Building the TTSH

 

TTSH Main PCB. Component side

TTSH Analog Synthesizer

  • 3/4 size ‘Clone’ of Arp 2600
  • VCO Sync modification
  • Gatebooster modification
  • Wave Shaper modification to VCO1 & VCO3
  • Component selection modifications

TTSH Main PCB. Hardware side

 

What is the TTSH?

The TTSH is really just a set of printed circuit boards, that you can either build yourself or find someone to build it for you.  Around 2014, a custom synthesizer outfit called “The Human Comparator” (THC) developed the PCBs based on a possible 3/4 scale clone of the Arp 2600. The target audience was the ever growing online synthesizer DIY community original forum posting is here. Aside from forum posts, the only other documentation for building the original TTSH was a set of schematics and the Arp 2600 Service Manual. I believe that there were three versions released by THC over the years before THC stopped making it completely. When I first heard about the TTSH, they were releasing version 3, and I was seriously interested. But by the time I looked into the project, the PCB stock was sold out.

I actually ended up obtaining a couple V2 sets of PCBs from an online forum user back in 2017, and then spent months building them for another person (basically, they paid me to obtain the PCBs, parts, etc and build it). I only built the PCBs and did not add the from panel, or case, so still I never played with the fully completed version. At the time, I was also was getting involved in the LS Arp 2600 project, and had obtained a lot of parts for it. But the LS Arp project too would eventually stop.

note: I do build synths for other musicians or studios, but I do not write about them on my site. This is also rare as I would rather play synthesizers and teach people how to build things themselves, by sharing any information I have.

Last year (2019), Synthcube offered an updated version 4 (through a license agreement with THC) and I jumped at the chance. The version 4 has 99% of the errors fixed from the previous versions, and there is also now an awesome build document courtesy of Tony Flagg, aka ‘FuzzBass’. Additional issues, fixes, etc can be found on both the muffwiggler V4 forum, and the TTSH FaceBook group. The V4 kits come in 4 basic flavours:

  • PCBs Only
  • PCBs & Rare components
  • PCBs, All components and Case
  • Fully built TTSH.

I have ordered many of my synth PCBs from Synthcube, they are highly reliable and have great customer service. Never before however, did I order a complete kit from them. Some of my prior builds like the Deckard’s Dream, Klee sequencer, modular circuits, etc can also be purchased as complete kits (PCBS, Case & Components), but I have always sourced my own components. I have a huge stock of resistors, capacitors and semiconductors so I generally never needed to go with the all in one kits. The TTSH however, has so many different parts, from various suppliers around the world, and import taxes, shipping charges, etc can add a noticeably large amount to the overall costs of any project. Buying all the components at once can save a ton of money, and maintains a single vendor contact if components are faulty, etc. So, if you plan on building this synth, please consider the “All In” component kit from Synthcube. It is not perfect (as discussed later) but it will certainly save money, time and headache.

The one caveat I would state here is that the quality of the PCBs, from a layout and design perspective, are the worst I have ever seen. Pads are too small, vias are in the totally wrong place, traces are run in places they should not. Soldering will be a challenge for some, as components in places are very close to other components, traces, or vias. Components are placed on both sides, some resistors are standing on end. This is not a fault of Synthcube, they are using the original artworks and CAD files from THC. The TTSH started as an unfunded DIY project and all original engineering and design may never have been compensated effectively, so they are what they are, and that is understandable.

Things you will need if you want to build an Arp 2600 or TTSH:

2600 SERVICE MANUAL 1975

Arp 2600 Service Manual 1977

ARP 2600 Patch Book

How close is the TTSH to the real Arp 2600?

The TTSH electrical circuit and user functionality (control panel layout) is identical to the circuits found in the Arp 2600 service manual. It is just laid out, component placement-wise, differently. The table below shows the various differences in layout. It is possible to replace many of the components in this project with identical OEM components, alternate components or even experiment with functional equivalent components. That is why this project is so awesome, as it allows for the builder to easily customize the overall sound and experiment!

Module Description TTSH Location Arp 2600 Location Notes
4012 VCF core module Separate PCB Separate PCB Moog Ladder Filter
4014 Balanced (Ring) Modulator module Main PCB Separate PCB
4015 Sample & Hold module Main PCB Separate PCB
4019 VCA module Main PCB Separate PCB
4020 ADSR module Main PCB Separate PCB
4022 Noise module Main PCB Separate PCB
4027 VCO core module Separate PCB Separate PCB
4072 VCF core module Separate PCB Separate PCB Later model Odyssey type filter
All other circuits Main PCB Split over 5 separate PCBs
power supply +/- 15 VDC switched with 12V wall wart supply 110VAC to +/-15VDC linear

 

Here are the approximate locations of the various Arp modules on the TTSH: (Right click and select “Open in new tab, for a larger image”)

 

The TTSH community also has provided several modifications that can be completed to the TTSH, 5 important ones are:

  • AC coupling on the VCF Input jacks
  • External clock signal to the electronic switch circuit.
  • GateBooster Mod: Allows the envelope in the TTSH to initiate given gate & trigger signals from lower voltage Eurorack systems.
  • VCO Sync mod: Allows VCO2 and/or VCO2 to be synched with VCO1 (or other combinations).
  • Wave shaper mod: Provides sine and saw tooth waves for both VCO1 & VCO3, along with a sub harmonic sawtooth wave from VCO1

How close will the TTSH sound to the real Arp 2600?

