AudioNervosa

Self Medicating => DIY Electronics => Topic started by: rollo on October 01, 2020, 12:06:19 PM

Title: Volume pots
Post by: rollo on October 01, 2020, 12:06:19 PM
  Looking for the quietest one made. There are variable resistor types and stepped as well as Autoformers. The use will be for an amp.


charles
Title: Re: Volume pots
Post by: tmazz on October 01, 2020, 08:38:24 PM
I'm not sure I understand what you mean by quiet. As a passive device a volume pot should not make any noise at all, except when you are moving it. And I am not sure why having the pot make a little noise while you are moving it would be a big deal. It's not like you would be doing any critical listening during the second or two it takes to make a volume change.  What am I missing?
Title: Re: Volume pots
Post by: P.I. on October 01, 2020, 11:28:47 PM
Resistive elements have a parameter that is called the “temperature coefficient of resistance”. It is quantified in parts per million (ppm).  These numbers can run any where from 0.01 to over 1200 with lower being better.  Most commercial pots run in the 750 - 1000 range.  This directly correlates to “self noise” generated in the resistive element.  At very low voltages, where TCR noise is most prevalent,  this can be a big deal.  Take a low output moving coil and we are talking about possible serious consequences.

So here is my take:

VHQ stepped attenuators can utilize resistors like the bulk foil one made by this company-

http://www.texascomponents.com/store/VishayFoilResistors.asp

They are a great company and make and quickly ship small order products.  Using all TCC resistors in a stepped attenuators can get very, very, VERY expensive.  I once built a 47 step, stereo attenuator for a customer and the cost for resistors alone was over $1500.00.  Made me nervous during the build due to the 380+ solder joints with an extremely difficult to work solder.  Done with that!

There are some great attenuators available here:

https://www.hificollective.co.uk/attenuator/glasshouse-elma-a47-jumbo-stepped-attenuator-mono.html

When it comes to pots I am a fan of the plastic element TKD products:

https://www.partsconnexion.com/tkd-potentiomters.html

They ‘sound’ very good which is to say they don’t sound at all. 

DACT is another great option.  This is the best “bang” I know of:

https://www.ebay.com/itm/283538214885

I’m not a fan of Alps. I had too many fail in studio applications.  They are, however, a good source for motorized pots.

For autoformers, Dave Slagle is THE Man! :  http://www.intactaudio.com/atten.html

There are so many options.  Pick a price point and do a search.
Title: Re: Volume pots
Post by: Folsom on October 02, 2020, 06:15:08 AM
The eBay DACTs are crazy good for the money. I'm not hesitant to use one at any price point except the fact that it has a limited number of positions.
Title: Re: Volume pots
Post by: rollo on October 02, 2020, 09:35:05 AM
  Was leaning towards the TDK plastic. Good reviews. Thanks Guys.

charles
Title: Re: Volume pots
Post by: Response Audio on October 07, 2020, 10:07:53 AM
Hey Charles. Just curious why you are installing a volume control in or prior to an amplifier?
Title: Re: Volume pots
Post by: rollo on October 07, 2020, 10:40:53 AM
  The Alan Eaton design uses one. I really would prefer my preamp. I am experimenting either by bypassing gain control and using preamp OR using a better gain control without preamp.



charles
Title: Re: Volume pots
Post by: rollo on October 13, 2020, 09:24:47 AM
  The Alan Eaton design uses one. I really would prefer my preamp. I am experimenting either by bypassing gain control and using preamp OR using a better gain control without preamp.



charles

  OK bypassed the volume pot and put Lamm Ref Preamp back in. No contest. More body, slam and bigger stage. I appreciate the K.I.S.S. theory simpler not as good. So enamored with the 45 tube now considering a Tektron mono blocks.

charles