mic pre with feedback limiter.
- Thread starter ioaudio
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Bo Hansen
Well-known member
ioaudio,
Yes, that`s nice, a magic eye as light source, easy to get work very fast or slow.
I remember I find one or two similar application in a old German electronic magazine "Funkschau" around 1960`s
I will see if I can find this articles in my archive.
--Bo
Yes, that`s nice, a magic eye as light source, easy to get work very fast or slow.
I remember I find one or two similar application in a old German electronic magazine "Funkschau" around 1960`s
I will see if I can find this articles in my archive.
--Bo
ioaudio
Well-known member
bo,
i would appreciate that!
i would appreciate that!
Viitalahde
Well-known member
Looks very interesting! :thumb: I have saved many of your schematics and I'm going to try some of them once I get around and build a bench PSU for tube experiments. Analag & NY-Dave, too.
[quote author="Viitalahde"]Looks very interesting! :thumb: I have saved many of your schematics and I'm going to try some of them once I get around and build a bench PSU for tube experiments. Analag & NY-Dave, too.[/quote]
Should I post my poor man's version of the Fairchild 660?
analag
Should I post my poor man's version of the Fairchild 660?
analag
Bo Hansen
Well-known member
ioaudio,
Yes, I find one of the article I talk about, but the text is only in German language.
Fotoelektrischer Expander Kompressor
Maybe Kubi can help, if there are some imortant description in the article.
--Bo
Yes, I find one of the article I talk about, but the text is only in German language.
Fotoelektrischer Expander Kompressor
Maybe Kubi can help, if there are some imortant description in the article.
--Bo
clintrubber
Well-known member
Uhh, cool idea ! Surprising it isn't used more often :shock:
Thanks io for the circuit & Bo for the scan. :thumb:
Bye,
Peter
Thanks io for the circuit & Bo for the scan. :thumb:
Bye,
Peter
rafafredd
Well-known member
feedforward optical tube comp? not economic, with those EF86 and ECC83 just for driving the magic eye, but might be great. I don´t remenber of anything alike out there. Ever...
ioaudio
Well-known member
thanks bo!!!
i understand german, so if there are any questions ask me!
the signal is ampilified with ef 86 and cathode follower for feeding the diode rc timing chain. i think its not necessary if you just take the timing of the em84/ldr.
i understand german, so if there are any questions ask me!
the signal is ampilified with ef 86 and cathode follower for feeding the diode rc timing chain. i think its not necessary if you just take the timing of the em84/ldr.
VacuumVoodoo
Well-known member
This scheme was used as tremolo in guitar combo "Fonica" which was produced in Poland in mid 1970s.
A photographic documentation including schematic diagram is HERE
the text is in polish but pictures and diagrams say it all. The photoresistor is placed after the first gain stage off the ECC83 anode.
A photographic documentation including schematic diagram is HERE
the text is in polish but pictures and diagrams say it all. The photoresistor is placed after the first gain stage off the ECC83 anode.
Bo Hansen
Well-known member
Alex,
Nice litle combo amp, and on same web site, a amazing collection of schematics over old time radio/TV and Hi-Fi amps.
BTW, hope I can see you some time, you know, we live in same town.
--Bo
Nice litle combo amp, and on same web site, a amazing collection of schematics over old time radio/TV and Hi-Fi amps.
BTW, hope I can see you some time, you know, we live in same town.
--Bo
rafafredd
Well-known member
http://geek.scorpiorising.ca/MicPreamp.html
The Kid
Well-known member
They don't. But the negative ones do. Like PRR said, both halves of the wave. It's also called a dual half- wave rectifier.
ioaudio
Well-known member
so i finally came around breadboarding this
i left out the mic input part as originally shown in the schematic, just to try the compression part around the em84.
bottom line : that magic eye is not bright enough to significantly bring down the ldr´s resistance. i tryed a couple of different em84, em87 and em81.
my best result was 0.1 db gain reduction. :?
i left out the mic input part as originally shown in the schematic, just to try the compression part around the em84.
bottom line : that magic eye is not bright enough to significantly bring down the ldr´s resistance. i tryed a couple of different em84, em87 and em81.
my best result was 0.1 db gain reduction. :?
rafafredd
Well-known member
I think the idea is great. Why don´t you try getting another, more sensitive LDR and keep the magic eye idea. I do think you could find something that would suit your needs.
ioaudio
Well-known member
thanks for your encouragement :grin:
problem i found is, that i cant get enough contrast. the luminescent screen isnt really dark when below level
and not really very bright when above.
i tryed the ldr with a led which worked much better, i dont know how he managed to do it. anyway, i already ordered some different ldr´s to try.
problem i found is, that i cant get enough contrast. the luminescent screen isnt really dark when below level
and not really very bright when above.
i tryed the ldr with a led which worked much better, i dont know how he managed to do it. anyway, i already ordered some different ldr´s to try.
ioaudio
Well-known member
ahh, some more figures would be nice....
ldr´s resistance:
dark >2Mohm
with led ~ 25kohm
em84 below threshold ~ 700kohm
em84 above threshold ~ 3-400kohm
ldr´s resistance:
dark >2Mohm
with led ~ 25kohm
em84 below threshold ~ 700kohm
em84 above threshold ~ 3-400kohm
ioaudio
Well-known member
here´s the circuit from what you can hear above.
