Technology of the Mini-Booster?

[pappasmurfsharem]

Is there a thread somewhere around the forum that's similar to RGs technology of the TS but about The mini booster?

I've actually ordered Jack's CD just for fun.

The only details on the page at his site talk about mods and changing those components.

Is there one around or does someone want to take a crack at it

[R.G.]

http://www.geofex.com/Article_Folders/modmuamp/modmuamp.htm

[pappasmurfsharem]

http://www.geofex.com/Article_Folders/modmuamp/modmuamp.htm

DAMMIT I SWEAR I LOOKED AT YOU SITE FIRST DIDN'T SEE IT!!!!

Well if its any consolation for my stupidity. I bought your book from SmallBear =)


So in your description RG. You replaced the 10 megs with 10ks and added a 4.7M in series.

Whats the functional difference of that versus the standard 1M bias ala the BSIABII?

[R.G.]

So in your description RG. You replaced the 10 megs with 10ks and added a 4.7M in series.
Whats the functional difference of that versus the standard 1M bias ala the BSIABII?

The arrangement in the article at geofex is quieter, or at least has the ability to be quieter.

The 1M/1M divider electrically looks like a half-power-supply voltage with a series resistor of 500K. Any current noise caused by the current through the 1M's appears directly on the gate of the upper JFET and is amplified. In the second version, the current through the 4.7M resistor is nonexistent, and current noise from the 10K/10K bias string is shunted to ground by the bypass cap. There is still the thermal noise of the resistors. If you use a 2M series resistor instead of a 4.7M, you get the same thermal noise as the 1M's, but no current noise - or immeasurably small current noise at least.   

The three-resistor version is known as "noiseless biasing" in the EE biz. It's not truly noiseless, but it can be better than the two-resistor case with good component choices.