As promised yesterday, here is the bass version of the overdrive pedal I posted yesterday. http://www.ssguitar.com/index.php?topic=2679.0
A few notes on the differences between these pedals. The bass version uses green 3mm led's instead of the reds I used in the guitar version, just for the slightly higher forward voltage of the greens. With the higher output from bass pups, I just figured it would keep things from being too harshly clipped. I also went to the 4558 op-amp instead of the LM1458 I used in the guitar version because while the 1458 produced the smooth grind I was looking for in my guitars, the 4558 has a bit more harshness on the guitar, but adds that nice bit of grit to the bass.
When I was first asked to do a bass version of the pedal, I took the easy way and just recalced the filters to drop them an octave. This, while somewhat pleasing, had the same problem as most bass OD pedals on the market, as you drop down the neck, the grind disappears on the lower register. So I went back and re- did things to drop two octaves, and when I saw on the scope that clipping started at 17 hz, I plugged in the Squire P-bass and liked what I heard. Boxed it up, demoed it and had to build 10 more. :cheesy: One of my bass friends described it (Aguilar SS bass head) as giving him back the sound of an Ampeg SVT that is severely ticked off. Both it and the guitar version are in a pair of local recording studios, so I think the sound came out ok.
The PNP is the same for both versions, I've never made a layout sheet for the bass version, just scribbled the values next to the guitar layout. I've never made an off board wiring guide for either, after making close to 30 OD's of these the wiring becomes automatic, so I need to take the time to throw one together. Promises, promises. Enjoy...
Bob
A few notes on the differences between these pedals. The bass version uses green 3mm led's instead of the reds I used in the guitar version, just for the slightly higher forward voltage of the greens. With the higher output from bass pups, I just figured it would keep things from being too harshly clipped. I also went to the 4558 op-amp instead of the LM1458 I used in the guitar version because while the 1458 produced the smooth grind I was looking for in my guitars, the 4558 has a bit more harshness on the guitar, but adds that nice bit of grit to the bass.
When I was first asked to do a bass version of the pedal, I took the easy way and just recalced the filters to drop them an octave. This, while somewhat pleasing, had the same problem as most bass OD pedals on the market, as you drop down the neck, the grind disappears on the lower register. So I went back and re- did things to drop two octaves, and when I saw on the scope that clipping started at 17 hz, I plugged in the Squire P-bass and liked what I heard. Boxed it up, demoed it and had to build 10 more. :cheesy: One of my bass friends described it (Aguilar SS bass head) as giving him back the sound of an Ampeg SVT that is severely ticked off. Both it and the guitar version are in a pair of local recording studios, so I think the sound came out ok.
The PNP is the same for both versions, I've never made a layout sheet for the bass version, just scribbled the values next to the guitar layout. I've never made an off board wiring guide for either, after making close to 30 OD's of these the wiring becomes automatic, so I need to take the time to throw one together. Promises, promises. Enjoy...
Bob