microphone circuit help

[fkuk]

hi


i have this circuit that i found on the internet

**broken link removed**

this is where i found it
**broken link removed**

i want to know a few things

1. what voltage would you expect to get from this circuit at the end
2. the transistors are npn does that mean i can use any npn transistor or do i have to use a persific one
3. if i attach the positive of this circuit to a lm3916 with a Vref of 1.25 will all the lights light up properly or do i need to do something else
4. the capacitors used in this all of them have one straignt line and one curved line does that mean that they are electrlitic capacitors because they do not have the plus sign next to them
5.the capacitor in the top left does not have a what value is it or doesnt it matter
6. what would the supply voltage be and where will it be placed after reading the persons website am i right in saying that the TRS connect is where the supply goes in
if so where does the signal come out

sorry if this is long

 

[audioguru]

i have this circuit that i found on the internet

It is garbage.

1. what voltage would you expect to get from this circuit at the end

It has a DC output which is bad.

2. the transistors are npn does that mean i can use any npn transistor or do i have to use a persific one

It uses a low level microphone as its input so low noise 2N3904 or BC549 transistors should be used.

3. if i attach the positive of this circuit to a lm3916 with a Vref of 1.25 will all the lights light up properly or do i need to do something else

Its DC output will light all the LEDs all the time. The LM3916 needs at most a 1M resistor to ground at its input then audio signals capacitively coupled to it.

4. the capacitors used in this all of them have one straignt line and one curved line does that mean that they are electrlitic capacitors because they do not have the plus sign next to them

Only one is a polarized high capacitance electrolytic capacitor (maybe 47uF) . The others are low value non-polar film ones.

5.the capacitor in the top left does not have a what value is it or doesnt it matter

It is a filter for the supply voltage to the preamp transistor. Its value depends on how noisy (hum) is the supply. It is probably a 47uF or 100uF electrolytic.

6. what would the supply voltage be and where will it be placed after reading the persons website am i right in saying that the TRS connect is where the supply goes in
if so where does the signal come out

The supply voltage is probably in series with the headphones at the output which is a horrible way to destroy headphones.

 

[killivolt]

Guru, Angelo.

Colorful expressions with precise conclusions. Well done.

I'll never view audio the same. "One should always know when you have crap."

If not guru will tell you.

Golf Clap

kv

 

[Rajaneesh]

It is garbage.


It has a DC output which is bad.


It uses a low level microphone as its input so low noise 2N3904 or BC549 transistors should be used.


Its DC output will light all the LEDs all the time. The LM3916 needs at most a 1M resistor to ground at its input then audio signals capacitively coupled to it.


Only one is a polarized high capacitance electrolytic capacitor (maybe 47uF) . The others are low value non-polar film ones.


It is a filter for the supply voltage to the preamp transistor. Its value depends on how noisy (hum) is the supply. It is probably a 47uF or 100uF electrolytic.


The supply voltage is probably in series with the headphones at the output which is a horrible way to destroy headphones.

Hi guru....

Appreciate your precise answer... Proud to have you in this forum as a senior techie....adviser

 

[audioguru]

The circuit is garbage because it is partially from the cheap Spy Ear toy.
My son bought one. It "amplifies" sounds to the same volume as you hear things without it, it is completely useless.

We discussed the simple and cheap Spy Ear circuit and another from Talking Electronics on one of these forums a few months ago.

 

[Rajaneesh]

The circuit is garbage because it is partially from the cheap Spy Ear toy.
My son bought one. It "amplifies" sounds to the same volume as you hear things without it, it is completely useless.

We discussed the simple and cheap Spy Ear circuit and another from Talking Electronics on one of these forums a few months ago.

Ha ha ha....That's nice guru anyway thanks for your valuable points....... I wonder...why don't you suggest him a good working circuitry with your wide experience.......

 

[audioguru]

why don't you suggest him a good working circuitry with your wide experience.......

He didn't say what it is for. I think it is a simple school assignment. Then he should design it, not me.

 

[chemelec]

Actually it looks like a Workable Circuit with two minor changes.
I Think the person that Drew it up just Goofed a Bit.

The Output as shown should be the Battery Source and the Audio Out should come off through a capacitor from the Collector of the second transistor.

 

[audioguru]

Actually it looks like a Workable Circuit with two minor changes.
I Think the person that Drew it up just Goofed a Bit.

The Output as shown should be the Battery Source and the Audio Out should come off through a capacitor from the Collector of the second transistor.

The original "Spy Ear" toy had the earphone as the DC load for the output transistor. The modified one (the output transistor that drove the earphones is removed) uses the same bad idea and is powered through the output from the resistor in a pc mic input that would normally power an electret mic.

 

[audioguru]

I found it.
The Spy Ear circuit from Talking Electronics had a frequency response that was flat from 190Hz to 210Hz. The lows and highs were rolled off to make it sound worse than a telephone or AM radio. The earphones were in series which put them out-of-phase. Here is my simulation: