Does anyone have info on the Bear Boost Plus from Small Bear?

[wintercept]

Hi all. I was scrolling through Small Bear’s clearance sale and noticed that they’re PCBs are pretty well discounted.

I want to take a crack at the Bear Boost Plus, but I can’t find info on it aside from the write up from Steve at Small Bear found here. However, it’s missing some crucial info. So here’s what I need:

1) What are the capacitors, C4-C9 actually supposed to be? The layout in the article just says “390pF to .0068mF” for these caps, which are switched between with a 6 way rotary switch. There’s a lot of options in that range. I’ve calc’d the high pass filter with different values (with the 120k resistor), and found that 390pF, 680pF, 1nF, 2.2nF, 4.7nF, and 6.8nF would give a decent range of options. I would love to know what values actually came with the kit.

2) How am I supposed to power this thing with the external adapter? The way the schematic shows it:
It just doesn’t make sense to me. It looks like it needs a -9V adapter. I’m fine with whatever, I just need to know for certain. I would prefer to not use batteries.

3) Finally, does anyone have the PDF for the instructions for the kit? The article includes a link for it, but it’s dead. It would probably answer most of my questions. Anything about this would be great, like pictures of paper instructions that might have come with the kit, or even anecdotes.

I know this build is weird, but it has some interesting oddities (P-channel JFET?!, germanium?!, DPDT switching with LED that uses a darlington and a 100Meg resistor?!) Yup... but I think I can handle it. Any info on this would be much appreciated.

 

[Gordo]

I'd email Steve, he's a good cat (well...bear I guess...) and I'm sure he'd forward over any docs. He probably doesn't realize the link is broken. And given that's it's a SB project he encourages a lot of experimentation so it's not surprising he didn't nail down cap values. I'd use whatever you have and see how you like it.

This is a -9v project because of the transistors, so you're correct. +9v to ground. Keep that in mind if you are powering it with a power supply, it may not play well with others. You can always build a charge pump based power supply if this becomes a problem. A very nice example is the 3PDT Charge Pump Board project here. A 9v battery won't be an issue though.

The DPDT switching works very well and I believe is based on the old Geofex "Millenium Bypass". Back before 3PDT switches were the norm this was a superb way of including an LED indicator but still being true bypass.

 

[wintercept]

I'd email Steve, he's a good cat (well...bear I guess...) and I'm sure he'd forward over any docs. He probably doesn't realize the link is broken. And given that's it's a SB project he encourages a lot of experimentation so it's not surprising he didn't nail down cap values. I'd use whatever you have and see how you like it.

Thanks for the response! I was considering that, might as well reach out and see if he has it. He really does encourage using what you got, and the article explains the circuit was for him to use germaniums that didn't work well in the usual circuits.

This is a -9v project because of the transistors, so you're correct. +9v to ground. Keep that in mind if you are powering it with a power supply, it may not play well with others. You can always build a charge pump based power supply if this becomes a problem. A very nice example is the 3PDT Charge Pump Board project here. A 9v battery won't be an issue though.

Sounds right, I looked at it more and realized you could use a +9V adapter, but it has to be its own adapter or isolated. Otherwise, it would mess up a daisy chain by shorting everything through the jack sleeves.

The DPDT switching works very well and I believe is based on the old Geofex "Millenium Bypass". Back before 3PDT switches were the norm this was a superb way of including an LED indicator but still being true bypass.

I can't wait to try it out. I don't really like 3PDT switches so I would like to find something else for my own designs. This circuit, or the later iterations of the Millenium Bypass with a MOSFET, with one of those DPDT Carling switches would be indestructible. I think this is what the Spaceman pedals do, too.