THE GYRAF ADAPTATION OF THE PULTEC EQUALISER:

This is a nice sounding passive equalizer with a tube makeup gain stage and transformer input and output. The amp stage and circuit board layout is from Jakob Erland at Gyraf Audio. The frontpanel layout is borrowed from the solid state version of the Pultec EQP-1A3 equaliser.

This build uses a 60ies Telefunken PCC88 tube, a close relative of the ECC88, with a different heater setup. The heater regulation circuit was modified as suggested in this forum thread.

You can download the Schaeffer frontpanel file here - feel free to use this frontpanel if you like it!
Please be aware that this is not an exact copy of the real EQP-1A3 equalizer frontpanel and that you must check all the hole diameters for your pots and switches. The knobs are all Dakaware style, the BOOST and CUT knobs are skirt knobs with a bottom diameter of 1.5" (eBay), the frequency selectors are standard 2300 series chickenheads (banzaieffects.de part Nr. SKU17441) and the HF and power knobs are small eagle knobs (banzaieffects.de part Nr. SKU17445).

some images of the finished unit:




frontpanel low frequency section:


frontpanel high frequency section:




filter board and back of frontpanel:


amp board and power supply:



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