Herron Audio VTSP-2 Line Stage

Herron Audio VTSP-2 Line Stage
Great Things Do Come In Small Packages


November 2006


The first time I met Keith Herron and listened to his handiwork was at a Chicago Audio Society (CAS) meeting a number of years ago. His system, while rather unassuming looking at the time, had a sound that was simply unforgettable. In subsequent visits to the CAS he has consistently put on some of the best demonstrations of audio reproduction I’ve heard.

The 2005 CES afforded me the opportunity to hear the latest Herron electronics along with a prototype three–way speaker system. The sound was simply awesome. And though I heard many systems that cost $100,000 or more, none of them touched me musically the way the Herron system did. This past May, the CAS membership was treated to yet another great Herron Audio system demonstration. The system was comprised of the latest Herron electronics and a more refined version of the speaker system that I heard at CES. The sound was even better than what I had heard before.

As you’ve probably guessed by now, I think that the Herron system is really something special. Well it is! You also might be wondering how the individual components stand on their own. This review will attempt to address that, in part. I say “in part” because the focus will be on one Herron Audio component, the VTSP-2 vacuum tube line stage.

The VTSP-2 is the product of innovative engineering and many hours of critical listening. It is a single chassis, tube based, remote controllable, line stage that has a beautifully designed faceplate with an oval shaped opening in the center for the function display. The unit that I reviewed had the silver finish but a black finish is also available. The chassis is black and made of heavy gauge sheet aluminum. There are chrome finished push-button switches and control knobs on either side of the display. To the left of the display is the balance control and five input selector switches. These switches select the video, tuner, cd, aux, and phono inputs. A blue LED above each switch lights when the input is selected. To the right is the volume control and five function switches. The functions are mute, mono, invert, tape, and display. For the sake of clarification, the tape function is the same as a tape monitor, and the display switch provides a dimming feature for the display and LEDs. There is also a LED above each function switch. The mute LED is red, mono is amber, invert and tape are yellow, and display is blue. The display readout is green.

Taking a look at the back panel there are high quality RCA jacks for inputs and outputs. There are two main outs and a tape out. There is also a grounding post. The AC input is via an IEC connector. There is a power switch as well as an AC phase reversal switch. The AC phase reversal switch is a really nice touch. The reversal of the AC input can result in a quite noticeable improvement in sound quality.

Internally there are three double sided printed circuit boards (PCB). Great care has been taken in the layout of each pcb regarding component placement, grounding, and signal path. The main PCB covers almost the entire bottom area of the chassis. The 6922 tube based audio circuitry, digital volume control integrated circuits (ICs), and system power supplies reside on this PCB. The power supplies occupy slightly over half of the area. The second PCB is located behind the faceplate. The micro-controller circuitry, relay logic, display readouts, input and function switches and associated LEDs, volume control encoder, reside on this PCB. The third PCB runs a little more than half way along the back panel. The RCA jacks and input switching relays are connected to this PCB.

There are three 6922 tubes per channel. The 6922 is a very popular tube for use in line-stage applications and is used by a number of high-end audio manufacturers. The tube has good linearity, low noise, and current capability which make it attractive to designers. What sets apart the sonic performance of various line stages that use the 6922 is the circuit topology, components, and layout the designer chooses. Keith Herron has spent countless hours in the development of circuit topologies and selection of components for the VTSP-2. His engineering expertise, love of music, and attention to detail is what makes the VTSP-2 such an exceptional product. 

All of the power supplies in the VTSP-2 are fully regulated. Regulated power supplies provide a stable output voltage even though the AC power line voltage may fluctuate. The filament and high voltage power supplies are brought up slowly together at power on to prevent cathode stripping. This feature along with conservative biasing serves to significantly extend tube life. Even though the toroid power transformer is located within the chassis there is absolutely no audible hum. The unit is dead quiet. As a matter of fact, I can’t even hear tube noise with my ear to the speaker and the volume control wide open. The VTSP rivals the best solid state line stages when it comes to low noise, low distortion, and inaudible hum. 

The digitally controlled volume control is really innovative. This is the most sonically transparent electronic volume control I have ever heard, or not heard. I am an old school purist. Give me high quality pots or attenuators made with high quality resistors and switches. I have not been impressed with the performance of digitally controlled volume control ICs. Keith’s implementation, however, has made me a believer.

The input impedance is 100k Ohms which is determined by the volume control ICs. The output impedance is 100 ohms which makes it suitable to use with amplifiers that have input impedances of 10k Ohms and higher. Input impedances of 100k Ohms and higher seem to be ideal for tube line stages. I would recommend using high quality low capacitance interconnects, especially for long runs between the line stage and power amplifier(s). If you don’t have a favorite interconnect brand, I would recommend trying Herron Audio interconnects. They are excellent and sanely priced. 

When the VTSP-2 is turned on a LED test is run. All the LEDs on the faceplate light momentarily. The mute LED will remain lit. The display will show “SP2” followed by “r2” which indicates the model and firmware revision respectively. The display will then show a 60 second count down timer. When then counter reaches zero the mute relay and associated LED will be disengaged. The display will count up to ten. This indicates that the volume control is at level 10. The volume level has a range from 0 to 100. The volume level is adjusted by rotating the volume knob which is connected to a mechanical digital encoder instead of the typical pot. It has the feel of a quality pot with no end stops. The balance control is a high quality pot that provides the full range from left channel only to right channel only. The remote control is a nifty little unit that fits in the palm of your hand. Input selection and all of the line stage functions, with the exception of the balance control, can be operated from the remote control.

