SandSpur Fuzz biasing?

[MichaelW]

Hey guys,

Just got my SandSpur board in the mail today and putting together the parts for the build. (Recommended by @thewintersoldier, thanks Chris!)

Any tips on biasing Q2? I'm a little confused by how the external "Sun" pot and internal 5k trimmer and R3 interact.

From the schematic it looks like 3 resistors in series to me, do I have that right?

I'll be using BC108's per the BOM.

TIA!

 

[Coda]

I usually target between 1.35-1.5 vDC on Q1c and 4.5-5.75 vDC on Q2c.

The internal is meant to set the range of the external trim.

I concur…except I don’t think I’ve never measured Q1 on a Fuzz Face. The internal trimmer sets the bias, and the sun dial control adds a bit more or takes a bit away, to taste…

 

[Coda]

Make sure you socket the transistors, since you can use lots of different combos, as they all sound different. I prefer BC109C, personally. BC108 is a the standard, 109c is a little hotter/aggressive. BC183 (I think it is) is darker, and a little thicker…though not as fuzzy…

 

[MichaelW]

So I have 3 BC108's. 2 of them measure in the 470's and one of them 780. My plan is to use the 780 in Q1 and one of the others in Q2.

I do intend to socket and try some other SI trannies as well.

 

[Coda]

Also, just a comment of my own; I biased mine to 5v exactly, and I have the sun dial at about 2:30…

 

[MichaelW]

Try the 470s in Q1 and Q2.

EDIT: 470 is approximately at the high end of the B range and low end of the C range so it should have a good middle ground between the standard Si tone and a more sizzlely 109C type.

I've also got some assorted BC109's and BC107's to try once I get it all working. But thanks for the tip! I'll start with your suggestion.

 

[Coda]

No, been too busy building memory men and electric mistresses

Drag…

 

[Coda]

Someone had to leave the kids table and build real pedals

There’s nothing wrong with building another rat/TS variant…

 

[Coda]

I think that was a Mu-Tron III, wasn’t it?…

 

[Robert]

Someone had to leave the kids table and build real pedals

For future reference, it's probably poor judgement to reference "leaving the kids table" then post an R Kelly meme two posts later.

Context is key.


Only kidding, I know there were like, trim pots that had to be turned one way or the other..

 

[HamishR]

I've been meaning to build a Memory Man but keep forgetting to.

I've been thinking about studying how this stuff works because I still have no idea why it does. But I'm afraid that if I learn how it works then it won't . It is magic, right??

 

[giovanni]

I've been meaning to build a Memory Man but keep forgetting to.

I've been thinking about studying how this stuff works because I still have no idea why it does. But I'm afraid that if I learn how it works then it won't . It is magic, right??

Science is more art than science. Even if you learn how it works, it’s still quite mysterious. Semiconductors are all based on quantum mechanics so…

 

[fig]

Science is more art than science. Even if you learn how it works, it’s still quite mysterious. Semiconductors are all based on quantum mechanics so…

That’s why I learned quantum mechanics first, to have an edge in pedal-building.

 

[Robert]

This is how I felt when first learning how CRTs worked way back in the day.

So we're firing an electron beam using 30,000V and bending it with electromagnetism to deflect it all over the screen? Which then glows in different colors when it's struck?

Right. It's time to stop watching so much Star Wars, tell me how they really work.

 

[ICTRock]

"real pedals" where's the lovetone then?

 

[giovanni]

This.

I was trained as an electrical engineer and there were times that reading my textbooks felt like reading Lord of the Rings or the Old Testament or something.

At the quantum level, shit kind of IS magic.

Same here. My professor just started talking about the NP junction and how electrons would do all kinds of crazy shit and I thought it was some weird alchemy nonsense

 

[Robert]

Oh man I had the hardest time with PN junctions.... So like, we trickle a few electrons (or holes, depending on who showed up that day) through here and they're all like "Hey guys, let's jump off this bridge together!" and then all their friends follow along and... what? This school sucks, you guys are just making this s**t up as we go along.

 

[benny_profane]

Serious question for folks that studied EE: Did you have practical labs that involved working with components (either solderless breadboard or actual soldering), or was the entirety of instruction theoretical?

 

[Robert]

I'm no EE, but we had hands on. Not as much as I would have liked, but it did happen.

We had these big Heathkit training lab things that were connected to a PC as well. There was a room full of them for the various technologies / subjects.

 

[benny_profane]

Is that Protoboard v2?

When I worked as a tech writer, the number of EEs—regardless of generation or level of education—that actually had practical instruction was surprisingly low.