Banned
Joined 2002
Banned
Joined 2002
I'm about to try my first noble, soon. It's on the way. Many have bragged about it, and the money/value. So i bought one, at this moment i can't afford a 5000$ volume pot.
clicky clicky per turn
I bought a Valab SMD 1% stepped attenuator for 25 bucks. The clicky action was far too physically resistive. I took it apart and observed the mechanical parts. Two steel balls fall into indents in the steel ring. 12 indents. One of the balls falls into an indent and the other ball sits half-way to the next indent in its path. Each click of the attenuator is when a ball finds the hole. 12 holes and two balls make 24 steps.
Under the balls is a spring sitting in a cyclinder. I simply cut off the flat landings of the springs that sits at the bottom of the cylinder at the first coil. Keep the flat landing at the top of the spring for the ball to sit in nicely. Now the springs are not so strong and provide less physical resistance to the turning motion of the attenuator. I had to replace the mangled clip that retains the mechanical portions of the device. The clip I found was thinner and also helped to lessen the physical reistance.
Reassemble the resistor disks and wiper plates in a logical manner so that it works. Voila!!!
Enjoy...
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Last week i added a source switcher to my preamp courtesy of an Elma switch. It was beyond disappointing sonically (volume is a Shallco). No idea why i keep buying all this rubbish (have also a Seiden) when Shallco is so damn good. Ended up using Panasonic TQ series relays for the source switching and they sounded preferable to the Elma.
How about 1024 steps?
Here is my idea of controlling the source signal...
http://www.diyaudio.com/forums/pass-labs/158261-novel-control-b1-input-level.html
When I get everything put together, then I will start evaluating different pots.
And thanks to this thread, I can track down the different parts to evaluate!
Here is my idea of controlling the source signal...
http://www.diyaudio.com/forums/pass-labs/158261-novel-control-b1-input-level.html
When I get everything put together, then I will start evaluating different pots.
And thanks to this thread, I can track down the different parts to evaluate!
My last couple of volume controls were Lightspeed based. Tracking was a little challeging, using mono controls and mismatched pots was the answer.
For source selection, I am using switch with lots of poles and positions. Last couple built are made from 11 pole 12 position Greyhill PCB rotary.
Paralleled four contacts for each input and grounded every other position in the 6 position version. With four contacts in parallel and adjacent tracks grounded the is no signature or source leakage. This sounds the same as direct connection.
George
For source selection, I am using switch with lots of poles and positions. Last couple built are made from 11 pole 12 position Greyhill PCB rotary.
Paralleled four contacts for each input and grounded every other position in the 6 position version. With four contacts in parallel and adjacent tracks grounded the is no signature or source leakage. This sounds the same as direct connection.
George
Another improvement to these inexpensive Asian stepped attenuators can be realized by giving them a fresh track on the wiper disks for the contact ball to ride on [they are more like indents made from mechanical pressure in the stamping process].. This is accomplished by making two [or 4 for balanced] new wiper arms with the contact balls [not to be confused with steel balls in mechanical clicky portion]. You can get a ready made wiper arm to modify with a dremel and small files by using parts from a Bosch air flow meter from the fuel injection systems on old import cars like BMW's and Porches. There are still dozens of old Bimmers in every junkyard that have these. Taking apart the air-flow meter simply involves four screws and a razor blade to break the silicone sealing contact of the box. The procedure to renew the wiper arm/contact path is standard renewal procedure on these cars by DIYers simply by bending the wiper arm for a new contact path, so I don't see why the same concept won't work on the cheap Asian stepped attenuators. You would need to pirate two different air-flow meters for a stereo pot. Just modify the Bosch wiper arms to fit similar to the ones in the pots but make them a little longer or shorter in order to provide a fresh track for the contact paths. You do need to make an additional indent on the bent over reverse side of the wiper arm simply by using a hammer and appropriate center punch. These Bosch wiper arms are excellent strong, but springy conductive material. Silver plate 'em if you're real picky.
Not into taking apart Bosch air-flow meters in junkyards?
...'den ya pays da Big Bucks for other more expensive pots. Simple really...or ya live with existing contact path of the standard parts in da pot.
