my measurements of amplified ear.

[Johan Wagener]

here is my measurements taken on the amplified ear with a 16ohm load
(one earpiece) connected and a 1.48V battery used as power source

Q1
E - 0V
B - 0.506V
C - 1.451V

Q2
E - 0V
B - 0.554
c - 1.342

Q3
E - 0V
B - 0.4V decreasing to 0V (after 1 minute)
C - 1.37

Q4
E - 0V
B - 0.63
C - 1.461

I get a very faint amplification of the mic at the output. Increasing
battery to 3V gives better amplification but still only blowing into
the mic or knocking it against the table, and so on.

 

[Michael A. Covington]

Where is the circuit diagram?

 

[Paul Burridge]

Where is the circuit diagram?

I assume he's referring to this one:
http://www.electronics-lab.com/projects/audio/023/

I built it out (with real components!) of sheer curiosity and it does
work fine.
What are you using for D1? The prescribed part or just any old diode?
This fault should be pretty simple to find.

 

[John Woodgate]

I read in sci.electronics.design that Paul Burridge
[email protected]>) about 'my measurements of amplified ear.', on Thu, 12 Aug
2004:

I assume he's referring to this one:
http://www.electronics-lab.com/projects/audio/023/

I built it out (with real components!) of sheer curiosity and it does
work fine. What are you using for D1? The prescribed part or just any
old diode? This fault should be pretty simple to find.

Disconnect Q3 base and D1 from C3, leaving them connected together. Does
it work then? Check that D1 is the right way round. If you are not sure,
try reversing it. You can't damage it by doing so.

 

[Andrew Holme]

here is my measurements taken on the amplified ear with a 16ohm load
(one earpiece) connected and a 1.48V battery used as power source

Q1
E - 0V
B - 0.506V
C - 1.451V

Q2
E - 0V
B - 0.554
c - 1.342

Q3
E - 0V
B - 0.4V decreasing to 0V (after 1 minute)
C - 1.37

Q4
E - 0V
B - 0.63
C - 1.461

I get a very faint amplification of the mic at the output. Increasing
battery to 3V gives better amplification but still only blowing into
the mic or knocking it against the table, and so on.

Q2 base voltage sounds low and the Q2 collector sounds high. I've
just pushed a 2N2222 and a couple of resistors (R4=100k, R5=3k9) into
a breadboard and I'm getting Vb=0.59V and Vc=0.79V for a 1.5V supply.

Q3 (auto-level control) is off as it should be when there's no input.

Q1 base voltage sounds a bit low but may be OK. You might try
slightly reducing the value of R2, but I would check the circuitry
around Q2 first.

 

[Graham Knott]

Where is the circuit diagram?

--

You haven't by chance connected the top of the volume control to the
junction of R6/R7. The circuit shows a "crossover" not a join.

My most up-to-date website
Electronics for Beginners & Intermediate Electronics
http://homepage.ntlworld.com/g.knott/index.htm