The remote control paratactic volume control - Page 2

amplifierguru · 25th April 2005, 01:39 AM

Hi Hugh,

From memory (1990), I managed to track down an alps agent in Australia. They had to be specified by a code that would do an eye chart justice - and I waited a few weeks for the production and delivery. They were 50K but had some crosstalk which improoved dramatically when I wrapped them in a (rubbing) copper box and earthed it. Using a 10K would lower crosstalk by 14 dB.

They may be more available from Taiwan, HK, or Singapore as an off the shelf these days.

Trust that helps. I could do with one.

audio-gd · 25th April 2005, 01:48 AM

The volume is use 12 switch to control 80 step and control -80DB to -3DB, it have a blue LED displayer , and it have four input select.

amplifierguru · 25th April 2005, 02:06 AM

Audio-gd,

80 position is good , for Rmb 430 - is that same as HK$6 =a$ ?

Is that with an IR remote controller board , don't think I'd want the visual display. What are the resistance range options?

audio-gd · 25th April 2005, 03:45 PM

430RMB =HK406
and 430RMB=$52

The resistance is use more DALE and two Holco, it have a IR remote controller board and have a remote controler and a volume control board.

HFGuy · 25th April 2005, 06:10 PM

I dont want to rain on your parade but i would like to mention a few dissadvantages with your design. Depending on your volume setting your input impedance is different this means a different noise figure and a different bandwidth (which again means different noise figure).

amplifierguru · 26th April 2005, 12:54 AM

Yes that's essentially what I was asking in my last post - resistance ranges for both in and out?
audio-gd?

audio-gd · 26th April 2005, 02:30 AM

In this volume, it's input impedance is between 24K-60K,
but I think , all volume are need a buffer after,then can neglect the influence of next stage . If then ,it don't be neglect the rang.

HFGuy · 26th April 2005, 02:39 AM

Yes adding a buffer before and after will minimize the effects of the changing load impedance but then you lose simplicity. Even the worst R2R attentuator will be alot better then 2 buffers.

HFGuy · 26th April 2005, 02:43 AM

Sorry but i just noticed your image. Iam not a big fan of having the volume control ONLY on the output (or in the middle). While having the volume control not on the input increases the noise performance it degrades the distortion. Your input stages are going to be swinging large voltages compared to a circuit with a volume control on the input. I guess its one trade off for another, designer's preference

audio-gd · 26th April 2005, 02:49 AM

The R2R still need a buffer after it , because R2R have 10K output impedance and will with the capacitance (of next stage ) be a high frequency RC filter.

25th April 2005, 01:48 AM	#12
audio-gd diyAudio Member Join Date: Oct 2004	Hi The volume is use 12 switch to control 80 step and control -80DB to -3DB, it have a blue LED displayer , and it have four input select.

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25th April 2005, 01:39 AM	#11
amplifierguru Account Disabled Join Date: Aug 2004 Location: Earth	Hi Hugh, From memory (1990), I managed to track down an alps agent in Australia. They had to be specified by a code that would do an eye chart justice - and I waited a few weeks for the production and delivery. They were 50K but had some crosstalk which improoved dramatically when I wrapped them in a (rubbing) copper box and earthed it. Using a 10K would lower crosstalk by 14 dB. They may be more available from Taiwan, HK, or Singapore as an off the shelf these days. Trust that helps. I could do with one.

25th April 2005, 02:06 AM	#13
amplifierguru Account Disabled Join Date: Aug 2004 Location: Earth	Audio-gd, 80 position is good , for Rmb 430 - is that same as HK$6 =a$ ? Is that with an IR remote controller board , don't think I'd want the visual display. What are the resistance range options?

25th April 2005, 03:45 PM	#14
audio-gd diyAudio Member Join Date: Oct 2004	430RMB =HK406 and 430RMB=$52 The resistance is use more DALE and two Holco, it have a IR remote controller board and have a remote controler and a volume control board.

25th April 2005, 06:10 PM	#15
HFGuy diyAudio Member Join Date: Sep 2004 Location: Toronto, Ontario	I dont want to rain on your parade but i would like to mention a few dissadvantages with your design. Depending on your volume setting your input impedance is different this means a different noise figure and a different bandwidth (which again means different noise figure).

26th April 2005, 12:54 AM	#16
amplifierguru Account Disabled Join Date: Aug 2004 Location: Earth	Yes that's essentially what I was asking in my last post - resistance ranges for both in and out? audio-gd?

26th April 2005, 02:39 AM	#18
HFGuy diyAudio Member Join Date: Sep 2004 Location: Toronto, Ontario	Yes adding a buffer before and after will minimize the effects of the changing load impedance but then you lose simplicity. Even the worst R2R attentuator will be alot better then 2 buffers.

26th April 2005, 02:43 AM	#19
HFGuy diyAudio Member Join Date: Sep 2004 Location: Toronto, Ontario	Sorry but i just noticed your image. Iam not a big fan of having the volume control ONLY on the output (or in the middle). While having the volume control not on the input increases the noise performance it degrades the distortion. Your input stages are going to be swinging large voltages compared to a circuit with a volume control on the input. I guess its one trade off for another, designer's preference

26th April 2005, 02:49 AM	#20
audio-gd diyAudio Member Join Date: Oct 2004	The R2R still need a buffer after it , because R2R have 10K output impedance and will with the capacitance (of next stage ) be a high frequency RC filter.

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