Rakit Drum Synthesizer DIY kit

[Drew Stephenson]

Got one of these at Synthfest at the weekend, thought I'd do a quick build diary here in case people are interested (and in case I get stuck!)


Right, counted everything twice now, time to get on with it...

[garrettendi]

Looking forward to this!

Idiot question, how exactly do you operate it? I saw the SOS review but I'm still unsure. Does it have MIDI in?

[Jumpeyspyder]

It has a piezo built into the enclosure - so you can tap it to trigger it.

It also has a trigger in and CV in sockets

[Drew Stephenson]

What Jumpy says ^^^. I have nothing that generates either CV or trigger outputs so I shall be hitting it. Gently. Unless it doesn't work in which case I might hit it harder.

Heading out now so here's a couple of progress shots:


Chips, transistors, capacitors and LEDs attached.


Legs clipped off the back to give working room. Next up is about 40 resistors so I'll be leaving that to tomorrow.

[garrettendi]

Drew my soon-to-be wife (less than 5 weeks now!) won't be happy with you!

I checked the YouTube video Rakit posted for this and ho-lee cr** this thing is amazing!

I can't solder to save my life but it's a skill I want to learn. Might ask my missus to get it as a Christmas present!

[The Korff]

I can't solder to save my life but it's a skill I want to learn.

It's not too difficult, but well worth learning! The main thing is to equip yourself properly — decent iron, solder sucker, wiping sponge, good lighting and patience. Half a day in front of a few YouTube tutorials (and some 'donor' boards and components) and you'll be good to go!

[garrettendi]

Given I have another hobby which is model trains, I think my taking the time to learn soldering is a no-brainer!

[The Elf]

If there's one 'old guy' skill we need to pass on it is soldering. If *I* can do it, ANYONE can!

You will never need to buy another over-priced jack-to-jack cable again...

[Drew Stephenson]

All resistors attached:

Don't worry about not being able to solder, you will be able to after this!

On a serious note, a good iron, a bit of patience, and let capilliary action do the work.

[Drew Stephenson]

You will need quite a lot of solder though...


Finished article? Maybe, not sure I've got the right leads to test it!

[garrettendi]

Looks great! Very neat and tidy. Does it not just plain TS cables on the output jack?

I've also seen the Baby 8 Step that can be used as a sequencer for this

[James Perrett]

On a serious note, a good iron, a bit of patience, and let capilliary action do the work.

I'd just like to emphasise the need for a good iron. When I started everyone said go for a basic 25W iron - they're OK for occasional use but can easily run out of heat if you try to solder a large connector. I'd say a 40-60W temperature controlled iron is much better - I've had my current temperature controlled iron for over 30 years.

[BigRedX]

Looking at the controls, this is for "pitched" drum sounds only? No noise for "snare" or "claps".

I used to have a great (but very unreliable) noise-based percussion synth, and IIRC the design was originally published in E&MM magazine. It had a very sharpe attack and a real "crack" to the sound that I haven't heard from any other percussion module since.

Anyone know what a modern equivalent would be?

[Drew Stephenson]

Looks great! Very neat and tidy. Does it not just plain TS cables on the output jack?

I've also seen the Baby 8 Step that can be used as a sequencer for this

Yep, but it's mini-jack and, it turns out, the only TS cables I have in the house are 1/4".

I am not getting good noises out of it at the moment, might be because of the adaptor I'm using but I'm not convinced.
I've dropped them a line so we shall see what comes back.

[garrettendi]

Moron question here (as per usual) but have you tried it with a plain 9v battery?

[Drew Stephenson]

Yep, it is plugged in...
(I know that's not what you meant, yes i'm using a battery, tried two in fact just in case one had flattened).
I'm in touch with the man at Rakits - I think I've probably boogered something up somewhere.

[garrettendi]

I apologise unreservedly for my presumption!

[Drew Stephenson]

Not at all, by adaptor in the earlier post I meant the audio-plug adaptor not the power supply, I can see how that could have been confused.

[garrettendi]

Yeah I thought you might have meant you were powering it from a wall wart which made no sense as it has a battery clip thingy

[Drew Stephenson]

Nope, it's a tip +ve so none of my guitar pedal adaptors would have worked.

[MarkOne]

If there's one 'old guy' skill we need to pass on it is soldering. If *I* can do it, ANYONE can!

You will never need to buy another over-priced jack-to-jack cable again...

As a gentleman of a certain age, my close-focus ability is getting worse. (like everybody's - As we age the lens in our eye gets stiffer and the muscles that focus it cant pull it to the right shape to close focus)

For years as a youff I made my living sat at a bench with a soldering iron but these days soldering up an XLR is just as likely to end up with burned fingers and dry joints.

Until I bought one of these:

https://www.amazon.co.uk/gp/product/B01882K0OC/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1

It's transformed things for me... I have just soldered up 8 XLR panel sockets and 8 plugs to add mic inputs to the front of my rack from the rear of the Focusrite Liquid 56. How did live without one of these? Ever?

[Wonks]

That's great. I've just ordered one for myself!

[Hugh Robjohns]

I think I've probably boogered something up somewhere.

Leave it for a couple of days, just so you come back to it afresh, then under a good light (or on a sunny day), check the solder side of the board carefully, looking for dry joints, solder hairs, shorts and that kind of thing. Use a magnifying glass if necessary.

If you're happy that everything is good there, look at the component side of the board, and check first for all those standing resistors touching and shorting each other. Then check all the diodes and transistors are in the right way around, then the polarised capacitors, and finally the ICs. Also make sure all the IC legs go through the holes and you haven't got one folded back under the chip.

If there's nothing obvious there, you'll need to start with a voltmeter and 'scope to check power rails and the signal generation and through the signal path.

H

[Martin Walker]

I'd say a 40-60W temperature controlled iron is much better - I've had my current temperature controlled iron for over 30 years.

I've had mine for around 40 years now, and it's still going strong

Martin

[Drew Stephenson]

Cheers Hugh, Darren at Rakits has given me some pointers to check but I've also got doubts about my 3.5mm > 1/4" adaptor so I should have another of those turning up tomorrow.

And the magnifier stand looks bang on MarkOne - I've got one of those little helping-hands things but the lens isn't good enough to actually help.