any
old
kit at them' - I reckon you could get a superb tuner/CDP system going for
less than 200 quid!!


OK - we can stop calling you Grasshopper now; you've graduated.


(Ooh! Does this mean you've got ping-pong balls for eyes? :-)


Anyway, I'm not sure I have 'graduated' (I suspect you are referring to the
perennial valve vs, ss argument) - I've recommended cheap (eBay/secondhand)
amps to people for ages. I've long suspected there wasn't much to choose
between ss amps in a given price range and still think they all sound pretty
boring/dull/grey/dreary/barren/bleak on 'normal' speakers whereas, by
contrast, valve amps can be tweaked across a fairly broad range to *tailor*
a particular (more pleasing) sound. But that's not the issue, what is a
revelation to me is just how much the speakers are dictating the final
result from a 'hifi' system - I now believe a ****e pair of speakers
(includes Famous Names) can fatally cripple just about *any* source or
amplifier!!

I'm not thumping any particular tub here - I just think it's a pity that
people are unloading a *lot* of money to get something satisfying from a
pair of speakers that ain't *ever* going to deliver the goods when the
solution (OK, not for everybody, possibly) is so damn cheap! If I wuz 10
(OK - 20 or 30....) years younger I would be seriously thinking of producing
a VFM horn speaker on a commercial basis!!

Two things, I think, have steered the modern trends - the inexplicable* need
for unnecessary, loud, pistonic bass in (paradoxically) a small 'user/wife
friendly' enclosure! Consequently amplifiers have to be capable of
outputting three figures of totally unnecessary and expensive watts (in the
average UK room) to get 'em to work at all and that brings a raft of other
considerations into the equation which are simply not of much consequence
when driving sensitive speakers with low-power amps. (Distortion, power
supply issues etc.)

Interesting that there's nothing particularly small about 'high end'
speakers, innit?


*Actually, not that inexplicable, given the nature of much modern *tribal*
music....!!

Digital volume control question....
 

Keith G wrote:
"Serge Auckland" wrote


(If it is, I wonder why more manufacturers don't use them?)

As far as I know there are two sorts of "digital" volume control. One is a
digitally controlled analogue attenuator, that changes its attenuation
according to the numeric code it is given. This can be linked to a
physical rotating control, driven from up-down counters etc. The second
sort is a DSP function that multiplies the digital audio signal by varying
co-efficients and outputs a digital signal who's values are an attenuated
(or can be amplified) version of the input. I would imagine that the
volume control of your amplifier is the former as it takes in and gives
out analogue. The latter would require A-D and D-A conversions.


OK. Makes sense.


Your Marantz CD player with the variable output could be of
either sort but I suspect more the latter, as changing the digits before
the D-A conversion would mean that the variable output would work on both
the digital and analogue outputs simultaneously.


And again.


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.


Carbon pots can be as
much as 6dB out at low levels.


Even more interesting (but not surprising).....


This will move the stereo image around as
you change volume settings. An electronic attenuator chip is a lot cheaper
than a conductive plastic pot, and the actual mechanical control can be a
cheap device, as all one is sensing is position.

As to audio quality, a conductive plastic pot will have zero effect on
audio quality. It is virtually pure resistance, and that doesn't have
non-linearities or generate noise (other than Johnson noise, which is not
terribly relevant.)


Oh I don't know - I would have thought a noisy Johnson could be a bit
embarrassing at times!! ;-)


A digital attenuator will have a finite level
before overloading, and will generate some noise and distortion. However,
that can be so low that it is essentially swamped by the inherent noise
and distortion of the rest of the amplifier circuit. The only disadvantage
of a "digital" volume control I can think of is that volume changes can
only be made in discrete steps, typically 1dB at low volumes, perhaps 2 or
even 3dB at high volumes.


-1.25 dB steps across the range on this amp it appears....

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...???

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??




I would have thought that as soon as the word "digital" is mentioned
many valve amp owners will run a mile.....

There are a number of passive volume controllers available albeit at
ludicrous prices for what is basically a good quality pot in a tin box;
and not forgetting the multi-tapped transformer controller which will
have all the benefits and cons of a digital controller, but again at
vastly increased cost and price.

