Synthi HiFLi Re-Release

Here are some photos of the 2010 prototype of The Synthi HiFLi effects unit. Designed by legendary EMS electronics genius David Cockerell (of Synthi AKS/VCS3/Synthi100 fame) in 1973 probably primarily as a guitar effects unit (though it certainly has uses as an analogue effects for synth sounds) and used by the likes of Dave Gilmour (Pink Floyd) and Steve Hackett (ex Genesis) and others. I was intrigued by the air of mystique surrounding this unit. It seems to be regarded by many guitar player out there as the ‘Holy Grail’ of vintage analogue guitar effects.

Whether this is because it’s also one of the rarest effects in the world, maybe in part explains this. Although guitar playing is not something I am good at ..I was also intrigued by its possible uses on synth type sounds.  The prototype is an exact duplicate of the circuits of the original mk2 HiFLi..down to using the same obsolete transistors and the same opamps. The only 'electronics' difference is my use of a very stable toroidal transformer based internal power supply.
The case design is of course different. The original was in a wonderful white fiberglass (very 1970’s style!) console..something that is beyond my skills to easily reproduce. Therefore I opted for a powder coated black steel chassis with iroko end-cheeks and a cnc engraved and machined top panel (I made this myself with my CNC engraver/router) in satin anodized silver aluminium. Part of the project was also to clone the original pedal unit..this being a crucial part of the HiFLi in my opinion.

I used 2 new Moog expression pedals suitably adapted and fitted with a preamp as the original. The audio input (eg guitar or synth) is via a jackplug built into the side of the left pedal. Control voltages and amplified audio go to the main unit via an 8 way umbilical cable with Jones plug on the end (just like the original). The right hand pedal has a convenient pot to control the amount of preamp gain. This scaling pot was part of the original Moog pedal so I made good use of it!   

HiFLi Main Features  

The HiFLI consist of several sections. Those on the left half are Top Boost, Octave Shift (containing Sub-Octave and Ring Modulation features) and Sustain Fuzz. Then a Bypass Mixer (mixing wet/dry signals) divides the left and right parts and the right half consists of probably the most important part as regards sound shaping, a wonderful multi-feature Phase Filter. I also added 2 features that appeared on the original HiFLI mk2 units: a bypass front panel slide switch to bypass the left hand side effects completely and send the audio signal directly into the Phase Filter (very useful!) and an additional ‘Growl’ switch that drops down the fundamental note extracted from the audio in by 2 and 3 octaves (The Sub-Octave drops it by 1 octave). These sub-harmonics are not just combined with the original sound but used to modulate the phase filter thus allowing very strange/bizzare new sounds to be created.  The pedal unit is a fantastic idea. All the front panels sliders simply provide a control voltage to operate each effect..yes all the effects are voltage controlled! On the bottom of each slider is a 3 way slide switch  marked  ‘+,0.-‘. In the ‘0’ position the pedal has no affect on that effect as you operate it and the slider acts as the effect control. In the + or - position operating the left or right pedal sends a control voltage that swings from +12v to -12v or -12v to +12v as you move the pedal up/down. The left/right pedals control the left/right hand effects when viewing the top panel. Since there is an independent pedal slide switch on every effect..you can imagine the creative possibilities here! There are many many different sounds you can create simply by altering the state of each pedal voltage slider switch. This is a really great idea and is why I said earlier that the pedals unit in my opinion is crucial to getting the most out of the HiFLi. 

The Effects

Before we get on to the effects, an important function of the HiFLi is to detect an attack/decay time from the input audio. So for a plucked guitar string the initial attack and the point at which the amplitude drops below a certain level is detected. The attack detection is used to trigger other effects which I’ll discuss later. An exponentially decaying envelope is also generated from this attack/decay section. The attack/decay extraction is rather sensitive and its ‘correct function’ (ie single rather than multiple triggers as each string is plucked) depends on how you play (solo/strum) and the input level of the audio from the preamp. Thus there is a panel slide switch for flipping between sensitivities..one for ‘solo’ and the other for ‘strum’ guitar playing. In practice I found you can play as you wish in each mode and you get different responses/sounds..! 

Top Boost

Audio in from the preamp in the pedal unit is fed to the Top Boost that is basically a treble boost. Makes quite a big change to the sound when you push the slider up ..particularly on fuzz sustain. 

Octave Shift/Ring Modulation

This section involves a suboctave generator that extracts a fundamental note form the audio in and drops it by one octave. Rather than simply mix this suboctave with the original signal something more sophisticated is done. A ‘pseudo’ ring modulation effect occurs where instead of multiplying 2 waveforms, the RingMod just adds a half wave rectified version of the fundamental to the output of the Top Boost and thus can produce a fundamental that is double in frequency..so a bit like what happens with a standard RingMod where the frequency of eg a sine wave sent in is doubled though waveform multiplication.

