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What size volume potentiometer do I need given the following gear specifications?

Hi Folks, 

I'm looking to build my own passive volume control. My inspiration is the Emotiva Control Freak. From what I have found, it uses a Bourns 4-gang, 10k potentiometer. It seems to work well with my gear. Would I be correct in that I would use the same impedence pot (10k) if I build my own? Also, what brands do you guys recommend? I was thinking of an ALP blue velvet, TKD, or EIZZ? As for cabling, I'm going to use Mogami W2549 mic cable in 1 meter or less length. I'm looking to make XLR, as well as RCA at some point.   
  
GEAR & SPECS:
Odyssey Stratos Amp
Input Impedence: >10k ohms (manual), 47k ohms (magazine). 

Adcom GCD-750
Output Impedence: 50 ohms RCA / 100 ohms XLR
Output Voltage: 3.0 volts RCA / 6.0 volts XLR

Emotiva Control Freak (XLR)
Bourns 4-gang 10k pot. 
XLR cables. 
(Emailed Emotiva to see what cable they used. They said they use a type-b, high speed HDMI wire). 

Thanks, 
JSB

jsbach1685
3 responses Add your response
kijanki's avatar
kijanki
4,394 posts
 
For active preamp higher value would be better, but for passive volume control 10k sounds OK. You can get high quality ALPS RK271. You could also use TDK variable attenuator CP2500 (ladder with 20 steps). I believe that both have conductive plastic track. TDK supposed to have a little bit better gain matching, especially at lower volumes. I used ALPS RK271 in small headphone amp I built and matching between channels was perfect. It also felt high quality and robust. Mouser.com sells them but 10k value is less common (zero stock). ALPS Black Beauty would be even better but it is large and was discontinued a long time ago. Get it, if you can find one.
You could also get Danish DACT attenuator (SMD resistor network 24 steps), that has amazing 0.05dB matching but it will cost you over $200. Parts Connexion sells them.

http://www.alps.com/prod/info/E/PDF/Potentiometer/MetalShaft/RK271/RK271.PDF

http://www.tkd-corp.com/products/att/pdf/cp2500as-e.pdf

http://www.mouser.com/ProductDetail/ALPS/RK27112A0-S20-C0-A103/?qs=%2fha2pyFaduju6Dyl2KOrNtbj25hBght...

http://www.dact.com/html/attenuators.html

http://www.partsconnexion.com/product1187.html

http://www.dact.com/html/attenuator_data_sheet.html

I think that DACT recommends 10k for passive pre.  I found this:

http://www.dact.com/html/passive_preamp.html
czarivey
5,680 posts
 
Neither for active or for passives I found 10K is sufficient enough.
Maybe it's just me always wanting to have a luxury of WIDE volume range as well as WIDE choices of my meals menus.

georgehifi's avatar
georgehifi
10,312 posts
 

With a source 3v and output impedance of 50ohms, an amp input load impedance of 10kohms.

A 1kohm passive log stereo pot is the order of the day, and is properly impedance matched, input and output.

I would opt for an Alps Blue Velvet if they have one.

Couldn't find an Alps but you could try these.

http://www.jameco.com/1/1/51187-rv24bf-10-15r1-a1k-dual-audio-potentiometer-1k-%CF%89-resistors.html


http://cpc.farnell.com/1/1/29631-omeg-pc2g16eco1kb-pot-dual-gang-log-1k.html


Cheers George

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