VTPH-2A Vacuum Tube Phono Preamplifier
silver face plate - click on image for larger view
titaniun gray and black anodized face plates also available
Silver Gray Black
back panel - click on image for larger view
Totally unique circuitry configuration and layout that extracts high end performance from the tubes and extends tube life.
Immediately You Know!
"Pick up an acoustic instrument and the better it is, the greater the sense of life, of energy just waiting to burst forth. This is exactly the quality that the Herron phono-stage captures. All that texture it brings to instruments is built on micro-dynamic definition and the ability to capture the harmonic envelope, the pattern of energy that extends from instruments."
"The colour and ability to reveal each step in the growing intensity of a crescendo mark out the beautiful balance that the VTPH-2 strikes between the instrumental detail that gives music its beauty and the body and presence that gives it its drama and so much of its passion."
"The Herron VTPH-2 gives listeners all the benefits of a tube unit with few of the failings and a text-book technical performance to boot. It offers a level of vacuum-tube engineering (carefully combined with solid-state circuitry) that's rare at any price, unheard of at this one."
- Roy Gregory hifi+ issue 58
The Herron VTPH-2A Phono Preamplifier was created to address the retrieval of musical information from vinyl LPs without any compromise. The original design was only intended for use by a few dedicated music lovers in their cutting edge audio systems. The design was so good, and demand so high, that the unit was refined and engineered to meet the requirements for a more durable unit manufactured in larger quantities. In the process, important refinements were developed and discoveries were made about tolerances and the threshold of human hearing limits.
external MC load resistor RCA plugs
Separate moving coil and moving magnet inputs
The Moving Coil "MC" Inputs:
The moving coil inputs have an additional 22 dB of gain which is provided by a proprietary FET very low noise linear gain stage connected directly to the MC inputs. The moving coil FET gain section is connected in front of the tube section when the unit is in the MC mode. This moving coil FET gain section has been designed specifically to avoid the sonic artifacts found in many solid state designs.
Moving coil loading RCA resistor plugs can be inserted into the back of the VTPH-2A at the "MC Load" connectors to properly load specific moving coil cartridges. Check with your cartridge manufacturer for recommended loading.
The Moving Magnet "MM" Inputs:
The moving magnet inputs send the cartridge signal directly to the tube section and bypasses the MC FET gain stage. The moving magnet inputs provide all tube amplification of the signal from the cartridge. The moving magnet inputs have an internal 47k Ohm loading resistor for each channel and 100pF "Miller Effect" loading capacitance which is provided by the grid of the first 12AX7 tube.
The moving coil inputs can be loaded to a particular cartridge specification by externally connecting the appropriate resistors using the "MC LOAD" RCA connectors on the back of the unit, or they can be internally soldered at the MC INPUTS circuit board (this should only be done by a competent technician).
Why loading plugs instead of dip switches?
The moving coil inputs have no load resistors installed unless specified by the customer when the unit is ordered from Herron Audio. We recommend trying the VTPH-2 in the no-load configuration as the unit is supplied for most moving coil cartridges. 47,000 (47k) ohm RCA load plugs are supplied with the unit for optional use. Additional user specified loading plugs can also be purchased with the unit.
The moving magnet inputs are factory loaded at 47,000 (47k) ohms, 100pF (standard loading for moving magnet cartridges).
Herron VTPH-2A Vacuum Tube Phono Preamplifier Features
- Switchable moving coil and moving magnet operating modes with separate input connectors for each
- Additional RCA connectors for external moving coil loading
- Cartridge biased moving coil input stage allows for infinite load resistance (operation with MC cartridge totally unloaded)
- Very low noise - both versions work nicely under 0.1mv in the MC mode
- Passive RIAA equalization for accurate phase and amplitude response with no inductors for maximum emf noise immunity
- Reversing power line (AC) polarity switch for minimizing line-to-chassis reactive currents and noise pickup
- Low plate operating currents and controlled warm-up for cool operation and extended tube life
- Class A operation
- No mechanical switches in the signal path
- Zero feedback - no feedback loops in the audio circuitry
- Gold plated RCA and ground connectors
- Audio path capacitors are high quality very low dielectric absorption film type
- Hand-picked components for accurate response
- Automatic muting at startup, shutdown, and mode selection
- Four levels of high voltage regulation
- Regulated soft-start DC filament and high voltage supply
- Regulated tube bias supply
- Toroidal power transformer
- Front panel indicators for power, voltage, and output (mute release)
|Tube complement||(2 x 12AX7, 3 x 12AT7) - most popular, or
(4 x 12AX7, 1 x 12AT7)
|Gain MC Mode||(2 X 12AX7, 3 X 12AT7) 64 dB
(4 X 12AX7, 1 X 12AT7) 69 dB
|Gain MM Mode||(2 X 12AX7, 3 X 12AT7) 43 dB
(4 X 12AX7, 1 X 12AT7) 48 dB
|Frequency response||RIAA 20 Hz to 20 kHz ±0.1 dB at 10k Ohm output load impedance and higher|
|Distortion||Less than 0.03% at 2.45 volts output at 1kHz at 20k Ohm and higher output load impedance (tube selection dependent)
Note: Lowest distortion and best performace occurs with output loading above 20k Ohms - this gives the most dynamic sound
|Signal-to-Noise Ratio||88 dB, A weighted|
|Output impedance||(2 X 12AX7, 3 X 12AT7) 400 ohms
(4 X 12AX7, 1 X 12AT7) 500 ohms
|Input impedance||Infinite with no load resistors connected
Note: load resistors can be connected externally via RCA connectors or soldered internally
|Absolute polarity||Non-inverting (all modes)|
|Power Requirements||Standard IEC connector - most international voltages available|
|Overall dimensions||17.6" wide x 4" high (including rubber feet) x 10.25" deep|
|Warranty||3 years, parts and labor; tubes: 90 days|
|U.S. Retail Price||$3,650 U.S.D.|
NOTE: The VTPH-2A is an improved version of the VTPH-1 single input version which was reviewed by Stereophile in March of 2000
Stereophile: March 2000, Vol.23 NO.3 Herron Audio VTPH-1 Phono Stage
"It's competitive with anything I have rated 'Class A.'"
- Michael Fremer
"It was a pleasure to measure such a well-engineered phono stage."
- John Atkinson read the review
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Herron Audio, div. of Herron Engineering, Inc.
12685 Dorsett Road #138, Maryland Heights, MO 63043 U.S.A.