Testing an IC

[TNblueshawk]

Hey guys, much of this stuff is new to me and I thought I would ask you guys before I go fishing around Google on this.

How does one go about testing a delay type IC for ms's? In other words, how do you confirm the chip you got actually has the ms's it purports to have? For example, take some of Small Bears Cool Audio. If I wanted to test those to see what exactly I can expect from the cirucit how do you do that?

And, I love the Bear's place, so I'm not implying anything here whatsoever. Just used his as an example. You can subsititue anyone's PT2399 if you want for my question.

Thanks,
John

[jimmybjj]

http://www.madbeanpedals.com/forum/index.php?topic=2187.0

[TNblueshawk]

So for the sake of discussion then, lets say I have a known working cirucit. I still don't know how you measure the ms's coming out of the pedal? Should I know this already  . I'm willing to be embarrassed.

[jkokura]

What do you mean by ms's? Perhaps I'm getting lost in what you're trying to communicate.

The problem with testing any part is that there are so many variables in circuits, you really need to experiement on something you know well.

For example, if you have a PT2399 delay you are familiar with, you can swap out IC's to see how the sound changes. You can't really measure persay, as the measurements will be particular to your circuit based on the specific values of parts and voltage and such. The same with an overdrive - using different Op Amps in your favourite overdrive you may find one that you love, that in another overdrive would sound crappy. It's all subject to your own personal preferences and the individual circuits themselves.

If you're talking about chips themselves - the cool audio ones as an example - the chips should come out with tolerances that the manufacturer should be able to verify. So if you bought 2 of the same chip, they should be exactly the same within tolerances the manufacturer states.

Jacob

[lloyd17]

When I tested my Echo Base build I also wanted to know the max delay time I was getting. The stopwatch method was pretty lousy so instead I downloaded a free delay VST that features a ms readout of delay time then cranked the EB delay time while matching [close as I could] the VST delay time. Not a precise method by any means but I'd say it was within 10 ms or so, close enough for bedroom work.

Hope I understood your question!

[jimmybjj]

you might be able to use a audio editor and measure peak to peak. A low tech solution would be to try and match your metronome to your pedal.

[TNblueshawk]

When I tested my Echo Base build I also wanted to know the max delay time I was getting. The stopwatch method was pretty lousy so instead I downloaded a free delay VST that features a ms readout of delay time then cranked the EB delay time while matching [close as I could] the VST delay time. Not a precise method by any means but I'd say it was within 10 ms or so, close enough for bedroom work.

Hope I understood your question!

Bingo, that is what I'm after.

So, let's say I have a "real" MN3005...difficult at best to find. But, I can get a "fake" one. What makes one real and one fake? I thought it was the delay time measured in ms's. So how do you know if you bought a real one vs. a fake? I know I can listen to the pedal but that isn't very scientific, at least in terms of measuring something.

Sorry to be so obtuse on this. Even Small Bear's site says you can stack two "fake" MN3005's to get the delay time of a "real" one so there has to be a way to measure this?

[JakeFuzz]

I would get a decent microphone. Download Audacity and record the cleanest sounding repeats (maybe with no regen) into your computer. Audacity will read out in milliseconds the time signature of the original and repeated signal then you just subtract the two and get a good approximation of the delay time. That is the easiest way I can think of that will yield any accuracy.

Edit: MN3007's should have half the delay time of an MN3005 (~150 vs 300ms)

[lloyd17]

Yea the audio app method seems like the best way to go, wish I had thought of it!

[TNblueshawk]

Well,that certainly rules out any notion I had of using a DMM 

Great info guys, thanks.