The Buzz Audio Tonic is simple but incredibly useful inductor based 3-band equalizer for 500 Series racks.

The Buzz Audio Tonic offers three bands of equalisation with a versatile sweep midrange section and fixed two frequency high and low bands.  The tonic also has a high pass filter utilizing another real choke.  The signal path of the tonic is all True Class A discrete transistor with the output balanced via a Lundahl LL1517 high spec transformer. The tonic is designed to fit into the popular API 500 Series modular racks and requires a rack to function. 

The Tonic high band is switchable bell or shelf and features two frequency settings of 5kHz and 11kHz.  The low band is also switchable bell or shelf with two frequency setting at 120Hz and 60Hz with both bands providing +/- 15dB of boost and cut.  Thanks to the use of passive choke based filters, users can expect a very tight sounding bottom end and sparkly clear highs when applying boost with these two bands. 

The sweep "bell" midrange extends from 75Hz to 1500Hz (x1 mode) or 750Hz to 15000Hz (x10 mode).  The midrange "Q" or bandwidth can be selected tight(ish) or broad and utilizes the Constant Amplitude Phase Shift (CAPS) filter circuit developed by Mr Steve Dove. +/-15dB of midrange boost and cut is available. 

The Tonic 18dB/oct high pass filter is completely passive with two turn over frequencies (50Hz or 90Hz) selected by the user via jumpers on the circuit board. Completing the picture is the "OL" LED which illuminates when levels exceed +20dBu and the "BYP" switch which completely removes the tonic from the signal path. 

Maximum Input Level; +23dBu
Maximum Output Level; +26dBu into 3k ohm load
Frequency Response EQ set flat; 17Hz to 175kHz (+1dB, -3dB)
Harmonic Distortion measured +10dBu output level; 0.08% @ 100Hz, 0.02% @ 1kHz, 0.005% @ 10kHz
Signal to Noise Ratio; -88dB A wtg, input shorted
Input Impedance; 20k ohms approx balanced
Indicators; Single LED overload indicator
Size; (37Wx132H). Fits 1 space in API* 500 series rack format
Power requirements; 120mA +/- 15-18 volts DC, as supplied by frame power supply.

The Gear Rack

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