Saturday, December 3, 2011

Black Iris EQP-1A complete!

Since it's just me and the dogs this weekend, I've had some time to watch some bad movies and wrap up the hand-built EQP-1A inspired build I've been working on for Cam DiNunzio of Black Iris Music and Heks Orkest. I haven't had a chance to fire it up yet  -- I'll wait 'till I'm fresh and fully alert before I confirm the circuit and give it the juice for the first time and put it through its paces -- but in the meantime I thought I'd post some pictures of the final product, including some obligatory gutshots.  I'm really pleased with the way the layout all came together! 

If you've been following the blog, you'll notice it's a companion piece to the LA-2A inspired build I did for Cam previously.  Thanks again to my friend and Gothik Amps cohort from Alexandria, Virginia (you know who you are!) for assistance with the laser engraving of the front panel. I love the way the natural aluminum knobs contrast with black anodized aluminum of the chassis!

If you're of the generation that's only used to using a parametric EQ, the EQP-1A is a bit different.  Check out the user manual of the original.  It basically has four low frequency (20, 30, 60, and 100 Hz) and seven high frequency bands (3, 4, 5, 8, 10, 12, 16 kHz) that can be boosted.  In addition, the same four low frequency bands can be attenuated, along with three high frequency bands (5, 10, 20 kHz).   In addition, the width of the boost-able high frequency bands can be adjusted with the bandwidth control. Finally, there's an in/out switch that optionally bypasses all of the filters.  It turns out to be a quite amazingly flexible arrangement.

The overall layout uses three boards... The large one is for the main amp section, the long one near the front is primarily for the filter section, and the small one at the back is the DC regulator for the tube filaments.

Main board close up.    Tubes are (L-R) 12AX7, 12AU7, and a 6X4. The only shielded run in the build is the long white wire running from the input to the control panel. It looks like it's close to the 12AU7, but in fact it's just an illusion of the photograph -- it's inches away.

Most of the wiring work went into the filter section.  Getting all the wires to and from the seven-position rotary switch was, frankly, something of a pain in the ass.

Another couple of views...

The flash on this one gives you a better idea of what the silver on black panel looks like in real life!  Too bad I can never get rid of the glare.

1 comment:

  1. to get rid of glare, use a tripod and open the shutter for a longer timeframe to expose the pic longer. You need less light and don't use flash.

    What font was used on that panel? Was this some sort of windows artistic font?