analogue VU-meter - Page 2

sled108 · 20th March 2010, 05:34 PM

This is how 1mA meters work when run thru a 10k Alps from the Speaker Posts..

YouTube - Too Old2.mp4

cliffforrest · 20th March 2010, 07:16 PM

From a discrete PPM (Peak Program Meter) built to BBC standards with a Dolby B processor on my Revox 15" dual track.

1970's - thank you Wireless World!

These have special ballistics which are critically damped and have to be driven with a fast rise-time / slow fall-time meter driver.

I don'r suppose I shall ever get round to using these again - are they worth anything to anyone?

Cliff

PhantomBox · 28th March 2010, 08:29 PM

Now I built a circuit based on the ESP project 128. Instead of 2 TL072's I use 1 TL074, and as power supply I use a regulated single rail unit with virtual ground and set it at +24V (+12/-12V). In theory, voltage should not affect the output signal but it does. The higher I set the total voltage the more does the needle swing. I'm almost certain that I made a mistake but cannot figure out where it is.
My last project was a PIAA phono preamp with a TL074 and a 12V wallwart and virtual ground and it works just fine, so I think the PS is OK.

Any suggestions?

cliffforrest · 28th March 2010, 08:57 PM

Quote:

Originally Posted by PhantomBox

Any suggestions?

Yes! Post a schematic!!

You have something V+ referred rather than ground referred - but how do you expect anyone to help without a drawing?

PhantomBox · 29th March 2010, 03:08 AM

Here's the schematic of the VU driver: Project 128 (figures 3 and 4. See the 2nd reply to my post by Col from AustrAlia) and here is my power supply: http://kitsrus.com/pdf/k124.pdf (end of page 2, acts s a "wall wart"), followed by a dividing circuit with two 220uF capacitors and two 4.7k resistors (that's the virtual ground).

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20th March 2010, 05:34 PM	#11
sled108 diyAudio Member Join Date: May 2008 Location: Deep in the Heart of North Jersey	This is how 1mA meters work when run thru a 10k Alps from the Speaker Posts.. YouTube - Too Old2.mp4

28th March 2010, 08:29 PM	#13
PhantomBox diyAudio Member Join Date: Jan 2008	Now I built a circuit based on the ESP project 128. Instead of 2 TL072's I use 1 TL074, and as power supply I use a regulated single rail unit with virtual ground and set it at +24V (+12/-12V). In theory, voltage should not affect the output signal but it does. The higher I set the total voltage the more does the needle swing. I'm almost certain that I made a mistake but cannot figure out where it is. My last project was a PIAA phono preamp with a TL074 and a 12V wallwart and virtual ground and it works just fine, so I think the PS is OK. Any suggestions?

29th March 2010, 03:08 AM	#15
PhantomBox diyAudio Member Join Date: Jan 2008	Here's the schematic of the VU driver: Project 128 (figures 3 and 4. See the 2nd reply to my post by Col from AustrAlia) and here is my power supply: http://kitsrus.com/pdf/k124.pdf (end of page 2, acts s a "wall wart"), followed by a dividing circuit with two 220uF capacitors and two 4.7k resistors (that's the virtual ground).

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