Promitheus Transformer Volume Control (TVC): The Epitome of Transparency

Promitheus Transformer Volume Control (TVC): The Epitome of Transparency

March 7, in Hi-Fi Systems Reviews

Specifications:

  • REV3 single ended transformers
  • Improved chassis rigidity by using a top and bottom stainless steel plates
  • 4 inputs of RCA and 2 outputs RCA
  • Single Stereo 23 pole switch for volume selection
  • Pure 4N silver wiring used for internal wiring

Simplicity. That’s what I wanted. With only one source (CD player) and one amplifier on my two-channel system, I basically needed a mechanism to volume control and serve as gatekeeper for my source and amp. That’s when I began a search for a non-traditional preamplifier. My search ended when I read a very lengthy thread on the AudioCircle forum about the Promitheus Transformer Volume Control (TVC).

How a TVC Works

A typical volume control is a cheap variable resistor. A resistor’s job is to take the energy of an electrical signal and convert some of that energy to heat, thus making a smaller signal.

A TVC, on the other hand, uses a transformer instead of a resistor to decrease voltage. A transformer takes a high-voltage, low-current signal and converts it into a low-voltage, highcurrent signal of essentially the same energy. This creates a decrease in voltage at lower volumes without sacrificing any of the signal’s energy. A TVC is designed to match the input impedance of a source (i.e., CD player) with the output impedance of the amplifier. By matching voltage and current without adding noise, grunge, etc., the signal remains intact. This maximizes voltage transfer and presents a much easier load to your amp.

From the Promitheus website:

“The TVC is essentially an electronic gearbox that operates without wasting significant energy. Potentiometers and stepped attenuators adjust the signal level by literally turning the excess signal into heat. On the other hand, when A TVC is adjusted for low volume level it actually makes things easier for the source, much like a low gear makes things easy for your car engine.”

What It Is

The Promitheus TVC is a passive preamplifier. There are no capacitors, resistors, op amps, tubes, etc. in the signal path to color the sound. Nada. Zip. It doesn’t even have a power supply, so you don’t need to plug it in. Plus, it produces the blackest background possible. The only thing you’ll hear is pure music, baby!

The base model sells for $380 shipped from Malaysia. Five reference models are available. Reference models include improved transformers, pure silver RCA jacks, military spec grayhill switches for input selection, stainless steel base, and waxed finish. Ebony knobs are optional. Reference models start at $425 shipped. There’s also an aesthetically unappealing stainless steel version for $515 shipped. Be prepared to wait several weeks for the TVC to arrive once you’ve placed your order.

I didn’t expect the build quality of this unit to be what it is. The Promitheus TVC is about the size of a cigar box. The reference model comes with a stainless steel top and bottom plate and heavy for its size. The remaining chassis is made of a wood indigenous to Malaysia. There are no feet; the manufacturer provides small wooden footers, and encourages experimenting with various types of footers. Be forewarned the reddish color wood won’t match any of your components. That’s why I painted mine black. Other color options would be nice. In terms of overall aesthetics, it’s a love/hate kind of thing. Who cares, anyway? Let’s move on to more important considerations…

Promitheus TVC inside

Promitheus TVC review

Listening Promitheus TVC

I was so excited when the DHL courier arrived with my package. Of course, I immediately grabbed the nearest knife, opened the box, and installed the TVC (Reference 2 model). Right out of the box it sounded dull. After only about 3 hours, the TVC opened up tremendously. I played my worst recorded CD and it sounded great. That’s when I knew I hit the jackpot.

I thought my system was transparent before, but now the bar has been raised. The TVC brings out all of the subtle nuances of the music. The Promitheus has more depth and width than the Audio Experience Symphonies Plus it replaced. I like how it presents the music at very low volumes. Even at whisper quiet levels, the TVC has the bass and transient attack of a good active preamp without additional noise.