S.

Digital volume control question....
 

On Fri, 19 May 2006 16:01:35 +0100, "Keith G"
wrote:


"Don Pearce" wrote in message
...
On Fri, 19 May 2006 13:33:54 +0100, "Keith G"
wrote:


Its revised my views completely, my advice to anyone looking for good
sound
on the cheap would/will be 'build a pair of speakers and then chuck any
old
kit at them' - I reckon you could get a superb tuner/CDP system going for
less than 200 quid!!


OK - we can stop calling you Grasshopper now; you've graduated.


(Ooh! Does this mean you've got ping-pong balls for eyes? :-)


I did have last weekend when I was headbutted in the nuts by a
two-year-old.


Anyway, I'm not sure I have 'graduated' (I suspect you are referring to the
perennial valve vs, ss argument) - I've recommended cheap (eBay/secondhand)
amps to people for ages. I've long suspected there wasn't much to choose
between ss amps in a given price range and still think they all sound pretty
boring/dull/grey/dreary/barren/bleak on 'normal' speakers whereas, by
contrast, valve amps can be tweaked across a fairly broad range to *tailor*
a particular (more pleasing) sound. But that's not the issue, what is a
revelation to me is just how much the speakers are dictating the final
result from a 'hifi' system - I now believe a ****e pair of speakers
(includes Famous Names) can fatally cripple just about *any* source or
amplifier!!

No, not referring to valves vs SS - that is just preference. More the
fact that there is nothing more to be had from SS by spending more
money. The plateau starts *really* low.

I'm not thumping any particular tub here - I just think it's a pity that
people are unloading a *lot* of money to get something satisfying from a
pair of speakers that ain't *ever* going to deliver the goods when the
solution (OK, not for everybody, possibly) is so damn cheap! If I wuz 10
(OK - 20 or 30....) years younger I would be seriously thinking of producing
a VFM horn speaker on a commercial basis!!

Two things, I think, have steered the modern trends - the inexplicable* need
for unnecessary, loud, pistonic bass in (paradoxically) a small 'user/wife
friendly' enclosure! Consequently amplifiers have to be capable of
outputting three figures of totally unnecessary and expensive watts (in the
average UK room) to get 'em to work at all and that brings a raft of other
considerations into the equation which are simply not of much consequence
when driving sensitive speakers with low-power amps. (Distortion, power
supply issues etc.)

Expensive watts? No, those watts are really, really cheap, especially
for subwoofers that use switching supplies and power amps.

Interesting that there's nothing particularly small about 'high end'
speakers, innit?

Some friends of mine have Willson Maxx speakers. They weigh about half
a ton and sound equally good when bending the walls or barely
murmuring. They also stand about five feet high.


*Actually, not that inexplicable, given the nature of much modern *tribal*
music....!!


Truth.

d

--
Pearce Consulting
http://www.pearce.uk.com

Digital volume control question....
 

Keith G wrote:


My exploration into all this has been a staggering success AFAIAC - I have
proved (to myself, if no other) that the *speakers* drive the whole 'hifi'
thing *bigtime*! I would/will put this sound I'm getting off a cheap POS amp
against anything I've heard to date!! In fact, I'll go as far as to say I
don't much care about sources and amplification, the speakers can (and do)
make or break it all!!

I shudder to think how much money people are throwing at the game, trying to
get a pair of iffy speakers to sound good. I swapped the Pinkies for a pair
of very respectable JM-Labs the other day and the sound (from the exact same
kit) slumped like punctured tyre!! I've got turntables/tuners/CDPs here that
cost nowt and they all sound superb on the firewood horns, irrrespective of
the amplifiers used!!

Its revised my views completely, my advice to anyone looking for good sound
on the cheap would/will be 'build a pair of speakers and then chuck any old
kit at them' - I reckon you could get a superb tuner/CDP system going for
less than 200 quid!!

If me little mic weren't bust I'd post a track or two!!

(Off to check out the mic anyway..... :-)


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.

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.....

S.