A twist on the LA2A... and some questions with it! Transformer & VU meter

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thomasdf

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Aug 10, 2011
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Location
Paris, France
Hi everyone

I am currently building an opto comp inspired by the LA2A with some tweaks in the input circuitry, sidechain and the power supply. But the overall is close to the LA2A, and I intend to make it fit in a old radio casing.

I was simply asking myself 2 simple questions:

1) What would you suggest as a cheap output transformer that I can buy for the tests (I am in Europe, and around 40 euros would be perfect)? If it is not that great I can still change it once I'm done wiring up the unit. I was thinking of the Xicon ones (such at the TM006 if my memory serves me well) but it's so tiny...! They go for 3,90euros online and are pretty bang for the buck on small trannies circuits. But I am willing to get a bit more mojo here. (If anyone has an offer for a cheap OPT, please message me)
It would have to be 15 or 20Kohms : 600 Ohms

2) Second question, easier one I guess : what kind of VU meters should I use? I cannot find any informations about that, sensibilty, impendance? I have some gorgeous vintage Galvanometers at home... How can I know if I can use them? How can I measure them and make them fit to my LA2A?

If the unit sounds cool, I won't forget to share schematics, pictures and sound samples!

Thanks in advance for your help

Cheers

Thomas

 
For the VU, Check out those from Hairball. They are really nice and not very expensive. For the tranny, do you tried Edcor? They are not that expensive and I think the quality is cool.
 
Hello Deepdark!

Thanks for your answer. I know these hairball VU meters but their sensibilty is not specified... The best case scenario for me would be to fit one of the vintage meters that I have.

I'll check the Edcors transformers thanks. I may also I find some cheap secondhand Lundhals
 
I know these hairball VU meters but their sensibilty is not specified...

Yes it is.
Configured to read 0db at 1.228V through an external 3.6k resistor +/- 10%
Internal Resistance: 3.9K ohms +/- 10%
Built in germanium diode bridge rectifier
80mm x 37mm cutout
Lamp box included w/ dual LEDs
Mounting hardware included
 
Oh I see. Am I going wrong if :

U = R . I , so I = U / R

Meter sensibily > I = 1,228V / (3,6KOhms + 3,9KOhms) = 1,228 / 7,5 = 163,7333 mA ?

Now I need to figure out what is the sensibily of my vintage meters and how to tweak it, not only to tweak their resistance...
 
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