Simple analog vu-meter driver ?

[00940]

Wrapping up some projects...

I cased an headphones amplifier into an old tape recorder and it has a pair of nice analog VU-meters (Kyoritsu KM-86) on the frontplate. I'd like to use the meters to roughly monitor the output level into sennheiser HD650 (300 ohms). I don't need perfect ballistics. Cheap and easy to breadboard are more important factors here.

Would the following circuit do it ? (it's mostly a simplification of http://www.jlmaudio.com/AT51 DIY VU.pdf ).

R7-R8 are trimmers to adjust the vu-meter (I'm aiming to set the 0VU at a max "reasonable" level for long term listening). The headphones amplifier I'm using won't clip before +/-13V (peak) into 300r, so I need the to pad the signal going into the tl072. 10k in // with a 300r load is ok.

Thanks 🙂

 

[franzm]

Here are some integrated VU-meter drivers K 157 DA 1 ( = 2 Kanal Ansteuer - IC für VU - Meter ) | eBay

 

[00940]

Thanks, those look like interesting parts but I've got all the parts on hand for the schematic above with the tl072. I'd rather avoid collecting even more parts ;-)

 

[gpapag]

Ben
I think you will be OK with you circuit.
If you don’t care about ballistics you can go with something really simple, like the attached, one transistor circuit..

for a better circuit (VU-PPM), you can have a look here
VU And PPM Audio Metering

George

 

[00940]

Thanks George. I'll save this schematic, very simple indeed 🙂

I put the first one together this evening. It works quite ok. 100uf is too much in // with the meters I have, it makes it too slow. I'll try 10uf later on.

Btw, I enjoyed some fireworks in the process. Soldered the PS backwards and fed a poor tl072 -20Vdc. It didn't explode but started fuming and slowly split in two right in the middle. Oh happy times.

 

[gpapag]

Yes. 1uF to 10uF.

When I test new circuits or repair old ones, I wear safety glasses. 🙂

George

 

[stoppage]

Thanks George. I'll save this schematic, very simple indeed 🙂

I put the first one together this evening. It works quite ok. 100uf is too much in // with the meters I have, it makes it too slow. I'll try 10uf later on.

Sorry could I ask if you're referring to the one-transistor circuit, I've planned to try that out too. Did it originally have a 100uF cap., it's not in the circuit?

 

[00940]

I was referring to the one in the original post (with the tl072). I finally didn't try for myself the one suggested by gpapag.

 

[stoppage]

Thank you

 

[stoppage]

Ben
If you don’t care about ballistics you can go with something really simple, like the attached, one transistor circuit..
George

Hi ...quick question...is C31 Electrolytic?

 

[gpapag]

No

George