MFB Kraftzwerg modular

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meatballfulton
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MFB Kraftzwerg modular

Post by meatballfulton » Tue Aug 12, 2008 3:10 am

This initial post is not a full review, it's just my first impressions. I'll add more over the next few days.

The Kraftzwerg is advertised as a semi-modular version of their Synth II . At 580EU/899USD it's the cheapest fully assembled analog modular synth available . It's only about 12" wide, the picture below shows it atop my Motif workstation giving you an idea of it's size.

Image

For those not familiar with MFB products, the construction is best described as adequate. It uses the same plastic case as the Synth II and is just a step beyond a homemade hobbyist's project. It should stand up fine for studio use, live you will want to be a bit protective of it especially the pots. The wall wart supply is 16VAC, so if you misplace it you won't be able to swap it out with some other adapters you might have on hand.

The circuitry is identical to the MFB Eurorack modules except the MIDI interface lacks the clock outputs (pitch, gate, bend and mod wheels only). While it is technically semi-modular because normaled connections allow use without patch cords, it duplicates all the patch access of the individual modules. There are only two connections not patchable: the input to the ring mod (hardwired to VCO 1 and 2 outs) and the inputs to the VCO mixer (it cannot be used for mixing anything but the VCOs). This is actually superior to most semi-modulars past and present. Missing features compared to the Synth II are program memory (doh), step sequencer (likewise), portamento/glide and external audio in. While you can patch into the filter, there is no preamplifier to boost the signal to the appropriate level. All patching uses 1/8" (3.5mm) jacks, five 18" cords are provided.

Rather than discuss every feature (see the MFB website for all the specs and the manual) I'll mention some of the more interesting highlights.

LFOs
The exciting news is that there is a CV input to modulate rate of each LFO. They will easily get into audio range for FM/AM applications. The patching is normaled so that you can use each LFO to modulate the other's rate.

VCOs
There are three following the Minimoog design MFB has used as it's inspiration. VCO 1 and 2 offer 4/8/16 foot ranges and PWM, VCO3 has 8/16/32 foot ranges but no PWM. There is one master tune and individual detunes for VCO2 and VCO3, all have ranges of about +/- 1 octave. Unlike the VCOs on many modulars, you cannot access all waveforms at once, a switch for each VCO chooses saw, triangle or square (no sine). Manual pulse width adjustment is not offered. There is an output for each VCO plus ring mod of VCOs 1&2. Each VCO has a main pitch CV input normaled to the MIDI interface plus a second for modulation with a depth control.

VCF
The filter is a 4 pole LPF modeled after the Minimoog. There are two inputs that can be mixed, one is normaled to provide a feedback path which thickens the low end while reducing resonance. There are two CVs for cutoff, one normaled to an EG the other to follow the MIDI pitch. Resonance has it's own CV input. All three have depth controls. Self resonance is easily achieved and with the tracking CV depth at 100% it will stay in reasonable tune.

VCA
The VCA has three audio inputs (one with a attenuator control). There are two CVs, one normaled to an EG. There two outputs, one with a volume knob...yes, finally a modular with a master volume control 8) The gain pot is unusual, at settings above 5 it opens the amp up without the CVs to allow droning sounds. At lower settings, it acts as a gain boost and the CVs must be used to open the amp. So the actual output level depends on the settings of three pots: gain, EG CV and output. Quirky but flexible.

EGs
There are two, one normaled to filter cutoff and one normaled to the VCA. Each is an AHDSR type, the H for hold. This keeps the EG output at a steady level between the attack and decay phases. The normal response is exponential but a switch allows setting either EG (but not both :cry:) to linear response. The release time in particular seems rather short to me in expo mode, changing to linear response increases the time significantly.

Stay tuned for some demo mp3s.
I listened to Hatfield and the North at Rainbow. They were very wonderful and they made my heart a prisoner.

