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Hello, I'm Steve, from Coventry in the UK. I'm currently half-way through building my x0xb0x, after having never built anything like this before. I've finished the bloody thing! Hooray, x0x 445 is go. Took me about a week to get it all done.

It's completely as stock at the moment, with just the crucial 733p transistors in SIP sockets and all the ICs in sockets, but I've got some mods planned.

Hugely glaring mistakes that I made

In my defence, I'd say it was the first time I'd ever really built anything of this size. I'll make a note of these in the Fabrication sections as well, but here's a quick list of the daft errors I made:

  • 2K30AO / AY transistors transposed. In the fab manual, the text says rather airily "2SK30 JFET, 2SK30AO sub-type if there is one" for the VCO, and next to it is the picture of the AY type. Yeah, it's my fault, but I can see why I messed up here
  • 733P transistors in Q3 and Q4 rather than the 536Fs. I was confused by the stars. Really I am easily confused.
  • Q5 the wrong way round. Meant that the mode select knob didn't do anything, and the LEDs above the black notes did nuffink.
  • An electrolytic in the filter - wrong way round. I am a fool.

If I had to give someone one piece of advice for building the x0xb0x, apart from "go slowly", I'd say check your polarity, both as you go along and again at the end before you jumper it together.

Building in the UK

Being in the UK, it's expensive to get components from the usual US suppliers (well, Mouser) mentioned in the Ladyada forums.

I bought most of my stuff from Maplin. They've got stores all over the UK, and you can generally just walk in and get the components you need. They might look a bit confused, but they will get there in the end.

They didn't seem to carry any SIP sockets at the store I visited, so I bought a load of DIP sockets and just chopped them up, which seems to work, but I don't trust them not to work themselves loose. I'll probably put a dab of glue or something just to hold them fast.

As far as I can tell they don't carry things like the 733ap transistors needed for that special 303 sound. I thought a supplier near me had them in stock, but it turns out they're just middlemen for some companies in the US, and they wouldn't deal with little old me anyway. Not for 10 transistors, at any rate. Any suggestions on this, beyond buying and testing a load of 733p transistors, are welcome.

The power supply that came with the x0xb0x obviously had the US-style two prong plug, so I bought a Binatone 9v AC 300mA psu from a car boot sale. Looked like it had originally been used on a phone, and it seems to work fine.

Planned mods

  • Precision tuning mod. The 5.33v, width, tuning, and filter trimmers are hard to get to when it's all put together, so I'd like to get some trimmers accessible from the outside.
  • Molex connectors for jumpers.
  • VCF mod
  • Power supply mod. I'm intrigued to see if actually has an effect.
  • Gate on. Sounds like a good performance control.
  • Env mod. x2, let's not go mad
  • Resonance boost - maybe, it's quite good now.
  • Overdrive. As long as it's not too complicated, my brain can't take it

Also Chairman Meow's modded firmware (with the "save as" into another pattern functionality - essentially a copy and paste for patterns) sounds like a winner too.


I'm on the Ladyada forums as equaliser. I'd include my email address, but damn those nasty spam bot.


thats for all yoru contributions to the wiki so far. Awesome. :) – Jonnay

/home/ladyada/public_html/wiki/data/pages/x0x/users/equaliser.txt · Last modified: 2016/01/28 18:05 (external edit)