Hallo, I want to share my last pt2399 project.
It's a really simple thing, and I had to omit a level control: I put it in a 1590LB box, so I had space only for two knobs.
I think it is possible (but I did non try) to substitute the 4,7K buffer's base resistor with a 5K pot (or a 10K one maybe), to control the delay level.
The pedal works good with a band in a live situation (and at home too); before I tried in a lot of ways to avoid using buffers, but I ended always with poor results: mostly unity gain problems when the effect was engaged. In the end I came to the conclusion that I don't like true bypass delays... maybe it's just that I am not good enough.
The buffer is actually a darlington transistor, not a bjt (but an high gain one will probably work).
The delay is quite clean and nice sounding, until the time pot does not pass the mid point; I had only 50K pots btw, but a 25K would have been just perfect (if you, like me, need only short time repeats of course).
The key for getting undistorted repeats was a small (well, smaller than the usual 100nf) cap between pins 9 and 10.
(http://i60.tinypic.com/33vlvz7.jpg)
That's a neat diagram and an unusual way of mixing the dry and delay (to me anyway).
Why not post links to some audio clips?
Hallo. I don't have audio clips right now. Monday I will rehearse, so I will try to record something.
It's a crude way of mixing, but it works; I had to use very few components due to space problems.
Actually I only wanted to share the pins 9 and 10 cap trik: for me it solved a lot of problems with the quality of repeats, avoiding distortion.
Lowering the 9-10 cap also lowers the output volume, i have messed with it too to keep away from self oscillation
Hallo harp.
You are right of course: lowering that cap lowers the wet volume; but you can get around this problem adjusting the gain of the op amp between pin 16 and 15. That's what I did.
I did not try 33nF, but 47nF still showed some clipping with hard hit notes (or when an overdrive or boost drive slams the input :icon_wink:).
But now I am reading about the Hamlet delay by our fellow Midwayfair (really nice sounding unit, and the player too on the demo) and I noticed the diode trick on pin 7.... wow, I will definitely try this out.
I will soon start again on the breadboard because I have another insane idea: use the free op amp (pins 14 and 13) to make an overdrive. What do you think about it?
Cool,
You can also use the free opamp as an envelope follower and modulate the delay time.
Brrrr, please not. I hate modulated delay, and chorus btw.
I only love phasers and flangers; but they are difficult to build and I rarely find a way to use them making music (my music, at least).
The only problem I expect is digital noise bleeding in (but it's a dirt box afterall), and copyrights problems when I will steal the "stupid simple overdrive" idea from pinjimiphoton ;D
Hallo, I finally had a chance to breadboard this circuit again; it fired up only at the second try... :icon_rolleyes: and I had to change the values of the delay output path components (47nF cap and 4,7K resistor coming from pin 12): with the value as I draw on the schem the delay is too high and the circuit oscillates, I had to use a 22nF cap and a 100K resistor... maybe it's the breadboard, maybe it's the chip who knows...
After the delay was ok again, I tried to use the op amp between pins 13 and 14 as an overdrive and first results are good: 22nF input cap, then a 22K resistor, 500K gain pot and a 470pF cap between the pins, 100 nF output cap and anoter 22k resistor before the output; you don't even need diodes to get dirt (I tried the usual 1n4148 ant they were too fizzy, maybe leds would be better?), probably because at 4,5 V it's easier to get the op amp to distort.
I made a negistor LFO for this circuit to modulate the delay time, here is what a came up with:
(https://farm2.staticflickr.com/1621/26615209025_e7054d6a57_z_d.jpg)
Strangely enough, I have never had any luck getting a 2n2222 to work in a negistor circuit. At any rate you could probably play around with this to reduce a few components. Not sure about latch up in this case, or if that would be a concern at all.
Also you can play around with the 15 uf to change the duty cycle, it does have a discernable effect on the sound...
Your minimum resistance to ground from pin 6 appears to be 4.9k. Isn't this a bit long of a delay time for a chorus? I've seen anti-latch minimums of 1k (that I believe correspond to around 30 ms IIRC,) that being fairly long for chorus but good enough. Is it working well for you?
To the OP- love it. Minimized and dirty. I myself have long been considering a delay with two switches and no knobs at all - I always end up using
1.a doubling/slap, something like 30-50 ms, and no repeats, and
2. Around 300 ms, no repeats, for guitar hero moments.
A bypass (with only one repeat, little need for "tails") and a long/short switch. I'm a recuperating knob junkie - trying to cut down.
Quote from: blackieNYC on April 24, 2016, 03:44:42 PM
...I always end up using
1.a doubling/slap, something like 30-50 ms, and no repeats, and
2. Around 300 ms, no repeats, for guitar hero moments.
A bypass (with only one repeat, little need for "tails") and a long/short switch. I'm a recuperating knob junkie - trying to cut down.
Me too, I love this idea. Please make it happen and share! ;)
Here's what I'm thinking: Two footswitches, bypass w/LED and fast/slow w/2 LEDs.
Inside would be trim pots for mix, rate and repeats of each channel.
Does that sound too far fetched?
Quote from: blackieNYC on April 24, 2016, 03:44:42 PM
Your minimum resistance to ground from pin 6 appears to be 4.9k. Isn't this a bit long of a delay time for a chorus?
This is not a chorus ???
Thank you Mac Walker, I was really curious about the use of the negistor to modulate delay time.
Btw I made a single knob overdrive with the free opamp of the pt 2399 and, even without diodes, you get a nice dirty mid bump. I think I posted a sort of schem, but not here ;).
Next time I will work with the pt I will give it a try.
Sure no problem. I think you could get a square wave oscillator LFO from the following, with fewer components, using the spare op amp as suggested earlier.............maybe. Not sure if it would work in a unipolar configuration without modification. I might have to try that next, also using the emitter follower buffer.
(http://www.eevblog.com/forum/beginners/op-amp-relaxation-oscillator-how-can-this-one-even-work/?action=dlattach;attach=94626)
It could be a nice idea, but I admit I am not expert with IC oscillators.
Since you plan to try this with an IC, in order to keep minmum parts count, you could try with a double opamp: so you will be able to use the second half of the IC to make a buffer, avoiding the bjt buffer.
Quote from: Mac Walker on April 24, 2016, 10:15:34 AM
I made a negistor LFO for this circuit to modulate the delay time, here is what a came up with:
(https://farm2.staticflickr.com/1621/26615209025_e7054d6a57_z_d.jpg)
Strangely enough, I have never had any luck getting a 2n2222 to work in a negistor circuit. At any rate you could probably play around with this to reduce a few components. Not sure about latch up in this case, or if that would be a concern at all.
Also you can play around with the 15 uf to change the duty cycle, it does have a discernable effect on the sound...
Any update on this?? I'll try this one ;D