Build story + low volume hi-hat/maraca?

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Build story + low volume hi-hat/maraca?

Postby halides » Aug 24th, '16, 14:23

Hi all!

Long time soldering iron warrior, though I don't have that many projects under my belt, maybe 30-40 hours of keeping the iron hot in total over the past 20 years. Was looking for an 808 for about a year, was aware of the Yocto but it had been out of print for a while back then. Bought the PCB's in May immediately when they came available again. Didn't have time to build until my holiday in August.

Got components from Mouser a week ago on Tuesday and spent a couple of long days (10h) and a few shorter ones on the project. Finished the project late at night on Monday, in a week, estimating 40hours of build (yeah, I think I more than doubled my time with the soldering iron). Had to do it quick as I don't have a proper bench, thus I took over the kitchen table. Accidentally ordered a 15VDC adaptor, couldn't find -15V anywhere ;-) Luckily my x0xb0x had a variable AC/AC so I could continue with the project right away (zero sanely priced 15VAC adaptors in stock at major retailers in Finland at that time). Mouser screwed up the order, was missing a few caps, one for the PSU which I promptly parallelized together from smaller ones and a bunch of films which I bought from a local shop. Got the caps from Mouser on Monday, just in time to switch over from the temporary PSU cap before the first powerup.

Had four piles of bags for resistors (<1kohm, <10k, <100k, the rest) and three for caps (films in two piles, one pile for electrolytics), rest of the stuff around the table. Thinking back, I should've gotten a piece of styrofoam and stuck the resistors and caps into that, sorted by resistance/capacitance. Shuffling about with the bags added at least 2 hours into the build. Didn't use extra IC-sockets, only for the ATmega and the EEPROM. Soldering iron set at 330degC, which was fast enough and hopefully not too hot to screw anything up. I usually laid quite a lot of components in one go, 15-20 usually, sometimes maybe up to 30, but I was really careful when soldering tight spots and un-bent a lot of leads after the first one was soldered.

This was enough for me to get it all running succesfully on the first power-up after inserting the digital parts, which was AMAZING as I didn't believe for a second that it would actually happen. Well, maybe I believed that for a total of 15 seconds during the build but then came to my senses, also didn't wanna jinx it :-)

Waiting for my enclosure from Ericasynths, who just informed me they got my order but decided to go on holiday. So I'll be waiting for that for a while..

On to my questions!

1. My closed hihat is quite low on volume. I also noticed my maraca is very quiet also and the toms are missing a bit of noise, so am going to try if viewtopic.php?f=16&t=830 would help. Any other ideas? Also this leads into my question number...

2. I didn't check my pots I received with the PCBs before starting the build, just went through the bag and found the correct values when needed. Thus I found myself in a situation in the Master-section that the pot that was supposed to be 50k audio (A503) was actually a 100k audio (A104). And I have no clue if I have messed up at some point as, as far as I can tell, there are no visible markings on the soldered pots anymore. Hell will also freeze over before I start desoldering all of them to check. My question: if the volume pot for the closed hihat is a 50k instead of 100k, could this explain the low volume? I checked the schematic and the pot seems to be in the feedback-loop of the op-amp but that's where my understanding of op-amp circuits ends :-). Desoldering the pots is a total pain in the ass (I desoldered one) so would be nice to know if I actually messed up before I start fixing things that might not be broke :-).

3. I put the 100k pot in the master section. Volume from the main out seems to be ok and looking at the Master schematic the pot seems to be just an adjustable voltage divider, so the value of the pot shouldn't matter. Am I thinking correctly? for the schematics I was looking at, don't know if it's correct.

Thanks for reading and may the Bass be with you!
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