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Old 8th May 2015, 10:20 PM   #1
Gusser is offline Gusser  United States
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Default My PGA2310 Box

I build this a year ago, It's 16 channels of analog volume control using PGA2310. Audio path is ultra simple, SSM2141, PGA2310, SSM2142. All linear power supplies.

Last month I changed the DIY Atmel 8515 CPU to a JK Micro FX186 card which is PC DOS compatible. I added 5 level assign groups and the paultry 8515 RAM was too small.

Yes, that is a rack mount PC chassis.
Attached Images
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File Type: jpg VCA Board.JPG (885.3 KB, 149 views)
File Type: jpg Unwired chassis.JPG (944.9 KB, 143 views)
File Type: jpg Rear Panel.JPG (894.3 KB, 133 views)
File Type: jpg Test and Debug.JPG (897.3 KB, 134 views)

Last edited by Gusser; 9th May 2015 at 01:54 AM.
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Old 9th May 2015, 03:38 PM   #2
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impressive.
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Old 10th May 2015, 02:57 PM   #3
Dimdim is offline Dimdim  Greece
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Very neet design, but how did you manage to get 16 channels of balanced signals from just 8 x PGA2310s? I would have expected to see you use 16 PGAs.
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Old 10th May 2015, 05:48 PM   #4
Gusser is offline Gusser  United States
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Very neet design, but how did you manage to get 16 channels of balanced signals from just 8 x PGA2310s? I would have expected to see you use 16 PGAs.
Well the PGA2310 is a stereo 2 channel device albeit single ended. The SSM2141 and 2142 chips are balanced to unbalanced, unbalanced to balanced converters. Burr Brown also makes an equivalent part.

They are a tad expensive but as you can see, need no external RC components and are very good performance.

SSM2141 | datasheet and product info High Common-Mode Rejection Differential Line Receiver | Analog Devices

http://www.analog.com/media/en/techn...ts/SSM2142.pdf
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Old 10th May 2015, 09:45 PM   #5
Dimdim is offline Dimdim  Greece
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Oh, I see! I didn't really check to see what the SSM chips were, I thought they were just opamps used for buffering.

I have at times wondered whether a PGA2311 could be configured for balanced operation (one per balanced channel). Do you know whether that could be possible?
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Old 13th May 2015, 03:26 AM   #6
Gusser is offline Gusser  United States
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Quote:
Originally Posted by Dimdim View Post
Oh, I see! I didn't really check to see what the SSM chips were, I thought they were just opamps used for buffering.

I have at times wondered whether a PGA2311 could be configured for balanced operation (one per balanced channel). Do you know whether that could be possible?
Well you could do it. It's all a matter of the control software. But I wouldn't use a PGA2311 for balanced audio. The 2311 is a +/- 5V analog device while the 2310 is a +/- 15V analog device. If you are using true +4dbm balanced audio, you will have a headroom problem with the 2311. The reason IMO the 2311 is cheaper is this difference and is targeted towards unbalanced low level (-10db) consumer audio applications.

My distributor of choice, Digikey in the USA, has the DIP 2311's for about $9 ea while the 2310's are $22 ea. So what I would do on a budget is to use a 2311 but have a 5532 or your OPAMP of choice to drop and then raise the signal before and after the 2311 if going balanced with pro audio levels. And now you have all the problems of designing a good gain stage and the levels through the 2311 are also lower which invites data crosstalk. You also now have a more complicated power supply as you need a +/-5v analog as well as a +/-15v for the OPAMPS, in addition to the +5V digital side supply. Based on these issues, a 2310 might actually be cheaper in the long run.
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Old 13th May 2015, 04:10 AM   #7
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or just say 'fark it' and go with cs3318 (a chip I consider FAR better than the TI or cirrus PGA chips.

3318 is 8ch.

limit is dual 9v rail, but you can't have it all its SE too, of course, so no balanced free lunch.
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Old 13th May 2015, 06:53 AM   #8
Dimdim is offline Dimdim  Greece
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Quote:
Originally Posted by Gusser View Post
Well you could do it. It's all a matter of the control software. But I wouldn't use a PGA2311 for balanced audio. The 2311 is a +/- 5V analog device while the 2310 is a +/- 15V analog device. If you are using true +4dbm balanced audio, you will have a headroom problem with the 2311. The reason IMO the 2311 is cheaper is this difference and is targeted towards unbalanced low level (-10db) consumer audio applications.

My distributor of choice, Digikey in the USA, has the DIP 2311's for about $9 ea while the 2310's are $22 ea. So what I would do on a budget is to use a 2311 but have a 5532 or your OPAMP of choice to drop and then raise the signal before and after the 2311 if going balanced with pro audio levels. And now you have all the problems of designing a good gain stage and the levels through the 2311 are also lower which invites data crosstalk. You also now have a more complicated power supply as you need a +/-5v analog as well as a +/-15v for the OPAMPS, in addition to the +5V digital side supply. Based on these issues, a 2310 might actually be cheaper in the long run.
You are right. In your case, with 16 channels, 8 x PGA2310 with the SSM converters make more sense, financially speaking.

It's just that all these conversions (BAL to SE, SE to BAL) are giving the audiophool in me a hard time.
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