  • It can sound as close as good as any Arp 2600 will sound like.
  • It can sound totally different than any Arp 2600
  • It can sound worse, it can sound better.
  • Sound is a relative thing!

What I find funny, are folks on social media either complaining about, or promoting the sound of analog synthesizers they hear on YouTube, FaceBook, Instagram, etc… These platforms are all digital mediums with very degraded audio quality. Nothing I hear on YouTube sounds anything like any of the synths I own and use, particularly analog synths. I also have analog and digital mixers, speakers, monitors, amplifiers which all change the sound. So, comparison is ok for a broad sense of a synth’s sound palette, but you really need to hear it, with all your own gear to get a real sense of the sound. And quite frankly, I doubt 99% of people could really tell the difference between Arp 2600 software and recordings of an Arp 2600 on the internet. Only experts in an Arp 2600 might be able to tell, and only if the Arp is pushed to some of the known limitations with the filter, etc.

“No, really. If I built this is, it useable as an instrument and will it sound good enough, something like an Arp 2600”?

It depends on how it was built, and how much care was taken. I personally think the sound difference is really indistinguishable, But you need to consider your skill set.

  • Do you have the tools?
    1. Knowledge of electronic schematics?
    2. Good soldering iron and skills?
    3. Oscilloscope?
    4. Multimeter?
    5. Decent problem solving or debugging skills?
    6. Transistor test equipment?
    7. Frequency counter?
    8. Waveform generator?

“Is all that stuff really needed”?

No. But having most of them will certainly increases your odds of building an awesome sounding, professional synth. This is not a difficult electronics project from a circuit design point of view. It is however one of the hardest DIY synth projects from a technical building perspective. The poor layout of the PCB, specific selection and matching of components, tight soldering of some parts, (that are hard to re-obtain if you pooch them) and complex debugging if something does not work right.

  • Do you know how to
    1. Match transistor pairs for Vbe?
    2. Select transistors for Hfe?
    3. Match JFets?
    4. Select an Opamp for minimum Input offset voltage?
    5. Think twice, double check and take your time before soldering?

“Do I really have to match transistors and JFets, etc”?

Yes & No. There are people who claim to have built this synth without specifically matching transistors. But I have never, seen any analog synthesizer that was capable of tracking (maintaining scale tune) over 3 or more octaves, without matching. I have built dozens of VCOs an every time I measure transistors for Vbe, even from the same lot, sitting beside each other on the tape, they are normally +/- 4mV different. Most designs should be within +/- 2mV. I select my matched pairs that are no more than 0.5mV out at 110 degrees F. I can usually obtain 15 NPN or PNP pairs, per 100 tested. Matched transistors is relatively easy to implement for analog mono synthesizers. But really complex for polyphonic synths and one of the reasons DCOs and hybrid synthesizers became so popular. They were always in tune, and made polyphonic implementation smaller, cheaper and easier to implement. Most current synthesizers utilize an analog audio path, but implement the control voltage through digital techniques. This is how they can fully implement MIDI and save patches and configuration with analog synths.

“Why is a pre-built TTSH expensive? Even building this DIY is not cheap…”

What I would also say, is that with care, the right tools and materials, there is no reason the TTSH could not last 30 or even 40 years. Through-hole technology, may be somewhat outdated commercially, but it is far more robust than modern SMT. Search for “electronic product life expectancy” on Google. Hey, no doubt that modern components are made more accurately with much tighter tolerances, but the materials used or more accurately stated, the incompatibility and chemical reactions between the materials used, is where the problem with life expectancy lies. The fact is you get what you pay for. Yes, you can get inexpensive commercial clones of analog synths from a few vendors, but they are intended to be profitable at a minimum price point, and only need to last beyond a warranty.

I am not knocking Chinese made equipment, they have managed to become the world’s supplier of commercial electronics. But making electronic products here in the USA or Canada, is really expensive. We charge way more an hour to work, we want benefits, vacation, holidays and a 5×8 hour work week. Price out a Moog Mini Vs a Behringer Model D. The Moog will is high quality and will be working 30 years from now, I doubt there will be many working Model Ds after 7 years. The Moog can be repaired, the Model D requires specialized equipment and skill set to repair. It would be less expensive to throw it away and buy another.

Most of all, the infrastructure for an electronics industry is inherently poisonous. It was not that long ago when rivers and lakes in the USA caught fire, because of the chemicals dumped from making stuff domestically. You really don’t want these metals and chemicals in your environment or drinking water.

TTSH Build and Modifications.

TTSH Main

Main