The 391x series takes a different approach to envelope detection - it lets you brain do it. The input stage is designed to clip off the negative half-cycles of the incoming audio, acting as a precision half-wave rectifier. But after that there is no integrating capacitor. The signal goes straight to the comparators, so the LEDs blink one every cycle of every note with a brightness that is proportional to that half-cycle only. Your retina and brain smooth this out to what appears to be a light that follows the energy of the note. Because of this, you might not need the two diodes and shunt capacitor after the BPF, just the series cap and shunt R to shift the DC down to the 3914 input range.

If by first amp you mean the one after the input pot, a gain of 1000 is too high. At 10 kHz that is a gain-bandwidth of 10 million; that's a lot. What is your highest frequency of interest for the color organ, and what is the input signal level?

ak

 

Well, I won’t know what the signal level output of the DAC is until I get it and do some tests. The ad says 5 volts. That could mean anything.

But I’m not really looking for values at this point, I just put those in based on what I have seen, I really just need an idea of what amp to use.

So I’m thinking that 1meg should be much lower huh?

I should just take all of the values off of the schematic, and do my own calculations.

As far as how high I’m interested in, well I would have to say whatever I need to get common sounds like cymbals and such, this is also something I haven’t really gotten to yet, was going to leave the BPFs, high and low filters and certain things to later.

Regarding the 391x series, I’m not even sure what you are referring to…sorry. I assume it’s an OP Amp, but I also assume it would mean redesigning the entire thing, or maybe just not using the VG at that point???

Can you give me some actual numbers so I can look them up, and if they don’t produce a through hole version, I can’t use them anyway.

 

Hello,

The LM3914 is a linear dot/bar display driver:



The LM3915 is a 3dB steps dot/bar diaplay driver:



Bertus

 

Oh, by 391x series he meant 3914 and 3915.