JH Variable Slope Filter/Phaser: Building a Prototype

Front panel of the JH Variable Slope Filter/Phaser first posted here and here.

notes from JH:
"Well, the first prototype was part of my JH-3 Modular, of course.
But for testing the PCB layout and fine-tuning the circuit for which I
intent to offer PCBs, I wanted to build a standalone effect. For this, I'm
using the same tabletop enclosure that I've used for my Wasp Filter Clone
some years ago. (Pultgehäuse from Conrad Electronic, Best. Nr. 520772 -
Manufacturer is APW)
The focus is on the on-board LFO modulation, so you won't find any
potentiometers for external CVs on this front panel. (The circuit allows a
lot of external CVs, of course.)

Here's a screenshot of the panel in Frontplattendesigner (Schaeffer):

http://www.jhaible.de/varislope_filter_phaser/varislope_proto_fpd.jpg [pictured]

Input Level - Audio signal input level control
Feedback - Resonance Loop. Can burst into self-oscillation. Inverted or
non-inverted feedback for unusual effects.
Mix - Wet / Dry mix of filtered and unfiltered signal. Inverted or
non-inverted mix. Mandatory for phasing; interesting for LPF mode because of
phase cancellation effects.
Ouput Level - Output attenuator for audio signal
APF / LPF - Switches to change the function of the 6 filter stages from All
Pass Filter (Pole/Zero pairs) to Low Pass Filter (Poles only). 3 Switches
for 3 pairs. (6 individual switches would be possible as well.)
Mix / Filter - In "Filter" position the "Mix" potentiometer is disconnected
for 100% filter signal without any crosstalk from the dry signal (important
for powefull 36dB/Oct LPF effect).
Clean / Dirty - Dirty applies some dynamic load to the single-ended buffer
of the last filter stage.
Active / Bypass - True hard bypass
Slope - Spreads the pole frequencies of the individual stages. This means
less filter steepness in LPF mode (ccw end is 36dB/Oct), and wider notch
spacing in Phaser (APF) mode.
LFO Amount - Modulation amount of on-board LFO
LFO Wave - Crossfade between LFO waveshapes: Tringle -> Sine -> Square ->
Sample&Hold -> Audio-Rate Self-Modulation (see video).

Also possible, but not on Front panel:
Slope Control Voltage Input
LFO Amount Control Voltage Input
LFO Waveshape Control Voltage Input
LFO Rate Control Voltage Input
External Filter or Phase Control Voltage Input (for ADSR etc.)
External 1V/Oct Control Voltage Input (no tempco, though.)

Project page with audio samples:
http://www.jhaible.de/varislope_filter_phaser/varislope_filter_phaser.html"

JH Variable Slope Filter / Phaser

via JH on the AH list:
"I'm thinking about making PCBs for this.

A mean little module from my JH-3 Modular.

6 filter poles, realzed with OTAs and combined FET / Bipolar buffer stages.

Variable Slope function for 6-pole VC LPF.
Voltage controlled Pole Spread for Phaser mode.
Zeroes switcahbel in pairs, i.e. a lot of combinations of all pass and low
pass stages. Positive and negative feedback. Positive and negative wet/dry
mix. Rather special overdrive behaviour (Dirty!), and (IMO) pleasant way of
breaking into oscillation.

Old picture (from JH-3) [pictured]

Demo 1 (Arpeggio from OB-8, with delay and reverb. First few seconds dry - then playing with phaser.):
http://electro-music.com/forum/download.php?id=16715

Demo 2 ( This is something I recorded a few years ago. I don't remember all the details. But it was a Split on the OB-8, bass sound on left hand and organ sound on right hand, and the whole thing was processed with the Variable Slope Phaser / Filter to get that "pulsating" sound. Lots of delay and reverb as well, obviously.):
http://electro-music.com/forum/phpbb-files/oct_06_zwischenstand_edit_189.mp3

JH."

Juergen Haible Variable Slope Filter / Phaser PCB

Image of the PCB layout for the JH Variable Slope Filter / Phaser. You can find more info including samples at the JH website.

JH Variable Slope Filter / Phaser Order Info

follow-up to these posts (scroll). via JH:

"now that a good number of people have shown interest in this project, I'm ready to take pre-orders.

(See
http://www.jhaible.de/varislope_filter_phaser/varislope_filter_phaser.html

for details about the project.)

Pricing is EUR 27.00 per board

plus a single EUR 6.00 shipping flat charge for worldwide shipping,

regardless how many boards you are ordering and where you live.

It does *not* include any customs fees or tax that you may (or may not) have

to pay in your county.

What you get is a double-sided printed circuit board with component overlay,

approx. size 160mm x 100mmm.

You have to buy the electronic components for this, and build the device,

yourself. (Check the above website regularly for updates and building hints,

bill of matrials etc.)

If you want to place a pre-order, please send me an email to the following

adress:

jhaible@debitel.net

and use the FOLLOWING FORM (fill in your data instead of [],

for instance: "2 Boards" instead of "[quantity] Boards")

===== Start of Email Order Form ===============

Email Subject line: 36dB Varislope order: [quantity] boards

Email text:

I'm ordering [quantity] pieces of the 36dB VCF and Variable Slope
Filter/Phaser PCB

for EUR 27.00 per board + EUR 6.00 single shipping flat charge for any

number of boards.

I'm aware that I may have to pay additional amounts of customs and tax in my

country.

I'm aware that I'm only buying blank PCBs that may help me building an

electonic module - I'm *not* buying a diy kit, not a "project" - just pieces

of FR4 with copper traces.

I know how to build electronic circuits and I am trained in electrical
safety matters.

The seller of these PCBs will not be held responsible for any damage that
results

from these PCBs, directly or indirectly.

My shipping adress is

[Your Name]

[Your street, number, city, ZIP code, in exactly the form

that is generally used in your country]

[your country]

My paypal adress is [your paypal adress].

I===== End of Email Order Form =========

Looking forward to hear fom you :)"

Tellun JH Variable Slope Filter/Phaser Mods

full details on tellun.com

1. Change Input Gain for 10Vpp Signals
2. Add Three Input Mixer
3. Change Output Driver
4. Add Reversing Attenuator for FM1 Input
5. Add LED Driver for LFO Output
6. Change AUX Input Gain for 10Vpp Signals

Variable Slope Filter / Phaser Progress

New images of the prototype via JH

"No new sound samples yet (front panel wiring is still missing). Old sound samples and general information is here"