But in the HiFLi RingMod version one doesn't hear the typical metallic/bell like sounds. Rather this pseudo ringmod signal is sent to a pair of FET’s which act as modulators..modulated by the suboctave signal.  The result is some great deep suboctaves the amount of which are controlled by the ringmod and suboctave levels.

 Sustain Fuzz

A fairly standard but nice sounding fuzz section that can be mixed with the output of the Octave Shift. The fuzz input is the from the Top Boost section. The fuzz attack time is controlled from the attack/decay section and is variable. On fast rise times..the fuzz appear instantly a string is plucked. Slower rise times allow the fuzz to ‘swell’ in amplitude after the string is plucked. So you get a slewed fuzz effect. Great! 

Phase Filter  

Here is where the major soundscaping effects occur. The phase filter is in fact 6 filters and FET/bipolar transistor switches that alter the signal path through the filters of audio fed from the left hand effects. The 6 different ‘Treatments’(selected by front panel rotary switch) are Vibrato, Phasing 1,Phasing2, Waa, Waw and Meow are the result of different paths the audio is fed through the filter sections. For any given phase filter configuration above, there is in addition, 6 different modulations you can apply to vary the frequency of the phase filter. Varying the frequency alters the amount of phase shift that occurs in the audio signal. These modulations take the form of ‘transients’ ie waveforms that are produced  only between the attack and decay sections of eg a plucked guitar string. Outside of this ‘attack/decay’ envelope the modulation waveform goes back to a simple sine wave. The 6 transients are slow sine, fast sine, increasing amplitude sine, decreasing amplitude sine, ramp up and ramp down. Modulation speed is controlled via slider (or pedals) and modulation amount by another slider. Here is a great feature. The time taken for transients to appear modulating the phase filter is controllable. So there is a slew option ..controllable via the modulation ramp time slider/pedal. Finally there is a slider/pedal that directly shifts the frequency of the phase filter. This allows you to ‘sweep’ the audible range of the filter if you use pedal control. 

The ‘Growl’ switch option drops the fundamental by 2 or 3 octaves depending on the switch position. As mentioned above, these sub-harmonoics are used to modulate the phase filter not simply mixed with the orighinal sound. This gives amazing/bizzare new modulations! The amount of growl is controllable via the depth slider and also if the increasing/decreasing sine modulation is selected, by the decaying envelope extracted from the attack/decay section of the input audio.



My impression of the phase filter is that its the ‘guts’ of the HiFLI and produces an astonishing range of phasing effects form subtle vibrato to screeching wah sounds all with transient modulations on top! The Envelope and Fuzz bypass switch allows you to bypass completely the left hand effects section of the HiFLi and send audio directly into the Phase Filter. This was something (along with Growl) that EMS seem to have added in the mk2 version of the HiFLI..so you wont see it on earlier mk1 versions. Its a simple idea but allows for yet more different sounds..’clean phasing’ if you wish Finally the bypass mix slider is a simple dry/wet mix control of the audio output.

The Sounds

I would also suggest checking out the superb original HiFLi demos by David Walter Mohr
on youtube. All the effected sounds he makes I can recognize and reproduce on the re-release HiFLi.

I wish I could  play guitar as well as he does...thats not soemthing I can so easily reproduce :0) !

 A/B Guitar demos of the re-release HiFLi  vs 1972 mk1 original HiFLi

Here are some  direct A/B  sound comparisons of the new re-release HiFLi compared to a 1972 mk1 original, kindly loaned by Robin Wood at EMS.

Rather than my ropey guitar playing I have used free public domain clean guitar samples to
do the test. This is more scientific in that the exact same sample is played through both units.

Credits for the original guitar samples are given below.

Note: The original 1970's mk1 has no growl switch (that came in later versions) and so no A/B comparison was done with the growl switch settings in my test. Also the original unit loaned to me has a non-standard bypass switch (not the same as the one that appeared in later EMS units and which I have implemented in the re-release version ) so again no A/B test was done in bypass mode.


Phase Filter  Treatments : Vibrato, Phasing 1, Phasing 2, Waa, Wawa, Meow

Small amount of reverb added.

Note the modulation depth of the phase filter in the demos below is quite subtle. The HiFLi is easily capable of mad and very deep modulations! Its just I choose these as they seemed appropriate for the demos.


