Where (and which) will you place an od/distortion in this circuit, to make it sound "LO-FI" and boost with a JFET preamp?
Similar to an Echoplex, to get some tape distortion..
I suggest as example this simple/basic PT2399 delay that clearly shows where end the first buffer ends and where the second one start:
(https://i.postimg.cc/RqBDCR49/Schematic.png) (https://postimg.cc/RqBDCR49)
(https://i.postimg.cc/HWcD2ZNJ/Schematic.png)
When people think "lo-fi" they tend to think older telephone-type bandwidth, which implies bandpass filtering. That's certainly not what "lo-fi" always means, or the complete solution to achieving it, but it is often an important piece.
The circuit provides the usual lowpass filtering. All that is needed to get a bandpass-like sound is to restrict the low end.
I don't see a schematic here, but I'd start by trying to put it after the feedback is mixed in but before it goes into the delay.
I agree with Mark that a bit of judicious bandwidth limiting will help to give the thing some lo-fi heard-it-on-the-telephone character. I'd put the component values of those filters into the filter tools here and see what you get:
http://sim.okawa-denshi.jp/en/Fkeisan.htm (http://sim.okawa-denshi.jp/en/Fkeisan.htm)
They look like 3rd order MFB filters, so this would be the page:
http://sim.okawa-denshi.jp/en/MultipleFB3Lowkeisan.htm (http://sim.okawa-denshi.jp/en/MultipleFB3Lowkeisan.htm)
If they're fairly full-bandwidth, you might want to cut them down a bit so the top end is lower (but they might be pretty limited already, I dunno). Then go through and change any DC-blocking caps to purposely remove some bass too (C10, C7 for example). Everything below 800Hz say. Experiment. It's a question of taste and objectives.
After that, if you want some actual grit added (beyond what the PT2399 provides itself) I'd patch something in where C23 sits - after the delay output filter, but before the repeats. You want a fairly soft distortion, since it will build up on each echo, so I'd maybe go for a differential transistor pair rather than clipping diodes.
Thanks everyone for your advices and answers.
In this case, you're right Mark about the therm "lo-fi".
In this case, I'm looking for some grit and dirt over repetitions.
I saw, for example DBA, adds a simple fuzz circuit at the end of all the schematic.
I don't know about MI Audio LoFi Delay, but it have a "Input" knob that adds 'distortion' to the repeats.
Another one is the Caroline Kilobyte
Lo-Fidelity Digital Delay w/Analog Overdrive (
"We've kept your original, dry signal path analog and pure, then given you a +21db boost/overdrive preamp to smash a low fidelity digital delay chip designed for karaoke machines and kids' toys into smeared, repeated glory").
The main idea is to smash a momentary footswitch, to max feedback and start to oscillates while get distortion.
Quote from: ElectricDruid on July 02, 2021, 07:38:33 PM
After that, if you want some actual grit added (beyond what the PT2399 provides itself) I'd patch something in where C23 sits - after the delay output filter, but before the repeats. You want a fairly soft distortion, since it will build up on each echo, so I'd maybe go for a differential transistor pair rather than clipping diodes.
I think the goal could be reached over here...
ACLARATION: DBA Echo Dream 2 haven't a fuzz circuit at the end.
It just messing the gain of the output stage: 1M pot over R22 as "fuzz" knob.