Ping Pong delay is easy, right? Just tick a box in a plugin, or flick a switch on your handy stereo delay unit and you’re done, right? Well, sure, but that’s all digital. What I’m talking about is ping pong delay, old school. Patching 2 mono, analog delay units in order to create ping pong delay in the stereo field.
When I first started thinking about how to do this, very few ideas came to mind. Of course there is the pseudo ping pong trick of setting one delay time at X with the other delay at 2X, which would give you a repeat on one side then the other. But that only works for exactly 1 repeat per channel. If there is any feedback, the first delay will sound again each time the second plays, which means it’s not really ping pong at all. It’s only kinda sorta ping pong. I wanted something better. The real McCoy.
As I started to research analog ping pong patching via Google, I was quickly dismayed. There aren’t really any good sources I could find to explain the method for patching ping pong delay. Nothing. Nada. After I couldn’t find the info I was after via research, I decided to ask. I asked on an audio engineer forum. Crickets. I asked a home studio group on Facebook and was met with “Just use a plugin. It sounds the same”, as if that’s a good answer to the question of how to patch analog hardware. I looked in my own studio recording books, which were all silent on the matter. It’s as if this information just doesn’t exist, or, more accurately, was outdated by the time the internet arrived, and the knowledge on how to perform this studio trick was simply never recorded digitally. It’s a lost art from the days of yore when everything had to be patched manually, and no one outside of studios used it. A voodoo spell that not even those inside of professional working studios seem to use any longer. Analog ping pong delay is dead.
After searching for what seemed like forever, I finally happed upon a video which explains using 2 analog delays in ping pong fashion, with the aid of a desktop mixer. The patch is fairly simple, even if it’s not intuitive.
Sound Source > Ch 1 input (panned center)
Ch 1 Aux Send > Delay 1 input
Delay 1 > split directly to Ch 2 input (panned hard left) and Delay 2 Input
Delay 2 > Ch 3 input (panned hard right)
Ch 3 Aux Send > Delay 1 input
Mixer Stereo Output
Be sure that both delays are set to the same time. Be extra sure that the feedback (repeats) for both delays are set to the minimum (1 repeat). The Aux Send of input 3 (Delay 2) controls the number of repeats. BEWARE: This is a feedback patch. It can get out of control very quickly. Use the Aux Send wisely.
But I don’t have a desktop mixer, and although they can be had inexpensively, I didn’t really have much use for one outside of wanting to do tape echo ping pong delay. I used to have a Xaoc Devices Praga in my eurorack synth, which would have been ideal, but I sold it in favor of decentralized mixing alongside using a matrix mixer. Hmmmm….
A matrix mixer is nothing if not a set of inputs, sends and returns. “I think I can make this work, even in the context of my matrix mixer being full stereo”, I thought. And sure enough, after several drafts in my Notability folder for synth patching, and experimenting with dummy cable theory, I had a solid plan. I just didn’t know if it would work.
The theory with a matrix mixer is the same, but because mine is stereo, I had to use make clever use of some dummy cables in order to defeat L> R normalization at the inputs to ensure everything was in the correct channel at the outputs, while still having access to the dry and wet signals independently to mix their respective levels later in an output mixer. To mix the dry and wet in the matrix as it’s patched would leave the dry signal in the left channel only. No good.
Sound source > Input 1L, with dummy cable in 1R
Output AL/R > mono mixer > Delay 1
Delay 1 > Input 2L, with dummy cable in 2R
Output BL > Delay 2
Delay 2 > Input 3R, with a dummy cable in 3L (it is not necessary to use a dummy cable here, but I’m using one for consistency)
Output CL > Output Mixer (Pan Center)
Output DL/R > Output Mixer (Pan L/R respective, or use a stereo input)
Knobs with an X are fully CCW (off). Knobs with a green check are mixed to taste. Knob with the red check is controlling feedback for the repeats. BEWARE: Ch 3A is feedback from Delay 2 to Delay 1. It can easily run away out of control and blow your speakers, headphones, and/or ear drums. Use it sparingly.
This method also makes use of a separate mono mixer to act as a send for both the source and Delay 2 to Delay 1. It what helps make the magic happen. Without the mixer, I couldn’t get the source and Delay 2 to Delay 1 without getting channels mixed up. Everything must remain on discrete channels in the matrix. As a result of the several dummy cables, Ch A’s outputs are discrete channels being used in a dual mono setup rather than in stereo, with those signals being mixed separately before going to delay 1. It was the only way to accomplish the task of sending both the source and Delay 2 inputs to Delay 1 while keeping those signals unmixed and discrete inside of the matrix mixer for final output.
Heed the inputs and outputs used very closely. It seems a bit odd, but it ensures that the stereo field is intact and signals remain properly separated until the final output mix. Deviate at your own peril.
The dry output is from Ch C, with the wet stereo output from Ch D. Pan the Ch C output to the center, with Ch D being panned L/R respectively.
This patch can likely be simplified (and perhaps sound better as a result) by splitting the audio at the Delay 1 output rather than relying on the matrix mixer to send the output of Delay 1 to Delay 2. This experiment, however, is for another day.
Although I haven’t pondered the nitty gritty of this patch in a mono matrix mixer, I think it would likely be a better tool for the job, but my first inclination is that you would need 5 outputs, and not the standard 4.
Enjoy!