Original guitar Solo Credits
 
Demo 1 : -http://soundcloud.com/soundonsound/sets/guitar-technology-sos-july-2010-issue
Demo 2 :-  http://soundcloud.com/search?q%5Bfulltext%5D=cln-orange
Demo 3 :- http://soundcloud.com/search?q%5Bfulltext%5D=cln+ac30
Demo 4 :- http://www.freesound.org/samplesViewSingle.php?id=52082
Demo 5 :- http://www.freesound.org/samplesViewSingle.php?id=52048
Demo 6 :- http://www.freesound.org/samplesViewSingle.php?id=15753


Vibrato  

original1.mp3       re-release1.mp3   
original2.mp3       re-release2.mp3  
original3.mp3       re-release3.mp3  


Phasing 1 

original1.mp3       re-release1.mp3   
original2.mp3       re-release2.mp3   
original3.mp3       re-release3.mp3 
original4.mp3       re-release4.mp3 
original5.mp3       re-release5.mp3 

Phasing 2 

original1.mp3       re-release1.mp3   
original2.mp3       re-release2.mp3
original3.mp3       re-release3.mp3      
 
Waa 

original1.mp3       re-release1.mp3   
original2.mp3       re-release2.mp3 
original3.mp3       re-release3.mp3 
original4.mp3       re-release4.mp3 


Wawa 

original1.mp3       re-release1.mp3 
original2.mp3       re-release2.mp3
original3.mp3       re-release3.mp3 


Meow 

original1.mp3       re-release1.mp3   
original2.mp3       re-release2.mp3  
original3.mp3       re-release3.mp3  
original4.mp3       re-release4.mp3  
original5.mp3       re-release5.mp3  
original6.mp3       re-release6.mp3  

Delay Fuzz

Maybe a unique sound effect of the HiFli is the delayed fuzz 'swell'. A front panel potentiometer controls the fuzz 'attack time' after a string is plucked. The amount of fuzz depends on the loudness of the playing. The effect has been described by Steve Hackett (ex Genesis) as a kind of 'backward' guitar..he used this effect for example on the excellent Genesis track 'Ripples' about half-way through the song. It takes some mastering to get the right strength of pluck and timing and the preamp level setting in the pedal unit is crucial to get the volume envelope to do its job.

Here is an A/B demo  I made with some reverb  added. Sounds almost like a bowed acoustic instrument !

Patch setting:  Top Boost: 0; Sub Octave 0; Ring Mod 0; Fuzz Level 10; Fall Time  slow; Rise Time '7 O'Clock position' ; Bypass Mixer 0; Control Mod:N/A; Speed N/A; Ramp Time 0; Mod. Depth 0; Phase Filter Tratment Phasing 2; Direct Shift 5.  Some reverb added.

original.mp3       re-release.mp3   

Conclusion

I think the tests show that  he re-release is a very close match to the orginal. Any variations are likely due to my inconsistent playing in switching from one unit to the other and to precise fader settings on each unit. 

Small differences in fader settings can make quite noticable sound differences especially the Phase Filter direct frequency shift fader.

The new release HiFLi uses professional 100mm long faders. The original uses 60mm faders and precise setting isnt easy using these and the faders are also not the best quality (cheap plastic type !) unlike the solid metal bodied faders used in the re-release  version)

  Further samples of the new HiFLi

Delay Fuzz

delay-fuzz1.mp3
delay-fuzz2.mp3
delay-fuzz3.mp3
delay-fuzz4.mp3

More extreme Samples with fuzz and growl (using guitar)

Fuzz + swept filter
fuzz_sweep1.mp3      fuzz_sweep2.mp3   fuzz_sweep3.mp3
 
Fuzz + Growl
fuzz_growl1.mp3  
fuzz_growl2.mp3  

Clean guitar + Growl
clean_growl.mp3      


Vibrato+Growl
vibrato_growl.mp3      


VCS3 Processed by the new HiFLi

Here are some quick attempts at processing a VCS3 generated sequence through the new HiFLi.

In all cases I deliberately used the same very simple repetitive sequence generated using my TKS sequencer using osc1 and osc 2 through the unmodulated filter on the VCS3 in order to focus on the HiFLi effects.  All the various sound changes you hear (filter sweeps, etc ) in the demos are generated purely by playing with knobs and sliders of  the HiFLi only.

NO knob twiddling at all on the VCS3. A little bit of echo to add ambience is the only other effect.

dry.mp3

  Various examples of processing the above dry sequence. First I bypass the front section of
  the HiFLi and only process through the Phase Filter section.

   proc1.mp3     proc2.mp3    proc3.mp3     proc4.mp3

  Next I now  include the front section (top boost/suboctave/growl/ringmod/fuzz) again just
  playing with sliders:-

   proc5.mp3     proc6.mp3    proc7.mp3      proc8.mp3    proc9.mp3    proc10.mp3

 

VCS3 Drone note processing

2 oscillator drone note from VCS3 constantly repeated by a TKS fed into VCS3 filter.

dry-drone.mp3

Processed sound through the HiFLi. Left hand effects bypassed as well as  envelope follower.
Filtered through Meow Phase filter. Dynamics produce by slow sine modulation of filter + right pedal control of direct phase shift. Also some knob twiddling on the VCS3 to add further  dynamics.

drone-meow.mp3




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