If you want your preamp to be able to accept 2Vrms at it's input, then if the input noise must be lower than 92dB, this will equal:
2 x 10^-4.6 / sqrt(20KHz (bandwidth)) = 349nV/sqrt(Hz)
It's hard to design something so noisy. Every opamp known to me has an input noise lower than 40nV/sqrt(Hz), take you pick, NE5534, or opa227 (both about 3.5 nV/sqrt(Hz)), opa134 (about 8nV/sqrt(Hz) ? ).
Edit..: oops allmost forgot: Nelsons MOSFET preamps will meet this criterium too. BTW what is the EIN of a IRF610? something like 20nV/sqrt(Hz) ?
But if you want 92dB S/N for a 2mVrms (max input) preamp, you'll have a challange... you'll have to build a discrete BJT preamp, eg. a 6 transistor symmetrical input stage with Vbc = 0Volt and 300uA Iq each transistor, or a handfull 2SK170's in parrallel...
Goodluck,
Thijs
2 x 10^-4.6 / sqrt(20KHz (bandwidth)) = 349nV/sqrt(Hz)
It's hard to design something so noisy. Every opamp known to me has an input noise lower than 40nV/sqrt(Hz), take you pick, NE5534, or opa227 (both about 3.5 nV/sqrt(Hz)), opa134 (about 8nV/sqrt(Hz) ? ).
Edit..: oops allmost forgot: Nelsons MOSFET preamps will meet this criterium too. BTW what is the EIN of a IRF610? something like 20nV/sqrt(Hz) ?
But if you want 92dB S/N for a 2mVrms (max input) preamp, you'll have a challange... you'll have to build a discrete BJT preamp, eg. a 6 transistor symmetrical input stage with Vbc = 0Volt and 300uA Iq each transistor, or a handfull 2SK170's in parrallel...
Goodluck,
Thijs
tschrama said:2 x 10^-4.6 / sqrt(20KHz (bandwidth)) = 349nV/sqrt(Hz)
That's what I get, too.
You will be amused to know that the output noise of the First
Watt amp is about 20 uV, for an output floor of about 140 nV,
and an input floor of about 28 nV using an IRFP240 pair.
MuuuHahahahaha
I found this datasheet, but I cann't find any info on the noise specs. But generally, a discrete BJT preamp design can be made to have excellent noise performance, especially with low Z sources, pretty much with all comman transistor types.
http://s89326750.onlinehome.us/marantz/parts_specs/2sc458.pdf
http://s89326750.onlinehome.us/marantz/parts_specs/2sc458.pdf
Are you after a preamp of "Nelson" style or any style?jinkuchi said:I want pre-amp schematic, please.
with a s/n ratio 92 db or more.
I'm new in pre-amp. never have one.
tiger.
Do you mean 92 dB at fulll, output?
A plain transistor has 1-3 uV noise max => 100-120 dB
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