The best attribute of the TVC is its great tonality. Instruments sound natural and the sound is very balanced. Vocals are out front where they should be, but the music, in general, is not forward.

Many preamplifiers have a tendency to add their own “signature” to a sound when, in fact, a good preamp should have nearly no impact on the sound at all. In addition, many amps and preamps are known to emphasize certain aspects of the sound such as bass or cymbals; what should be in the background is brought to the foreground. While this may sound impressive, at first, a truly balanced sound places all of the instruments and vocals in the proper perspective.

The TVC also has virtually all of the dynamics and articulation of any active preamplifier. Equally impressive is the decay of instruments. In many solid state systems, decay is usually truncated, but the TVC creates a very natural decay that would make many tube amps envious.

Something very interesting occurred during an early listening session with the TVC – the depth of the vocalist sounded like she was about four feet behind the speakers which is beyond the boundaries of my room. In other words, the music made the room bigger. Unfortunately, I don’t recall which CD I was listening to at the time. I was too engrossed in the music to take notes. This TVC will force you to stop rolling preamps because there’s simply no reason to do so. The more I listened, the more I can’t get over how good this thing is! I’m discovering there is music on my reference CDs that I’ve never heard. In fact, the TVC improves the sound of nearly all of my CDs!!

Previously, I constantly found myself getting up from my sweet seat and increasing or decreasing the volume. With the TVC, I can sit back and just listen, regardless of the volume. This TVC is super quiet – no hum whatsoever. There’s absolute blackness, at any volume setting. Turn on the amp and CD player with no music, put your ear right on the speaker grille, and the only thing you’ll hear is silence.

The Promitheus sounds like tube gear – lush midrange with no harshness whatsoever. In fact, I unhooked my tube CD player and installed my DVD player (Oppo 970) and I was astounded at the result. The Oppo/TVC/amp combo still sounded as lush as a full tube gear system.

My only complaint is that on my system, at the highest volume level, it doesn’t sound loud enough. Luckily, I never play music loudly, but for those who play music at ear bleeding levels, this issue could be a bit disconcerting, particularly if your amplifier’s sensitivity is greater than 1 mV. The sound level will depend on the voltage of your source, and to a lesser extent, the level at which the CDs in your collection are mastered. This shouldn’t be a problem at all if you use balanced connectors.

Promitheus TVC backside

Conclusions about Promitheus TVC

You know you’ve got a winner when everything in the music sounds effortless and natural. Your ears don’t tell you how good your system sounds; ultimately, music must resonate with your soul. And the day the TVC arrived, my soul confirmed the feelings that only the sound of truth can convey.

I can find no faults with the sound quality of the TVC. The reason is simple a perfect preamp imparts no sound signature of its own; it allows the source signal to reach the amp unimpeded by sound artifacts. The TVC achieves this feat, and what comes out on the other end is music as it was intended to be heard. What more can be said?

The Promitheus TVC is the best audio purchase I’ve ever made. For this reason, I see no reason to “upgrade,” unless I need balanced connectors, more inputs, etc. If so, I’ll buy another Promitheus. Besides, what is there to upgrade to? Several TVC owners have favorably compared the Promitheus to preamplifiers and other TVC’s costing several thousand dollars.

external link: Promitheus website

from affordableaudio, by Brad Mitchell

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1 comment

  1. Richard Waxberg January 15, at 2:31 am

    I love your review of the Promitheus Passive Attenuator. I am looking for a Passive and there seems to be several circuit approaches besides the usual step ladder, or resistance circuit.

    May I share an insight with you. It is incredibly difficult to read the thin white type on black background that your review text is set with. Even on my high resolution Mac computer and even with my enlarging the text considerably. Please redesign your web-review pages in the future with the ease of reading as a primary emphasis. I am a graphic designer with an extensive background in design so my advice has a great deal of value to it.

    Again, I love your review of the Promitheus Passive. Keep up the great work.

    With Warmest Regards ~ Richard Waxberg / Ojai, California

    reply

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