808 Kick Drum [PCB]

jmejia · Joined: Mar 12, 2009 Posts: 114 Location: portland

I posted this on Muff as well - so apologies for any cross forum redundancies, but..

I have a bunch of PCBs of final rev of my 808 kickdrum layout. It's basically the Roland circuit, with some minor changes to the trigger input (based on Eric Archer's website), and with the common mods incorporated. (A frequency pot, and the optional decay mod via a resistor value change)

I don't have the BOM online yet - but I'll throw it on my website soon. It's an easy/quick build, nice small pcb.

This is the first PCB I've offered, but it's been tested by a bunch of folks with lots of happy kickin finished projects out there. It's a double sided, very high quality lead-free board - fabbed in the US.

I'm selling them for $25USD - free standard international shipping. (I'll ship a replacement if something is lost or damaged)

You can see from my pics that I have a solid test bed for comparisons. It sounds legit and awesome.

PICS and redundant info: http://www.anestheticaudio.com/?page_id=153

Bipolar power - works great with 2 9volt batteries, or a +/-12 or 15 supply.
I have a Mouser Project/BOM I can share if anyone wants it. (The parts I buy for it come to around $15USD.

PM me if you're interested! (Also more drum modules to come - either the 909BD, or the Simmons SDS3 will be next - both are in some sort of middling stage of development.)

Dougster · Joined: Sep 20, 2005 Posts: 272 Location: Tucson, AZ, USA

Hope you don't mind me asking a few questions... Wink

What is the format of your board? (In other words, what is overall size and the mounting hole geometry?) Have you been able to compare the sound of the BC transistors with the original 2SC versions? And what is the 1n914 for? I'm not familiar with that one...

FWIW, my vote for the next pcb would be the SDS3...

Regards,
Doug

jumunius · Posted: Wed Mar 07, 2012 5:21 pm Post subject:

Dougster · Joined: Sep 20, 2005 Posts: 272 Location: Tucson, AZ, USA

jmejia · Joined: Mar 12, 2009 Posts: 114 Location: portland

Dougster · Joined: Sep 20, 2005 Posts: 272 Location: Tucson, AZ, USA

LektroiD · Posted: Thu Mar 08, 2012 4:25 am Post subject:

One question, does it have a scalable pitch CV input?

sneakthief · Joined: Jul 24, 2006 Posts: 569 Location: Berlin

When I was building my MB-808, I had a little "accident" and broke my maracas, claves & rimshot.

While troubleshooting, I tried swapping the transistors with BC's. As far as I could tell, there wasn't much sonic difference - and certainly not the difference that you find between real TR-808's.

However, I did notice that when placed in the trigger circuit, the BC's are slightly quieter.

I'm really lucky because the local electronic store, segor.de has a whole bunch of Japanese 2SC's and 2SA's. I'm not sure if Segor ships internationally though.

jmejia · Joined: Mar 12, 2009 Posts: 114 Location: portland

xpmtl · Joined: Aug 10, 2007 Posts: 162 Location: Brussels, Belgium

richardc64 · Posted: Fri Mar 09, 2012 5:18 am Post subject:

This is silly.

Why is there so much concern over transistors that aren't doing anything special? Most are simple inverters. One is a voltage-variable resistance. The only one that might be critical -- if you're some sort of audio snob -- is the output xistor, Q44.

Get a grip.

sneakthief · Joined: Jul 24, 2006 Posts: 569 Location: Berlin

richardc64 - as I said, everything sounded pretty similar but BC substitutes created a lower trigger (and also accent) signal. That's pretty significant in my books.

If you're pinging a Bridged T-network with a trigger and the ping level is lower, then the tonality of the kick will certainly be affected. This isn't simply a matter of volume: http://www.soundonsound.com/sos/Feb02/articles/synthsecrets0202.asp

In any case, this was my experience and the results may vary depending on the rest of the components and their respective tolerances.

jumunius · Posted: Fri Mar 09, 2012 12:14 pm Post subject:

infindebula · Joined: Sep 29, 2011 Posts: 29 Location: Canada

Very nice looking board! Crayola should take note of this new phenomenon and bring out a "LAEN VIOLET" crayon.

I vote for SDS-3 next.

