Is there a way to reduce the background noise on PT2399 delays ?

[alltrax74]

I lately built a DBD (my 5th so far) that's works and sounds very well, but just like with the 4 others, I have this kinda shhhhh on very clean settings when the note is fading.
I read that this is to be expected with PT2399 delays and I can live with that, but I was wondering if there is way to reduce this ?

[tjdracz]

How many pt2399 you went through? I had 8 from Tayda and with one faulty, rest had quite some variance in noise? Seem that many people had problems with them and furthermore, ones sold by likes of Dr Tweek have completely different markings (are ones "fake" then?)
With well regulated supply, noise is quite bearable and it's mostly a problem with longer delay times. I mostly use slapback anyway so I don't care but that's just a thing with pt2399, live with that or wait for Madbean to release that mn3007 based small clone layout.
I also originally jumpered that 33r resistor from power supply because it kept overheating and falling. Guess rating was too small? Thought that 1/4W would do it but apparently not, unless I've got 1/8W that were sold as other rating. That resistor is part of filtering and helps somewhat with noise. Curiously enough, after replacing the jumper with carbon film 1/4W resistor, had no problems whatsoever and noise went down.

[IvIark]

With PT2399s all I can say is get a lot of them in and don't even consider using them without socketing, they're much too variable to be able to rely on the results.

[alltrax74]

Ok thanks guys, I have more or less 10 PT2399 to test, all from Tayda, I'll let you know.
I also noticed that the opamp has an effect on the noise. I tried a few of them and so far the best result was with a LM833 or TLC272CP. Worse was with TL072.

So Mark, do you recommend to swap that 33R CLR which is on the layout for a 100R ?

[IvIark]

It really depends on the current draw and plenty of people have built this using 33R without problem so I wouldn't worry about it.  If I was doing that layout now I would probably put 100R in there instead, just because I don't see much point in pushing limits.

[alltrax74]

And wouldn't it be even better to increase further more the CLR value to decrease to voltage on the input of the regulator in order to protect it from heating too much ?

[IvIark]

It's the temperature of the CLR at the supply that would increase as more current was drawn through it.    The regulator will draw whatever current it needs from the supply (providing the capacity is there of course), so its temperature shouldn't change.  If the required current isn't available then it simply wouldn't work and so neither would the effect.  

I bought 50 of the TO220 versions of the regulator for any time where the TO92 version didn't seem up to the job.  They can be bought for very little if you want extra capacity in the regulator (and a handy heat sink if you need it).

[alltrax74]

Ok, thanks

[alltrax74]

I tried 7 PTs and 3 were almost noise free
I'll order a few ones from Musikding to see if they are better quality