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I replaced the volume pot on my tube preamplifier.

Replaced the two mono Alps pots in phono preamp with Tocos (Tokyo Cosmos), RV24 units. I heard good things about these pots on other forums. Fair bit of work getting them to fit into the Croft 25R. I had to loosen the tube boards and drill out the mounting holes for the larger threads. The pots were only $26 for both inc tax and shipping. Huge improvement in speed, clarity, solidity, and transparency. I'm blown away. 

noromance
sns
4,218 posts
 

Gave up on volume pots years ago, only high quality stepped attenuator or TVC for me.

mulveling's avatar
mulveling
2,451 posts
 

After reading this post, i checked the motorized volume pot on my LTA MZ2 and it appears to be the RK50A. And it's well under $10k. 

The only MZ2 pics I see online clearly show an RK27 - some motorized, some not. An RK50 wouldn't even fit in there without a motor - it's massive. IIRC motors for RK50 have to be custom made; VAC is the only one I know of doing it in their preamps, which start at $30K. Never heard of an "RK50A". If you're seeing a huge shiny brass cylinder, then it's definitely an RK50.

Getting a great sounding analog volume control with good granularity (at least 40+ steps) and reasonable price is hard enough. Adding motorization / remote control just adds to the challenge. No wonder some (like Audio Research) have gone to digital chips. Khozmo Poland is worth a mention; they produce some very good looking analog volumes w/ controllers, high quality resistors, and fine-grained steps (60+). Lots of flavors to choose from: Shunt, Ladder, Stepped. "Ladder" sems to be the most premium of discrete options. 

Verified good sound:

  • TKD 2CP-2511 
  • Alps Black Beauty RK40
  • Alps RK50
  • Stepped & Ladder attenuators (DACt, Goldpoint, etc)
  • Khozmo? (haven't tried yet)
mashif
472 posts
 

@mulveling 

I was going by the label on top that shows

50KA X 2

I this to indicate some stereo version of the RK50 but I may be completely mistaken. One can hope. 

mulveling's avatar
mulveling
2,451 posts
 

I was going by the label on top that shows 50KA X 2

@mashif

That’s a specification - 50,000 ohm input impedance, x2 for stereo (2 gang) - not a model number. If you were looking at an RK50 model you’d think "wow!" - it’s massive, shiny, beautiful and gold :) 

The RK50 doesn’t imply 50,000 ohms either (though that is a very common choice); it comes in a few different impedance values. 

mashif
472 posts
 

Yeah, it's a $16 pot available everywhere, probably on par with the 27. But the RK50 is about 100x the price, $1500 or so. So there's another reason for an upgrade. Oh well. 

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