So ... I'll order up one of these boards from you, probably on Thursday (my payday). In the meantime I think you should consider posting your mouser BOM to this thread.

strategy · Joined: Jan 03, 2009 Posts: 87 Location: portland, oregon

I just built jmejia's project, great fun and CHEAP way to an 808 kick drum! Just waiting for some of the enclosure elements so I can finish that part of it.

Strategy

jmejia · Joined: Mar 12, 2009 Posts: 114 Location: portland

infindebula · Joined: Sep 29, 2011 Posts: 29 Location: Canada

hehehe no... not a member of PDX, but I've had a few boards made by Laen. Such a nice and helpful guy who makes small runs of great quality boards for dirt cheap. They're turning up all over the synth DIY community.

I designed this oddball circular MIDIbox 808-based sequencer last year and had Laen make the boards. The firmware will send MIDI notes and/or analog triggers. All I need now are some cool analog drum voices!

http://www.youtube.com/watch?v=QHNgT8ISTMI

Anyway, yes, I'll take a board if you've still got 'em ... email to follow shortly.

>>EDIT: Thanks for the Mouser BOM, but the link doesn't work. For those who have trouble, here is the access ID:

950b04d9fc

ian-s · Posted: Fri Mar 16, 2012 4:36 pm Post subject:

LektroiD · Posted: Fri Mar 16, 2012 6:42 pm Post subject:

infindebula · Joined: Sep 29, 2011 Posts: 29 Location: Canada

[quote="LektroiD"]

jmejia · Joined: Mar 12, 2009 Posts: 114 Location: portland

Woops sorry about the link typo guys. Somehow a space snuck in there! This should work for you:
http://www.mouser.com:80/ProjectManager/ProjectDetail.aspx?AccessID=950b04d9fc

And I can certainly post a more generic bom if you like.. though the mouser bom is maybe more useful since you can look up pin spacings, etc if you like!

infindebula · Joined: Sep 29, 2011 Posts: 29 Location: Canada

I decided to make an easily-readable BOM for my own reference, so I could quickly compare it to my own stock. I made a quick Macro to convert the Mouser table into a reasonably tidy spreadsheet. On the positive, I don't think I need to order anything!

I'm sharing it here for anyone who would like to look at it. Here it is as a CSV.

CSV can be imported into Excel / Google Docs / OpenOffice as a spreadsheet, or you can look at it as a text file. The prices are from the Mouser site in Canadian dollars. Note that one of the caps as specified is no longer available (marked "NLA") but is an easy sub (it's a 0.1 uF ceramic).

808bdbom.csv

Description:

Download (listen)

Filename:

808bdbom.csv

Filesize:

3.74 KB

Downloaded:

517 Time(s)

infindebula · Joined: Sep 29, 2011 Posts: 29 Location: Canada

Got my board! Good job, Mr. Mejia, this thing is smaller than the pictures would suggest.

infindebula · Joined: Sep 29, 2011 Posts: 29 Location: Canada

OK, I've been populating this board as I find spare time. I decided (because of this thread) to use some 2SA733 and 2SC945 transistors instead of the BC transistors on the BOM.

(For those doing this, don't forget that the BC transistors are pinned C-B-E, while the Japanese 2SA/2SC transistors are E-C-B)

Now I'm just wondering:

The device calls for a pair of 5.9K resistors, which I don't have any of. No problem, I could get some - but I don't see 5.9K resistors on the original TR-808 bass drum schematic! Any explanation?

Also: Do I understand correctly that the only bass drum decay mod that's present here is the 42.2 K resistor? Is there anything else that is part of this circuit making up the decay mod? I was contemplating switching here between 42.2K and 47K (the original) - should I bother?

Thanks

jmejia · Joined: Mar 12, 2009 Posts: 114 Location: portland

Thanks for putting that spreadsheet together! I'll point others to it as needed!

a 47k resistor instead of 42.2k will give your circuit the factory decay. 42.2k extends the decay - to a point which should be more in line with the common decay mods that were/are done to a tr-808. I based this mod off of Robin Whittle's info here: http://machines.hyperreal.org/manufacturers/Roland/TR-808/mods/808.kick.decay.and.tuning.txt

Instead of putting a resistor in parallel I just change the value of the one.

I can't remember why I used a 5.9k resistor.. the original schematic calls for a 6.8k resistor in the same location. I imagine either would work fine... maybe any value in between? I don't know what the function of that resistor is.. it's R173 on the factory schematic.. maybe someone more knowledgeable can enlighten us?