Before modern semiconductor technology, audio filters and equalizers were made with passive components - capacitors and wound coils of wire that formed inductors (or chokes). Audio frequency chokes were bulky and expensive so these days it's easier (and cheaper) to use an electronic circuit to simulate the inductors. However, we have discovered that the difference in sound between the real thing and a simulator is quite noticable. So with the tonic equalizer we have brought you the best of both worlds, utilizing both real chokes and electronic filters in perfect harmony.

The tonic offers 3 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 glistening 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.

Rack Compatibility
The tonic power consumption is higher than most other 500 series modules and this may stress some rack power supplies depending on what other modules are fitted. Please check the following list to see if it will work OK in your rack.

API Lunchbox 6B - recommend only two tonic modules are fitted along with other modules.
API 500VPR with L200PS - no problems.
Atlas Pro Audio Revolver - no problems.
OSA Power Rack & Track Pack - no problems if you have the 3 amp external power supply.
B.A.E. 6 & 11 Slot Racks - not tested, check with B.A.E. for power capacity.
Purple Audio Sweet 10 - not recommended in it's current form due to power supply issues.

• API* 500VPR Series rack module format - plug in and play!
• Real choke based EQ offering superior sonics.
• Advanced analogue technology - not a clone or copy of products from the past.
  
• Fully discrete hi-bias wide bandwidth differential Class A amplifiers.
• High performance Lundahl* output transformer.