@paul Got my PCBs today. Very quick! Haven't ordered any of the components yet, so it's going to be a while before I'm up and running. Still haven't found a non-US supplier for the illuminated switches.
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[Need Help with SPI] Euxoloti for axoloti (Eurorack Module)
toneburst
#92
@paul the MLCC caps https://www.mouser.co.uk/Search/ProductDetail.aspx?R=C322C102F5G5TAvirtualkey64600000virtualkey80-C322C102F5G are pretty expensive, I guess because of the 1% tolerance. Could a cheaper alternative be used instead, or is the low tolerance required?
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toneburst
#93
Ordered everything from DigiKey in the end. They had everything except the 14-way DIP socket (think I have 2, anyway) and MCP6004-I/P. I went with the MCP6004-E/P-ND instead, which seemed to have an identical spec. (apart from operating-temperature), as far as I could see. Hope this works.
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gloom_and_glare
#94
As long as it's a NP0/C0G type, it's not entirely evident why they would have to cost that much or be 1%. I'd guess it's because the Mutable Instruments BOMs specify ≤ 2%? But what's the rationale?
toneburst
#95
Dunno. I ordered them, anyway. Still saved, as they bumped my order over the £50 free-shipping threshold, so I'm not complaining, really. I'll bear that in mind next time, though. I have a feeling I may be building a couple of these. I'll reserve judgement until I've built and tested this one, but the Axoloti platform seems to offer the best solution for a relatively powerful generic/programmable Euro module, at the moment, at least.
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paul
#96
@toneburst
sorry for late answering. I don't know any EU source for the pushbutton. I know, that digikey sells them, too. Can you upload your digikey shopping cart? It will be helpful for other people.
@gloom_and_glare and @toneburst
The 1nF 1% capacitors are very expensive and I haven't checked every alternatives at mouser or digikey. I can't give a competent explanation about why better as 2%.
The used circuit is a First-Order inverting low pass filter.
(orginal source/page 16-3)
So what have read is, that real op amps produce more noise above 10kHz (german wikipedia) and supply voltage drops can influence the output voltage depending of the gained voltages. So I have to check the PSRR and CMRR of the used mcp6004:
My max cutoff frequency should be 10kHz or less…If, I'm using a capacitor with more tolerance it will be possible to exceed the 10kHz max freq..or I have to put less cutoff frequency and use a capacitor with higher tolerance.
gloom_and_glare
#97
Sure, that I have seen in the schematic. But I'm still not convinced. (Though I might be missing something).
So, in an ideal world the cut-off frequency (-3dB) would be at ~4823 Hz, right? Then, if I used a cheaper, say, 5% NP0 capacitor, I'll end up somewhere in between 4593Hz - 5078Hz, so things will be off a few hundred Hertz, of course, but that doesn't sound too scary. With 2x MCP3208s, audio rates will be mostly out, anyways.
But maybe there's cheaper options even at 1%. I haven't looked it up. It may be a through hole thing ? Even if you just got a 100 of the 0603 ones, ie the 1% ones spec'd by the Mutable Instruments BOMs, they'd cost a mere 0,038 €
(And sorry for pestering, I don't mean to be smart. It's merely in the interest of saving money).
paul
#98
no problem, you're right and I'm glad that here are some others thinking about good solutions.
I don't know if it will be make a huge different in real world by using 1%,2% or 5% capacitors. My technical expertise is limit and this project is my first bigger project in this kind of eurorack module. So to reduce and avoid problems and prototyping costs, I'm trusting in work and expertise of oliver from mutable instruments.
This 2% capacitor is a bit cheaper (0,77€).
toneburst
#99
I've made up quite a lot of synthDIY projects over the past few years (though to my shame, I still know next to nothing about electronics), and it's almost always the capacitors that are a pig to get hold of, especially here in the UK.
When self-sourcing, they're always the things I struggle to get hold of from local sources. On this occasion, I just went with DigiKey, as they also had the illuminated switches (an in stock, unlike Mouser).
Here's my DigiKey shared basket:
http://www.digikey.co.uk/short/33tzhz
I actually bought the pots from them, too. Rather than going for the round-shaft Alpha ones from Thonk, I thought I'd try these Panasonic D-Shaft parts, as I'd heard good things about them on Muffwigglers. Haven't soldered them up yet (parts only arrived today), but I have to say, they feel really nice. Lovely and smooth to turn, but not too stiff.
