Affordable TVC preamp options?

Ski

Junior Member
I keep reading about TVC preamps and I'm curious. I've tried a couple inexpensive passive preamps and have found them a little too sterile sounding for my tastes. I've not tried one on my current system: Maverick D1+, Luxman M-02 (150wpc), ADS L-1530 (95dB/1w @ 6 Ohm} if that matters. Thanks in advance.
 

Redboy

Knobophobe
I should expand on my comment a little because I have experience with "inexpensive passive preamps", too.

I've experimented quite a bit with passive preamps over the years, and I am a big fan. The first one I built was a simple "pot-in-a-box" affair, and I was immediately struck by how revealing the thing was; there's a lot to be said for simplifying your signal path as much as possible! I learned that everything in that path can affect your sound, and that some things have a greater impact than others.

I built a bunch more using various attenuators in different configurations, including the cheapest Radio Shack Alps pot in a shunt-to-ground design in my $8.01 cigar box preamp. I've used potentiometers from Alps, Apha, Audio Note, Bourns, TKD, and more. I tried the cheap stepped resistor units from China and the good ones from DACT, Goldpoint, Khozmo.

This is an overly broad statement, but pretty much all of the above are better than the standard issue, cheap potentiometer unit found in 99% of the commercial audio gear built today...

But in my opinion, a transformer volume control (TVC) is better than all of the above.

Autoformer Volume Controls (AVCs, or Autoformers) are technically slightly different than TVCs, but most people lump them in the same category and call them all TVCs. That's fine by me. We could also call them Inductive Volume Controls but that hasn't really caught on...

I've used, built and/or listened to TVC units from Dave Slagle (Intact Audio), Stephens & Billington (S&B), Silk, and Prometheus Audio and they are all really really nice. My favorites thus far are the Slagle and S&B.

I don't pretend to fully understand why these things sound better, but they do. I think it has to do with reflected impedances and loading of the respective source units. Inductive volume controls present a "friendlier" load to our source components, especially at lower volumes, than a resistive element.

My current passive preamp is a DIY affair that I built with Dave Slagle's autoformers in John Chapman's (Bent Audio) packaging. Mine were silly expensive but the great thing is that you can get the very same sound from Dave's $200 autoformers as you do from EMIA's Elmaformer at many multiples the cost.

In my system, TVCs are non-negotiable. Give 'em a whirl -- I think you'll like them, too.
 
A question for the experts here. I have in front of me a wall mounted remote speaker volume control. It was a two dollar thrift store purchase. The control consists of a 10 position switch, a pair of autoformers and stereo input/output terminals. Clearly this item lacks the number of steps of volume control and the audiophile approved components of the Dave Slagle devices. Could it still be used as a passive preamp?

John
 

Redboy

Knobophobe
A question for the experts here. I have in front of me a wall mounted remote speaker volume control. It was a two dollar thrift store purchase. The control consists of a 10 position switch, a pair of autoformers and stereo input/output terminals. Clearly this item lacks the number of steps of volume control and the audiophile approved components of the Dave Slagle devices. Could it still be used as a passive preamp?

John
John, there's a decent chance it would work. If I recall correctly, I think Joe Roberts was using some cheap-o autoformers in a speaker crossover, and I think Bottlehead used a similarly pedestrian product as an output transformer in one of their early kits... Heck, a lot of the sanctified-and-glorified Western Electric parts that people worship now were built for telephone closets and switchboards! Give it a shot and report back! :)
 

rogerfederer

Junior Member
A question for the experts here. I have in front of me a wall mounted remote speaker volume control. It was a two dollar thrift store purchase. The control consists of a 10 position switch, a pair of autoformers and stereo input/output terminals. Clearly this item lacks the number of steps of volume control and the audiophile approved components of the Dave Slagle devices. Could it still be used as a passive preamp?

John
i bought a pair of those and tried it. didn't work. guessing the signal coming from a source is higher than that coming from amp via speaker cable.
 

