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.
The Alps "Blue Velvet" RK27 is almost ubiquitous in analog preamps and headphone amps below $10K - especially tube units which are less likely to use a digital volume chip. Which is a shame, because EVERY TIME I’ve compared this pot to a better alternative - RK50, TKD (the 2CP-2511 is fantastic!), stepped or ladder attenuators - the RK27 has been exposed as a significant performance bottleneck. JUST like you’ve found. Alps used to make an RK40 "Black Beauty" pot which was better, and much more reasonably priced than RK50, but sadly it’s long discontinued :(
Now every time I see a component with that dark blue plastic Alps pot inside, it’s enought to make me lose interest. If it's also above $10K MSRP, I cringe. I think it’s become so common for its low relative cost and motorized option (and laziness on the designer’s part).
I’m pretty sure a digital volume chip sounds better than RK27 too, but I haven’t compared them on "relatively equal" terms - just guessing here.
Thanks @viridian. I've played a bunch of tracks to get a measure on the changes. Everything is louder–much more dynamic, music soars–it's almost unsettling, deeper bass, sweeter highs, more air, hidden instruments and voices revealed.
@mulveling It’s certainly an eye-opener for sure. Most manufacturers are component lazy, compromising their product sonically and economically.
Agree! I’m normally a fan of "affordable, but reliable and sounds good" parts (like resistors, caps), and get a little hesitant to just blindly go in for exotic $$$ parts which can sometimes change the sound a little too sterile, bright, or analytical IMO. But the Alps Blue is defintely NOT a good sounding part in a very critical position; most of its alternatives sound better :)
@erik_squires No. There’s not enough room to fit a discrete unit. The TACOS are carbon wipers whereas the Alps were plastic film. And, truth be told, I’m somewhat frugle in wringing out the best bang for the buck.
Interesting that these probably would fit but I’m not sure how well SMD resistors sound, and I wasn’t gonna take a $300 tryout! If I was building my own phono amp (some day!), I’d use a switched unit with bulk foils.
I agree with @mulveling. The Blue Velvet is a real bottleneck. It floors me to see otherwise respectable preamps with a Blue Velvet. It is a genuine loser. I first tried the Blue Velvet about 25 years ago and didn’t like it. I then bought an Alps Black Beauty and I loved it. That led me to order a number of pots to see if I could find something even better than the Black Beauty. These included Noble, TKD, a stepped Alps, vintage Allen Bradley, a couple stepped attenuators, and an expensive Penny and Giles. None of them sounded as good as the Black Beauty so I bought a few spares. Two decades later they still sound just as good and they are just as quiet as they were when I first installed them. Definitely a good investment.
The Alps RK50 is supposed to be even better than the Black Beauty. I have never heard one so I don’t know that for a fact. In any event, they are not only hard to find they are also quite large, too big to fit in my main linestage. However, if I do come across an RK50 I will try it just to find out.
I replaced the damaged OE pot in my Krell pre with a TKD 2CP-2511.
I originally wanted a resistor ladder attenuator, but couldn't find one that physically fit in the limited space. So I settled on the TKD 2CP-2511 and, as @mulveling shared, it is fantastic, in terms of both sound quality and feel.
I ordered mine from Michael Percy and I am comfortable recommending both (the TKD and Michael Percy that is).
My understanding is that Goldpoint is working on a new subcompact resistor ladder attenuator suitable for space-constrained retrofits.
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.
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.
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.
@noromanceThanks for posting about this! I built a Waynes 2018 preamp, a DIY design from the good folks at Pass labs that I put an Alps 27K in and it is good. But you and the other contributors here have given great leads on what promises to be a significant upgrade. Thanks too to @mulveling. I don't think I can swing the RK50 but the Alps RK40 looks doable! Great stuff.
OP has touched on a very overlooked part of preamps. An afterthought piece which is quite critical to everything. You guys are technically beyond me, but I can hang with the best when hearing the differences in quality.
There are some volume pot geeks who've drilled deep into the subject. Thanks for the posting.
I wouldn't say the standard RK27 is complete junk. But it's a $20 (retail) wiper that is inside of a lot of good sounding equipment. It does absolutely amaze me that a builder will put together a $5k plus piece of gear & stick a Blue Velvet in it. Stick a bunch of pricey boutique capacitors, resistors, & overpriced rca jacks in a preamp then skimp on the volume control.
I think the consumer would gladly pay a little extra for a volume control that can really take the overall performance to the next level.
The main problem with switching out a pot is that there is rarely any room to make the change. It can be a major pain in the butt & an easy way to add noise if not grounded correctly. You gotta get creative. I just replaced a RK27 in a tube preamp with a Goldpoint SMD attenuator. Better clarity, separation, & depth of stage vs the Velvet. And the GP is just a regular stepped attenuator. I have a couple of Nobles from the 90's that still work well.
Yeah, yeah...heard it before.....
"Pirate picture intercepted; squeak cleared." from the SelfControl 'bots....pesky 'chits.... Only defense is to get offensive and go moto-vated....hide in plain sight, move when it blinks.
@bolong...Yup, ask the lobster at your next gastroventure...;)
@noromance...(Surely you jest? ;) Always wanted to ask that and "NONE?!" *LOL*
Look on it as a Public Service; keeping it out of the lungs of those who would just waste it and the hands of Public Servants who waste it as well.... ;)
...and then, consider it as another PS as keeping it under control and put to Good Abuse...🙄
It's bad pot stories in bigger $ pre's and amps that drove me to near-total digital switching with my picks for twitch...nothing wears out or dusty, leaving me to get corroded....
The matrix switcher is the only exception, but due for some TLC...
This is the pot in my tube pre - the dreaded Alps Blue Velvet. Aside from not being granular enough, it also has a "missing" volume stop right where it is most noticeable and irritating. Based on the photo is there any room for a better replacement? It has to be motorized and controllable from my remote.
TKD is a little hard to get in the US. Michael Percy is normally the best source, but I'm not sure whether he stocks motorized versions. Google him and reach out to him.
ROWD and I have been through this and if anyone does not think this is a MAJOR ISSUE they cannot hear….here is my short story I by accident ruined a khozmo attenuator while painting a faceplate on a dual mono passive and pulled the other out and then substituted with ALPS and I was floored which led me to another world….and as a result I even took a 5K ARS SONUM FILHARMONIA AND ripped it apart to replace the ALPS with a pair of KHOZMO which now set externally on the chassis and the difference made a 5K integrated sound like a a 10 k integrated…..CHEAP POTS TURN MY STOMACH.
@jordi Obviously, I concur. Contrary to the seeming naivete of my opening post, I have run into this issue before. I built an overkill phono preamplifier back in the day and it sounded fantastic (with a cheap RS sourced pot). I was to demo it to a dealer and wanting to make the best impression, replaced the pot with a Sfernice unit ordered from France. I hastily swapped out the pot, tested on the scope and packed up the amp. The demo went well with the dealer saying, "don’t call us, we’ll call you." Let’s just say, the fancy pot destroyed the sound. And that is why I’ve waited all these years to try a different pot.
Maybe we need to pressure manufacturers to use better pots.
Too many audiophiles are incurious what is inside their components and never take the covers off, and some manufacturers take advantage.
Meanwhile, the 2P65CS is superb. The stepper mechanism (whose only function is to provide tactile and auditory feedback) is a thing of beauty, with its exposed gear and ball-bearing detent.
Unfortunately, the limited space in my Krell pre only allowed for a 25 x 25 mm form factor, but had I installed a 2P65CS in there I don't think I'd ever put the cover back on 😃
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