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回覆 (833): Volume pot
nothing new. Just an alternative to analog approach. I do not have the very good pot that many have here so I wonder......  
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well, for you i think a digital volume is o.k. look at this way, your convolver is already doing something similar. of course you tone down some large correction as i do for the exact reason of not losing too resolution. but for me, i have other sources so digital volume does not work.
drwkng
09-11-01
13:32:03
回覆 (832): Volume pot
See if this old reading by Mr.Stuart from Meridian may draw your attention again on digital domain stuff  
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i thought instead of my mind this should change your mind about going to anything higher than 48K and 16 bit ^-^
drwkng
09-11-01
13:29:15
回覆 (831): Volume pot
Good morning doctor(s),  
 
See if this old reading by Mr.Stuart from Meridian may draw your attention again on digital domain stuff.....  
 
http://www.meridian-audio.com/ara/coding2.pdf
Vash
09-11-01
07:54:04
回覆 (830): Volume pot
nothing new. Just an alternative to analog approach. I do not have the very good pot that many have here so I wonder......
ackcheng
09-11-01
00:42:48
回覆 (829): Volume pot
i'm afraid i can't see anything new there.
drwkng
09-11-01
00:35:47
回覆 (828): Volume pot
This thread is also very informative  
 
http://db.audioasylum.com/cgi/m.mpl?forum=pcaudio&n=27913&highlight=digital+volume+control  
ackcheng
09-10-31
23:30:48
回覆 (827): Volume pot
Some more info here  
 
http://www.audioasylum.com/forums/pcaudio/messages/4/42338.html  
 
ackcheng
09-10-31
23:27:31
回覆 (826): Volume pot
Well, I mean DSP kind of digital volume control. It will definitely work for digital source only without the need for AD.  
 
In this setting digital volume control is descripted here  
 
http://extra.benchmarkmedia.com/wiki/index.php/Digital_volume_control  
 
In other to achieve that, we are shifting bits. But the more the available bit depth we have, the lesser the error. Up to a certain stage, the distortion can be lower than analog vision especially for the issue of channel matching. When you use your DAW during masting, any EQ and gain changes are in fact a form of volume control. That is why DSP should always be done at high bit depth and than dither it back to 24 bit or 16 bit for distribution.
ackcheng
09-10-31
23:27:03
回覆 (825): Volume pot
do you believe in digital volume control like 64 bit and dithering? I found that it is quite OK as long as we limit the attenuation to within 10dB.  
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i don't have any first hand experience with it. i suppose there are two possible configurations. firstly, you can do this completely in digital domain. this is only applicable if one's source is only digital. i don't understand how it works. your digital source no matter what is 24 bit at best . this assumes you have 24 bit source otherwise you are losing more. and most source is still red book cd. the 64 bit is nice to know but to me it makes no sense. it only makes sense if one is going to do a lot of digital processing in addition to volume control. as you mentioned, it will be losing more resolution as attenuation increases. but with just a volume control, what does 64 bit matter? care to share?  
the other configuration will be performing a AD and DA. this does not strikes me as interesting at all^-^. just imagine how much problem we have reproducing CD.  
 
of course there are other 'digital pots' as well. these are more like digital control analogue potentiometer. these are more popular among high-end amps.  
drwkng
09-10-31
20:07:50
回覆 (824): Volume pot
Interesting discussion. Drwkng,  
 
do you believe in digital volume control like 64 bit and dithering? I found that it is quite OK as long as we limit the attenuation to within 10dB.
ackcheng
09-10-31
18:03:29
回覆 (823): Volume pot
I remember King said his old 27 series did tried Electroswitch, quite good. I am also using Electroswitch in my current SS pre. but only for source selection.  
Vash
09-10-31
11:28:17
回覆 (822): Volume pot
>you are making it far more complicated than what it is. signal does not pass through the led in the application of a volume control. the resistance of the cell just depends on the light intensity. signal only pass thru the cell. is there any bleed thru? yes but it shouldn't be that significant with a good dc supply  
 
Too much alcohol last night, yes, King, you are absolutely right, no signal modulation at all, just in my imagination, will take it all back. It's just simply a material issue, though that's the key.....it's pretty dynamic within...need more study : )
CFT
09-10-31
09:43:21
回覆 (821): Volume pot
Agree, ELMA switch is still my favorite.  
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ELMA is not even close. try shallco. even electroswitch is better than elma.
drwkng
09-10-31
09:23:15
回覆 (820): Volume pot
>>>...that switch is a piece of crap. ...  
 
