Dead End FX - TerraHawk

[gordo]

I just can't help myself.  Right about the time that I think I've built one of everything I find an effect I'd never heard of and also discover it was the core sound of one of my fave guitar players: Rory Gallagher.  I always knew he used a treble booster to get his Vox or Bassman to break up but didn't realize it was this obscure beast.  The pedal is a clone of the  Butcher Pistol Slapper, itself a variation on the S. Hawk Tonal Expander that Gallagher used.

The Hawk, and it's successor The Hawk II were only made for a couple of years (73 and 74) and were an 18v affair that was closer to a channel strip from a recording console than an effect.  It had no stomp switch and was intended to be used on any instrument or microphone.  It had sliders for Bass/Mid/Treble and an on-off switch, a treble boost switch, and a gain boost switch.  The cool part is that the tone controls are inductor based and the circuit has a ton of gain available (with 18v headroom).  The Pistol Slapper added a variable gain pot as well as an output level control.  It also made the Boost footswitched and added a 3 position switch to change the range and a boost level (Filter) control.  The TerraHawk has the same feature set.

Most Hawks were gooped and a major PITA to work on if they failed (18v from two nine volt batteries...what could go wrong?) so they're exceedingly rare in the wild and if you can find one it's stupid expensive.

Dead End's version is designed to be put in a 1590BBS chassis (deeper than a 1590BB) and I got a bit too aggressive with the jack placement and ended up having to lay down a couple of the film caps to clear it.  I'd blame it on having WAY too much room to work with.  A rare luxury....it went to my head.

This is the Hammond deep red powdercoat and it's a really nice finish but thicker than I expected and I'd have turned up the power on the laser if I had a do-over.  Still, it's clean, if unimaginative and I'm happy with it.

This is a booster that eats all other boosters for dinner.  I'm REALLY loving this thing, and if there is to be such a thing as Rory-in-a-box...this is it.  He sat thru my band's last set of the evening in Worchester MA in a little bar.  This was in the early 80's and he was opening for Rush at the time, and I believe it was his last American tour.  He was all by himself at a table and bought a bottle of Jack Daniels at bar prices and a glass.  I walked by him and said Hi, and wanted to explain to him that he was the reason I played electric guitar and specifically a sunburst Stratocaster and chickened out.  I could hardly even breathe I was so in awe so I just kept going and left.  I regret that decision on a regular basis.

So all that sob story aside, here it is...The S. Hawk Tonal Expander...

[Invertiguy]

That thing looks great! Did you laser etch the graphics? Those knobs fit it super well!

[cooder]

Epic build and I had never heard of this either! Must check it out , sounds great and thanks for sharing the story there. Man, having Rory sitting in the bar while you play a set... I can imagine that you were lost for words. What memories though.

[Bret608]

What a great story! Really awesome build too. I knew of the Pistol Slapper a while back but never did look up a sound clip really. Now I'm even more curious!

[jimilee]

Pistol slapper... that looks fantastic man.


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[bcalla]

That's a beautiful build (and a great story)!  Now I want to build one!

Looking into buying components for this I see that Mouser no longer has the 27mH inductor.  I can't find it anywhere else either.  The build doc says that suitable replacements are available, but I know zero about inductors.  What other characteristics are important when determining a proper replacement?

For example, the datasheet for the Bourns RLB0812-273KL lists the following:

Inductance: 27 mH
Tolerance: ±10%
Current Rating (Amps): 22 mA
DC Resistance (DCR): 102 Ohm Max
Q @ Freq: 60 @ 79.6kHz
Frequency - Self Resonant: 200kHz
Inductance Frequency - Test: 79.6 kHz

Do I need to pay attention to any of these values?

Better yet, does anyone actually know a specific available inductor that can be used for this pedal?

[Zerro]

For inductivity of coil is improtant only deisred value, which you can measure at multimeter with this function. Wire is mostly 0,15mm thin, which is limited only by current, which this wire must withstand. For common audio purposes as so as for HF devices is used this 0,15mm. Number of turns is depending on used diameter (overall size) of coil skeleton, and used ferritic enclosure.