Redboy

Knobophobe
@Redboy do you mind share your experience with the Silk AVC?
It was a very brief experience and quite a long time ago. My overall impression at the time was positive, but not top-of-the-heap positive... I would like to hear them again.

Another type that I have not heard yet, but would really like to are the Noguchi autoformers with Hitachi Finemet cores...
 
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Redboy

Knobophobe
Clearly this item lacks the number of steps of volume control and the audiophile approved components of the Dave Slagle devices. Could it still be used as a passive preamp?
This brings up a good point, actually. The difference in cost between Slagle's entry-level $200 Autoformers and his absolute finest offerings is driven by only a couple of factors; the total number of and spacing between attenuation levels or "volume steps", and the rotary switches used...

He uses the same nickel cores in all of his offerings, and the same copper wire*, too. What this means to you and me (and I love this!) is that we all get the same gorgeous sound regardless of which model AVC we buy. Awesome!


*unless you spring for silver
 

Pboser

Junior Member
A question for the experts here. I have in front of me a wall mounted remote speaker volume control. It was a two dollar thrift store purchase. The control consists of a 10 position switch, a pair of autoformers and stereo input/output terminals. Clearly this item lacks the number of steps of volume control and the audiophile approved components of the Dave Slagle devices. Could it still be used as a passive preamp?

John
In the deep recesses of my memory (obviously wasted on this stuff, since I can't remember anything relevant to current life!) I had an inkling that jeremy epstein (prefers lower case, I think) of Brooklyn NY tried one of those wall autoformers for a volume control. A little Googling and I found this: jeremy.htm
Since the autoformer is designed for speaker levels he used a transformer to step down the linestage to 8 ohms. I have no idea if that is necessary, or what else would make it work. I have in my stash a couple of these autoformer volume controls to try j's idea, but it's like many many of my projects - planned but not (yet) implemented. But I probably should just buy some Slagleformers instead!
Anyway, interesting discussion - hope this helps!
Pete
 
I actually tried one a long time ago. I had mixed results with it. I recall it worked very well with the output from a cd player. I also recall it did not work as well when the source was a Bottlehead Seduction (tube phono stage). I guess that this suggests that its performance will be source dependent. I am sure that I still have the passive pre that I mocked up somewhere in this mess. If it ever surfaces, I will try it again.
 
I recently drank the @Redboy TVC Koolaid and it led me to start a minor gear purge. I use one that he built (S&B) in my main setup (efficient) and love the resolution. I still have a few regular preamps in systems but as funds allow, I’ll likely have TVCs controlling them as well. @watt ‘s nice Slagle TVC pre build has me thinking of getting back into a little DIY. IMO, that’s the way to do it if on any sort of budget. If you try it and decide it’s not for you, it seems like you could recoup costs fairly easily (if you don’t count your time). We’re all a bunch of enablers.
 

Salectric

Senior Member
I should expand on my comment a little because I have experience with "inexpensive passive preamps", too.

I've experimented quite a bit with passive preamps over the years, and I am a big fan. The first one I built was a simple "pot-in-a-box" affair, and I was immediately struck by how revealing the thing was; there's a lot to be said for simplifying your signal path as much as possible! I learned that everything in that path can affect your sound, and that some things have a greater impact than others.

I built a bunch more using various attenuators in different configurations, including the cheapest Radio Shack Alps pot in a shunt-to-ground design in my $8.01 cigar box preamp. I've used potentiometers from Alps, Apha, Audio Note, Bourns, TKD, and more. I tried the cheap stepped resistor units from China and the good ones from DACT, Goldpoint, Khozmo.

This is an overly broad statement, but pretty much all of the above are better than the standard issue, cheap potentiometer unit found in 99% of the commercial audio gear built today...

But in my opinion, a transformer volume control (TVC) is better than all of the above.

