Analog Attenuator?

[Superdad]

1 hour ago, The Computer Audiophile said:

Thanks John. Is the autoformer similar at all to what The Bespoke Audio Company is doing with its transformer design?

 

Hi Chris:

I think the Bespoke units are nice, bu way too much wire.  

Here is the link to the Slagle Elmaformer: http://www.intactaudio.com/atten.html

47 silky-smooth positions, 1.25dB steps.

 

I built mine into a small case with a really big knob. In the case you see is the copper version. It blew me away (compared to my $10K Hovland HP200P-i with rhodium-contact relay attenuator) so much so that I had Dave Slagle make me his silver version.

 

As with John, I have been searching for decades for the finest attenuation means, and of course was involved in building fine resistor-based stepped attenuators--LONG before anyone in the high-end (I'm talking late 1970s; Hovland was the very first audio customer for Caddock resistors).  

This Slageformer is far and away the most transparent level control I've ever used--and it has no trouble driving 25 feet of single-ended cable into my amp.

 

Balanced versions are possible as is remote control. You have to hear one to believe it.

 

[Superdad]

Also see:

https://www.whatsbestforum.com/threads/emia-elmaformer-volume-control-review.29910/

and EM/IA, the collaboration between Jeffrey Jackson and Dave Slage: http://myemia.com

[Superdad]

54 minutes ago, acg said:

The beauty of the autoformers is that the good ones can handle more than 8V at 20Hz so are able to be used between the source/preamp and amplifier.  They have this wonderful knack in this position of lowering the source impedance as seen by the amplifier as soon as any attenuation is used.  So at -6dB attenuation the source impedance as seen by the amplifier is improved 16 fold, and it increases logarithmically from there reducing to pretty much zero by no later than -10dB attenuation.  Compare that to a stepped attenuator (Goldpoint, Khozmo etc.) used in that position, the impedance seen by the amplifier is increased as you start attenuating and after a while starts to fall again.  What does this all really mean?  Well, it means that with an autoformer volume control, you do not have to limit yourself to gain stages with low output impedance (read: high levels of global negative feedback) if you do not wish to...you have more options in selecting the active linestage/preamplifier circuit to craft the sound you want.  It also means that if you are not caught in the "race to the bottom" of THD and other specmanship, and cannot hear the difference between 0.001%THD and 0.01%, that you have options.

 

Great post! 

One of the most remarkable aspects I discovered right away when using the Slagle autoformer is the amount of detail and engagement with the music that remains ever when you turn the volume way down. The experience is completely unlike that of even the very best resistor-based attenuator.