EQ901B Series User Guide


The Deer Creek Audio EQ901B Series is a direct replacement for existing BOSE 901 equalizers. The EQ901B features dual output equalization (EQ) curves, Normal and Enhanced, either of which will accommodate your 901 Series and can be selected based on personal preference. See below for instructions on using this feature.

The EQ901B installs in your tape monitor loop, pre-out/pre-in loop, or between your preamp and power amp. Switchable input levels between 0.9 Vrms and 2 Vrms accommodates use with most preamplifiers, amplifiers, or receivers. The EQ901B series is based on the miniDSP 2x4 digital signal processor.


Precision engineered 901 Series model specific equalization curves

Dual output EQ curves Normal and Enhanced

Simple drop in replacement

High fidelity and low noise

What’s Included:

EQ901B Equalizer

Frequency equalization curves for your 901 Series

Regulated power supply


Analog audio input and output connections are made directly to the RCA input and output jacks. When making these connections, make sure that the equipment being connected is powered off.


The EQ901B does not have a power switch. We recommend that it be left powered on, power consumption is very low.  When you power the EQ901B off and on ensure that you turn the connected equipment off before disconnecting power from the EQ901B, and also connect power to the EQ901B before turning connected equipment on. It is OK to power your EQ901B from a switched outlet on your receiver.

Setting Input Levels:

The analog audio input levels are switchable between 0.9 and 2 Vrms to accommodate use with most preamplifiers, amplifiers, or receivers.   If you are experiencing excessive signal level or distortion and you may need to switch the unit to the 2.0 Vrms setting

This EQ901B is shipped with the input level set to 0.9 Vrms.


0.9 Vrms position - The maximum input signal voltage allowed before clipping the A/D convertor is 0.9 Vrms. This position is typically used when the EQ901B is connected between a preamp and a power amplifier.

2 Vrms position - The maximum input signal voltage allowed before clipping the A/D convertor is 2 Vrms. This position is typically used when the EQ901B is connected in a tape recording loop (REC/in to PB/out).

Accessing the Input level Switches:

Using the Dual Output EQ Curves:

The EQ 901B is equipped with two equalizer (EQ) curves, the Normal EQ curve is available on outputs 1 & 2, and the Enhanced EQ curve on outputs 3 & 4.

If you're using an amplifier or receiver with two tape monitor loops you can connect the EQ901B outputs 1 & 2 to tape playback inputs 1, and outputs 3 and 4 to tape playback inputs 2.  Then you will be able to switch easily between the two equalizer curves.  If your configuration is a pre-amplifier out / main-amplifier in setup you'll need to manually move the cables from outputs 1 & 2 to outputs 3 & 4,  be sure to turn power off all your equipment before you do this.


Distortion:  <1% THD at maximum input

Maximum input voltage: 2 Vrms or 0.9Vrms - jumper settable

Dynamic range:  un-weighted >98dB

Analog Devices ADAU1701 Digital Signal Processor Engine

Dimensions:  26h x 107w x 94d mm

Warranty Terms:

This product is warranted to be free from defects in materials and workmanship for a period of one year from the invoice date.  Warranty does not cover failure of the product due to incorrect connection or installation, improper or undocumented use, unauthorized servicing, modification or alteration of the unit in any way, or any usage outside of that recommended in this manual. Return shipping is the responsibility of the customer.

Please contact us with any questions you may have