www.diykits.com.hk stepped volume control ... any good?

[poynton]

Originally posted by kvk
[B]Shouldn't this chart give you the info you need? You might need to check which contacts are open/closed in a couple positions but once you know that, the list of R values should do it...

Originally posted by kevinkr


Exactly what I have on paper, this is much better. Spliting the switch into two separate blocks of 4 rows you have the following:

The outer row is the input row, "R1" the next row has just two pins which can be tied together is the first wiper row the next row is the ground row, "R2" and the final row of 2 is the other wiper row.. The pattern then repeats.

The pins in row 1 & 3 that line up with the lefthandmost pins in rows 2 & 4 are the 0 position when switch is fully ccw. (Measure to confirm.) The two sets of wipers need to be connected together to work and this signal then goes to the input of the pre-amp or amp.

Note that there is a strong reflection off of the surface this attenuator was photographed on which makes it look like there is a fifth row of resistors - there isn't.

Incidentally there is another better way to do this if you think about it. Apply input to first wiper, wire R1 resistors from first to third row, and third row resistor R2 to ground buss. Take output off of wiper in row 4.. Instead of driving all of the contact capacitance, two sets of long wipers and all of the resistors simultaneously you drive just one resistor pair, this should lower input capacitance significantly. It will not look as nice and is harder to do as well.

Thanks for the info guys !!!

Andy

[kmtang]

I bought two of the 100K volume control as shown in kevinr's message. I tested them by feeding it with signal generator and see the output with an oscilloscope.

I was surprised that there were very high sharp spikes at the leading and falling edgies of the square wave at the output especially at low volume positions, lower the worse. I broke one in pieces to find out why that happens. May be it was caused by my test set up or may be it was caused by internal stray capacitance within the switch.

I have better success in building stepped volume control with resistors in series that I could see very favourable square wave response.

I just hope someone would test it and confirm my finding.


Johnny

[Stixx]

I also have one of those attenuators as pictured in kvk's and Kevin's posting. I tried to measure this thing in order to find out how it is supposed to be wired up, but no real success yet.

The pins in row 1 & 3 that line up with the lefthandmost pins in rows 2 & 4 are the 0 position when switch is fully ccw. (Measure to confirm.) The two sets of wipers need to be connected together to work and this signal then goes to the input of the pre-amp or amp.

Also not entirely clear to me...

I also coincidentally found the pic attached (courtesy of triode dick's page)... so can anyone provide a simple schematic or description how it should be wired up?

thank you!

[ErikdeBest]

Hi Stixx

I edited your picture in paint. I think it is right, but it is easy to test. Put a DVM across the (marked) input and ground: this meter should read the pot's value (10k, 50k, 100k, whatever) in any position of the wiper. A second DVM is connected between the output and ground. This one should read low ohmic values for the low level settings, and increased values for the higher level settings.

Viel spass mit ausprobieren, und lassen Sie bitte wissen oder es funktionirt. (Good luck finding out, and please let us now if it worked)

Erik

[Stixx]

Viel spass mit ausprobieren, und lassen Sie bitte wissen oder es funktionirt. (Good luck finding out, and please let us now if it worked)

Hello Erik, dank u zeer, waardeer ik werkelijk uw hulp! (crude translation by babelfish...;-)

Thanks alot, I will try out... It is going to sit in my aikido headphone amplifier that I'm about to finish (breadboard version first). I'll post my impressions...

groet

(my boss is dutch but I'm hearing only the bad words in nederlands from him...;-)

[OzMikeH]

How to assemble?

Try this:

http://www.penguinlovers.net/audio/Attenuator.html

[kvk]

Originally posted by OzMikeH
How to assemble?

Try this:

http://www.penguinlovers.net/audio/Attenuator.html

That rocks. Thanx for the post.

[Stixx]

I compared the information with my stepped attenuator and found that two pairs of pins are connected as shown in OzMikeH's link.

When I measure across input and ground I am having 51K (both channels very exact), whereas across output and ground I am having ~0 - 36K...

So everything looks fine to me!

Thanks again Erik (and all the others...)!

[OzMikeH]

Beautiful workmanship there Stixx

[samoloko]

I bought a rottary switch with 24 steps like the one from from upper pics
now I have to get a resistors
can somebody recommend a place to purchase online good resistors
I need 20 K or 10 K attenuator
anybody tried the attenuator resistor set from thlaudio http://thlaudio.com/VishayDaleRmnE.htm