Things you will have to source yourself:
* I'm still not sure if I've got all the required headers. I think I may be missing some
* 14-way IC sockets. They didn't have these, unfortunately, so they're also not in the basket
* Minijack sockets. Thonk probably still best for these
* Knobs. Thonk used to sell lovely Rogan (Mutable Instruments-Style) knobs, but they're sold out, sadly. I can recommend these Cliff parts. They're cheap, but have a nice feel to them (and they're available in a range of colours, too)
I think everything else is there, however (and the majority of the components are identical parts to the ones on the Mouser BOM).
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paul
#100
some interesting notes about the different VDD outputs of Axoloti from Johannes at the official pinout thread.
cool and thanks, I didn't know the Panasonic pots.
The Rogan knobs are very popular. I think thonk restock them last mid January.
I will post later a detailed list with quantity etc. ok?
toneburst
#101
Can I request that the next revision of the PCBs have part values printed on them, rather than just names?
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toneburst
#102
Also, just noticed the pots are in different orientations, which means I can't use the Panasonic pots, or the pointers on the knobs will point in the wrong directions.
Might have been a good idea to make a note of that in the BOM or, preferably put all the pots the same way round, so people can use D-Shaft pots if they want to. It's not a dense board, wouldn't be difficult to orient them all like the top row, I don't think.
I'll order some Alpha pots from Thonk.
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paul
#103
I think, part values will be no problem.
hups, yes I have't thought about it, I will add it to the BOM. Sorry!!!
the pots are different in orientation because of a simpler trace routing.
edit @toneburst: I think, you have insufficient ordered female headers. You forgot the female headers for your euxoloti <-> axoloti connection. check the Readme.md at github
edit 2 @toneburst: If you don't get them around you for less shipping cost, I can buy them at a local store (conrad). shipping should be max. 0.90€ to you…
toneburst
#104
@paul if you could get me the extra headers, that would be cool. I can get them locally, but shipping (even within UK) is prohibitive on small orders.
I was confused about the headers because there were some on the BOM, so thought you'd added them after you wrote the note. Should have double-checked.
I'll do a new shared basket, with extra headers added.
Also, I notice there's only 2 screws and spacers in the BOM. Is this enough?
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paul
#105
@toneburst The headers for euxo <-> axo connection is a bit tricky because there are maybe some axoloti owners, who soldered femal headers at his/her axoloti core…
I will check, how much the female headers cost and send you an email.
paul
#107
yes, they will work.
so, you need for axo core:
1x37 male header (main pinout PA PB etc)
1x5 male header (Power, VBUS GND)
and for euxo core:
1x36 female header (main pinout PA PB etc)
1x5 male header (Power, VBUS GND)
You can cut the 1x36 female to 1x31 and 1x4 (1trash) like following pic (female headers must be on the backside)
place without female headers are GND connections which will be done by other gnd pins…and don't forget the mods
edit @toneburst :
here is a overview fe-/male header placements (red = female headers; green = male headers):
toneburst
#108
I think I have enough male headers. Will need the female ones though. That 10-pack of female headers I linked to above should do the job though, no?
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toneburst
#109
Incidentally, I picked up my Whitewall panel this morning. It looks really nice! Unfortunately, though, mine had a fibre or hair under the ink on the top surface. I've emailed them, and hope they will either refund me, or send a replacement free. Or both, would be nice...
Any tips on drilling the holes? Is it possible/advisable to attempt it with a hand-drill? If not, I may be able to get access to a pillar drill at work.
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paul
#110
there is nothing selected at the ebay link. But if you pick up the right qty. they will do the job.
I don't have any experience with hand drilling the panels, but if you lock the panel tide so it holds still, it shouldn't be a big challenge.
I drilled the hole with a pillar drill in 3 main steps. first step I used a 3mm drill and second step the exact size for each thing (pot, jacks etc.) . third and last step the new holes were rasp withe a "kegelbohrer": .
The panel is really simple to drill. which typ of panel you have selected (HD metal or Alu-Dibond)?