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Tech 21 Sansamp PSA1

Ever since my first encounter with the prototype programmable Sansamp at a trade show a couple of years back, I've wanted to try one, and now that I've finally got round to it, I can confirm that it was worth the wait. For those not yet familiar with Tech 21's Sansamp units, the underlying principle is that a tube amp circuit is recreated using solid state devices, but retaining the same circuit topography, including the push‑pull output stage. A lot of attention has gone into recreating the coloration of real valves and loudspeaker cabinets, and because of the relentless enthusiasm of designer Andrew Barta, there can be few people who'd recognise Sansamp products as solid‑state in a blind listening test.

Originally, Sansamp products were built only as pedal‑type units, but then the Rack Sansamp was added to the range for the benefit of those who wanted more control and a full rackmount format. The PSA1 takes this concept one step further, adding programmability and MIDI patch changing, thereby allowing the player to switch between a large number of virtual amp channels during performance. Unlike some attempts at programmable guitar amps, the Tech 21 people have realised that guitar players want separate knobs for each function — they don't like buttons and menus. So, knobs is what you get.


The Sansamp PSA1 is a neatly‑styled, single‑unit rack processor, controlled by means of eight knobs, a pair of Up/Down buttons, and a recessed Save switch (to prevent accidental overwriting of programs). There are 49 preset factory programs, plus a further 49 user memories — patch 00 and 50 are bypass settings. A two‑digit display is used to show the current patch number selected, but this also provides additional information when editing or setting the MIDI channel. If there's a limitation here, it is that patches are only numbered, not named, and while this makes for very simple operation, it also means you have to remember which patch sounds like what.

Because the knob positions are digitally encoded, they have 256 discrete steps, rather than being continuously variable, but in all other respects, they behave much like conventional preamplifier controls. There is one MIDI In socket and a single MIDI Out socket, the latter of which also doubles as a Thru. Any of the programs may be called up directly over MIDI using program change information, as well as by using the front panel buttons. The MIDI Out facility is required when data dumps of the Sansamp PSA1's memory are being transmitted to a MIDI data storage device, or when MIDI patch numbers are being sent. An optional footsw itch may also be used to step through the presets for live applications; the number of presets through which you cycle is user‑determinable.

Though the unit is a single‑channel mono processor, there is an alternative, dual‑level input jack on the rear panel that will accept line level signals, as well as a stereo effects loop which allows any mono‑in, stereo‑out effects unit to be patched in. For this reason, the Sansamp PSA1's outputs are stereo rather than mono, and in addition to standard jack outputs, there are also balanced XLRs for use in professional applications. Both sets of outputs are switchable between ‑10dBV and 0dBV operating levels. A Mix 50/50 switch is fitted to the rear panel, which automatically splits the signal, half into the effects unit and half direct, so that when using an external effects device, you don't have to send your entire signal through the effect unit's A/D and D/A convertors.

The Controls

The Sansamp PSA1 is fed from a single jack input. After this, the input signal passes through the initial Preamp Gain control, plus three EQ controls charmingly entitled Buzz, Punch and Crunch. These are pre‑overdrive EQ settings, and are directly followed by the Drive control, which determines how hard the output stage is being driven. High settings here give the classic smooth valve distortion sound, independent of the front‑end sensitivity. At the end of the signal chain, High and Low post‑overdrive EQ and output Level controls allow overall tone and level to be set independently of the distortion. Because both pre‑ and post‑overdrive EQ is available, the tonal range available is incredibly wide, and encompasses just about any guitar sound you can think of.

To edit a sound, you simply turn the appropriate knob on the front panel, just as you would with a regular amp. If the physical position of a knob is different from the value used in a preset, the display shows a dot on either the left‑ or right‑hand side, depending on whether the knob position is too high or too low. These dots blink at a rate which increases as the knob position approaches the internal parameter value, and when the two match, both dots are extinguished. The edited patch may then be memorised by pressing Store, stepping through to the desired program location, and then pressing Store again.

Star Quality

Like previous Sansamp units, the Sansamp PSA1 has a built‑in speaker/amp simulator, which means it can be plugged directly into a mixing console for recording, although you do need to add your own effects, as there are none built in. For live use, the manual recommends that the PSA1 be plugged into a standard guitar amp, and that the EQ controls be used to compensate for any tonal change brought about by having both a speaker simulator and a real speaker working at the same time. In practice, this seems to work just fine.

Used DI'd in the studio, the PSA1 has the characteristic Sansamp sound, which is both valve‑like and ballsy, but because it has both pre and post‑overdrive EQ, the range of sounds you can coax from it is much wider than from the 'box' versions. The PSA1 isn't just good at dirty sounds, it's also capable of emulating most clean sounds, with the possible exception of the characteristically 'glassy' Rockman sound. In most cases, a touch of reverb and possibly chorus is all that's needed to give you a fully‑produced guitar sound. Unfortunately, when I used the unit with my PRS guitar (before reading the manual, of course!) I found that preset 00 gave the nicest clean sound of all, but when I tried to edit it, I realised it was the bypass position!

What I particularly like about this unit is that the overdrive sounds are very responsive to playing style — the guitar actually seems to 'feel' different as you switch from one patch to another, just as a real amp does. There's also plenty of overdrive on tap, which gets you into the world of screaming harmonics and hammering without having to patch in a fuzz box.

Criticisms are few, though I do wonder why the Buzz, Punch and Crunch pre‑overdrive EQ controls couldn't have been labelled low, mid and high. There's also a hint of a low‑level fizzy buzz as the note expires when a bright, biting overdrive setting is used; to be fair, this happens on most other guitar DI preamps too, but I wouldn't have thought it beyond the bounds of technology to get rid of it, even if it is an exact emulation of something that some valve amps do!

On the whole, the PSA1 is good news. It DI's beautifully, it's as quiet as you can reasonably expect for anything with the capacity for so much gain, and the operating system makes it as easy to use as a traditional guitar amp. When you 'dig in', the harmonics squeal and sing, just as they do with a 'real' amp, and though you lose the contribution of acoustic feedback when DI'ing (unless you monitor very loudly!), this is about as close to the 'real amp' sound as it gets. The rock sounds also have the ability to sound loud, even at low listening levels, something that not all other units succeed in doing.


  • Superb range of convincing guitar sounds.
  • Very easy to use.


  • Patches cannot be named, only numbered.


This may not be the cheapest guitar preamp on the market, but it is certainly one of the most effective and most versatile.