Boss SP-1 Spectrum

[MAndrews]

An interesting filter come 'sort of' auto wah.  https://www.youtube.com/watch?v=nFEmYKBYVTA
One just sold for ridiculous money on ebay http://www.ebay.co.uk/itm/Extremely-Rare-BOSS-Spectrum-SP-1-Effects-Pedal-/121062953371?pt=UK_Guitar_Accessories&hash=item1c2fea119b
I think this is the schematic http://www.stompboxzone.com/forum/viewtopic.php?f=5&t=1574
Can't find anything else.

Cheers.

Mark Andrews.

[IvIark]

Yes I'll add this one

[MAndrews]

Thanks Mark. Look forward to it!

[MAndrews]

I found this service manual has more details http://www.scribd.com/doc/77611613/Boss-SP-1-Service-Notes

[MAndrews]

http://www.ebay.co.uk/itm/221200815296?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Another one for a ridiculous amount!

[fx-fidden]

Hello, we still don't have a veroboard layout, maybe the problem to build this pedal si the dual pot 10kA/10kC. It's not just hard to find it, but it's IMPOSSIBLE.

I found these project pages of the Spectrum.

Here there's even the istruction "to build" the right pot fot this circuit.
https://aionelectronics.com/project/chroma-boss-sp1-spectrum-equalizer/
And the schematic is based on the original, but without buffer and Boss switching system.

And here there a version where is possibile to use the normal dual pot 10kA/10kA.
http://www.griffineffects.com/projects/248-sp-1-spectrum-pcb.html
It says: «The original unit used [...] a 10KA/10KC. We modified the circuit board to use a standard 10KA/10KA dual potentiometer. The circuit functions exactly the same. [...]»

The link project we can find in the low part of the page, and it contains the schematic, that is probably partially mislabeled, because I can read 10kA and 10kC, but there's actually a modify. The 10kC side si simply reversed.
The project seemed verified, and it worked (perhaps before the mod?). But I am not sure about this "mod". Of course, I know that if we reverse a log pot we can get a reverse log, but in this case even the setting of the pot is reversed, I guess. Max and Min are inverted. Is this right?
If I am right, how it could work fine? Maybe in this circuit it doesn't matter? I hardly think so.

Is there really a way to use a dual pot 10kA/10kA?

[Highsmith]

Hi, just want to say that I built the Aion unit and it all went with out a hitch.

Building the required pot was easy and fun.

The effect itself is nothing spectacular, basically a cocked-wah type of sound. It is not  very versatile.

[fx-fidden]

Thanks for your reply, Highsmith.
I should watch some demo of the pedal, I did too much time ago. I didn’t expect a versatile effect, just a pedal to change the voice of the guitar. I have in mind some sounds of Marty Friedman (clean and maybe distorted, too). But he use a kind of Ibanez auto-wah, maybe without automatic sweep, or sort of it.
Anyway, probably nothing really special, I'm just curious.

I'm still wondering how could work the other one project reversing the pot in the schematic.

[HamishR]

Basic Audio make a fixed wah kind of pedal.  It's pretty good too!

I can't see how it would be too difficult to just build a wah pedal into a regular box and use the wah pot as a regular pot with a knob on it.  There are heaps of wah circuits here.  No fancy dual pots required.