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Re: LOW-Z Amp

Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Christoph,

At 05:31 AM 2/2/2005, you wrote: 
Hello Terry, All.

First thank you very much for your input and thanks
for opening up my IP pool to hot-streamer.com.

I think I am going to use Terry's design and already
ordered the LM12 and even custom wound a 2x20V
( for the LM ) and 7,5V ( supply for signal generator )
power transformer yesterday.

Now for the questions ( danger, tube guy goes solid state )

I studied the data-sheet to the LM12, in particular the paragraph
concerning protection circuits for inductive and capacitive loads.
Should I add the 4µH choke with de-Q-ing R on the output?

Since the gain is "1" I don't think you need it. I never had any trouble with stability.

Should I use input compensation?

I have about 1000 ohms and a x pF capacitor on the input just to limit RF getting into the thing. Never had a problem with that either.

Why do you use 2 470Ohms resistors inseries with the input?

Just for safety. Since I power some pretty messing things with it, the resistors are sort of like fuses. Voltage standoff is much higher with two. I probably didn't have a 1000 ohm one handy as well ;-))

Does this have any particular reson or is this just what you had on hand?
The data sheet suggests 20 up to 470µF supply bypassing caps,
should I use more than the 10µF from your diagram?

There are two 10,000uF caps on the power supply output ;-)) The 10uF are just right at the LM12 leads.


In the pics I see a grounding point in the center of your enclosure,
I guess this is one point where all the ground wires meet...?

Yes, And I try and mount a lot of components right on the LM12 leads to cut down on strays.


OK, lots of questions. I just want to make sure I get everything right
the first time, cause the LM12 is a bit too pricey to mess around
with it.

It is real hard to break since the power we supply to it here is not that great.

Cheers,

        Terry



regards

Christoph Bohr