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