I have a few extra Grayhill 7 pole, 7 deck, 20 position, non-shorting rotary switches for sale at $25/ ea. These are Mil Spec sealed switches with a 1/4" flatted shaft. I can take paypal. Free ship to U.S. addresses.
The following diagram will allow the switche's use as a 20 step volume control.
http://www.kbacoustics.com/images/grayhill2.gif
The following diagram will allow the switche's use as a 20 step volume control.
http://www.kbacoustics.com/images/grayhill2.gif
Bill Fitzpatrick said:
Since they are non-shorting, wouldn't they make a popping noise when changing volume control settings? (Great price, by the way!) Is there a solution to avoid the popping noises? My attenuator is making popping noises as I suspect that it isn't shorting.
Do you have any pictures of these items?
EDIT: nevermind, I found the old thread here:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=7528
You wrote earlier:
"The problem is that when the switch pole is in between positions and making contact with nothing, there is no shunt element in the circuit. The signal volume shoots up to maximum every time you rotate the switch one position."
Does the schematic that you posted a link to fully fix this problem?
--
Brian
Re: Re: Grayhill 7 pole 20 position rotary switch
The posted schematic will prevent the output shooting to max in between positions. Actually the output shoots to min with this wiring. As to popping, keep DC off the switch and it may help to add a resistor to ground at the output.
BrianGT said:
The posted schematic will prevent the output shooting to max in between positions. Actually the output shoots to min with this wiring. As to popping, keep DC off the switch and it may help to add a resistor to ground at the output.
Stepped Volume Control
Hi Bas,
Do you want to use the switch as a series ladder attenuator or as a shunt attenuator?. In the first case I have been using a graphical method on logarithmic paper.
In the latter case as I am now using I have one (only ONE) resistor in series with the signal and I switch each volume setting a different resistor to ground. So contrary to the first case the signal travels only through one resistor and there is only one resistor to ground. For the shunt attenuator the dB's attenuation are easy to calculate with dB= log V^2. Assuming a 10k series resistor I calculated for f.a. 13.5dB attenuation:
10logV^2=13.5
20logV=13.5
V= 4.7315
Then 1/V= 0.21113 as we need attenuation. The voltage is 1/4.7315 I assumed an input voltage of 1V to keep calculations simple.
R= 10k x 1/Vout /(1-1/Vout )
R =10k x 0.2113/0.7887= 2k68 or nearest standard value 2k7.
And so on, and so on....
Are you still with me?
Better I post a list of values for a 10k series resistor.
I also checked all values with a small program from Old Colony called Rescalc.
With the shunt attenuator the switch must be shorting meaning that in between two steps two resistors are switched to ground lowering the volume between detents. Suppose the switch is non shorting there will be no resistor to ground between settings and the volume would be maximum between detents giving loud bangs. I made my 47 position Shallco for 1.5 dB steps except a few of the very loudest settings giving a huge range. For the ear this pot feels as linear but of course it is logarithmic.
Bas Horneman said:
Hi Bas,
Do you want to use the switch as a series ladder attenuator or as a shunt attenuator?. In the first case I have been using a graphical method on logarithmic paper.
In the latter case as I am now using I have one (only ONE) resistor in series with the signal and I switch each volume setting a different resistor to ground. So contrary to the first case the signal travels only through one resistor and there is only one resistor to ground. For the shunt attenuator the dB's attenuation are easy to calculate with dB= log V^2. Assuming a 10k series resistor I calculated for f.a. 13.5dB attenuation:
10logV^2=13.5
20logV=13.5
V= 4.7315
Then 1/V= 0.21113 as we need attenuation. The voltage is 1/4.7315 I assumed an input voltage of 1V to keep calculations simple.
R= 10k x 1/Vout /(1-1/Vout )
R =10k x 0.2113/0.7887= 2k68 or nearest standard value 2k7.
And so on, and so on....
Are you still with me?
Better I post a list of values for a 10k series resistor.
I also checked all values with a small program from Old Colony called Rescalc.
With the shunt attenuator the switch must be shorting meaning that in between two steps two resistors are switched to ground lowering the volume between detents. Suppose the switch is non shorting there will be no resistor to ground between settings and the volume would be maximum between detents giving loud bangs. I made my 47 position Shallco for 1.5 dB steps except a few of the very loudest settings giving a huge range. For the ear this pot feels as linear but of course it is logarithmic.
Shunt Attenuator Schematic
Hi Bas , This is the idea, though I wouldn't draw it that silly......
http://www.goldpt.com/schm_shunt.html
This is more clear. The MINI-H in the link:
http://www.goldpt.com/compare.html
Bas Horneman said:
Not yet
Before I check it out...would it work with this kind of attenuator?
Thanks Elso and Bill
Hi Bas , This is the idea, though I wouldn't draw it that silly......
http://www.goldpt.com/schm_shunt.html
This is more clear. The MINI-H in the link:
http://www.goldpt.com/compare.html
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