Author Topic: Echo Base - a new PT2399 delay  (Read 830257 times)

RndSndRecords

Re: Echo Base - a new PT2399 delay
« Reply #1520 on: January 29, 2019, 09:37:52 PM »
Couple questions about the schematic:
How is the "LFO" power source derived? Is it just a tap off the other 5volt rail?

I'm thinking of building this for line level source by using a balanced line receiver. Any idea where to start with that?
I'll probably use a BB ina 137 on the front end and a DRV 134 out. I feel like I could ditch U3 (TL072) in that case.


garcho

Re: Echo Base - a new PT2399 delay
« Reply #1521 on: January 30, 2019, 12:53:28 AM »
The VDD for the LFO op amps is via the 220Ω and 9VDC. The reference voltage is from the 5VDC off the regulator.

it's just a PT2399, you could configure the op amps as receiver/driver. what's your plan?
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"...and weird on top!"

RndSndRecords

Re: Echo Base - a new PT2399 delay
« Reply #1522 on: January 30, 2019, 06:40:09 PM »
The VDD for the LFO op amps is via the 220Ω and 9VDC. The reference voltage is from the 5VDC off the regulator.

it's just a PT2399, you could configure the op amps as receiver/driver. what's your plan?

Just after I posted I saw the LFO tap coming off the lm7805. Missed that before.

Not much of a plan yet, but I'm scheming a sorta lofi delay for mixing.   I'd probably use a fixed modulation like an out of sorts tape machine and run everything off of +/- 16vdc

and I know Echoboy is awesome but where is the fun in that.


jdom1984

Re: Echo Base - a new PT2399 delay
« Reply #1523 on: March 12, 2019, 11:40:21 AM »
the schematic is gone

slacker

Re: Echo Base - a new PT2399 delay
« Reply #1524 on: March 12, 2019, 02:16:28 PM »

Re: Echo Base - a new PT2399 delay
« Reply #1525 on: March 24, 2019, 07:33:20 PM »
Hey, I just have a couple of questions - more for my own understanding than anything else..

What's the purpose of the 220r resistors on the 9v and ground connections from the modulation opamp?

I see that the 5v supply is being used as the reference voltage for the modulation opamp. Would it make any difference if I used a 4.5v reference voltage (I'm planning to build this in a box with some other bits and will already have a buffered 4.5v which I could use). It seems to me like using the 4.5v would make more sense but I might be missing something..

Thanks!


slacker

Re: Echo Base - a new PT2399 delay
« Reply #1526 on: March 25, 2019, 02:20:27 PM »
The 220R resistors are to try and keep noise from the LFO  getting into the audio parts of the circuit by decoupling the supply to the LFO. To be honest I'm not sure the one to ground does anything, it could probably be replaced with a jumper.
It shouldn't make any difference if you used a 4.5 reference voltage instead of the 5 volts. When I designed it I just figured 5 volts was close enough to 4.5  so I'd save a few parts and use that as a reference. With hindsight this wasn't a great idea because the 5 volt supply can be a bit noisy.

If you're going to build this I would use this version instead, which has a better input buffer and quieter reference voltage.

Echo Base version 2 schematic

Re: Echo Base - a new PT2399 delay
« Reply #1527 on: March 25, 2019, 05:58:59 PM »
Thanks! And thanks for sharing the design!

telebiker

Re: Echo Base - a new PT2399 delay
« Reply #1528 on: February 11, 2021, 07:23:50 PM »
Looking at the schematics I'm wondering, what need to be done in order to replace 50K time pot to the 10K to keep more or less the same delay time? Sorry if the question is silly.
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