js201 vs bf245 FET?

[gain-wire]

Originally Posted by Nigel Goodwin

No it's not - it's VOLTAGE transfer again, not power transfer, which would upset the sound quality. Can you give any examples? - certainly CD players don't, tape decks don't, tuners don't, mixers don't, record decks don't - I can't think of a single example? (or any reason to do so).



PU cartridges aren't 'matched', they have specific load requirements, both resistive and capacitive - which the preamp is designed to meet, but it's not the output impedance of the PU.

Well, I have always seen the typical impedance of audio equipment as 47kOhms - seems to make sense with BJT inputs, which most audio equipment has (even IC based preamps). Are you saying that the input impedance of typical preamps is actually much higher than 47kOhms, say by a tenfold? I doubt... But I can be wrong. Obviously you know more about this I do, having corrected me on the "characteristic" capacitance of the phono cartridge, which I realise doesn't have to be matched (a select few audio components actually allow this, some Sony and Marantz devices come to mind).

Anyway, this has gone way off topic from the original topic, which was guitar preamps with JFETs.

all I said was that transconductance and Gate-source capacitance were determining factors in the choice of what transistor to choose.

It's not because I know less than you that I talk jibberrish... please understand this.

[Nigel Goodwin]

Originally Posted by gain-wire

Well, I have always seen the typical impedance of audio equipment as 47kOhms - seems to make sense with BJT inputs, which most audio equipment has (even IC based preamps). Are you saying that the input impedance of typical preamps is actually much higher than 47kOhms, say by a tenfold? I doubt...

No, typical input impedance is roughly 47K, 100K, 220K, perhaps occasionally 470K. This is FAR higher than the output impedance of preceding equipment, which will normally be in the low single kilohms (or less).

Presumably you are confused about the output impedance of audio equipment?.