OTOH, I could just
stick an emitter follower stage on the end of the amp chain and have
done with it. :-/

Paul-

Now that you have a good grip on the problem, consider one more idea - that
most audio amplifiers have more gain than they need, and operate with the
volume control set at a fraction of full range.

If you were to use a series resistor (27 or 56 Ohms?) and NO transformer, would
the output stage have sufficient power to produce an acceptable audio level
with the volume control advanced?

73, Fred, K4DII

On 15 Jul 2004 11:03:36 GMT, (Fred McKenzie) wrote:

OTOH, I could just
stick an emitter follower stage on the end of the amp chain and have
done with it. :-/

Paul-

Now that you have a good grip on the problem, consider one more idea - that
most audio amplifiers have more gain than they need, and operate with the
volume control set at a fraction of full range.

If you were to use a series resistor (27 or 56 Ohms?) and NO transformer, would
the output stage have sufficient power to produce an acceptable audio level
with the volume control advanced?

I instinctively doubt it, Fred, but I'm in a position to give it a try
so I shall duly do so! I'll report back the results later.
BTW, this isn't a conventional hi-fi type audio amp; it's solely been
designed for picking up very faint, distant sounds. I was intrigued by
the design so set out to further examine how it worked. I've spiced it
and have now built it; the last piece in the jigsaw is the Z-matching
problem.
--

"What is now proved was once only imagin'd." - William Blake, 1793.

Oh, if it's something you built anyway, you might consider using
something like an LM386 for the audio output stage. Besides providing
considerable gain (which might eliminate some other stages), it'll drive
an 8 ohm earpiece with no problem. And it's reasonably efficient.

Roy Lewallen, W7EL

Paul Burridge wrote:

I instinctively doubt it, Fred, but I'm in a position to give it a try
so I shall duly do so! I'll report back the results later.
BTW, this isn't a conventional hi-fi type audio amp; it's solely been
designed for picking up very faint, distant sounds. I was intrigued by
the design so set out to further examine how it worked. I've spiced it
and have now built it; the last piece in the jigsaw is the Z-matching
problem.

On Thu, 15 Jul 2004 10:33:08 -0700, Roy Lewallen
wrote:

Oh, if it's something you built anyway, you might consider using
something like an LM386 for the audio output stage. Besides providing
considerable gain (which might eliminate some other stages), it'll drive
an 8 ohm earpiece with no problem. And it's reasonably efficient.

Well using an op-amp did cross my mind, Roy, but it's cheating in my
book. I like to use discretes so I get a better idea of what's going
on and it's more of a challenge to get right!
--

"What is now proved was once only imagin'd." - William Blake, 1793.