Agree, ELMA switch is still my favorite.
Vash
09-10-31
09:19:20
回覆 (816): Volume pot
Ok, and so it's just a transconductanc device! An opto-transistor type to be exact, but the interesting part is the material employed together with the transferring function of conversion from electricity to light, then back to electricity, and that's where the nonlinearity comes in, and comes in in such a vast amount too as King pointed out : ) I bet it this case, the nonlinearity is of highy even harmonic types !!  
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you are making it far more complicated than what it is. signal does not pass through the led in the application of a volume control. the resistance of the cell just depends on the light intensity. signal only pass thru the cell. is there any bleed thru? yes but it shouldn't be that significant with a good dc supply.
drwkng
09-10-31
09:09:33
回覆 (819): Volume pot
I have few pots of this DZ made, quite good in it's price range,  
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but that switch is a piece of crap. i've a few to give away if anyone is interested for the sake of a greener earth^-^
drwkng
09-10-31
09:05:25
回覆 (818): Volume pot
daiwok,  
 
I have few pots of this DZ made, quite good in it's price range,  
 
Vash
09-10-31
08:19:03
回覆 (817): Volume pot
http://www.penguinlovers.net/audio/Attenuator.html
daiwok
09-10-31
07:13:28
回覆 (816): Volume pot
 
i used to respect the opinion of these gentlemen. nowadays, i take them with a big pinch of salt. i couldn't audition their system so their sound impression is really useless to me. my experience tells me that most diyers's assessment of their own creation does not have anything to do with reality.^-^  
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How very true !!!! I have visited some of these fellow contributors in overseas forums and on many occasions the result can be disappointing - may be I have cloth ears ^_*  
 
>We welcome your input, as we know you are a most dedicated diyer.<  
 
Limage - yes I do like to DIY, but I am novice in the world of DIY amps .....I am listening and learning here
daiwok
09-10-31
07:07:18
回覆 (815): Volume pot
Principles on the Silonex optocoupler employed in the 'Lightspeed' volume control:  
http://www1.silonex.com/audiohm/principles.html  
 
Basically the heart of the volume control is the optocoupler, which consists of a light source and a light detector.  
 
The light source is an LED while the detector being a light sesitive resistor.  
 
So as an analogy, to turn up the volume is to pump in more light to the light- sensitive resistor making its resistance lower, thus letting go more electrical signal to the amplifier...  
 
Ah, o' sweat nonlinearity!  
http://www1.silonex.com/audiohm/constants.html  
 
So, the light sensitive resistor is a compound made of CdS and CdSe semiconductors, I see....  
 
Ok, and so it's just a transconductanc device! An opto-transistor type to be exact, but the interesting part is the material employed together with the transferring function of conversion from electricity to light, then back to electricity, and that's where the nonlinearity comes in, and comes in in such a vast amount too as King pointed out : ) I bet it this case, the nonlinearity is of highy even harmonic types !!!  
 
Hey, my point on the distortion box was to put in elements like this and you can make a ipod sing like a Fisher !!!!
CFT
09-10-31
01:40:31
回覆 (815): Volume pot
Take those carbon PEC pots as an example, it's claimed by Peter Daniels and others that they are 'musical', as compared to step attenuators with nice resistors (usually constructed with metal films )!!!!  
 
(Incidentally, others like Thorsten pointed out that linear pots always sound nicer than their log counterpart (due to manufacturing process), and further improvement is to bypass the output with a carbon compostion resistor with a ratio like 20:1 to law fake it to a log one)  
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i used to respect the opinion of these gentlemen. nowadays, i take them with a big pinch of salt. i couldn't audition their system so their sound impression is really useless to me. my experience tells me that most diyers's assessment of their own creation does not have anything to do with reality.^-^
drwkng
09-10-31
00:58:57
回覆 (814): Volume pot
Ah, King,  
 
Thanks for this enlightenment : )  
 
Now I understand why those carbon composition resistors, like AB, RMG, Kiwame "sound" better than metal film, it's simple......... they just yield higher amount of even harmonic distortions : P  
 
Take those carbon PEC pots as an example, it's claimed by Peter Daniels and others that they are 'musical', as compared to step attenuators with nice resistors (usually constructed with metal films )!!!!  
 
(Incidentally, others like Thorsten pointed out that linear pots always sound nicer than their log counterpart (due to manufacturing process), and further improvement is to bypass the output with a carbon compostion resistor with a ratio like 20:1 to law fake it to a log one)  
 
I will take a look at the optocoupler and check out what semiconductor material the LSR is....
CFT
09-10-31
00:18:03
回覆 (814): Volume pot
Now, you know what it will change the HiFi world next? A simple digital 2nd harmonic synthesizer, a distortion box that is .......(someone patented it though, I checked : )  
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why bother? buy fisher 50C. you will have plenty of it.
drwkng
09-10-30
23:57:45
回覆 (818): Symmetry DCB1
Hi Vash,  
 
Nice review on Symmetry DCB1 in the link below, better than the original First Watt B1 version with coupling caps, sonic improvements also attributed to the shunt regulators.  
http://www.diyaudio.com/forums/group-buys/147075-gb-dc-coupled-b1-buffer-shunt-psus-94.html#post1933330  
 
