Interesting there is only one for two VCOs. One would normally expect to see two, ie. one per VCO, if they are using the traditional heated NPN pair like the Moog Prodigy. However, I would expect to see an extra couple of trimmers to set the running temperature of the heater. There could be more stuff on the other side of the board though. I can only see one fancy capacitor in that picture - that suggests that we're only looking at one of the VCO cores here, the other is on the flip side.

But they could be using the 3046 as two matched pairs (actually one matched pair, and a couple of similar transistors on the same die) and then using a couple of temp co resistors, possibly mounted under the 3046 IC. This would be similar to the Oberheim SEM method.

Perhaps I'm going to have buy one and take a look.

Tony

I think once you calibrate it you should be fine.

I haven't noticed the tuning change at all once the module warms up.

While whatever-a-caltrans-is might make things easier, all you need is a tuner. A free phone app would do.

...assuming that the oscillator can be adjusted to track at exactly one volt per octave across the whole range. As a pure analogue oscillator it almost certainly won't - at least not exactly, and not across the entire frequency range.

What Caltrans (a module) and Silent Way (a DAW plugin that needs a specific type of soundcard) will do is deal with oscillators that won't track properly across their whole range by, literally, listening to the oscillator and storing a table of input voltage and output frequency - and using that to adjust each note that is played.

...think of calibrating the oscillator using the two trimmers as trying to draw a straight line through a set of dots that might actually lie on a curve, whereas Caltrans/Silent Way can join them up with a wiggly line...

Of course there's no excuse for these modules to leave the factory without being adjusted to the best of their capability - but they have to be judged for what they are: recreations of "vintage" analogue circuits untroubled by more recent advances in oscillator design (...like digitally controlled oscillators with the base frequency set by a quartz crystal, or pure digital oscillators). If you want "that vintage sound" then sometimes being a bit off (depending on the weather, the phase of the moon and the number of people in the audience) is part of it.

I think Behringer are making a bit of a ...courageous decision by making modules that, on the one hand, offer bargain-basement prices (by Eurocrack standards, at least) which will appeal to us noobs while - on the other hand - taking a quite purist "faithful warts-and-all reproductions of circuits from the 70s and 80s".

Pairing a Caltrans with these to make them play nice with other instruments is probably not daft (it also does quantization which will be helpful if you want to use the 100 series sequencer and aren't blessed with perfect pitch, and can calibrate 4 oscillators, so you can get your dual filters tracking nicely, too) but it is a setback to that ultra-cheap Broland setup you were dreaming of. Silent Way is only sensible if you are planning on blowing $400 on an ES-8 audio adapter and driving everything via your DAW (...but it's great fun, beats a MIDI-to-CV adapter with a measly one channel of modulation and can be paired up with VCV Rack as a virtual extension of your rack...)

People have managed to make music on analogue gear for decades without running them through the synth equivalent of Antares Autotune to achieve accurate tracking over all octaves. I'm delighted to learn such devices are out there for those who want them, but I'm willing to bet 99.99% of the synth using community have no burning need for them and will continue to get by just fine without. Including B100 buyers.

Regardless of price point I would however expect manufacturers to calibrate their synths correctly out of the factory, so far as is reasonable.

I'm using the CalTrans for other things - I actually purchased it for the SID GUTS DELUXE module by ALM. The C64 SID chip actually doesn't track that well to v/oct and the caltrans really helps here. Not only that but it also offers other tuning options - and a really useful tool to have in your Eurorack setup.
As it has 4 memory slots - I thought I'd try it out on the Behringer 112 module - it works fine - and for the moment suits a secondary need.
Making the decision about getting the Caltrans because of Behringer wouldn't be my first choice.

Hmm... left mine alone for a few hours and it's started breeding. Caltrans on order...

why the difficulty in finding the 297 module on the market ?

thank you all

They haven't shipped it yet.

I have the dual VCF. Purely out of interest, what was the purpose of dual items on the original System 100m?

