FETCODED

[Guest]

[quote author="PRR"]> my further improvement.

Noise figure is ~8dB. Working at 8mA ("for sound"?), you could do a lot better.[/quote]
WHAT?????????
Noise figure of that schemo and nearly all HiFi crazy schemos is greatly determined by 1k emitter feedback resistors
1k//1k+1k//1k
Greatly independent to tubes, fets and currents used here.

It is like embargo of oscilloscopes from America to Soviet Union.
Remove caps from scope amplifier and have 100 MHz bandwidth.

Short resistors from emitter and you will have superior noise figure.

and by the way. For what input resistance is noise figure referred?
10*log10((1k+47k)/47k)=0.0914 dB????
10*log10((1k+47R)/47R)= 13.48dB????

xvlk

 

[analag]

It works and very well I might add.

Now what shall I build next.
Analag

 

[Learner]

Want to share the joy and show us the pics of your new born?

 

[analag]

For an hybrid pre it has a warm tube like sound, punchy with lots of definition. Very quiet too. Anticipating the low PSRR of the cascode frontend I beefed up the PSU with 707mfd of filtering and tight discrete regulation. Limitation of space forced me to use TL783C for the B- reg.

It was almost too much work just to avoid the use of transformers in the signal path but definitely worth it. It sounds different from my other pre's. Bigger, really!

Analag

 

[analag]

I am thinking of a JFET/MOSFET version.

Rowan