Actually 落雨路 completed his SDCB1 and posted the unit's photos on r33, you saw them : )  
 
And I want one too ah :P
CFT
09-10-30
23:53:12
回覆 (813): Volume pot
>you talk about being musical not accuracy^-^  
if you look at the distortion specturm of lightspeed, you will know why. a good dose of 2nd harmonic comes with the package. i tell you what. it has more distortion than the 27D itself^-^  
 
YES! That's what I suspected : )  
 
In fact, a friend of mine built one and said it sounded better than a piece of wire ^ ^  
 
Now, you know what it will change the HiFi world next? A simple digital 2nd harmonic synthesizer, a distortion box that is .......(someone patented it though, I checked : )
CFT
09-10-30
23:41:07
回覆 (819): DIY 自作派同好同學會
That's not a question for me anymore as I put it aside already.  
 
Now I stick with DACT CT2 and Tents lab volume control.  
 
^__^
Vash
09-10-30
22:00:29
回覆 (818): Symmetry DCB1
Vash,  
 
you may not believe how magical the signal bleeder can perform ;)
8po
09-10-30
21:37:53
回覆 (817): Symmetry DCB1
There are two drawback, impedance is not same on input and output. Next, the volume level is not linear.  
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i think the issue with impedance is blown out of proportion. the delta is very small and i doubt it very much whether it would make any difference. as far as the linearity is concerned, it depends how you implement it. i don't have many complaints about 27D volume being non-linear^-^
drwkng
09-10-30
21:29:48
回覆 (817): Symmetry DCB1
CFT,  
 
Anymore information on the 'Symmetry DCB1' ?  
 
 
Thanks.
Vash
09-10-30
14:04:25
回覆 (816): Symmetry DCB1
King is right. There are two drawback, impedance is not same on input and output. Next, the volume level is not linear.  
 
But the 'signal' resistor do the magic, we only need one piece for each channel and this is low cost for resistor selection. I did installed it on one of my old tube pre. experimentally with using tantalum resistor.  
 
The structure is exaclty the same as King's stated in previous message, the 'shunt attentuator' type. It use 6 relays with resistor to form a 6bit, 64 steps attenuator. More information can be found in below link.  
 
http://www.keces.com.tw/3_audiodiy/K0709001/K0709001.htm
Vash
09-10-30
13:40:26
回覆 (815): Symmetry DCB1
King is right. The other one connected to ground still attenuates & modulates the signal, though effect might not be as crucial.
Derek2A3
09-10-30
13:29:11
回覆 (814): Symmetry DCB1
a shunt type design with only one resistor on signal path  
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Vash,  
 
Do you have any simple sketch to show the layout?  
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it is not quite true that there is only one resistor on the signal path even for the shunt. that one resistor might have biggest effect for sure. this is a common misconception.
drwkng
09-10-30
11:11:00
回覆 (812): Volume pot
What's the secret behind lightspeed?  
 
Better than using two resistors?  
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you talk about being musical not accuracy^-^  
if you look at the distortion specturm of lightspeed, you will know why. a good dose of 2nd harmonic comes with the package. i tell you what. it has more distortion than the 27D itself^-^
drwkng
09-10-30
11:07:38
回覆 (813): Symmetry DCB1
 
a shunt type design with only one resistor on signal path  
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Vash,  
 
Do you have any simple sketch to show the layout?  
 
limage
09-10-30
10:53:16
回覆 (812): Symmetry DCB1
Anyone has built this? Symmetry DCB1?  
 
How would that compare with the original First Watt B1 with coupling caps?  
 
Would be nice if there are kits available..... : )
CFT
09-10-30
10:45:59
回覆 (811): Volume pot
What's the secret behind lightspeed?  
 
Better than using two resistors?  
 
Must be the enhancement by photoelectric effect? ^ ^
CFT
09-10-30
10:43:08
回覆 (810): Volume pot
I did tried another approach, a shunt type design with only one resistor on signal path, relays switch various resistors to ground  
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i tried this approach as well. didn't have much success. for some reason there is always high frequency distortion with large signal. granted i have a few more relays than the kit shown but the problem started with a few relays albeit minor.
drwkng
09-10-30
10:39:45
回覆 (809): Volume pot
I did tried another approach, a shunt type design with only one resistor on signal path, relays switch various resistors to ground that governed by an ADC with the control of a cheap cheap pot.  
 
Kits available from Keces.
Vash
09-10-30
04:51:29
回覆 (808): Opto Coupler
Supposed be musical : )  
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if that's what you want, you can't beat a lightspeed^-^
drwkng
09-10-29
23:57:10
回覆 (807): Opto Coupler
How about using a linear 1M PEC carbon pot and by passed the output with a 50K Kiwame or RMG to law-fake it as a log pot? Has anyone tried this as the volume control? Supposed be musical : )
CFT
09-10-29
23:51:12