# Volume Potentiometer Questions



## CulinaryGod (Jun 5, 2008)

Question 1. What do the different values on potentiometers mean?
Question 2. How do I determine which potentiometer is right for my application?

I'm building a chip amp and am ordering parts but I've found a couple of Alps Blue Velvet pots with different ratings/values from 50k-250k. How do I decide which is right for me?


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## CulinaryGod (Jun 5, 2008)

Nobody? Even suggestions or educated guesses would be fine with me.


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## onebadmonte (Sep 4, 2008)

My guess is you need a 10K pot with a "log" taper. This will control the volume based of how the human hearing works. A linear taper pot would raise the volume too fast, lacking control.


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## CulinaryGod (Jun 5, 2008)

Wow man, you were right on cue with what Peter Daniels of Audiosector recommended. Now another question. If I'm buying a dual mono kit, will I need one or two pots? Or is the purpose of a dual mono to drive each channel separately from their own power supplies AND have the ability to control each channel's volume independently?


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## CulinaryGod (Jun 5, 2008)

Actually, he recommended a 25k, but geez louise those are hard to find if not damn near impossible. I've searched for a 25k Logarithmic pot and haven't been able to find squat.


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## t3sn4f2 (Jan 3, 2007)

Detailed Information

Frequently Asked Questions

Review of DACT's CT1 attenuator in internet magazine EnjoyTheMusic.com

Review of DACT's CT1 attenuator in the US magazine Audio Electronics


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## onebadmonte (Sep 4, 2008)

CulinaryGod said:


> Wow man, you were right on cue with what Peter Daniels of Audiosector recommended. Now another question. If I'm buying a dual mono kit, will I need one or two pots? Or is the purpose of a dual mono to drive each channel separately from their own power supplies AND have the ability to control each channel's volume independently?


On a dual mono kit two are required. Usually you'll have both levels set the same. There are special pots out there that are really just two pots in tandem ( one pot right behind the other sharing the same shaft) so you only have one volume knob. Cost is an issue going this route. I have seen others get creative a use a set of gears to get two pots to work together with one knob. The sky's the limit. Good luck and post some pics.


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## t3sn4f2 (Jan 3, 2007)

onebadmonte said:


> On a dual mono kit two are required. Usually you'll have both levels set the same. There are special pots out there that are really just two pots in tandem ( one pot right behind the other sharing the same shaft) so you only have one volume knob. Cost is an issue going this route. I have seen others get creative a use a set of gears to get two pots to work together with one knob. The sky's the limit. Good luck and post some pics.


Just to clarify a little, all stereo pots are dual mono configurations. You can't attenuate the required two unique channels of a stereo signal through a single resistive element. Even the little alps seen on amp gains are two monos stacked on each other.


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## CulinaryGod (Jun 5, 2008)

t3sn4f2 said:


> Just to clarify a little, all stereo pots are dual mono configurations. You can't attenuate the required two unique channels of a stereo signal through a single resistive element. Even the little alps seen on amp gains are two monos stacked on each other.


So you're saying going with a single stereo pot is what I need? Also, Hugo, I've seen the pot you're talking about in a couple of pictures and am thinking that may just be the route I need. The problem lays in finding one though. :laugh:


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## CulinaryGod (Jun 5, 2008)

I found one! It's a TKD Dual Log 25k pot. It's in the UK though for £72.00 which is roughy $113. Seems kinda steep, considering that the dual mono amp kit from audio sector is only $90. I also found a dual log Alps pot that's 20k for significantly less, though I'm not sure if it'll be a big difference from the 25k. Another thing Peter recommended was using a 50K Alps Blue pot.


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## t3sn4f2 (Jan 3, 2007)

CulinaryGod said:


> So you're saying going with a single stereo pot is what I need? Also, Hugo, I've seen the pot you're talking about in a couple of pictures and am thinking that may just be the route I need. The problem lays in finding one though. :laugh:


Yes.


And if you find that the one you need is 50K for sure, then this site has the blue velvet for $16. Page search "RK27112A"


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## CulinaryGod (Jun 5, 2008)

t3sn4f2, I read the review on the DACT CT1. I've been searching for it for about half an hour and haven't found anywhere in the US that sells it, and the dutch websites are hard to navigate. Any idea of an online retailer that I can pick one of these up from? Also, if I was recommended a 25log pot, is it the same thing as a 20k stepped attenuator in terms of compatability?


