Skyripper Tech Questions

[PeelingPaint98]

Hello all, I'm a nooberton around these parts.  For my first ground up build I decided to go big and build a Skyripper using the '07 PCB off John Lyon's site.  There are a few things that are confusing me as far as the wiring goes, I've searched through the current floating Skyripper threads but they're not really answering my questions.

The PCB layout is here for reference: http://www.mrdwab.com/john/Skyripper07.pdf

1. What are the two seperate -9V pads for on the PCB the lower central one (connected to the LEDs) would go to the power jack, is the one on the upper left a spare or is it supposed to connect to something?

2. Are the Buff sw and the Range sw lug 2 pads directly wired to the Buff sw and Range sw lug 2 Lugs on the stomps or are there actual switches that are supposed to go between them?

3. I'm using NPN trannies so I've reversed all the polar components, do the LEDs get reversed as well?

4. I got a hold of a spst switched pot for the Rip/rip sw, but I'm unsure which lug goes where on the pot and PCB.  Using the standard pot numbering system, the switch portion has 2 lugs one under the 1 and 3 lugs of the pot lugs.  My instinct is to wire the "off" lug to the #1 lug of the pot and the other lug to the PCB pad by the loop send/return.  If anyones built a Skyripper using this type of pot, is this correct?

My ambition for a sweet pedal may have outstripped my technical know how by too much, thanks for any help. 

[joegagan]

congratulations, i think you will like it.

1. not sure. the second one is probably spare.

2. what is marked on the pdf as ' buff sw' is actually the true bypass sw for the entire effect, S1. in other words, the pad marked buff sw is the input of the signal to the effect.   range is s2, the pdf has this pad mismarked as S1 ( the pad directly below the marking 'range 2') there are no other switches. i know it is confusing,, but it works.

3. yes.

4. think of the rip sw as a separate thing. it completes the connection of the rip feedback loop, connect exactly as shown on the schematic, it will work. the pot has sw lugs on the back, right?

the biasing is very important, do not gloss over the biasing instructions. getting the fuzz portion to get 1 volt and 4.5 volts in each respective position is critical, a bit of a balancing act between the two trimpots at Q3 collector, s4. keep going back and forth til each one holds correct bias.

you should be using this schematic with this layout, is this the one you are using? please keep us posted.

[PeelingPaint98]

Thanks for chiming in Joe, that is the scheme I'm using, sadly though my technical know how hasn't gotten so far as being able to read schematics 

That's why I'm kind of dependent upon the PCB labeling in the PDF off John's site.
I'll putter through I'm sure with some trial and error, hopefully I won't burn out the trannies I have in the process 

As a side question for anyone, can you install the bias pot without having a stereo input jack?  I'm not planning on using a battery snap so I didn't get a stereo jack for the input.  Only later did it dawn on me that the bias is hooked up to the ring.

[digi2t]

First off, I'm assuming that you want to go NPN, because you'll be using silicon trannies, or daisy chain to a neg. ground power adapter powering your other pedals. With that said, I would recommend doing some more research, and/or building, before tackling something like this. What worries me is your idea to run the circuit NPN by simply reversing the polarities. I mean it will work, but I've read of cases where PNP designed fuzz circuits don't necessarilly react well (at all) to being reversed. I would recommend researching reversing Fuzz circuit polarities, it may answer some of your questions. I'm no expert by any stretch of the imagination, but I tend to believe that when a certain circuit is designed a certain way, it's for a reason. I don't mind some experimentation, but I hate reinventing the wheel.

In my case, I've built 2 Skyrippers, first one based on the original PNP circuit, and a silicon NPN bastard variant. The first time out, I did originally use PNP germanium trannies as per original specs, and it's a fantastic pedal. By chance, I tried a 2N2904A in Q2, and a 2N2905A in Q4 (PNP silicon) in place of the 2SB172's, and I hit a homer insofar as sound is concerned. To my ears, just as good as the Ge trannies I had in there before.
Before, 2SB172's (hfe's: Q2 @ 95, and Q4 @ 160) and an AC128 as the diode. Now, 2N2904A in Q2, and a 2N2905A in Q4 (hfe's of 70 in Q2, and 185 in Q4), with a 1N34A as the ripper diode.

Even here, you're still just scratching the surface with this pedal. I already had a few builds under my belt when I built my first Skyripper, and it was a HUGE learning curve for me. Mind you, it did light the fire in my belly to build my second NPN twisted version, but it has nothing in common with the true Skyripper, other than the idea of the signal "flowchart", and the Ripper and Bias ideas. The rest was pure trial and error, imagination, and sheer lunacy on my part. I'm still trying to get my head around that one.

As Joe mentioned above, biasing is super-duper important on this pedal. Check, check, and re-check. Do yourself a favor, and use multi-turn trimmers. Much more accurate than the single turns, and you'll be glad you did in the end. 25K trimmer for the Range circuit, it's easier to bias to -7v in some cases.

So, in a nutshell, I would recommend sticking with the PNP design, and trying different (silicon even) trannies. Yes, it will sound a bit "edgier", but playing around with different lower hfe tranny values will probably be your best bet in honing the tone. You may want to read this, http://www.diystompboxes.com/smfforum/index.php?topic=89860.0 as well.

Cheers,
Dino

[PeelingPaint98]

Too late 

Actually I'm reversing it because I am permanently building another circuit into the effects loop, so that they could share a common ground and power I needed the reverse.  The main trannies I have are Ge, so whether it works or not I'm committed to making the build happen in reverse.

I've done a few paint by number kits and modifications of other pedals, this is just my first ground up build where I had to order all my own parts and rely not on explicit directions but notes and limited information.

[joegagan]

good. yes, you can just wire up the bias pot as shown, just place it between the ground lug and ground on your power supply jack.