IN DEPTH

Overview

Every modular system needs modulation sources to add variety and interest to static sounds. The more powerful and versatile the modulator, then the more interesting these sounds can become. We compiled a wish list of useful features, starting with obvious ones such as CV control of Frequency, Tap Tempo, Unipolar and Bipolar outputs and a wide range of waveforms, and then we just kept adding more features such as waveform twist, rate multiplication, Sync In/Out and an inbuilt dual VCA for modulation level control. Then we made sure that we had voltage control (and therefore automation) available for every single feature. This takes it way beyond the realms of regular LFO's and make the Tap Tempo VC-LFO a modulation powerhouse.

Ergonomics are important too, it can really spoil the workflow if we have to stop and refer to the user manual to find out what some obscure control or jack socket does - so it follows our usual format of having a very clear, intuitive and uncluttered front panel. All of the jack sockets are in two rows at the bottom, with the inputs on the left and outputs on the right hand side.

 

The Tap Tempo VC-LFO is available with either a Black or Silver front panel.

 

Front Panel Controls

 

Waveform and Bank Selection

The eight way rotary switch allows simple and accurate selection of the sixteen available waveforms, they are split into two separate banks and all of the waveforms are illustrated on the front panel. The second bank of eight is shown in white boxes to the outer edge of the scale, and selection between Banks can be made with the front panel toggle switch.

We can also use an external CV of between 0 to +5V to select waveform by patching into the WAVE input, and when the Bank select switch is set to EXT-CV position we can select between bank 1 and bank 2 by patching a Gate or CV to the BANK Input.

 

FREQ control

This control adjusts the LFO rate, which is indicated with the LED directly above. The range can be extended by using the Multiply function, so that the full range available is from 0.05Hz (one cycle every 20 seconds) to 50Hz .

We can also control the LFO rate by patching a CV of between 0 to +5V to the FREQ Input. The frequency changes in an exponential manner, so 1V/Oct contol is possible too. When using an external CV the FREQ control becomes an attenuator for the incoming voltages, so wider voltage ranges can be easily accommodated.

 

Tap Tempo Button

Tapping this button allows us to easily set the LFO rate to match the tempo of a track or external piece of music. It sets the LFO rate with two taps of the button, if the time between taps is very short then a fast rate will be selected, or with a long duration between taps a much slower LFO rate will be selected. The LFO range can be extended using the Multiply function, so if we use the 4x multiply setting the LFO rate will be four times faster than the tempo we have tapped in.

We can also use external gate or trigger pulses instead of the TAP button to set the tempo, to do this patch into the CLK jack and send two gate or trigger pulses, the tempo will be set depending on the time difference between the two pulses.

Tap tempo control can be easily cancelled simply by adjusting the FREQ control, and in this case the previously tapped tempo Rate will be replaced by the new setting of the FREQ control.

 

Multiply control

This control allows us to easily double, treble, quadruple or half the LFO rate, so that we can vary the LFO rate but still keep it relative to the tempo of the track. It also extends the range of the LFO and works in conjunction with the TAP tempo button to allow tempo's to be created that are too fast to be tapped by hand.

We can also control the Multiplication factor by patching a CV of between 0 to +5V to the MULT Input. When using an external CV the MULTIPLY control becomes an attenuator for the incoming voltages, so wider voltage ranges can be easily accommodated.

 

Level control and outputs

The Level control is connected to the internal dual VCA, so that we can simultaneously control the level of both the the Unipolar and Bipolar outputs from the front panel. This can be automated by patching an external CV of between 0 to +5V to the LEVEL input, and in this case the Level control becomes an attenuator fo the incoming CV, so that larger CV voltages can also be handled.

Having an inbuilt VCA is hugely useful and allows control of the modulation level from an envelope generator or second LFO, so we can automate delayed modulation or rhythmically increasing and decreasing modulation levels.

The BIPOLAR output gives a modulation waveform of up to +/- 10V p/p, depending on the setting of the Level control. This will produce an output that is both positive and negative going, so if we used this to modulate the frequency of a VCO the frequency would go up and down as the output transistions between the positve and negative voltage range.

The UNIPOLAR output gives a modulation waveform of (up to) 0 to +10V p/p, depending on the setting of the Level control. This will produce an output that is positive going only, so if we used this to modulate the frequency of a VCO the frequency would go up as the LFO waveform rises and fall as it lowers, however the frequency will not go lower than it started out at because there is no negative modulation component as the LFO waveform only goes down to zero. Unipolar modulation can be very useful with VCA's, which generally only respond to positive CV voltages.

 

Waveform Twist control

The Waveform Twist function allows PWM like duty cycle variation to be applied to fourteen of the sixteen available waveforms,

We can either set the WF-TWIST manually using the WF-TWIST control, or we can vary this automatically by patching a CV of between 0 to +5V to the TWIST Input. In this case the WF-TWIST control becomes an attenuator for the incoming voltages, so wider voltage ranges can be easily accommodated.

The WF-TWIST can distort and twist the waveform in both forward and reverse directions, so when the WF-TWIST control is in the centre 12 o'clock position it was no effect on the waveshape.

Note that Waveform Twist does not have any effect on the stepped random voltages or the sloping randomised voltages.

 

 

Clock in and Clock out

The LFO rate can be controlled by patching a clock signal (ideally a square wave) to the CLK Input, and this will synchronise the rate of the Tap Tempo VC-LFO to the incoming clock signal. This will also work with non-regular clocks, so for example we could use the Time Varied clock from the Dual RVG module and this would create a similar, non regular rate from the Tap Tempo VC-LFO outputs.

The rate of the LFO against the incoming clock can also be adjusted using the Multiply function, so if we have a clock that is a little too fast then we could divide it by 2, or if the clock is too slow then we can multiply it up to 2, 3 or 4 times the rate.

The CLK out can be used to control the tempo of sequencers, other slaved LFO’s etc, and the clock out is also affected by the multiply function, so multiply x2 will double the clock out rate etc This can be used as a clock frequency multiplier, feed the clock into the CLK and a multiplied version will be available from the CLK output - the multiplication factor will be determined by the seting of the MULTIPLY control. If this is set to 0.5 then it will divide the clock rate by 2.

 

Specification

Modulation range (in conjuction with Multiply function): 0.05Hz (one cycle every 20 seconds) to 50Hz

Multiplication range: 0.5x, 1x, 1.5x, 2x, 3x, 4x

Number of waveforms: 16 total, in two banks of 8

Bipolar Output: +/- 5V p/p max, or 10V p/p max, centred around zero.

Tap Tempo: either with front panel TAP button or with two positive going pulses of +5V or more to the CLK Input

CV Voltages: 0 to +5V for full control, however higher voltages up to +12V and negative voltages up to -12V can be tolerated

 

 

Introduction to the Tap Tempo VC-LFO video

This video gives an overview of the features of the Tap Tempo VC-LFO.

 

Video User Guide

Here's an in depth look at all of the different features of this very versatile modulator.

 

Divkid Demo

Here's an excellent demo video / review from DivKid Ben that gives a really good insight into the Tap Tempo VC-LFO module.

 

Availability

Both the Dark Edition and Silver variants of the Tap Tempo VC-LFO module are in production now and available from stock.

 

TheTap Tempo VC-LFO design is built under licence from "Electric Druid" Tom Wiltshire, with some modifications and additions by AJHSynth. We would also like to thank Divkid Ben for his suggestions and improvements that were implemented during beta testing.

 

 

 

 

 

 

 

 

 

 

 

 

 

Copyright © 2014 AJH Synth