WINNER TUBE?

Peavey VMP2 Dual-channe Tube Preamp

Published in SOS August 1999
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Reviews : Preamp

The fashionably vintage exterior of this US-made dual-channel preamp is matched by an all-valve interior. Hugh Robjohns gets a retro perspective.

The VMP2, from American company Peavey, is a 2U, rackmounting, dual-channel valve mic preamp that has clearly been styled to resemble the classic studio preamps of the '50s and '60s, with chunky silver toggle switches and 'bakelite' pointer knobs. Each channel boasts a simple bass and treble shelving EQ, phantom power, high-pass filter, input pad, and front-panel line (instrument) input. Balanced mic inputs and line outputs are standard, and vacuum tube amplification is used throughout.

Inputs to each channel are identical and comprise a quarter-inch jack socket, for an instrument or high-impedance mic, plus a balanced XLR input; a toggle switch introduces a 20dB pad into this input. The line input mixes with the microphone input, as there are neither break contacts on the jack socket nor an input selector. Unfortunately, it's also not possible to control the levels of the two inputs independently of each other.

PEAVEY VMP2 £919 pros ypical valve sound characteristics. Easy to use. Transformer-balanced inputs and outputs. Pleasing retro styling. cons No control over mixing of line and mic inputs. Only one sound character! Unprotected internal mains wiring. summary A retro-styled dual-channel valve preamp with rudimentary equalisation facilities but transformer-balanced mic inputs and line outputs, plus unbalanced line inputs on the front panel. The VMP2 exhibits the typical valve character in its sound, works well, and is easy to use.

As mentioned above, phantom power (48V) is provided, as are an EQ bypass switch and a high-pass filter. The last is controlled by a three-position switch offering 80Hz or 40Hz turnovers with a 12dB/octave second-order slope, plus an 'off' position. Three rotaries on each channel control overall gain (scaled 1-11!), high-frequency cut/boost and low-frequency cut/boost (both calibrated from -10 to +10). The equaliser is a simple active shelving type with a +/-10dB range turning over at 100Hz and 10kHz, and the gain control ranges from +26dB to +66dB on the microphone input, with 20dB less overall gain on the line input. All the rotaries, which are nicely weighted, feature retro pointer knobs, but there are no centre detents on the two EQ controls.

The VMP2's rear panel is very straightforward, hosting a pair of non-latching XLRs for the two transformer-balanced 600(omega) mic inputs, two male XLRs for the transformer-balanced main outputs, and a pair of quarter-inch jack sockets providing high-impedance unbalanced outputs. A captive mains lead completes the picture.

There are no solid-state devices in the signal path of the VMP2, all amplification being valve-based (see the 'Doing Things By Valves' box). The unit's internal construction is now of an acceptable standard, although initially I was sent a very well-gigged Peavey demo unit for review by mistake. On this first VMP2, I noticed that some of the internal audio signal wires rested on the valves, where they could get very hot and possibly suffer damage. Furthermore, none of the internal mains wiring connections were sleeved or insulated, although at least the metal outer casework was earthed via the mains lead, which was a comfort! A proper production VMP2 was sent to replace the first, and I noticed subsequently that the internal audio wiring was now cable-tied away from the valves. However, the mains wiring around the power supply was still not insulated, and this remains a concern.

The power supply is a substantial linear affair employing a 'low hum-field' transformer (which buzzed quietly at harmonics of 50Hz) enclosed in its own screened section. The main audio supply is regulated with a conventional solid-state device, and the entire power supply circuit -- bridge diodes, smoothing

Doing Things By Valves     Amplification inside the VMP2 is performed by six valve triode stages (three 12AX7 (ECC83) double triode valves per side), plus a 12AT7 (ECC81) double triode driving the balanced output to a healthy +22dBu into loads of greater than 2k(omega). The balanced mic input employs a 'triple-shielded' transformer to impedance-match and unbalance the signal, after which it mixes with the line input (if connected). Three interlinked stages of triode amplification (incorporating the Gain control) then boost the signal level before it passes through the first half of the passive high-pass filter and into the shelf equaliser. This has a further two triode amplifier stages, the output of which feeds the second passive stage of high-pass filtering. A triode buffer drives the push-pull output stage constructed around the 12AT7 valve, which feeds the unbalanced output directly and the balanced output through a substantial transformer.

capacitors, DC fuses, regulator and so forth -- is mounted on a vertical PCB inside the screened area. All the large components on the circuit cards are glued down.

Most of the base of the remaining portion of the case is covered by the main audio board. This carries the rear-panel input and output connectors, eight valves, the input transformers, and much of the associated circuitry. The various gain stages are linked to the inputs and front-panel controls via seven screened cables running across the PCB. Mounted on the rear panel are the output transformers, which are enclosed with metal shielding to prevent their magnetic fields interfering with the valves. Front-panel switches are secured to the metalwork and support, vertically, a shallow PCB linked to a second shallow board behind the rotary controls. The upper of these two cards appears to carry most of the EQ components, together with several small switching relays.

The VMP2's specifications are quite impressive for this kind of product, with a quoted frequency response of 10Hz-40kHz at the -3dB points (40Hz-20kHz at -1dB). Unweighted hum and noise is better than -80dB with a modest 26dB of gain, equivalent input noise is -123dBu with a 150(omega) source, and harmonic distortion is less than 0.25 per cent at maximum gain. The machine consumes a warming 200 Watts of power, but weighs a reasonable 18lbs (8kg) and is only around 10 inches (250mm) deep.

The VMP2's controls feel solid and reliable, and they behave exactly as expected. The gain control is 'linear' across its range, without any flat spots or rapid gain changes, and the 20dB input pad proves useful to accommodate dynamic mics in loud places! However, the high shelf control is situated to the left of the low shelf control on the front panel, which can be confusing, and the fact that it's set to turn over at 10kHz reduces its usefulness -- I would have preferred something a little lower, to give a touch more bite in the presence region without over-emphasising hiss. The bass control is fine, and the LF filters also show their worth on microphones with an extended bass response.

Sound-wise, the VMP2 has a warm, full character, although it did seem to make everything sound as though it was being recorded in the '70s! (Although of course this is a quality that's highly desirable to some.) It can also be slightly overdriven, with very usable results in the right application. It's not as quiet as a decent modern solid-state preamp, obviously, but the signal-to-noise ratio is perfectly adequate with a strong microphone signal, or for processing a line source. A unit like this is used for its sonic character anyway, rather than its specifications, and this one has all the qualities any 'tube freak' would enjoy.

For me, the VMP2 would have been improved by either a second gain control for the front-panel input, or a break-jack configured to isolate the rear-panel mic input -- having the two signals mix without any form of direct control seems more a cheap shortcut than a feature! The machine has good line-driving abilities and would suit onstage use as a preamp, using the unbalanced output to feed the stage power amp and the balanced output to provide a high-level DI to the front-of-house console.

Essentially, this is a basic but very nice-sounding preamp that works, and works well. It's perhaps a bit on the expensive side, given the existence on the market of worthy competitors from companies such as TL Audio and Joemeek, but it has an individual sound character and performs creditably on vocals and acoustic instruments. It does benefit, however, from a high-output condenser mic to maximise the signal-to-noise ratio, so the inclusion of phantom power is an essential. The VMP2 is also particularly well suited to recording and processing instruments such as guitars (via pickups) or keyboards -- indeed, anything which would benefit from the warmth and character of a valve preamp.

information

£919 including VAT. Peavey Electronics +44 (0)1536 461234. +44 (0)1536 747222. www.peavey.com