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## t3sn4f2 (Jan 3, 2007)

CulinaryGod said:


> t3sn4f2, I read the review on the DACT CT1. I've been searching for it for about half an hour and haven't found anywhere in the US that sells it, and the dutch websites are hard to navigate. Any idea of an online retailer that I can pick one of these up from? Also, if I was recommended a 25log pot, is it the same thing as a 20k stepped attenuator in terms of compatability?


The CT1 is the old one, the current is CT2. The sell it here DIYCable.com : Intro » Home » DACT Products » Passive Parts.

Detailed Information 

"-How To Choose the Correct Stepped Attenuator Value. General Rules and Considerations: 
1.When upgrading from a potentiometer, use the same value stepped attenuator. (5K, 10K, 20K, 25K, 50K, 100K, etc.) 
2. Choose the value to match the input impedance (of what the stepped attenuator will be controlling). This applies to both preamplifiers and power amplifiers when the stepped attenuator is to be installed at the input. If necessary, check your owner's manual to find the the rated input impedance of your unit. Or contact the manufacturer. 
3. When choosing the stepped attenuator value for an in-line level control or "passive preamp" (such as the Goldpoint Level Control Boxes), the attenuator value is chosen to match the input impedance of whatever it will be controlling. example: If the amplified monitor speakers or power amplifier you will connect the output of your your passive preamp to has an input impedance of 20K, then order a 20K stepped attenuator for that application. 
*4. You can usually use a level control value which is LESS than the rated input impedance of the gear it will be controlling. So, if your amplifier has a rated input impedance of 100K, instead of using a 100K level control, you could use a 50K, 25K, or even a 10K level control. (Avoid using a level control value which is HIGHER than the rated input impedance). *5. Vacuum tube equipment usually uses 100K or 50K level controls, due to the higher input impedance of tubes. Solid-state gear usually has 50K, 20K, or even 10K level controls. 
6. You typically begin to have high frequency roll-off beginning to appear with attenuator values above 100K. If you don't have an engineer handy, or just can't decide, 25K is usually a good choice for both vacuum tube and solid-state equipment, especially for passive line controls."

I don't know enough about circuits to tell you what would work for sure though. I would check with the amp designer or the pot company.

Personally I would go with a highend resistive element pot like a blue velvet. I prefer the feel of a seemingly infinite increment scale of those pots then the stepped feel of stepped attenuators like DACT and Goldpoint.

Volume control is an art really, it's not simply taking a LOG function and applying it in resistance. A lot of thought goes into how the pot sound like when adjusting the volume. IOW it can influence how you perceive the quality of the music. Right down to the feel of the knob you choose. I'd then go with something popular and high quality like the Blue which has a good track record. At that price range, they are all quality products and going to maintain the same signal iintegrity.


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## CulinaryGod (Jun 5, 2008)

Awesome information. Thank you so much for the help and a general understanding of volume control. I believe my mind has been made up. Alps Blue Velvet 50k dual log pot. I one for $15 + $2 shipping. For that price it's unbeatable compared to all of the TKD's, Nobles, and other pots I've found that are non-stepped.


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## CulinaryGod (Jun 5, 2008)

Hmm, upon further investigation I see that a lot of the pots I'm looking at are rated for low wattage, from 0.5 - 5 watts. What is the deal? Are these not suitable for my application as the chip amp I'm building will be producing roughly 60w @ 8ohms? Or is this rating in relation to something else? Any idea, t3sn4f2 or hugo?


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## robfive (Nov 3, 2006)

Those wattage ratings are fine. The potentiometers are not inline with the speaker outputs from the chips. In other words the speakers are hooked up directly to the chips and not directly to the pot. The pot will not see the output power of the amp.

Go with that blue velvet. It's a good deal.


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## t3sn4f2 (Jan 3, 2007)

robfive said:


> Those wattage ratings are fine. The potentiometers are not inline with the speaker outputs from the chips. In other words the speakers are hooked up directly to the chips and not directly to the pot. The pot will not see the output power of the amp.
> 
> Go with that blue velvet. It's a good deal.


Exactly. 

The pot attenuates the voltage coming _into_ the amplifier (ie the PREamp voltage). And the load which dictates the wattage rating needed is in the tens of thousands instead of the typical single digit a speaker load would have on the amp output.


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## CulinaryGod (Jun 5, 2008)

I see. Thanks a bunch guys. Y'all have provided some great information and it's very much appreciated.


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## t3sn4f2 (Jan 3, 2007)

Anytime


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