made a cake

Something like a Yorkshire tea loaf – about half a kilogram of fruit soaked over-night in tea, one egg, brown sugar, some bicarb, a bit of butter, plain flour, and some brandy that I randomly threw in ‘cos it’s Christmas.

And it turned out alright! Usually everything I make turns out flat, but this one wasn’t too bad. I suspect because it has a vast amount of fruit propping it up.

Apart from that, mostly I’ve been frenziedly drawing circuit boards to order from China to try and beat the UK customs changes come January 1st.

To explain a bit – at the moment there’s an arrangement called Low Value Consignment Relief, which means that any goods imported under the value of £15 don’t attract any VAT charges, which most of my PCB orders squeeze into.

Come January 1st, HMRC are binning this arrangement and have stated that the seller will be responsible for collecting the VAT, so that makes things less fun.

There were loads of things I was going to make (a Kobol clone with 3310s subbing in for the rare SSM2050s! an MS10! the DAC/gate output board for my imagined future MC-4 ripoff that I’ve been going on about for years) but mostly I’ve been churning out boring old clones of 100m boards. Yep, even the overly-complicated looking portamento module.

Other than that, the silliest is probably this board intended for my lovely Juno-6, which is basically a copy of the DCB interface in the Juno-60. Yeah! DCB!

At this point you’re understandably wondering why would anyone do this in this day and age, and I’d say, fair enough, it’s a bit daft.

Mostly it’s because I was too cheap to invest in a MIDI interface for this thing, but also because it’s more fun trying to work out how to get it going, even though it’ll be a bit more convoluted.

I’ve long missed the boat on buying an MSQ-700 for super-cheap, and OP-8/OP-8m are super-rare, so I guess I’ll end up writing a MIDI-to-DCB and CV/gate-to-DCB thing for an Arduino.

I’m sure it’d do-able to go from the Arduino to the Juno-6 direct, but I’m slightly nervy about knackering the MPU inside the Juno.

I opened the Juno up before I ordered the board just to see how much room I’ve got. Turns out I could easily fit some sandwiches and a banana in there as well as the board.

Loads of room. Probably not going to do the sandwich-box mod this time round.

Also there’s a suspiciously DCB-port-shaped hole covered by a plate at the back that will hopefully mean I can avoid any drilling, because you know that’s a bad idea. Potential Christmas fun to be had anyway.

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Roland System 700 716 mixer clone

Roland System 700 716 mixer clone front panel

It looks good, but it’s not very good.

Don’t bother trying to make a PCB of this one, you could stripboard it in half-an-hour or less, I’d imagine. As on the original it’s tacked onto the end of the sample and hold PCB.

Notice no screws for the slide potentiometers. The slide potentiometers are bunged on a bit of veroboard (at a jaunty angle to the strips), with acrylic spacers screwed to the board and glued to the front panel using JBWeld, which is as shit as it sounds.

I had a couple of failures before I got it to stick. I’ve also tried using some special/horrific acrylic cement, which totally failed. There would be a photo of the back of it here but it’s just embarrassing.

Since then I’ve reverted to making PCBs for the slide pots, with screws in the middle of the pot throw, which works much better, and helps reinforce the front panel.


Roland System 700 707 amplifier/integrator/envelope follower clone

Roland System 700 707 preamp clone

Argh, PCB is dated Dec 2015, it’s been a while… three simple circuits for the price of one on this board, which you should easily be able to stripboard. Here’s my version of the schematic – R3 has no value specified on the schematic, but the board overview in the service manual (and Yves Usson’s photo of the board) has it as 1K.

Here’s a video demo of the envelope follower, using the drum loop from “being boiled” as the followed signal, with the env follower output going to the System 100 envelope input socket. See how the red light goes on and off!

I’ve never found much use for envelope followers but maybe I’m not just creative enough with them. If the signal volume on the input gets boosted enough it bleeds through to the output, but at a normal sort of level there’s no problem.

The integrator works fine, but with the specified values when using it as a CV slew for a VCO it needs a fine touch to dial in the right amount. I used a CA3140 instead of the specified (ICL?) 8007.

The amplifier does the amplification thing as you might expect, and could be really useful (although I regret not putting a switch on the panel for DC coupling).

Also made a mistake on the panel – it should be E.F. on the switched input for the integrator. Had to correct the spelling of “integrater” too, couldn’t let that stand.

Roland System 700 707 clone module

…and round the back – aluminium bent up at the edges to try and stiffen the panel, though it’s not so bad at this smaller size.

Roland System 700 707 clone round the back

I’ve got better at arranging the board-to-panel wires since I did this, it looks a bit higgledy-piggledy.

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