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TTSH, spring reverb mods

Alritey let’s continue details of my TTSH with two spring reverb modifications. If you’re looking for other build / modification posts on the project, please visit the main page right here.

Opamp Upgrade

This modification is done to improve the noise floor of spring reverb, by upgrading the opamp in the output amplifier circuit (recovery amp). The mod was suggested by user Nordcore at Muffwiggler forum and looks like this:

TTSH reverb driver mod schematic by Nordcore.

TTSH reverb driver mod schematic by Nordcore.

I sort of failed with adding this mod in that I didn’t bother taking before and after audio recordings: So it’s rather impossible to say how much the noise floor was effectively reduced. On my TTSH the circuit was noisy before and is noisy after.. Yet I’d still say it’s better.

On to the build..:

The reverb driver circuit in its stock config

The reverb driver circuit in its stock config

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ProtoTypo PT2 – GRAM

One of the first modules I bought for this Eurorack 84HP utility skiff I’m putting together I was putting together to go with my TTSH, was a DIY kit of Ljunggren Audio‘s Roll Your Own (RYO) Penta sequencer. Upon building it I was delighted to notice that the PCB had marked solder locations on it, from which individual step gate output signals and a hold input (to pause the sequencer) can be sourced. Very modding friendly, just how I like it!

And that’s how Ljunggren Audio meant it too; they host a Penta modification page and also the Penta product thread at Muffwiggler forum has user ‘Stabilt’ (whom I assume to be among people behind RYO) suggesting a basic combined gate output circuit. I decided to use these two sources as a starting point for a gate output expander of my own, aka ProtoTypo PT2.

Basic gate output circuit by Stabilt @ Muffwiggler

Basic gate output circuit by Stabilt @ Muffwiggler

If you’re looking for download links to pdf schematics, they’re at the end of this post. Let’s try it this way for a change, because why not ;)

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TTSH, VCO sync mod

Heyyy I’m once again catching up my TTSH build documentation with yet another modification. Yayyyy!

This mod is based on Altitude909’s add-on board, which adds a Arp Odyssey style hard sync between oscillators. The build has been well-documented in this thread @ Muffwiggler, so please check there if you’re planning to add one to your TTSH (Hi Vlado!). I did a slightly alternate version for myself and on this post we’ll look at that instead! But first, here’s a video by Stephen Drake on what hard synced oscillators sound..:

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ProtoTypo PT1 – WOTI

Yay it’s a firstie, my soft landing to the world of Eurorack: A DIY version of Xaoc DevicesPOTI expander for Batumi (a quad LFO module). “What is ProtoTypo?” you might wonder? Then check my previous post.

The Build

Simple one yeah: three toggle switches mounted on a 3HP euro panel and connected to a 6-pin ribbon cable. Haven’t done anything this straightforward in ages, but still it’s a good crash course into eurorack mechanical specs and the like. As for Poti, there’s a good set of pictures of it at the Schneidersladen webshop, from which it’s easy to interpret wire connections.

Heatshrink stress relief for the cable solder joint

Heatshrink stress relief for the cable solder joint

Here’s a good generic build tip: As switches are connected to Batumi using flat cable (see photo below), it’s very much recommended to add some heat shrink tubing to cover solder joints. This is because flat cable is thin and flexible, and soldering any of its wires creates a sharp stiff-to-flexible transition point. If the cable is moved or flexed repeatedly then the wires will easily break off at this spot. So adding heat shrink over the joint will distribute the weight of cable to a wider area and thus lessen the risk of broken wires.

Cabling overview

Cabling overview

...and how it connects to Batumi.

…and how it connects to Batumi.

I have quite a neat leftover piece of this 4cm thick oak kitchen tabletop (from Ikea), so I figured I might just as well use some for building Euro panels. After all 4cm = 8HP (in Euro spec 1HP = 5.08mm / 1/5″) so it’s a perfect match size-wise. Once the oak is cut to 4HP slices 2mm thick, it’s very easy to trim down to required width. Simply running a sharp carpet knife along a ruler repeatedly will eventually create a straight groove deep enough to slice the thin wood panel in half. Minimal sanding required, yay \o/

So with panel cut & drilled, I treated it with white wood stain and then designed and printed a panel decal to a leftover Lazertran sheet (from my x0xb0x build btw!).

Now I have no clue if ‘Poti’ means anything, but I’m a big fan of abbreviations so I chose to call this build ‘WOTI’. That’s short for Wooden Output Toggle Interface. You know, oak panel and all! ;)

The finished module, fancy innit?!

The finished module, fancy innit?!

So there it is, ProtoTypo PT1. Of course I added it to Modulargrid.net too :). You can download the panel decal here for your own build. Poti manual is available from Xaoc Devices’ website.

The design of this module could be squeezed to 2HP too, provided that the switches were of sub-miniature type and/or oriented vertically. However I wanted a design to match Poti, so it was 3HP for me.

That’s that. Next up a ProtoTypo build with even some electronics in it!

TTSH, Gate Booster mod

If you’re all new into how analog synthesizers can be controlled, you may first want to take a look at this Wiki article on CV/Gate for some jargon busting. Other than that, let’s dive right in.

Among the first electronics mod I wanted to add to my TTSH was the Gate Booster. To fully open the ADSR envelope generator of TTSH a +10VDC gate needs to be applied, thus in it’s stock config the envelope can’t be fired properly by using eg. any external gear that outputs a +5V gate. Add to the common CV/Gate specs, the TTSH envelope generator also needs a trigger signal (very short pulse) to work properly. This can be used to restart the envelope without disabling gate signal.

So what the Gate Booster does is, it converts low voltage level gate signals to higher voltage and generates the trigger signal from the gate input. The particular circuit board I bought for myself is this modified version (sold by Oshpark) with a socket for a Midimplant MIDI-to-CV/Gate converter board. Having MIDI (keyboard) input just made so much more sense than eg. building a CV keyboard like the Arp 3620.

Gate Booster board all populated.

Gate Booster board all populated..

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