The World Of Eurorack Modules Does Not Have To Be Expensive
In the Facebook group Synth DIY, Mike Eckert has recently built a delay Eurorack module itself that is not only very cheap but also sounds good. He bought a PT2399 Karaoke OK Microphone Reverberation Audio Pre Amp Amplifier Reverb Board and transform it into an Eurorack compatible module.
The module is so cheap because everything is already assembled and even knobs are included. What is a small limitation of this cheap module is the selection of the input and output. The input here is mono and the output is stereo.
What Mike Has To Say About The Module
“I present to you my latest: A Eurorack delay fx module for less than $15? I call it the 卡拉OK! (karaoke) delay, a PT2399-based module that uses a chinese ebay seller ‘karaoke reverb’ board that costs literally <$9, fully assembled, knobs included!, with some very minor mods and a PCB panel I designed”.
“The whole thing comes assembled, with leads for the input headers and those little silver knobs. It is meant for power from an AC transformer with terminal blocks; However, +/- 12V eurorack power can go right thru the bridge rectifier it has on board without issue, so I wired up a 10 pin header after desoldering the terminal block. The board comes with two 1/4″ Mic input jacks- they both are in parallel, not separate channels or anything. I desoldered those and wired in a 3.5mm jack to one of the Mic inputs. I was worried that the mic gain would just clip a eurorack signal like hell but it doesn’t! this is because the gain control knob seems to be setup for powered mics maybe. The output is stereo, but the delay is mono. So I just used one of the included leads wired to a jack for output.”
“And for the panel, There is a input to the board for a ‘mix in’ (meant for the song audio you sing karaoke over) and a pot for the volume of that- I chose to keep that pot, however it currently does nothing as I deleted to input for the music mix in (as it would be nothing but a blend into the mix). I also threw a jack in between the in and out because there was room, and labeled it ‘Mod’ in anticipation for adding voltage control of something on the board, possibly with a vactrol. Currently I don’t have it wired to anything either but once i reverse engineer a schematic for the board it will get used for some mod.”
“The unit outputs is ‘stereo’, because in the karaoke application you can pass stereo audio thru it, but the input to the PT2399 delay circuit is only a mono signal, and thus gets applied to the output equally on both channels, so there is no stereo effect. The L and R sound the same. So it is just a single mono jack input and output. The input is 1 of the mic channels, the output is the Left channel of the output.”
A video demo is available in the Synth DIY group! Although this is not a high-quality delay effect processor, it has enough character in my opinion. If you have some DIY skills and love such projects, this could be your next project.
Source: Synth DIY