The VTSP-2 is a brilliantly executed design that offers flexibility, ease of use, and reliability. The unit operated flawlessly during the review period. 

“It’s easy to play any musical instrument: all you have to do is touch the right key at the right time and the instrument will play itself.” — J. S. Bach 

“It’s easy to design an amplifier to accurately reproduce music: all you have to do is select the right circuit topology, right components, and right layout so that there is no time related distortion of the audio signal.” — H. C. Osborne

The making of music or the reproduction of it is no easy task as the above quotes imply. Timing is critical to the making of music, and preserving timing is critical in the reproduction of it. This is where the VTSP-2 shines. It simply gets the timing right. This is a line stage you listen “through,” not to. Musical information is reproduced without any apparent obstruction. Your mind can effortlessly focus on the music. Listening to well recorded material is truly a treat. The VTSP-2 does not aid and abet poorly recorded music. Reproducing with accuracy is what this line stage is about. The distortion is so low that there is no artificial enhancement of tones due to even order harmonic distortion and no harshness due to odd order harmonic distortion. The low distortion is the result of careful design without the use of global feedback. Please don’t get the impression that just because the VTSP-2 is an accurate reproducer it is sterile, cold and lifeless. Nothing could be further from the truth. If there is life and warmth in the recording you will certainly hear it. There is no sense of dynamic range compression. Whether you listen to large scale orchestral or chamber type music the macro and micro dynamics are naturally reproduced. The wide flat frequency response of the VTSP-2 ensures excellent tonality and transient response. The overall tonal balance is ever so slightly to the warm side of neutral. The soundstage width and depth seem to be more a function of the recording and the ancillary hardware. Individual instruments and voices within the soundstage are clearly delineated if the recording is good.

The VTSP-2 comes into its own after about 100 hours of use. It doesn’t sound bad after a couple of hours of warm up just coming out the box. It just goes totally to another level once it’s fully broken in. Patience is a virtue. It is well worth the wait. 

The inclusion of the VTSP-2 in my system for a little over six months has afforded me the opportunity to listen to a lot of music. My taste in music runs the gamut. In my collection you’ll find Classical, Jazz, R&B, Folk, Blues, Gospel, and stuff in between. I’ll share a small sampling of the recordings were used for evaluation during the review.

First up is Muddy Waters’ Folk Singer [MFSL 1-201]. This LP was recorded in the early sixties by Chess Records and reissued by Mobile Fidelity Sound Lab. It features Buddy Guy on guitar and Willie Dixon on acoustic bass. The sound is open. Muddy’s voice is rich and full. You can hear a little tape saturation distortion on vocal peaks. The string articulation and tonal quality of the acoustic guitars are excellent.

Dave Brubeck’s Time Out classic reissued by Classic Records is an all time favorite. Listening to the cut “Take Five” through the VTSP-2 is really a sonic treat. Joe Morello’s drum work really shines. The cymbals ring out and decay naturally. The drum strokes have impact. You can clearly hear the reverberation in the studio.

Wood by bassist Brian Bromberg is one of my favorite CDs. This is an excellent recording in terms of musical content and recording quality. You can hear the finger work clearly as Bromberg moves up and down the finger board. The tone of the acoustic bass is rich and deep.

Engineer’s Choice II [Delos DE 3512]: This is a compilation of some of John Eargle favorite classical recordings. Cut three is a recording of Carol Rosenberger playing a Bosendorfer Imperial Grand. You can really sense the power and majesty of this massive piano.

Mezzo soprano and composer Lori Bryan’s CD Savior Lead Me [AT Music WP605] is a beautiful recording of Negro spirituals and original compositions. Lori’s voice is magnificent and the arrangements are first class. 

American Works for Organ and Orchestra [Cedille Records CDR 90000 063]. This recording was made at Orchestra Hall in Chicago. It features David Schrader playing the Orchestra Hall Casavant organ along with the Grant Park Orchestra conducted by Carlos Kalmar. This is another great recording. There is plenty of low frequency information and dynamic range. It will certainly test how well your system can reproduce deep musical bass.

Manuel De Falla “The Three Cornered Hat” and Bela Bartok “Dance Suite” [Everest Record Group EVC 9000]: This is a superbly mastered CD made from the original 35mm masters. The sound is open and very transparent. This recording has a “you are there”type of a presence. The attack of the percussive instruments really gets your attention.

The Herron VTSP-2 line stage is a highly innovative product offering first class sound, flexibility, and reliability. If you are looking for a line stage in the $5000.00 to $15000.00 range the VTSP-2 should be on your short list. It is truly a best buy among serious high-end line stages. Highly recommended!!! 

H. Courtenay Osbourne


Frequency Response: 1 Hz to beyond 100 kHz, 20 Hz to 20 kHz ±0.1 dB
Output Impedance: 100 ohms nominal at 1 kHz
Input Impedance: 100,000 Ohms
Gain: 14 db
Volume Control: 100-position electronic stepped attenuator, maximum differential ±0.1 dB channel to channel
Distortion: Absolute Polarity: Switchable
Dimensions: 18″ wide x 3.5″ high x 10.5″ deep
Warranty: 3 years, parts and labor
Price: $4995.00

©2004 Herron Audio
Division of Herron Engineering, Inc.
12685 Dorsett Road
# 138
Maryland Heights, MO 63043 (St. Louis area)

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