Autoformer Volume Controls (AVCs, or Autoformers) are technically slightly different than TVCs, but most people lump them in the same category and call them all TVCs. That's fine by me. We could also call them Inductive Volume Controls but that hasn't really caught on...

I've used, built and/or listened to TVC units from Dave Slagle (Intact Audio), Stephens & Billington (S&B), Silk, and Prometheus Audio and they are all really really nice. My favorites thus far are the Slagle and S&B.

I don't pretend to fully understand why these things sound better, but they do. I think it has to do with reflected impedances and loading of the respective source units. Inductive volume controls present a "friendlier" load to our source components, especially at lower volumes, than a resistive element.

My current passive preamp is a DIY affair that I built with Dave Slagle's autoformers in John Chapman's (Bent Audio) packaging. Mine were silly expensive but the great thing is that you can get the very same sound from Dave's $200 autoformers as you do from EMIA's Elmaformer at many multiples the cost.

In my system, TVCs are non-negotiable. Give 'em a whirl -- I think you'll like them, too.
I absolutely, totally, 100% agree with Redboy. Just as he described, I have tried "Pot in a Box" passives off and on over the years, in my case going back to 1973 (!), and each time I have gone through the same process---being wowed at first by the detail and clarity of the passive but later realizing what I had given up in terms of dynamics, body and weight. And like Redboy I tried all sorts of different pots including some expensive ones.

But my feelings about "passives" changed once I tried Dave Slagle's AVC. The only thing the AVC has in common with a "pot in a box" is the lack of a power cord. The AVC has superb dynamics, weight and body, as well as excellent detail and clarity. It gives up nothing to a "pot in a box."

Now, on an absolute scale I won't say the Slagle AVC is the very best. Right now my active linestage (Emotive Audio Epifania) is slightly better in terms of treble detail and air, but the two are really close. So close in fact that I use the AVC almost exclusively. I just like the simplicity, the lack of a power cord, and the lack of tube wear. Most importantly though I like the fact the AVC has ZERO noise---no hiss or hum and no transformer buzzing. As my system has become more and more quiet in recent years, I have little tolerance for ANY noise including transformer buzzing or humming.
 

Redboy

Knobophobe
Now, on an absolute scale I won't say the Slagle AVC is the very best. Right now my active linestage (Emotive Audio Epifania) is slightly better in terms of treble detail and air, but the two are really close. So close in fact that I use the AVC almost exclusively. I just like the simplicity, the lack of a power cord, and the lack of tube wear. Most importantly though I like the fact the AVC has ZERO noise---no hiss or hum and no transformer buzzing. As my system has become more and more quiet in recent years, I have little tolerance for ANY noise including transformer buzzing or humming.
The AVC is just an attenuator. Imagine what you'd hear if you replaced the potentiometer (stepped resistor?) in your Epifania with an autoformer! :)

I briefly owned a Thomas Mayer design DHT linestage. It's signal path comprised an 801A triode and a Lundahl output transformer, into a Slagle autoformer… that's all! It sounded incredible, but eventually I subbed in my Slagleformer preamp for just those same reasons.
 

Salectric

Senior Member
Well, you just brought up something that has puzzled me for years. Why would Thomas Mayer put an active linestage in front of the AVC? Assuming you don't need lots of gain (and his linestages don't have a lot of gain anyway), why would that be better than just having the AVC alone? I am guessing there must be some advantage to driving the AVC with a tube gain stage. Of course, some sources may not have adequate drive capability and so a good active stage makes sense in that situation.

Fred Volz at Emotive once told me that the very best sounding linestage he ever made was an Epifania with a Slagle AVC on the output. The AVC replaced the usual stepped attenuator at the input of the Epifania and he used a Bent Audio relay board to allow remote control for the volume setting. That also puzzled me. Why would that be better than the AVC alone? In my case, I tried inserting the Epifania in front of the AVC but I preferred the AVC alone. I wouldn't read a whole lot into that though because my setup required an extra set of interconnect cables, plus I still had the Epifania volume control in the circuit.
 
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