Transcendent T2000 Clone

Good luck with this. The Transcendent 2000, properly built with Q81 tempco resistors on the log CV inputs (VCO & VCF) works well. It got a bad reputation as they were all DIY, and some builders skimped on quality components.

Q81 resistors are impossible to find now, I am interested to know what you are using instead, and how…

I built (and still have) 5 Transcendent 2000’s, extensively modified. Beware- the self-oscillating VCF is treachorous and can blow speakers easily!

The pseudo-random noise generator uses a maximal length shift register that tends to lock up. There is a mod. to fix this.

The switches used on the original design are awful - I would build with toggle lever switches now…

I did read about the resistors and how to replace them with “normal” 1K Tempco, but I have to refresh my mind.
I did write this: “Also swapped the Cu-wire resistors to (modern) 1K PTC resistors and placing them as close to the CA3046s as I could.” Wasnt the CU-resistor mounted in series with another ordonary making up 1K??. But I have to check that up.

Could be a good idea to check up the VCF resonance and see how to limit that.

In the VCO R33 (130R) and R34 (870R PTC) makes up the temp compensator. Replace R33 and R34 with one 1K PTC, +3400ppm resistor would work.
Likewise R66 and R67 in the VCF are replaced with one 1K PTC resistor.
RV19 and R61 controls resonance; maybe fiddling with R61 would fix the “screaming cat” issue.

It’s not just the resistance of the tempco that it is important, it’s the temperature coefficient. I’ll try and find out what that was for the Q81.

My ‘cure’ for the VCF oscillation wasn’t terribly good. I put a variable resistor in series with the resonance pot and adjusted it until the VCF wouldn’t oscillate. Unfortunately this seemed to mess up the CV/octave characteristic of the VCF, but at least it didn’t blow the speakers.

The self oscillation of the VCF was promoted as a ‘feature’ but as it drowned out anything else going through the VCF, it was just a very loud sine wave of no real use.

I’ll have to look at my design notes (I did make some!).

OK from the original article, the Q81 1k has a temperature coefficient of +3400ppm/ deg C. I never noticed that the alternative suggestion was using a copper wirewound 870R resistor (and a 130R MF). An 870R WW resistor should not be that hard to find (?).

Thonk do 3300 and 3500 ppm 1K resistors.which may be better than nothing. Two of each in series-parrallel could make 1k resistor of (about) 3400ppm, but for best results they would all have to be glued to the 3046. Just a thought.

An early (1970’s) DIY Synth was the Practical Electronics Minisonic II. The designer originally used a ML3046P transistor array for lin/log conversion, but that part was obsolete by 1975 and the nearest alternative was the CA3046. The designer, G.D. Shaw, lamented that the CA3046 exponential tracking was not as good, so used a transistor pair instead. I do wonder if modern 3046’s are any better - it may be worthwhile trying 3046’s from different manufactuers for best results. The Transcendent 2000 had a tendency to go a little flat at the top end of the scale.

Thonk do 2K KRL 3500 tempcos and 2K Akaneohm 3300 tempcos. 1 of each in parallel should give you a good enough 1K 3400 tempco resistor!

If the Tempcos show a 3200ppm or 3400ppm doesn’t really matter in my humble opinion. This is definitely NOT a children’s toy, but not the most serious machine either.

Unicorn-Electronics sell original 3046 and Alfa produces their AS3046 in Latvia.

Edit - NOT a childs toy.

It’s up to you if you don’t want to use something simple that will improve the VCO stability.

At leaast my suggestion may be of use to anyone else makeing a Transcendent 2000 clone.

I missed a NOT which maybe made you think I sort of underestimated the usefulness of the T2000.

Else I am “lazy” and always try seek the simplest solutions possible to problems and often accept “good enough” as good enough.
Besides when dealing with old macginery it is always VERY appreciated to get advices how to fix this or fix that, especially when it comes to odd components.

No problem. Your English is better than my Dutch.

If you get your PCB working properly other people may be interested in one. Is your PCB the same size as the original?

In order to fit the PCB in myCAD-program I had to make it 2-3 cm shorter than the original.

Hello Magnus,

Don’t hurry I am very pleased with the files and program and to huilt it.
In 1977/1978 i build the elektor formant and stupid enough years later a sold it
Now in for something News
Greetings Henk

I am “struggling” with soime boards/modules from Ken Stone (Cat Girl Synth). Some older modules lack some info/docu to finish them just like that. The iNfinite Melody and Wighted Random Switch are such great stuff (when into regenerative music), but it is a bit unclear how to connect stuff to the panel.

I am soon about to revisit my old files, print out (jpg) the layout as well as the gerber files.

Here’s the Gerberfiles. I cannot guarantee that the design is flawless, but I did check it through several times (noted one mistake and corrected it).

T2000 gerfiles, zipped

Hello Magnus,

Did you find the transedent 2000 files ?
Still interestet for ordering the pcb in China where you bought it.
Greetings Henk

Yeah, sure. You find the link to the files just above. I did upload them a month ago.

With the tip sprintlayout i created one myself and bought the PCB’s by jlcpcb China and the switches from Ali. The keyboard is one from an old organ that was almost 65 cm .But a pitte he works not well.still looking by telefunkian and so an.the transistors are the L types and the bf244c turend 180’.may .sugestions are welcome


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