Calibrating Analog Peak LED Indicator

Hi

I'm in the middle of DIY VU Meter project, and i'm adding Peak LED Indicator into the circuit

the idea is, i'm try to model the peak indicator behaviour of my RME 9632 TotalMix control panel mixer, so my analog VU meter peak led will blink in sync with my soundcard control panel peak led

my method for finding treshold for soundcard control panel peak led :
- using 1 khz 0dBFS sine test tone vst plugin in Cubase 5
- adding another vst plugin to boost level above 0dBFS, i'm using sonalksis FreeG
- i found out my soundcard control panel mixer peak led start blinking with signal 0,7db above 0dBFS
- after that i'm calibrating my vu peak lead to match the soundcard control panel peak led

ps: my soundcard manual dont state at what level in dBu/dBV the peak led is blinking

my question is :
- is the 1khz sine test tone, "boost gain till it peak" is the easiest and valid method for calibrating peak led without using exact dBu/dBV number?
- at 1khz i manage to match my vu peak led treshold to match the soundcard peak led, but why at low freq (60-200hz) is totally different?, while the soundcard peak led is blinking, my vu peak led not blinking

here i attach my peak led schematic

thanks

> here i attach my peak led schematic

There's no LED there.

WHY do you have the opamp running a gain over 2,000?? TL071 will fade above 2KHz.

PRR said:

> here i attach my peak led schematic

There's no LED there.

WHY do you have the opamp running a gain over 2,000?? TL071 will fade above 2KHz.

Click to expand...

Hi PRR, thanks for replying

sorry i forget to note, i connect the LED via MOLEX connector

as about the "gain over 2000", i'm have very little knowledge about basic opamp and just using the schmitt trigger schematic from http://sound.westhost.com/project67.htm

since that schematic is the only peak led schematic (i test almost ALL peak schematic from this website and google) that work quite closely with my needs

what do you suggest for the peak schematic?

and i attach my full vu + peak led schematic

a bit spec for my VU :
- i'm using schematic from http://sound.westhost.com/project128.htm
- balance/unbalance input, via TRS connector
- toggle switch for dual operation, -6db (mastering) and -18db (mixing)

thanks PRR

> using the schmitt trigger

Sorry, I mis-understood the schematic.