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Post by crystalmsc » Tue Aug 12, 2008 3:42 am

thank you for the early review, the synth looks interesting. I'd be glad to hear the mp3 demo of that.
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Re: MFB Kraftzwerg modular

Post by meatballfulton » Tue Aug 12, 2008 12:43 pm

Here is the first demo.

1. It starts with a long drone patch using the 2 LFOs for motion. The filter feedback is adjusted as the drone plays.

2. Filter sweeps with the resonance being increased each time.

3. Self oscillation sine wave being swept through the audible range.

4. LFO used to modulate the self-oscillating filter into some FM effects.

5. The actual LFO output showing it easily reaches into the audio range.
I listened to Hatfield and the North at Rainbow. They were very wonderful and they made my heart a prisoner.

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Post by crystalmsc » Tue Aug 12, 2008 1:37 pm

thank you for the nice demo. it sounds on the MFB synth II side, only a bit better to my ears. made me wonder of the Synth III. I like the filter in the drone and when it sweep.
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Re: MFB Kraftzwerg modular

Post by Sir Ruff » Tue Aug 12, 2008 6:17 pm

sweet! very cool. Thanks for posting.
Do you even post on vse bro?

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Re: MFB Kraftzwerg modular

Post by meatballfulton » Thu Aug 14, 2008 5:05 am

Second demo, this time a (cheesy) song. All sounds made by Kraftzwerg including the drums. Reverb/delay FX provided by my Boss BR900 recorder, some compression applied to the kick drum sound to bring it up in the mix.
I listened to Hatfield and the North at Rainbow. They were very wonderful and they made my heart a prisoner.

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Post by crystalmsc » Thu Aug 14, 2008 8:30 am

very nice and fun to listen to, almost feels like I'm playing Prince of Persia on my DS :wink:
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Re: MFB Kraftzwerg modular

Post by novielo » Fri Aug 15, 2008 4:06 am

that sound very good!! mfb stuff are realy getting my attention at this time and this demo sure sound great! i realy have to learn how to make drum sounds out of synth tough, they sound so good
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Re: MFB Kraftzwerg modular

Post by jaypodesta » Sun Aug 17, 2008 4:14 pm

Nice review and those demos sound good.

From the photos it's a tiny little thing too which is very handy.

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Re: MFB Kraftzwerg modular

Post by Yoozer » Sun Aug 17, 2008 9:35 pm

I don't think your host supports hotlinking..
Image

Thanks for the second demo, I've had enough of modular demos that sound like a cat on fire ;).
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Re: MFB Kraftzwerg modular

Post by pricklyrobot » Wed Aug 20, 2008 3:30 pm

Nice demos, thanks for those. And I agree it's cool to hear something other than pure experimental noise wankery coming from a modular. :wink:

Looks like the Kraftzwerg is even smaller than I was picturing it. Now I just need to sell another $200 or so worth of stuff and I can grab my own.
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Re: MFB Kraftzwerg modular

Post by meatballfulton » Wed Aug 20, 2008 9:18 pm

Well, I could have posted some cat on fire noise wankery, after all a lot of people want to know how far out they can go...

Some followup after a few more days in the saddle:

PWM

I wrote above that manual control of pulse width wasn't supported. OK, I lied. VCO 1 and 2 each have a CV input with a 3-way switch that selects pitch mod, off or PWM. Both inputs share a CV attenuator control (marked CV4&5). If nothing is patched in, adjusting the attenuator does nothing when pitch mod is selected, but if PWM is selected you can manually sweep pulse width. It's not over the whole range though...I'd have to plug the output into a scope to see exactly what's going on. Throwing the switch from off to PWM the VCO will jump from a square to a narrower pulse which can be further adjusted but it can't be adjusted back to a square. Ah, the quirks of analog.

