Volume controls

A lot of time can be spent fretting about volume controls.  On the right, the ubiquitous ALPS ‘blue’  RK27 series potentiometer. IMG_7955 Usually specified with audio/log(arithmic) or ‘A’ taper action.  This is still the go-to choice for a ‘hifi’ quality pot.  It sounds reasonably well balanced.

Alongside is the ALPS so-called ‘black beauty’ pot favoured by many audiophiles.  A much larger 40mm pot, this one has solder tags and not always an easy drop-in replacement.  It’s been a few years now, but I recall a ‘big and forward’ sound, with strong mid-bass but also increased ‘brightness’ – I was not entirely convinced about this unit (now discontinued but still available).

Don’t forget the Noble AP25 pot (not shown), a very good sounding and economical  alternative to the ALPs.  The TKDs?  I never managed to lay hands on one of those.

DSC01108aYou can build ‘ladder’ resistor attenuators, as I did, using a good quality switch like this 29 position, silver contact, 2-deck unit that I used.  However, the problem with step attenuators is the choice of resistors.  Metal films like Roederstein, Holco, Vishays are too ‘hifi’ for me and costly.  You may prefer carbon film, like Riken.  Or tantalum film would be nice, but again costly.

DACTCT1a

This ready-made DACT CT1 ‘series’ attenuator, sounded surprisingly good to me.  Maybe it’s the SMD resistors, without leads.  Or the PCB, short signal paths, I don’t know.  This was/is the best resistor-type attenuator that I have heard.

Sowter TVCs

Transformer Volume Controls (TVCs) – the above pair were made by Sowter.  Only 16 positions was an economical option, as the highest volume positions are never used and can be spaced more widely.  In the main range 3dB steps, but in hindsight, closer spacing down to 1.5dB would be better.

To my ear, this TVC delivers much more power and energy from top to bottom, with powerful bass and sweet treble (the latter a weakness of resistor attenuators).  In short, lower distortion, better power transfer and wider bandwidth – more like music.

IMG_2855To make a TVC work, you need a high quality switch.  In this case, Swiss Elma 24 position, single deck, mono.  The completed TVC installation (below) in a partially rebuilt preamp.

This remains my current volume control.IMG_2859

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2 thoughts on “Volume controls

  1. Pingback: JE Labs Linestage | D a r k L a n t e r n

  2. Pingback: Magic and microphony | D a r k L a n t e r n

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