2 of everything is great 1 lead 1 bassline or sound effects etc

Any duo-phonic/paraphonic modes?

also running similar patches in a LR config with different filter settings and modulation for some nice stereo effects.

Two is one. One is none.

Get with the program.

They did make the rare 184, four channel polyphonic keyboard controller with arpeggiator. that outputs 4x CV and gate connections.

That said, they created a standard wider rectangle panel size than many builders with 5 spaces (later 3) per cabinet and stuck with the one size module. They filled their panels as mentioned frequently with 2x the featured circuit

For euro, Behringer sticks with the dual configuration like Roland/Malekko though do not stick to the uniform width.

>Any duo-phonic/paraphonic modes?

Modulars traditionally by their nature just do as they are CVed. One CV sends one control. Two CV patchcords send two messages to different places. So yes, if your controller/computer sends two pitch CVs you send a cable each to 2 VCOs and you have duophony.

Now something entirely different you might be getting an inkling of, is there are modules with digital engines inside (this isn't) so if it's running code that code could be to play a chord, mix several samples, whatever the code says, generally some of it listens to CV but that's not a given that you can CV every aspect of what's being generated, but you can send the audio out to your single filter and you get a paraphony thing going

Check out the modules really close-up!

The newest Synth Tech VCO (i forget the model number) tracks across something like 15 octaves, and is pure analog, a collaboration with Dave Rossum and a port of a 5U module.

Warning: Long technical post.

So I bought the dual VCO module - the 112. Straight out of the box it did not play in tune. What was interesting to me was that both VCOs were equally out of tune. This suggests that they are calibrating the modules but something is off (see later).

Most of the surface mount electronic components are on the underside of the board. However, there's a good chunk of circuitry on the front side of the board where it has to squeeze in between the sockets, switches and pots. One of the VCO cores is on the underside, the other is on the front side. There are also many trimmers on the front side of the PCB but all these are single turn types and it is not expected that you will be fiddling with these at all.

The circuit appears to be a straight copy of the Roland M-112 with a few exceptions. The Behringer is run from +/-12V while the original ran from +/-15V. In the Behringer all of the op-amps are 4580 except for the VCO cores which use TL072s. The Roland used a mixture of TL082 and 4558. The only additional bit of circuitry that I can see on the Behringer is a dual comparator circuit that beefs up the sync input signal so that it reliably synchronises the VCOs no matter what the input waveform. An excellent addition.

Like the original the sawtooth and pulse waveforms are unipolar and move between 0V and +10V. The triangle wave is bipolar and is +/-5V. Personally, I would have liked to see the Behringer use fully bipolar waveforms as many other modules in Eurorack expect to see +/-5V audio waveforms. Any DC coupled modules will easily overload with two +10V sawtooth inputs for example. I'll be correcting this on my unit as soon as I can.

The tune control on the Behringer spans over 2 octaves. This makes it very hard to fine tune the VCO - especially since it's very easy to brush against this control by accident and cause it to go out of tune. The original had a more restricted 1 octave span. Given the similarity between the two units I am surprised at this. I'll be correcting this on my unit as soon as I can.

The multiturn trimmers on the underside of the module allow for users to tweak their module to the standard 1V/octave input. Unfortunately, the quality of the trimmers on my unit was very poor and it was difficult for me to set the tracking and, in particular, the absolute pitch properly. The trimmers appear to be poor clones of the industry standard Bourns 3296Y. I'll be swapping mine out as soon as I can.

The original 112 module used the uA726 heated matched NPN transistor pair in the VCO's exponential convertor. The heating aspect allows the transistor pair to sit at a constant temperature even when the surrounding temperature varies. Without this constant temperature the scaling of the exponential convertor will drift and the VCO will fail to track accurately across the keyboard when the ambient temperature changes. There are other ways to achieve acceptable temperature stability; for example, one can use a temperature sensitive resistor in the CV summing circuit that counteracts the change in the scaling of the exponential convertor.

