Friday, 18 April 2014

ValveWizard Equinox II

Request, and also for those who want another PT2399 based reverb pedal.  Not one for the faint hearted with that many links and cuts! :o)

One thing you will notice straight away is that this doesn't have the usual 3PDT stomp switching to bypass the effect.  Because it has tails, the stomp will just turn the effect (and LED) off and not mechanically bypass the circuit, so in bypassed mode IC1 will just act as a buffer.  So the input and output wires go straight to the sockets, and only a SPDT stomp is required.

With this being a dual PT2399 build I don't think anyone will want to run it off a battery because if they do it really won't last very long, so this should fit fairly comfortably in a 1590B without making allowances for battery space, and especially with a single pot.

Info from Merlin about his project:

Equinox II: Reverb with Tails
This project came about because I wanted to roll my own reverb. A common way to do this is to use a tapped delay line, but no such chips exist any more. No matter; the result is the same as using multiple delay lines in series and/or parallel. Several DIY reverb effects use the excellent accutronics Belton Digi-Log reverb module, and the associated patent, US8204240, shows that it uses three PT2399 delay chips, one of which is modulated at a slow rate to give a more realistic spring reverb sound. The Accutronics module is not commonly avalable in Britain (also it's cheating to use a ready made effect module!), but I did have a tube full of PT2399s (I absolutely love these chips). I also wondered whether just two could do the job, and it turns out that for guitar use you can indeed get a primitive but usable effect this way. I think this makes the Equinox II the simplest DIY reverb project on the net at the moment!

In the Equinox II the reverb effect is acheived by passing the audio through two delay lines in parallel. One is arranged for a short delay (about 80ms), and the other a long delay (about 250ms). The outputs from each are summed and fed back to the input of the delay lines, and also mixed with the original audio via a mix pot- that's it. (I have an affection for one-knob effects.)

In detail, after passing through the input buffer the guitar signal is sent both to the output mixer and to the JFET analog switch. This switch allows the input to the delay line to be muted, creating bypass with tails (this is exactly the same as my Small Time delay).
Following the JFET the signal then passes through a 15nF capacitor which provides a little bass cut, to stop the reverb getting too muddy, and it then feeds into a second-order high-cut filter. This is also where the output of the delays lines is fed back in.
The output of this filter feeds the short delay line, and also the long delay line (via an unavoidable inverting buffer).
After the signals emerge from the two delay lines they are both summed and filtered again. All this filtering is necessary to reduce noise from the analog-digital-analog conversion inside the ICs.

I spent a long time tweaking the delay times, filtering, feedback, and mixing ratios, to get what I think is the most usable reverb sound using standard component values and the simplest architecture. My first Equinox prototype also had adjustable delay time on the long delay line, and a fat/bright switch. But I didn't find these to be very useful (at anything but the optimum delay time all you get are 'metallic bathroom' type sounds), so I trimmed the circuit down to the bare essentials, creating the Equinox II shown here.

To see more information including the schematic and a PCB for those who want an easier life, check out Merlin's page here, and a clip can be heard here which sounds pretty damn good to me!

And after discussions below, a version which omits the JFET and instead uses the second pole of the stomp to turn the reverb on and off.  This will also keep tails intact as per the original but because of the parts omitted has removed a link and a couple of cuts and is one column smaller.

Tuesday, 15 April 2014

Madbean Cave Dweller II Dub Edition

As requested, version 2 of the Cave Dweller with all noted mods included.
Info from Brian which can be found in the PDF linked in the version 1 thread

Cave Dweller II (“Dub Ed.”) expands upon the underlying design of CDI , but adds an additional PT2399 for roughly twice the delay time. It also combines the two feedback controls into one. An additional mod has been included if you wish to add a true Mix control to Cave Dweller II.

Cave Dweller II Controls

Time – This sets the delay time.
Dwell – This control is a combined version of the Dwell and Echo controls of CD1 (thanks, Alex!)


Cave Dweller II - Dub. Edition - is for those really cavernous delay needs. It utilizes the current mirror set-up of the “DM-5” delay project to achieve roughly twice the delay time of CD1. The max delay time should yield about 1 sec, although a mod has been included to artificially reduce this, if desired.

In this version, Dwell and Echo are combined into one. The control works slightly differently than CD1. At minimum, the repeats are filtered on the opposite end of the spectrum, meaning they are more “telephonic”. This setting sounds very similar to the Deep Blue Delay. At max, the repeats are dark and ambient similar to the CD1.

One caveat with the combined control is that there is minimal influence on the number of repeats produced by the effect. For those builders who wish to add an additional Mix control to limit the number of repeats, a simple mod has been included. Please see the illustration below on how to implement the Mix control mod.

Additionally, the dark repeats have been limited to non-oscillating by using a larger value for R12 . If you do implement the Mix mod, you can lower the value of this resistor from 750k to a value between 470k and 560k to re-introduce oscillation. This is not recommended when not using the Mix mod.

One other mod has been included with R20 . This resistor resides in parallel with the Time control and allows you to reduce the max delay time of effect. This mod was included for those who prefer a cleaner delay (max delay times with PT2399s tend to introduce some digital artifacts and noise). The value can be selected to taste, and a 200k is suggested. This results in roughly 20% less delay. A 150k resistor yields approximately 25% less delay. 

Madbean Cave Dweller

Nice sounding mini delay, designed by Madbean to fit in a 1590A box, and after checking with Javi this layout should fit in one too :o).  Tantalum caps or mini electros may be needed to keep things as compact as possible, and maybe a multi layer ceramic for the 1u.

Info from Brian about his original project:

The Cave Dweller I is a low parts count delay comprised of a single PT2399 chip and fitted for a 1590A enclosure. This ranks as a “mediumi-fi” type circuit, meaning that filtering of the PT2399 is kept at a minimum in favor of a small footprint. While you won’t get quite the fidelity of the Echo Base, for example, it still sounds very, very good and offers a somewhat unique flavor of delay. The effect takes advantage of the two on-board amps of the PT2399 for use as input and output mixers. The feedback and filtering are combined in a unique way which produces a slightly different set of controls than the typical PT2399 delay. This leads to some really “haunting” and musical repeats at long delay times.

You can read more about it in the project documents here, and if you prefer, the PCBs can of course be purchased at  Check out some of his other boards while you're there.  I just bought a Pork Barrel, Collosalus and StageFright from him which are fantastic quality, and are builds that I would always prefer to opt for PCB over vero.

Monday, 14 April 2014

EHX Satisfaction Fuzz

Note that the C7 and the D2-D3 are not present on the original pedal. There are holes ready for those components. Adding C7 as 4n7-100nF cap will increase bass response and adding diode clipping to the place of D2 & D3... Well. That will make this an different animal.

Grind Customs Electric Boogaloo Optical Tremolo

Another project collaboration between Rej at Grind Customs and CultureJam, similar to the Shoot the Moon but with a couple of subtle differences including a shape switch instead of the wave pot (similar to the 2 knob version we did).  If you don't want to roll your own with the LDR and LED, the Vactec VTL5C3 is the recommended vactrol.

I can't find a video anywhere, so if anyone can make one that I can post with the layout that would be great.

Should all layouts be verified before publishing? This would mean less layouts but more peace of mind?