"Richard Clark" wrote in message
...
On Thu, 1 Jul 2004 22:18:27 +0000 (UTC), "Reg Edwards"
wrote:

Rich, why don't you say you don't know. ;o)
---
Reg.

On Thu, 01 Jul 2004 20:43:37 GMT, Richard Clark
wrote:

I don't know

Hi Reggie,

What if I said 43?

Do you actually read responses to your questions? Let's see, there's
enough numbers in it to satisfy lord kelvinator, and enough principle
in it to make sir plushbottom happy, and it even contains the
structure of another unzipped program.

Too demeaning to say thank you, hmmmm?

88's
Richard Clark, KB7QHC

=============================
Thank you for what? ;o)

Anyway, what else do you expect from an Italian clown ?
----
Punchinello, G4FGQ

What if I said 43?

==========================

If you had also mentioned the measurement units, such as femto-Watts, that
would have been the ideal, even perfect, reply to my enquiry and would have
deserved the congratulations of all and sundry.
----
Punchinello, G4FGQ

On Thu, 1 Jul 2004 22:18:27 +0000 (UTC), "Reg Edwards"
wrote:

Rich, why don't you say you don't know. ;o)
---
Reg.

On Thu, 01 Jul 2004 20:43:37 GMT, Richard Clark
wrote:

I don't know

Hi Reggie,

What if I said 43?

Do you actually read responses to your questions? Let's see, there's
enough numbers in it to satisfy lord kelvinator, and enough principle
in it to make sir plushbottom happy, and it even contains the
structure of another unzipped program.

Too demeaning to say thank you, hmmmm?

88's
Richard Clark, KB7QHC

Reg, G4FGQ wrote:
"I would like to know, crudely, the audio input level to 2000-ohm, non
diaphragm head phones for a nice, comfortable, not too difficult
intensity level."

First problem is sensitivity of the phones. These vary widely.

Satisfactory reception also depends on competing noise in addition to
signal strength. According to the FCC in the U.S.A., you may need 1/2
millivolt for satisfactory reception.

A kilowatt radiated by a medium wave transmitter may produce about 200
millivolts/m at one mile. It depends on antenna and path. Field strength
is proportional to the square root of the watts per square meter times
377.

I used to live about 15 mile4s from a 50 KW station. The signal strength
at a mile from the station could have been 1.5 volts/ m, and at 15 miles
could have been 0.1 V/m. Point is, my crystal set drove a dynamic
loudspeaker directly through the output transformer mounted on the
speaker. It was clearly audible. Impedance presented to the crystal set
was closer to 10,000 ohms at 1 KHz than to 2000 ohms. The speaker and
its cabinet were from a battery vacuum-tube set. The audio power may
have been less than a microwatt, but as a kid my ears were acute.

My 2nd edition GE "Transistor Manual" has 2000-ohm headphone amplifiers
with 2 milliwatts maximum power output.

Chinese stereo headphones claim 20-20KHz response, 32-ohms impedance,
100dB/1mW sensitivity, 140 mW rated input, 400 mW max. etc. Much of this
spec. is target and untrue. Wide variations exist between samples of
these phones claiming similar specs.

The GE book is believable. Class A power output is from the familiar.
First formula says maximum power is 1/2 the product of the peak voltage
and peak current. Load resistance is then the peak voltage divided by
the peak current. So, Load resistance=Epk squared/2Po

When GE prints the circuit of a 2 milliwatt amplifier driving 2000-ohm
phones, I believe it works.

Best regards, Richard Harrison, KB5WZI

Rich, why don't you say you don't know. ;o)
---
Reg.

Reg, G4FGQ wrote:
"I would like to know, crudely, the audio input level to 2000-ohm, non
diaphragm head phones for a nice, comfortable, not too difficult
intensity level."

First problem is sensitivity of the phones. These vary widely.

Satisfactory reception also depends on competing noise in addition to
signal strength. According to the FCC in the U.S.A., you may need 1/2
millivolt for satisfactory reception.

A kilowatt radiated by a medium wave transmitter may produce about 200
millivolts/m at one mile. It depends on antenna and path. Field strength
is proportional to the square root of the watts per square meter times
377.

I used to live about 15 mile4s from a 50 KW station. The signal strength
at a mile from the station could have been 1.5 volts/ m, and at 15 miles
could have been 0.1 V/m. Point is, my crystal set drove a dynamic
loudspeaker directly through the output transformer mounted on the
speaker. It was clearly audible. Impedance presented to the crystal set
was closer to 10,000 ohms at 1 KHz than to 2000 ohms. The speaker and
its cabinet were from a battery vacuum-tube set. The audio power may
have been less than a microwatt, but as a kid my ears were acute.

My 2nd edition GE "Transistor Manual" has 2000-ohm headphone amplifiers
with 2 milliwatts maximum power output.

Chinese stereo headphones claim 20-20KHz response, 32-ohms impedance,
100dB/1mW sensitivity, 140 mW rated input, 400 mW max. etc. Much of this
spec. is target and untrue. Wide variations exist between samples of
these phones claiming similar specs.

