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Eric Archer TR808 kick bass veroboard clone issues
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dcjim



Joined: Nov 03, 2012
Posts: 4
Location: brooklyn

PostPosted: Tue Jul 28, 2015 6:38 am    Post subject: Eric Archer TR808 kick bass veroboard clone issues
Subject description: Voice and delay work though possibly quiet and with loud click on trigger, tone and level don't
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Hello all

Just finished a TR808 kick clone on veroboard using Eric Archer's layout

http://www.ericarcher.net/wp-content/uploads/2014/07/tr-808-bass-drum-diy-project.pdf

I've never done a veroboard build before (as in dot rather than strip layout or PCB) and it was challenging but happily the basic voice and delay work at least so I imagine my problems are just teething troubles

Here are my issues

1) I think the voice is quiet. I'm testing with a Roland Microcube through the line channel and the amp is at half volume giving a full but not deafening level. I imagine it should be very loud at half volume, they're quite beefy those little Roland amps

2) When I trigger the voice it is proceeded by a loud click, and not a musical one at that. However the voice does sometimes trigger without this. I'm not entirely sure of the circumstances. Happens when I fiddle with the trigger arrangement maybe, so no click, just a nice round boom. I am triggering as follows: with 'accent' tied to +12v I'm touching 'trigger' against the +12v rail. I wondered if it was just the clumsiness of crocodile clips and bits of wire so I tried wiring in a momentary push switch. Didn't help. I am using the diode-resistor-cap network Eric suggests between the trigger input and the trigger circuit. I intend to trigger the unit from an Arduino which would be only a +5v trigger but I don't have a spare ATMega right now to test

3) The tone pot doesn't work. I have checked connections and continuity around this part of the circuit. I assume the tone pot should make a noticeable difference? I'm using a 10k pot as per the original schematics and Eric's notes

4) The volume pot doesn't work. I have checked connections and continuity around this part of the circuit. I'm using a 10k pot as per Eric's notes but NOT as per original schematics - the value of the level pot is not specified but the parts list names 500k, 10k and 100k in use. The schematic identifies delay as 500k and tone as 10k so by deduction the unidentified level pot should perhaps be 100k?

Now ... obviously I need to give the whole thing a thorough check but any obvious pointers before I do would be helpful to narrow down the search and any expected voltage readings would be good. I have measured the TL072 and it's getting +12v and -12v where it should.

Hopefully it's something simple and so far it sounds great!

Thanks
Jim
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elmegil



Joined: Mar 20, 2012
Posts: 1676
Location: Chicago
Audio files: 14

PostPosted: Tue Jul 28, 2015 3:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

Try tying accent and trigger together instead of just tying accent high.

There's an older stripboard discussion of the bass drum circuit here somewhere that had a lot of discussion around the click, that might be helpful to read.

Can you post photos of your work? That might make it possible to spot errors that you're missing after looking at it over and over again (been there, done that, felt stupid when someone pointed out the problem, but it got fixed!)
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