On the pics you can see what I'm babbling about. I added the red lines in Paint [Microsoft] to show what you need to pirate. Because they are rounding a corner it may be possible that only the outside track one is useable but possibly the inside one as well. Otherwise that's why I mentioned pirating two differnt airflow meters.
Not into taking apart Bosch air-flow meters in junkyards?
...'den ya pays da Big Bucks for other more expensive pots. Simple really...or ya live with existing contact path
On the pics you can see what I'm babbling about. I added the red lines in Paint [Microsoft] to show what you need to pirate. Because they are rounding a corner it may be possible that only the outside track one is useable but possibly the inside one as well. Otherwise that's why I mentioned pirating two differnt airflow meters.
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Above pics and automotive procedure from here . Hey...the Bosch air flow meter potentiometer portion is made by Bourns. Disconnect a spring, attach a knob and cut tracks and soldering appropriate resistors could possibly make a rudimentary volume control...along with the TRX 390mm aluminum rims for amp heat sinks and BMW center cap for volume knob to air flow meter. Shop amp special.
12-step potentiometer...monoblocks. You see...you can put a round peg into a square hole.
Rikens and Caddocks to REALLY f with your friends ears.
12-step potentiometer...monoblocks. You see...you can put a round peg into a square hole.
Rikens and Caddocks to REALLY f with your friends ears.
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That looks just like the one I have. While I modified the mechanical front portion I have not yet tried modifying the wiper path...yet. If the Bosch air flow meter was good for 100,000 miles on the same contact wiper paths, I think my potentiometer should be good for awhile before I try the above mod. if I made mine too soft between clickies for full contact I can always add a secong clip to the front of the shaft for a bit more tension on the wipers. The clips I found are quite thin and stackable.
I haven't heard it yet but I've had it for a bit now. I think I'm real close to having it control a chip amp that's finally almost ready to test. I have a bit of time off now after today to catch up on things. I'm close to my preamp from Digi01 soon too for another project I've been putttering on, plus recapping the electrolytics and other explorations in my Luxman integrated. I want to change the front indicator bulbs to LED's so I have a bit of reading and farting around to do. The power leads to the bulbs appear to be around 12v 40ma so I don't know if I would need a resistor with the LED or not. Every two bulbs appear to share a common ground wire, I think, but each bulb has it's power wire that's switch activated by the selector switch I think. I'll have to look at the schematic and the amp some more.
The goal is have the Luxman reasonably refurbished as a base testing platform to give a fair comparison between my DIY projects and an old school discrete solid state from a typical manufacturer. I think mine, the L435 is at the higher end of the mid-fi models they had. I like it.
I haven't heard it yet but I've had it for a bit now. I think I'm real close to having it control a chip amp that's finally almost ready to test. I have a bit of time off now after today to catch up on things. I'm close to my preamp from Digi01 soon too for another project I've been putttering on, plus recapping the electrolytics and other explorations in my Luxman integrated. I want to change the front indicator bulbs to LED's so I have a bit of reading and farting around to do. The power leads to the bulbs appear to be around 12v 40ma so I don't know if I would need a resistor with the LED or not. Every two bulbs appear to share a common ground wire, I think, but each bulb has it's power wire that's switch activated by the selector switch I think. I'll have to look at the schematic and the amp some more.
The goal is have the Luxman reasonably refurbished as a base testing platform to give a fair comparison between my DIY projects and an old school discrete solid state from a typical manufacturer. I think mine, the L435 is at the higher end of the mid-fi models they had. I like it.
Banned
Joined 2002
If I can find a replacement for this 250K balance control
I wont get too picky. It has a 30mm knurled shaft (25 would work)
and the resistance is 250K
This isn't an industrial part - I think. This is custom made. Because there are 4 pins, I think it is for volume control with loudness function and not for balance control. I guess, the brand is ALPS.
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Thanks for the reply,
Its definitely a balance control because that's where I pulled it from.
You're correct it is an Alps control. I'm looking for something to replace
it because it's open. Ive seen some other controls that could work physically
but the resistance is only 10K. Its being used in a receiver where the preamp
consists of a 4558 op amp. If I cant find something with a high enough
resistance I guess my only other alternative would be to find out if the
circuit could be reconfigured to use something with a different resistance
value.