The GE book is believable. Class A power output is from the familiar.
First formula says maximum power is 1/2 the product of the peak voltage
and peak current. Load resistance is then the peak voltage divided by
the peak current. So, Load resistance=Epk squared/2Po

When GE prints the circuit of a 2 milliwatt amplifier driving 2000-ohm
phones, I believe it works.

Best regards, Richard Harrison, KB5WZI

I would like to know, crudely, the audio power input level to 2000-ohm, iron
diaphragm headphones for a nice, comfortable, not too difficult listening
level. Such as when the phones are used on a crystal and cat's whisker

Hi Reg, Don't know either, but if you have access to a scope and a signal
generator, you could find out what you want. I have these, but not some 2000
ohm phones.
When I was a child playing around with crystal sets, I listened to a 1KW AM
station about 1 KM away with a 25' wire, a germanium diode, and a 1000 ohm
crystal earphone. The diode drop would be around 250 millivolts, and the
listening level would be fine. Thats 250 mv into 1000 ohms. Ther are several
crystal radio web sites that may provide more help.
73 Gary N4AST

Reg Edwards wrote:

I am writing a program involving an antenna plus two coupled tuned circuits
plus a matched simple receiver.

I would like to know, crudely, the audio power input level to 2000-ohm, iron
diaphragm headphones for a nice, comfortable, not too difficult listening
level. Such as when the phones are used on a crystal and cat's whisker
radio receiver.

Such headphones are more sensitive than modern 8-ohm varieties. I have a
pair of 2000-ohm headphones but unfortunately no means of measuring power or
voltage input.

Just the number of micro-watts please. At what low power input level does
speech or music just BEGIN to fade out to a person of normal hearing? Any
ideas? I could take the average of a few replies.
----
Reg, G4FGQ

EH? WHAT DID HE SAY? :-)

--------------------
Irv Finkleman,
Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP
Calgary, Alberta, Canada

On Thu, 1 Jul 2004 19:43:02 +0000 (UTC), "Reg Edwards"
wrote:

I am writing a program involving an antenna plus two coupled tuned circuits
plus a matched simple receiver.

I would like to know, crudely, the audio power input level to 2000-ohm, iron
diaphragm headphones for a nice, comfortable, not too difficult listening
level. Such as when the phones are used on a crystal and cat's whisker
radio receiver.

Odd, I was just corresponding over this very matter recently.

Such headphones are more sensitive than modern 8-ohm varieties. I have a
pair of 2000-ohm headphones but unfortunately no means of measuring power or
voltage input.

Then we step into the area of conjecture.

Just the number of micro-watts please. At what low power input level does
speech or music just BEGIN to fade out to a person of normal hearing? Any
ideas? I could take the average of a few replies.

Hi Reg,

This will be have to be done through inference or Web research. As
far as inference goes, I will first state that magnetic speaker
efficiency is extremely poor, but I don't know if this extends to the
headphone implementation. Albeit, between 1 and 10% efficient.

The level of hearing for a child or teen fades out at 1db re
environmental impositions. Technically, in the absence of other
sounds:
1dB re 200µDynes per cM² at 1KHz

0dB = 200µDynes per cM² = 0.1 femtoWatt per cM²

a quiet whisper = 6 femtoWatts per cM²

conversation at 1M = 1 nanoWatt per cM²

Hearing at another frequency such as 400Hz (common sidetone for CW) is
10dB weaker (hearing peaks about 5dB in the 2-4KHz region) and worsens
as frequency lowers.

Hearing loss in the 50-59 Age group for men at 1KHz is about 10dB

Given "hearing" is subjective, a technical response is only as
accurate as the knowledge of these variables (age, sex, frequency,
efficiency).

73's
Richard Clark, KB7QHC

Harry Whitfield wrote:
"Sensitivity is given as 112 dB at 1 mW. I assume this means 112 dB
above the Threshold of Hearing (1pW per square metre) at 1 mW in."

That looks OK to me. My handy "Science Answer Book says:
Hearing starts at zero decibels. 10 units is a tenfold increase. The
sound made by leaves rustling is often 10 decibels. Office noise level
is typically 50 decibels. A pneumatic drill = 80 dB. A riveting machine
= 110 dB. A jet takeoff at 61 m (200 ft.) measures 120 dB. Noise above
70 decibels harms hearing. At 140 dB, noise is physically painful.

Acute hearing is sensitive. More so in some other species.

In a previous posting I may have appeared naive saying I believed GE
produced a circuit for a 2 milliwatt 2000-ohm headphone amplifier. But I
have additional evidence of the adequacy of 2 milliwatts. For many years
I worked at a radio station where we kept a pair of crystal phones near
the audio patch panel. These, because of their extremely high impedance,
could be bridged across any program line with no significant effect.
Program lines are usually adjusted to a zero VU level (1 milliwatt into
600 ohms) or 0.775 volt on program peaks. Magnetic phones produced about
the same audio output with 0.775 volts as did the crystal cans. The
difference is only in the circuit loading of the 2000-ohm magnetic
phones on a 600-ohm circuit. Point is, one milliwatt is plenty loud in
headphones. I know from listening.

Best regards, Richard Harrison, KB5WZI