schematics for VU peaks ??

Back in the 60/70's I had a big AKAI tape recorder where the VU-meters could be switced to show "peaks" of some sort and hold them for an adjustable amount of time.

I would like to have this functionality again on my VU-meters - I have done some Googling but ... argh, nothing like that comes up !

I remember there was a switch and the some small pot where the "holding-time" could be adjusted.

Any ideas for a schematic for such a jig ?

Sure... design a peak detector/hold circuit and send the smoothed DC to the standard meter.

JR

JohnRoberts said:

Sure... design a peak detector/hold circuit and send the smoothed DC to the standard meter.

JR

Click to expand...

Ha, ha, let me refrase then:

Any ideas where to find a schematic for such a jig ?  ;D

I'm looking for something similar. just an peak (clip) indicator with several seconds hold. http://www.groupdiy.com/index.php?topic=50794.0  8)

A noise gate side-chain circuit should give you what you want. These are simple comparator-based peak-detectors with a DC trigger output. Threshold/envelope parameters can be easily preset once you identify the appropriate resistors. Simplify, remove what you don't need.

This has BBC/ITU PPM characteristics.  It passes all the standard PPM tests but it's not a true PPM rectifier cos it is peak-to-peak rather than peak detecting.  But I haven't found any real life situation where it gives different results from a true PPM.

A slightly different version is in the Mk4 Soundfield Mike where the log scaling in the meter is done by bar graph drivers whose number I've forgotten.

I made some little cards that might do what you want.
They are described here: http://www.groupdiy.com/index.php?topic=47820

If you look, one of the functions that the card can perform is to isolate drive a regular galvanic VU meter (with or without rectifier) from a balanced or unbalanced input.

It can also perform the function of controlling meter rise and fall dynamics (rise can be faster than fall, which is what VU meters do)

It can provide a separate LED clip light, or set of lights.  These can be set to be fast or have a "hang time" or hold and reset with a switch.  A switch can be installed for each clip hold light, and a master reset switch can reset many clip held lights (for instance a whole meter bridge).

Important:  I have attached the actual circuit, but do not trust the schematic because it has errors.  This is the actual prototype board schematic, and I had to make patches on the board to make it work correctly.  If you want my corrected schematic let me know, I also have a bunch of prototype cards.

Basically it is 4 stage circuit Receiver Rectifier Peak Hold and Meter circuit, inspired or copied by from various sources :
A Balanced line receiver
modeled on "Op Amps in Line-Driver and Receiver Circuits Part 2 - by Walt Jung and Adolfo Garcia (figure 4 dual-inverter line receiver)
A Rectifier
modeled on ssl_82E05 - Phase meter schematic from Waltzing Bear, API vu meter circuit, Harrison PC 1020 light meter circuit,
A Peak Hold circuit
modeled on Intersil AN1097 and The art of electronics, Volume 816
and
A Meter circuit
modeled on lm391x, green pre,"Rane No such thing as Peak Volts DBU note", "understanding peak reading meters" by ethan winer, various posts in Group Diy  "LED VU Rectifier Schematic" "DIY LED meter bridge by abbey road d enter", and a google search on LM339 LED Meter

Bruce, looks great Thanks  8)

Thx, Bruce0 ... I'll look into it but I don't like all these LED's 

Drives regular meters too....

Cheap ones too... and controls dynamics of those meters.

Look at the post, there is a build with no LED's