S. Hawk Ltd. - Hawk II Tonal Expander

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
User avatar
Resistor Ronker
Posts: 339
Joined: 04 Jun 2012, 12:54
Has thanked: 60 times
Been thanked: 786 times

Post by apollomusicservice »

McRuff wrote:Just joined this site after seeing posts for S Hawk Ltd II tonal expander. Although I have a great photo component side, tracking down a photo of the solder/trace side has proven tough since there is a foam rectangle covering most of the board so battery cases do not come in contact with it. Does anyone have a clear complete shot of the solder side of the board?

I've owned S Hawk Ltd devices in the past (Hawk I) my first being purchased new (yes, I'm a dinosaur). The second being purchased years later on eBay. I successfully traced that board and built a clone in a more player friendly enclosure.

btw - any idea of the chip used in the II. The 'I' version used a common 741 op amp. I'm thinking that due to voltage requirements the II uses a 4131, but can't make out for sure.
I'm trying to draw the PCB with the help of "jujub" photos. If this device is still
in your property or at least good photos would be of benefit. Specifically on the photos I do not see the value of the capacitors and the inductances would have to measure. In fact I've already made ​​the SMD version of this unit that would fit in the 1590B housing.

User avatar
Breadboard Brother
Posts: 78
Joined: 27 Dec 2008, 17:23
my favorite amplifier: Vox AC30 TB, Marshall JCM800.
Location: Staten Island, NY
Been thanked: 9 times

Post by DavidRavenMoon »

I used to have one of these. They were REALLY noisy, so I never used it.
"You give a better performance if you skip the eyes" - Raymond Scott
SGD Lutherie

Degoop Doctor
Posts: 278
Joined: 09 Feb 2011, 16:10
Has thanked: 57 times
Been thanked: 364 times

Post by digi2t »

Cub wrote:Hey Lads,

Another interesting incarnation of the Hawk II is the recently released Maritime Analog Effects Pedal Pistol Slapper - Booster/EQ/Overdrive

[ Image ]

Flynn Amps' take on the Hawk II has the low pass filter on a tiny switch, the Slapper has it on a proper foot switch and it comes with a filter pot and rotary switch for different caps.
The Drive and Level pots are welcome additions as well, as the Volume pot on the Flynn pedal goes from "blimey, that's loud" on zero to "are you taking the piss ?" on ten, unity isn't an option.
I've recently come into possession of a Pistol Slapper, so I decided to investigate the inductors further. Using my inductance meter and DMM, I have the following readings (inductors removed from board);

Treble - 27mH / 81 ohms
Mids - 170mH / 287 ohms
Bass - 435mH / 518 ohms

All the pots are C10K. The following R/C combos are used from the inductors to ground;

Treble - 220 ohms / 150nF
Mids - 220 ohms / 47nF
Bass - 120 ohms / 2.2uF

The inductors themselves appear to be visually similar to the Bourns 70F series, however these are now obsolete, and impossible to find. I have found some possible radial replacements, with similar specs, and smaller footprints. The Bourns RLB9012-273KL may be able to sub for the treble inductor. It's spec'd at 27mH / 80 ohms. The mid may be covered by the Fastron 11P-154K-50, which is a 150mH, but might be close enough to work. As for the bass inductor, I couldn't find anything close/cheap/compact, so perhaps a series trio of the 11P-154K-50 might work. The resistance of this particular inductor is spec'd at 205 ohms, so a trio in series would place it at 615 ohms total. Some tweaking of the R/C below might be required to get it just right.

Might be cool if someone could sim these values, and see where they end up.

It's a wonderful pedal BTW. Great boost, with flexible EQ. The newer models have a 3 position filter toggle switch, which replaced the older 6 position rotary. I suppose that perhaps the three additional caps didn't make that much difference. Three settings is more than adequate.
No matter how many times I cut it, it`s STILL too short!


Post Reply