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Alps Pots?

Dansk

Dansk

cantus audio
Long story short, my brother and I are building a tube-based headphone amp from scratch. It's proved to be a remarkably fun project, with him being responsible for the electronics, and me being responsible for the design and styling.

Yesterday in our search for parts we came across an old Alps 50KΩ pot, a BX2 model. I'm wondering if anyone knows anything about the Alps pots here. The BX2 seems to be an old, out of production model, that (I assume) has been replaced by the RK27.

It seems to be in great shape, we hooked it up to a power supply and oscilliscope and the channels track together perfectly, with less than 0.1 volts difference between them at any point. The scale is definitely logarithmic and climbs smoothly.

(In contrast, we compared this to a Radioshack pot that jumped all over the place and had big dead spots. There's something to be said for quality manufacturing.)

So can anyone shed some light on the Alps stuff? As far as I can tell, they seem to be THE company for pots. Just going by what we found with the oscilliscope, this thing should be perfect for our needs (as a volume pot), although the resistance might be a little on the low side.
 
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hey-Hey!!!,
I found the inexpensive Radio Shack 100k Alps pots to be a little bit variable on tracking. I also discovered that they could be tweaked by twisting the plates and then applying a bit of super glue to lock them down. With $10 to buy three I could get a very nice one. I do prefer to get the $15 50k ones as sold by Partsconnexion. They match/track quite well, and the 50k gives an octave better response based on the grid capacitance creating an RC filter with the pot resistance.
cheers,
Douglas
 
Alps has produced a quality line of pots for a long time.

My late father....forever the pack rat....had squirreled away dozens of boxes of NOS Allen Bradley pots....mono and stereo.
I kept a few stereo pots (50K & 100K)....and gave the rest to my son for his DIY projects.

Steve
 
Dansk said:
Long story short, my brother and I are building a tube-based headphone amp from scratch. It's proved to be a remarkably fun project, with him being responsible for the electronics, and me being responsible for the design and styling.

Yesterday in our search for parts we came across an old Alps 50Ω pot, a BX2 model. I'm wondering if anyone knows anything about the Alps pots here. The BX2 seems to be an old, out of production model, that (I assume) has been replaced by the RK27.

It seems to be in great shape, we hooked it up to a power supply and oscilliscope and the channels track together perfectly, with less than 0.1 volts difference between them at any point. The scale is definitely logarithmic and climbs smoothly.

(In contrast, we compared this to a Radioshack pot that jumped all over the place and had big dead spots. There's something to be said for quality manufacturing.)

So can anyone shed some light on the Alps stuff? As far as I can tell, they seem to be THE company for pots. Just going by what we found with the oscilliscope, this thing should be perfect for our needs (as a volume pot), although the resistance might be a little on the low side.
Click to expand...

It's only 50 Ohms? I'm not sure that would work impedance-wise, and given that it came from an oscilloscope, it is most likely linear taper, not audio.

The least impedance I would use for a tube preamp is 100K Ohms.

In any preamp, especially if you are going for really good sound quality, the single most important part is the volume control, period. I've seen (but only rarely) a good preamp built with that $3 radio-shack Alps volume control, but never a great preamp.

The minimum quality I would suggest is the Alps RK27, also known as the "Alps Blue". They are usually around $20, and buy from a trusted source. The Alps RK27 is counterfeited more than Gucci handbags. A much bigger step up, and now out of production, but not too hard to find still is the Noble AP25 series of potentiometers. They are the ones in the black metal bodies, and generally can be found for $20-$25. The next step up, and it is a giant step, is the TKD conductive plastic pot. Yes, they cost about $60 each, but they are a worthy investment over the other two, at least to my ears.
 
BrassTeacher said:
It's only 50 Ohms? I'm not sure that would work impedance-wise, and given that it came from an oscilloscope, it is most likely linear taper, not audio.
Click to expand...

Sorry, that's a typo, I forgot the K! :)

And no, it didn't come from an oscilliscope, we checked it with the oscilliscope to see if it was logarithmic. It came from an amplifier that was scrapped years ago, and was found laying in a forgotten pile of parts.
 
BrassTeacher said:
It's only 50 Ohms? I'm not sure that would work impedance-wise, and given that it came from an oscilloscope, it is most likely linear taper, not audio.

The least impedance I would use for a tube preamp is 100K Ohms.

In any preamp, especially if you are going for really good sound quality, the single most important part is the volume control, period. I've seen (but only rarely) a good preamp built with that $3 radio-shack Alps volume control, but never a great preamp.

The minimum quality I would suggest is the Alps RK27, also known as the "Alps Blue". They are usually around $20, and buy from a trusted source. The Alps RK27 is counterfeited more than Gucci handbags. A much bigger step up, and now out of production, but not too hard to find still is the Noble AP25 series of potentiometers. They are the ones in the black metal bodies, and generally can be found for $20-$25. The next step up, and it is a giant step, is the TKD conductive plastic pot. Yes, they cost about $60 each, but they are a worthy investment over the other two, at least to my ears.
Click to expand...

You forgot about the stepped attenuator Alps. Black plastic, near twice the size of the Blue ones...switches and discrete resistors( not just detents ).

Why restrict yourself to 100k? Source impedance is usually quite low enough to handle a 10k pot comfortably; no sense making the corner frequency of the RC stage any lower than is absolutely required.
cheers,
Douglas
 
I've had good luck with ALPS, Noble and ($$$) Goldpoint. I recently bought a pair of PEC pots (for a monoblock project). The PEC pots are molded carbon and are supposed to sound rather good for the money - though tracking between channels is supposed to be an issue for the stereo pots.

There are a number of ALPS pots available on Flea-pay. I'm beginning to wonder if some of them are counterfeits.
 
Here's a picture of the almost-finished faceplate! All that it needs now is staining and laquering, and it's ready to be hooked up!

I'm particularly proud of the volume knob, it was made from scratch on a lathe. Why settle for something you find in a store? There's nothing better than making exactly the parts you want! :D
 

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PakProtector said:
You forgot about the stepped attenuator Alps. Black plastic, near twice the size of the Blue ones...switches and discrete resistors( not just detents ).

Why restrict yourself to 100k? Source impedance is usually quite low enough to handle a 10k pot comfortably; no sense making the corner frequency of the RC stage any lower than is absolutely required.
cheers,
Douglas
Click to expand...

Well, I tried to stick with what I knew was currently available, not sure the stepped ones are, and I know you can't get the RK40 any more either.

As for 100K, we're not sure if any of the author's sources are tube-based or not, nor do we know if there will be an input coupling cap. Just playing the averages.
 
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