RING MOD

The MFB docs call the ring modulator digital. On MFB's earlier Synth Lite this was indeed the case, the ring mod worked only on square waves (like the Korg MS-20) and was implemented by digital logic called an exclusive-OR. However, the ring mod of the Kraftzwerg works with all three waveforms which sure as heck means it's more than just an XOR function. It is hardwired to the outputs of VCOs 1 and 2 and you can't control the relative level between the two but that won't bother most users.

WHEELS

The pitch bend wheel is implemented as a +/- CV (0V at center) so patching for bending does not require retuning the synth =D> Since it is not blended in with the pitch CV you can tweak the bend range unlike some other low-cost MIDI/CV interfaces and it also can be used for bipolar modulations. The mod wheel CV varies from 0V to +5V.

MIDI

Not all MIDI-CV interfaces are created equal. One thing they vary quite a bit on is the supported pitch range. For example, the PAiA MIDI2CV8 interface supports all MIDI notes (0-127) while the one built into the Vermona Perfourmer responds only to notes 36 to 96 (typical 61 note keyboard). MFB has chosen to provide a gate for all notes, but pitch is only provided for notes 36 (lowest C on a 61 note keyboard) to 117 :?: which is the A an octave and sixth above the highest note on a 61 note keyboard. This is a rather bizarre map to be sure...82 notes? Keep in mind that on an analog synth pitch is not absolute as it is in MIDI, it's relative. Most analog monos are designed so the CV generated for the lowest key is 0V, that's usually a C but need not be. The lowest key on a typical 61 note MIDI keyboard is note 36, 3 octaves above the lowest MIDI note (0) so what voltage should a MIDI-CV interface put out...0V, 3V, something else (if you're wondering why anyone would need to handle MIDI notes below 36 anyway, keep in mind that the GM drum map...based on the mapping of Roland drum machines...places the kick drum at MIDI note 35.)?

There is no sustain pedal (CC 64) response. Legato playing is supported with last note priority; if you hold down one key then play another the pitch CV changes and the gate does not retrigger. If you release the second key, it returns to the pitch of the first key without releasing the gate.
I listened to Hatfield and the North at Rainbow. They were very wonderful and they made my heart a prisoner.

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Re: MFB Kraftzwerg modular

Post by Madrayken » Tue Sep 02, 2008 7:39 pm

Just received mine yesterday. So far, so 'nasty'. It's a really noisy, growly little beast. As such, I have to ask - have you managed to get something pleasant sounding out of the ring-mod? I'm used to ring mods producing 'oyoyoyoyoy' sounds by keeping one VCO static, and another sweeping through the audible range (see ARP2600, or even the C64!) but I can't seem to get anything of the sort out of it!

Any tips?

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Re: MFB Kraftzwerg modular

Post by Madrayken » Thu Sep 04, 2008 8:57 am

Update:
If you want a real retro analog synth 70's horror movie track (zombies anyone?) then this is a good place to start.

I've been playing around with sync and now the machine sounds like I'm playing lead for The Cars. :-) I'm surprised at how much body there is to these VCOs.

On a related point, you can allegedly sync VCOs 1 & 2, or just VCO 1 by itself to VCO 3. So far I've not been able to get VCO 2 to sync at all, regardless of the sync switch's position. I'm not sure if this is a design quirk or something broken internally. I'll update to anyone who's listening later if I hear back from MFB.

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Re: MFB Kraftzwerg modular

Post by Madrayken » Mon Sep 08, 2008 10:51 am

Just heard back from the manufacturer that the sync 1/2 switch in some models is borked, and does the same thing on both settings (i.e. only syncs the first VCO). I will be sending mine back for repair/tweak. They've also agreed to pay postage, which - from a small developer - is really nice.

Also had some issues getting it to receive midi messages reliably from my Alesis IO14. Sending midi via my Andromeda's Midi-through channel seems to fix it, so I'm inclined to blame the IO14.

I'll miss it more than any other synth I've ever owned while it's away. (I think I've contracted Modular Obsession Syndrome. There's something worryingly addictive about patch-cord sound design)

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