The uA726 is no longer available, and was expensive even back then, so Behringer have the used the LM3046, which contains five NPN transistors on one silicon die, two of which are pretty well matched. Because the Behringer uses only one LM3046 for both VCOs it is not easily possible to heat it, so other forms of compensation should be used to avoid scaling drift with temperature. Sadly, no other compensation that I can see* is provided on the Behringer 112, and as such the scaling and tuning will drift as your room and/or your modular case warm up or cool down. I could trim the 112 VCO module to track well, but some time later it would be off again. I will be looking into fitting some temperature compensation (PTC) resistors into mine to see if I can make it more stable. Right now, it's pretty unusable to me.

In summary, this could be a good module and at a great price. However, the major tuning problem, and some of the less serious niggles would stop me in recommending this to anyone. This is a real shame because their Dual Filter module I also have is very good.

* I'd be happy to be corrected about this.

If you are going to do all those mods, the price is no longer a bargain.

Not for everyone. But, I'll be upgrading my B55's for better performance. A couple of well placed bucks can do wonders here. B really cut into the bone in some places. A little rework, and they're still worth it.

Thank you!

I'm interested in starting my modular journey with these modules, but the VCO tracking issues seem a bit worrying.

Interestingly lots of user report similar issues for the Roland SYSTEM-500 512 VCO in this thread https://modwiggler.com/forum/viewtop...65304&start=25

Is it just a coincidence or are they suffering from the same issues?

I have also considered getting into eurorack with these 100m modules but the VCO tracking issues are giving me second thoughts. I think I'll wait for the next batch (once rest of the modules are released) and see if they have fixed these issues by then.

Suggested modifications to the 112 Dual VCO module:

1) To modify the unit so that all the waveforms are +/-5V bipolar signals is not an easy task - not only because all the resistors are tiny 0402 types, but because all the components needing to be changed are on the top side of the board bar one. This means that to desolder and solder you need to get your soldering tool in between all the pots, switches and sockets. I have done easier jobs.

The changes I made are as follows:

Remove D2, D3
Make R28, R25 both 4K7 (0402)
Make R3, R72, R9, R81 all 5K1 (0402)

The added benefit of changing the pulse wave to bipolar means that the unit will take less current from the negative power rail. As stock each VCO takes an additional -8mA when the pulse wave is in the low state. This is reduced to around +/-1mA if the above modification is done.

2) To correct for the poor tuning stability with temperature I modified the circuitry considerably to incorporate a couple of Akaneohm 1K 1/6W +3300ppm/K PTC resistors (available from Thonk) that straddle the LM3046 NPN array. Thankfully, this is all done on the underside of the module, so the parts are easy to get to. That said these components are tiny and good soldering skills are required.



The following changes were made:

R126, R131 both 56K (0603)
R115, R109 both 33K (0402)
VCO1 Width, VCO2 Width trimmers both 10K 3296Y
Remove R116 and R108
Fit two PTC resistors to top of IC3. One between pin 2 and 0V, the other between pin 9 and 0V.

3) The tune controls on the Behringer each span over 2 octaves compared to the original having a more restricted 1 octave span. To modify the Behringer 112 back to the original's behaviour the resistors R60 (top side of the board) and R111 (bottom side of the board) need to be changed. I swapped these 1M 0402 resistors with 2M2 0402 resistors.

Awesome work but I'm afraid most of these mods will be out of reach for most. Unless they want to pay a tech to do them in which case it starts getting pricey and might as well look elsewhere for equivalent modules. Shame that the qc seems off with all the modular range. Maybe in time they will have revised versions on the market

Indeed. To be honest I found them very challenging. I won't be doing another.

Has anyone had a chance to compare the any of the modules to the Roland system 500 series, I am most interested in the VCF comparison.

Wasn't the 500 series vcf based on the sh5 though so won't be that similar to the 100m

System 500 module 505 is based on sh5 , module 521 is based on system 100m.

Ah...