I have built a couple of Deep Blue Delays and with the last one I have a weird working one. Everything works fine except that there is a winning (almost theremin like) hi-pitched noise always present on the Delay side. It becomes even more obvious once I start Rotating the Delay Pot as the noise moves with it.
The only significant changes I have made to the circuit was changing the input Gain and impedance from r2-180k / r3-390k configuration to 470k/ 470k respectively and used Tantalum capacitors for all 1uf caps on the Audio path.
I anyone could give me an hint on what to look for it would be appreciated.
Voltage on Pt2399
1- 4.93v
2- 2.45v
3-0v
4- 0v
5- oscillates beetween 2.87 and 2.91v
6- 2.45v
7- 1.92v
8- 1.98
9- 1.5v
10-2.45v
11-2.45v
12- 1.42v
13-2.45v
14-3.85v
15-1.38v
16-2.45v
Did your tantalum caps come from Tayda? I and others have had problems with them.
I got them from Musikding in Germany. I'm wandering if that is the problem. Either that or a fecked PT2399, which I doubt.
Then it's probably not, there's nothing wrong with using tantalums, I'm just wary of the Tayda ones. I don't want to start a "always put tantalums in backwards" movement because that's a very, very bad idea and these things can spiral through misinterpretation but recently someone discovered on DIYSB that their Tayda tantalums had been labelled backwards which is why I brought it up. Usually I'd expect hiss rather than whine from that anyway.
The PT2399 does have a clock inside it which varies with delay time as you've found out, most of the time it should be out of the audible range and anything left should get filtered out by the support circuitry so it would be a good idea to check all your resistor and capacitor values and to double check all your solder joints. How are you powering this as well? Is it daisy chained with any digital effects or anything using a charge pump? You could be experiencing some form of heterodyning through the power supply.
I will double check my resistors values and loo for cold solder joints. I use a EHX Power supply just for testing my pedals, there's nothing else rather than the pedal and the power supply.
Some of those PT2399 voltages are way off. Pin7 and 8 should be about half of what you have. Pins 9-16 should all be about 2.45v.
Don't know if it's your PT chip or something else at this point.
Will check if there is anything sketchy around those pins. I have replaced the tants on the delay audio path, but after this new evidence I believe they are harmless. Could a faulty pot be an issue? As in the Delay pot?
Quote from: garfo on September 30, 2018, 03:21:22 PM
Will check if there is anything sketchy around those pins. I have replaced the tants on the delay audio path, but after this new evidence I believe they are harmless. Could a faulty pot be an issue? As in the Delay pot?
Not likely. Your voltage on pin6 is correct.
What happens when you ground pin 4? That's always a fun surprise when some of the PT2399 like it grounded and some don't.
Quote from: Scruffie on September 30, 2018, 03:49:39 PM
What happens when you ground pin 4? That's always a fun surprise when some of the PT2399 like it grounded and some don't.
Pin 4 is connected to ground via the Delay pot.
I get that but I meant directly to ground.