Spectrum analyzator help!

[SMT]

Hi
Does anyone here have a schematic for a high quality Spectrum Analyzator??

[the scum]

The schematics I've seen are usually for a low resolution device that makes some lights blink in time to the music. That's fun, but not a useful analytical tool.

I've been using a couple of plugins recently...incredibly high resolution in the audio band, and they're free.

There's voxengo SPAN and the Roger Nichols Inspector

[SMT]

Hi Scum!
I agree, those plugins are great, I use them a lot. But it would be really cool to have a good outboard Analyzator as well. I use a 32 channel console with busses, and I also EQ after the DAW, so an outboard Analyzator would make a lot of sense...
DOD used to make a good analyzator, but they are very hard to find today...

[Geoff_T]

Originally Posted by SMT

Hi
Does anyone here have a schematic for a high quality Spectrum Analyzator??

Hi

They aren't really a DIY project... unless you want a basic instrument with fairly low resolution.

Basically, all you need is an input buffer circuit and a whole bunch of bandpass filters whose outputs you'd send to pairs of LM3915's that would drive 19 or 20 leds giving approximately a 40dB range at 3dB increments between the leds. You need to wire the leds in series if you don't want the unit to draw a lot of dc current!

It's more of an issue about the case and display than the circuitry...

[dementedchord]

exactlly as geof gave it too you... minor point... what your asking for is a real time analyzer not spectrum.... spectrums are of necessity software based even if standalone units.... the difference is a spectrum analyzerateorum shows not just the current state but a change over time... the difference is NOT subtle....

[SMT]

Originally Posted by Geoff_T

Hi

They aren't really a DIY project... unless you want a basic instrument with fairly low resolution.

Basically, all you need is an input buffer circuit and a whole bunch of bandpass filters whose outputs you'd send to pairs of LM3915's that would drive 19 or 20 leds giving approximately a 40dB range at 3dB increments between the leds. You need to wire the leds in series if you don't want the unit to draw a lot of dc current!

It's more of an issue about the case and display than the circuitry...

Thanx Geoff.

[Ethan Winer]

Originally Posted by SMT

Hi
Does anyone here have a schematic for a high quality Spectrum Analyzator??

Look here:

www.ethanwiner.com/spectrum.html

--Ethan

[Geoff_T]

Originally Posted by Ethan Winer

Look here:

www.ethanwiner.com/spectrum.html

--Ethan

Hi Ethan

Isn't your diagram missing an input bias resistor to the second stage that you are also using as an unbalanced line input?

I think a pulldown resistor to 0v is needed on the non-inverting input. Seeing as it's connected to an external source, a blocking capacitor might also be needed.

[Ethan Winer]

Geoff,

> Isn't your diagram missing an input bias resistor to the second stage that you are also using as an unbalanced line input? I think a pulldown resistor to 0v is needed on the non-inverting input. Seeing as it's connected to an external source, a blocking capacitor might also be needed. <

I agree that would be a useful addition, though I have used this device both with microphones and line level signals (Radio Shack SPL meter) for many years now with no problems. But technically you are correct, since who knows what someone might plug into a line input.

Thanks.

--Ethan