Can Sparkplug Do LTD SR EQ & Small Fry "Dynamics"?

[DeepBlueC]

This one's probably for Brian, although anyone who has tried this build is welcome to chime in. I'm a longtime Barber aficionado. I still have and regularly use the LTD SR w/Mod Board, Small Fry, and Super Sport; I still have but find less use for the Dirty Bomb (though it's a lot of fun); and I've spent time with the original LTD, Custom Cool, and Direct Drive w/Mod Board. In the studio (including just this past week), the Small Fry & LTD SR are most useful for me: the Small Fry for its singing lead tones and the SR for its flat-mids EQ and incredibly sweet overdrive.

So I'm intrigued by the Sparkplug and am wondering, can it do the flat mids of the SR or will mids always be a bit boosted even with the Mids knob fully counterclockwise? And is there any mod that could be done to create the "Dynamics" control of the Small Fry? If not, about where in that Dynamics knob range is the Sparkplug voiced?

Thanks!

[DeepBlueC]

I'm surprised no one has responded to this... I can guarantee it's an important question for anyone who has had experience with Barber overdrives like me. I can't find any demos either.  The build doc mentions the Direct Drive & LTD, and Brian's initial post says, "It's probably closest to the Small Fry, although the clipping is totally different." Well, those three pedals are radically different from each other in both type of overdrive and EQ, and the SR version of the LTD (which has the most unique EQ footprint) is the one I personally like best... In addition, the most unique feature of the Small Fry is its Dynamics knob which totally changes the character of that OD, and there's non such adjustment on the Sparkplug.

So what tones are intended here? Anyone?

[jkokura]

Considering I can't recall seeing a build report for this circuit, I can't say I'm surprised you haven't gotten an answer.

Seeing that you're very familiar, perhaps you could do some testing and report to us what you find?

Jacob

[GermanCdn]

If I can kick this flu, I'll try and shoot a demo of the sparkplug vs my Silverfox.  Don't know if it will answer your question, but it will give you an idea anyway.

[DeepBlueC]

Yeah, you're right Jacob... I was hoping to get a better idea of what the Sparkplug was shooting for before building one, but that may be the only way. So much for being lazy.

Even so, hope springs eternal, so if anyone has built one and has a thought or two, here's your chance. If you do get a chance to do a demo GC, thanks in advance.

[midwayfair]

A few options:

1) You can add the dynamics control. Put a 5-10K pot in series with back-to-back Germanium diodes and a medium sized resistor (3.3nF in the Small Fry) to ground, and connect lug 3 of the dynamics pot to R6/Cut1. (Best to just tap the Cut 1 knob).

2) You can replace the "Clip_b" in the spark plug with a 5-10K pot, and use germanium diodes instead of LEDs for D2&D3. Consider using a SPST for Clip_a, or put the 5K pot between lug 3 of Clip B and the board.

Here's the Small Fry's schematic for reference:


Edit: in other news, the Small Fry is one of the only examples of a variable series resistor to the diodes I've seen. Most builders would omit this sort of control (externally at least) because it's such a subtle change.

[DeepBlueC]

Thanks Midway! VERY helpful. Unfortunately, the schem isn't showing up in either Chrome or IE for me... 

[midwayfair]

Thanks Midway! VERY helpful. Unfortunately, the schem isn't showing up in either Chrome or IE for me... 

http://www.freestompboxes.org/download/file.php?id=16860&mode=view

?

[DeepBlueC]

That works. Thank you.