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SansAmp picture © T. Relph-Knight 2003


Tech21 SansAmp Acoustic DI

Now replaced by the SansAmp Para Drive DI

Price - £ 199.99

Available from -

The Soho Soundhouse



Pros - Excellent sound with lots of control. Very feature rich.

Cons - High cost and complexity. Manual isn't clear on certain points.

Verdict - One of the best DI's for the acoustic guitar on the market. Lots of features and a great sound.


Review update

The SansAmp Acoustic DI has been replaced by the SansAmp Para Driver DI. Tech 21 say that this is based on their RPM rackmount unit, which in turn was developed from the SansAmp Acoustic DI. There are two obvious additions or changes to the design, a footswitch, that toggles between the active EQ and transparent active DI modes and a drive control that adjusts the overall amount of gain and overdrive (similar to when the output stage of a valve amp is being pushed). Unfortunately the addition of the footswitch has meant the loss of the alternate 'input to XLR' and as a result the effects loop configuration, using the 'output' jack as an output to the effects, using the 'input to XLR' as the loop input and taking the final signal out from the XLR, is no longer possible. The Blend control is now a smaller control next to the Mid shift control, allowing the other controls to shift along one step to make room for the Drive control on the end. The slide switch that performed the footswitch function on the Acoustic DI, now on the Para Driver DI switches a -20dB pad in and out for the XLR output.

The SansAmp Acoustic DI reviewed

The controls

In 'active' mode the SansAmp Acoustic DI has a three section equaliser with treble, mid and bass controls all providing both boost and cut from the centre flat position. The mid control is augmented by a mid shift control to sweep the mid boost or cut between 170Hz and 3.5KHz. In cut mode this is useful for taming acoustic feedback. The treble and bass control range is plus or minus 12dB, while the mid peaks or notches by plus or minus 16dB. With such an effective EQ it would be useful to have some panel markings to indicate the approximate flat position, although the 'active' switch can be used to bypass the EQ for comparison. Next to the EQ controls is a 'Blend' control that blends in an amount of 'valve warmth'. Turn this fully anticlockwise and the valve emulation is turned off. The final control is the level control that controls the amount of signal sent to the outputs. With the level at maximum the SansAmp does provide a certain amount of gain. Setting level to the middle of its rotation appears to be the unity gain position.

The switches

A pad switch provides for use with high sensitivity mixer microphone channels by switching in a -20dB gain reduction on the XLR output only. The centre ground connection can be lifted and as a result the phantom power turned off, with the 'phantom & ground connect' switch. Turning off the 'active' switch bypasses the EQ, the Tube/Microphone emulation circuitry and the Level control and turns the SansAmp Acoustic DI into 'transparent' DI box. The active LED goes out with the switch in this position and you might expect the SansAmp to be switched off, but even in bypass mode the SansAmp Acoustic DI still requires some power. The only way to turn it off is to remove any jacks plugged in to the inputs.

Power supply options

Power for the SansAmp Acoustic DI is either from the usual 9 Volt battery, easily accessed through clip-on hatch in the base, from an outboard supply plugged in to the co-axial external power socket, or, very usefully, from a phantom power feed via the XLR output connector when the DI is plugged in to a mixing desk with an XLR lead. Battery power is activated in the usual way by pushing a jack plug into either input socket

Inputs and outputs

The SansAmp Acoustic DI is designed with passive piezo pickups in mind. Passive piezo's require very high input impedances otherwise they lose bass. The 'input' is ideal for passive piezos at 4.7 Megohm while the 'input to XLR' is a little lower at 1M impedance, which is ideal for passive magnetic pickups. The signal from the 'input' jack routes via the tone controls and feeds both outputs while the 'input to XLR' routes directly to the XLR output connector. An external effect insert path is available through connecting the effects input to the SansAmps 1/4 inch output jack, connecting the effects output to the 'XLR input' jack and taking the final output signal from the XLR connector.

In Use

In use the SansAmp Acoustic DI is very quiet (unlike an amazing number of other pedals and DI devices) and the active EQ provides plenty of tonal adjustment. It even works very well for recording clean electric guitar - plug in an archtop guitar, add a little valve warmth with the blend control and you're rewarded with a gorgeous jazz tone. The phantom powering is a very handy feature, since you never have to worry about flat batteries and in any case with a power consumption of only 7mA maximum, the battery life is pretty long. The only criticism we have is that for such a feature rich product the user manual is a little vague on certain points. For example it's easy to assume that the SansAmp Acoustic DI is in totally passive mode and not draining the battery, when the 'active' switch is in bypass and the 'active' LED isn't illuminated.


If you're looking for a simple 'plug-n-go' DI then the SansAmp isn't it, this is one of those pieces of kit where you really do need to read the manual and learn all of its features, to get the best out of it. For something simpler the new SansAmp XDI, designed for DI guitar recording on a PC based digital recording rig, is worth considering and we are hoping to review this new unit soon. However if you're looking for a really quiet active DI with powerful tone controls and great sound on acoustic or clean electric guitar then the SansAmp Acoustic DI really nails it.

Copyright 2003 Terry Relph-Knight


Tech21 and the solid-state, analogue 'valve sound'

Tech21 has built a reputation for making great sounding guitar pre-amplifiers and amplifiers using solid-state components to create analogue emulation of the valve sound. Tech21's proprietary valve emulation was originally developed to reproduce, often quite aggressive, overdriven valve distortion sounds. In the SansAmp Acoustic DI it's employed in a modified form to add a more subtle warmth and fatness, similar to a high quality tube microphone.

We recorded the track 'Harbour Nights' from Hugh's soon to be released jazz CD 'Synchromatic' using a Gretsch C400 archtop guitar with a Dan Armstrong pick-up plugged into a SansAmp Acoustic DI feeding the line input of an M-Audio Audiophile USB audio I/O box.