On Tue, 16 Nov 2010 19:19:09 -0600, "amdx" wrote:

You have the diode to drive before the audio section and you want to match
the
diodes impedance.

Hi Mike,

This seems to wander the field when there are conflicting agendas on
the table. The wandering is due in large part to the absence of
specific numbers, and in this particular case, even the sense of
scale.

We have an audio Z match. We have a diode Z match. There is no sense
that if this is a high-Z or a low-Z for either/both/neither.

To this point, you have hewed to the commonplace magnetic speaker, and
from that I can only imagine that the problem with audio match is
transforming from a high (diode) Z to a low (speaker) Z. But from the
numbers, it would seem that both diode and speaker Zs are on par. I
could be wrong because this drift takes me into guessing.

Solve your problem and get a piezo headphone (or make one, this is the
tradition of Xtal radio, n'est pas?). They have to exhibit at least
10KOhm if not a bajillion ohms. If there isn't enough current to fire
the diode, Guess What? Slap a sacrificial resistor across the piezo
leads!

Radio Shack sells (or used to the last time I bought one) two or three
inch barium titanate ceramic disks that are offered as buzzer elements
(or rob a clock alarm for its buzzer - these things are a drug on the
market).

* * * * * * * * * * *

Now, if you only return to complain that the Hi-Z phones cause a
problem somewhere else; then I would recommend you abandon circuit
design and take up the study of math employing figures of merit. Such
assignments of merit are subjective, of course, but then you get to
own your personal solution. Discussion that follows this satisfactory
conclusion then enters the appropriate arena of philosophical or
religious controversy. This will certainly garner far more
participation in this group.

73's
Richard Clark, KB7QHC