Benjolin PCB layout for the real DIY

Rob

This is for those who know and have the means to etch and drill a PCB by themselves. You can use e.g. a 3M CG3300 transparent overhead sheet and a laser printer to make the film. Make sure that the toner side will make contact with the PCB when exposing, but you already know exactly how to do this, right? The PCB is eurocard format, 10 by 16 centimeters, so slightly different to 4 by 6 inch. Dó use the eurocard format. In Europe you can get Bungard single sided positive resist PCBs at Conrad.

As these files are for the experienced DIYers that go all the way all by themselves, there is no further support and you are on your own! I only support those who have been to a Benjolin workshop. So, don't bother me with questions if you etched and stuffed your own board and you think something doesn't work.

Note on parts

All resistors are stock 1% metalfilm types.
Pots are Alps STRK09K07

Every part of the schematic has been properly reasoned out and every value properly calculated. Using 1% resistors will insure everything works properly like it is meant to be. Changing values of components or using 5% or 10% resistors voids my warranty on proper operation.

For getting a SSM2164 you are on your own, I will not supply them.
And again, I only supply kits at the start of a workshop, you can NOT order a single kit from me if you don't come to a workshop. Two reasons for this. First of all there is the whole idea of the workshop where one gets full assistence in assembling the kit, and thus properly learn how to do such a project. The Benjolin is not only a fun box but the workshop is also a social and fun experience, and educational as well. And at the end of the workshop we make sure that all kits work. Second reason is that I simply don't have the time to sell kits over the net and give proper support. And if anyone has the bright idea to start supplying kits without my authorization you can be sure that you will forever be haunted by the evil eye and everyone will look down on you. So just you know.

But if you think you are up to conducting Benjolin workshops yourself in your area simply contact me in private and we work something out.

Tip:
When you run the board with a power supply it is a very good idea to solder two diodes instead of the two battery connections. Do it in a way that the cathode of the diode is connected to the + of the battery connector and the anode connects to the - connection. This way the diodes do NOT conduct. The reason why this is a good idea is to insure proper startup of the voltage regulators when powering up. Without these diodes there is a chance that one power regulator starts up before the other and this will prevent the other from starting up, resulting in silence. The diodes fix this properly. If you use a non-symmetrical power transformer, like a wallwart thingy, two rectifier diodes and two elcos, either the + or the - voltage comes up before the other one, and that voltage will pass a regulator and make the other regulator sense an "inverted" voltage on its output and force the other regulator into permanent short circuit protection mode. The diode will short this "inverted" voltage to ground and assist the other regulator when it comes up just a fraction of a second later. These diodes can be simple 1N914 types.
Check the 78L09 and 79L09 datasheets on the web if you would like to know more about this issue and little fix.

BenjolinV2Layout.pdf

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BenjolinPCBV2.pdf

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BenjolinBillOfMaterials.pdf

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Luka · Joined: Jun 29, 2007 Posts: 997 Location: Melb.

great thanks rob

i might give this a shot

Danno Gee Ray · Joined: Sep 25, 2005 Posts: 1332 Location: Telford, PA USA

Thank you Rob.

fluxmonkey · Joined: Jun 24, 2005 Posts: 687 Location: cleve

thanks, Rob! this is quite wonderful. i would love to attend a workshop for all the reasons you describe, but unfortunately i doubt i'll be able to travel to do so. but this lets me in on part of the fun, anyway! thank you for your generosity.

sincerely,
bbob

xi-boy · Joined: Dec 16, 2008 Posts: 18 Location: germany

thanks a lot for sharing this wonderfull circuit
hopefully once i will get the chance to participate one of your workshops

PickNick · Joined: Oct 16, 2009 Posts: 80 Location: BP

diablojoy · Posted: Tue Mar 23, 2010 11:52 pm Post subject:

very

rob thankyou will try this one out when i get a chance

Luka · Joined: Jun 29, 2007 Posts: 997 Location: Melb.

just a tip to all
if your going to use toner transfer to etch the pcb
you need to reverse the layout

macumbista · Posted: Wed Aug 22, 2012 5:16 am Post subject:

Since the SSM2164 is obsolete and Small Bear is out of them, the option is either to go with expensive and possibly risky EBay sellers, or to try the CoolAudio V2164D from Small Bear. Has anyone used this replacement chip? Is it a drop-in replacement in this situation?

Rob · Posted: Wed Aug 22, 2012 11:08 am Post subject:

The V2164 from Coolaudio seems to be a safe drop in replacement for the SSM2164.
Though to me it is a bit getting used to the idea that in the future there may actually be a Behringer part in the Benjolin...

/R

macumbista · Posted: Fri Aug 31, 2012 6:06 am Post subject:

I found an error in the PCB overlay. The pads for OSC1 CV are swapped in regards to input and ground. Input is on the left side and ground is on the right. Take care!