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Old 6th May 2008, 09:39 PM   #1
patherb is offline patherb  United States
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Default Help with an active / digital system

Hi All,
I am in the early phases of designing an active / digital bookshelf system. I am planning on using a squeezbox as a source. I'd like to run the SPDIF output from the squeezebox into a digital crossover / processor. I've investigated a few options here:

Behringer DCX2496 (modded)
Rane RPM 26z
Ashly Protea 3.24CL

Is there any problem going from the SPDIF output of the squeezebox to the AES/XLR input on these? Any good recommendations on cables? Also, it seems like volume control is an issue. I know Selectronic has a 6 channel volume control that could work here. Are there any units where the volume control is integrated? How about the Ashly?

I haven't put too much thought into the amps as there are a lot of pro or home audio options there. As far as drivers, I was thinking about going with a Raal ribbon tweeter and a Scanspeak Revelator mid/woofer.

Any thoughts or opinions especially regarding the crossover / processor are greatly appreciated. Many thank in advance
Jim
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Old 6th May 2008, 11:04 PM   #2
preiter is offline preiter  United States
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I use a Roku SB500 feeding a Behringer DCX2496 for a 3-way active system. Any RCA-XLR adapter should work, I made my own cable.

I know it's heresy, but the Roku has a volume control that affects the SP/DIF output, so I just control volume that way.

I use Trends TA-10s for high and mids and a Gainclone for bass. Speakers are Hawthorne Audio Silver Iris Coaxials and Augies.

All in all, it's a nice little system. Surprisingly inexpensive and simple for a 3-way active.
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Old 7th May 2008, 04:35 PM   #3
patherb is offline patherb  United States
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Thanks vm. Will I have any sound degradation by doing the volume control from the squeezebox?

Also, I want to make sure I understand the signal path correctly. I'll be sending an unbalanced digital signal from the SPDIF output of the squeezbox to the AES/XLR of the digital crossover / processor. Then I'll be sending a balanced analog signal from the XLR output on the processor to the XLR inputs on the respective amps (assuming I get amps with balanced inputs). Is my understanding correct?

I've been leaning towards the Ashly. It looks like a nice piece of equipment. Does anyone have any experience with it?
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Old 8th May 2008, 06:09 PM   #4
patherb is offline patherb  United States
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bump. help pls
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Old 12th May 2008, 07:56 PM   #5
preiter is offline preiter  United States
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Quote:
Originally posted by patherb
Thanks vm. Will I have any sound degradation by doing the volume control from the squeezebox?

Also, I want to make sure I understand the signal path correctly. I'll be sending an unbalanced digital signal from the SPDIF output of the squeezbox to the AES/XLR of the digital crossover / processor. Then I'll be sending a balanced analog signal from the XLR output on the processor to the XLR inputs on the respective amps (assuming I get amps with balanced inputs). Is my understanding correct?

I've been leaning towards the Ashly. It looks like a nice piece of equipment. Does anyone have any experience with it?
There is definitely sound degradation using the volume control of the squeezebox, whether you can hear it or not is another matter. What it's doing is attenuating the signal digitally. If you set the volume at half, instead of a 16-bit range of values from 0-65,535 you will be getting a 15-bit range of values from 0-32767. Effectively, you lose 3dB of dynamic range every time you halve the signal.

Of course, other methods also cause degradation of sound quality. And there's nothing stopping you from adding a 6-channel, ganged volume control at a later time.

Your understanding of the signal path is correct. You can use amps with balanced inputs, or convert the signals back to unbalanced.
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Old 13th May 2008, 06:41 AM   #6
patherb is offline patherb  United States
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I can't seem to find any 6 channel volume controls with balanced inputs and outputs. Anyone know of one?
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Old 13th May 2008, 02:43 PM   #7
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Quote:
Originally posted by patherb
I can't seem to find any 6 channel volume controls with balanced inputs and outputs. Anyone know of one?
Could you use 6 dual gang motorised pots (or 2 6 gang pots)? Have a remote that turns all the pots at the same time?
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Old 13th May 2008, 10:20 PM   #8
patherb is offline patherb  United States
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Quote:
Originally posted by MikeHunt79

Could you use 6 dual gang motorised pots (or 2 6 gang pots)? Have a remote that turns all the pots at the same time?
Do you have a link so I can check one out? My main requirement is maintaining SQ. I'd also like it to be balanced I/O.
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Old 13th May 2008, 11:09 PM   #9
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Here is a project for a six ch volume control for DCX2496:

http://www.linearaudio.nl/6chan-1.htm

Another source is :

http://electronics.dantimax.dk/

RELVOL3 is a stereo balanced attenuator and you can put three in a CONTROL2 board.

Hope it helps
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Old 14th May 2008, 12:02 AM   #10
preiter is offline preiter  United States
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You could easily do a variant of the Lightspeed Attenuator.

Lightspeed Attenuator a new passive preamp

Modify the circuit for balanced operation (I'm not sure exactly how you do series-shunt attenuation on a balanced circuit, but I'm sure someone does). Then use one pot to control all 6 channels.

Should be one of the cheaper options available and very good sound quality.
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