Author Topic: Test Post - No need to reply  (Read 10925 times)

Offline TelePlay

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 6754
  • A Ringy-Dingy Thingy
    • . . . been good so far
Re: Test Post - No need to reply
« Reply #30 on: December 03, 2015, 09:47:19 PM »
Here's the . . .
« Last Edit: September 15, 2017, 04:48:33 PM by TelePlay »
            John . . .

              

Offline TelePlay

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 6754
  • A Ringy-Dingy Thingy
    • . . . been good so far
Re: Test Post - No need to reply
« Reply #31 on: February 08, 2016, 08:49:55 AM »
Wiring A Touch Tone Pad To Any Antique Telephone
 
By Stan Schreier  
http://atcaonline.com/ttpad.html

along with this adapter . . .

http://www.classicrotaryphones.com/forum/index.php?topic=458.msg73211#msg73211

« Last Edit: September 14, 2017, 01:53:37 PM by TelePlay »
            John . . .

              

Offline TelePlay

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 6754
  • A Ringy-Dingy Thingy
    • . . . been good so far
Re: Test Post - No need to reply
« Reply #32 on: February 10, 2016, 05:02:53 PM »
Here's the . . . .

====================================
Up early this morning waiting for my tea to steep and had a few questions about using a single speaker (I have one rated at 90 to 15000 Hz) to a Creative PC card speaker out. Lucky morning, found all this stuff.

When I first started this project, I used a wood box I built for something else and cut a 2" dia hole in the top. Layer down two neoprene flats with 1.5" holes in them so I could lay the faceplate with attached transmitter on the neoprene or a F1 or T1 over the hole and had a sound source inside the box. It was a piezo buzzer and I stuck a T1 inside the box for reference. I used two heavy gauge copper wires mounted to bolts on the top to both hold a F1/T1 to the hole and to make electrical contact with them. My first trial I got this



Realized a lot of problems with this and the only thing that showed me was they were "working." The buzzer was simply white noise of unknown frequencies.

So, created an audio file in Audacity that played 500 to 3000 tones each for about 2 seconds to replace the buzzer to see what the mics were picking up over that range. That was more promising in that this is what I got.



But that was too course and so went out and found a site that allowed my to build a sine wave track from 10Hz to 15000Hz. They only allowed a 10 second sweep so created 10 sweeps of 500 Hz and spliced them together to get a 10 to 5000 Hz sweep over 100 seconds. Every 10 seconds was 500 Hz so easy to notate the X-axis on the plots and this was what I got.



Now, give what I found below, I will go back to using my box (did the above in open air), put the speaker inside it, sound deaden the inside, wrap the outside with sound deadening material, build a cover lid to keep the back of the mic under test from being influenced by ambient sound and try again. Now that I think I have a circuit to bridge a stereo out to a mono speaker, figure 2 in this image,



I can feel safe in doing this without fear of damaging my external sound card. And as I mention below, knowing carbon mics have an impedance of 30-100 ohms, I may put a resistor in line to make them look more like the PC reference mic output (right now the carbon mics are much louder than the reference mic) and better match the carbon mics to my card's mic in port.

I know the basics and have the questions and without the web and google, I couldn't do this. Amazing what google can do that would take hours if not days in an old dead tree library. Here's what I learned  this morning:

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

Got up for an early morning cup of tea and while steeping, found this on the internet, ah, what would we do without google? And I'm using an external Creative Sound Card. So, maybe 470 ohms would work well. I had forgotten that ear buds IIRC are in the 300 ohm range anyway, which would make sense.

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

General specs for input/output of Creative Soundcards:

     http://forums.creative.com/showthread.php?t=298919

> MIC-IN
> Sensitivity : 10mv to 200mv
> Impedance 500-600 Ohms
> Stereo input jack:
> TIP Signal
> RING Bias (if available)
> SLEEVE Ground
>
> If it's a condenser mic the TIP and RING should be tied together.
>
> Studio mics, like low 25 Ohms, do not work with PC sound cards.
> Suggestion: For cleaner recordings use a powered/pre-amped mic
> into the line-in.
>
> Line-In:
>
> Line level inputs.
> Sensitivity: 0v to 2v Most new PCI cards are RMS, most or all
> the old ISA cards are peak to peak.
> Impedance 47K-50K Ohms.
> Normal input should be about 1V.
>
> Line-Out:
>
> 0 to 2V RMS or peak to peak.
> Normal output level about 1V.
> Impedance assumed 10K Ohms, some cards 600 Ohms.
> Described as: Given a full Sine wave at 1Khz tone
> and a 10K Ohm > Load should produce about 1V RMS
> output.


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

And then I found this at the Rane site saying L1/L2 of an off hook phone has the impedance of about 600 ohms.

     http://www.rane.com/note150.html

with a simple circuit to connect a phone to a balanced mic line in to amp (could have used that about 8 years ago for a show).

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

And this, what I was looking for, the impedance of a carbon mic:

     https://mysite.du.edu/~jcalvert/tech/phones.htm

"A carbon transmitter is shown in the diagram at the right. This schematically represents the classic transmitter of the 1920's and 1930's as used in a desk set. The principles are exactly the same in earlier and later examples. Carbon transmitters used in later handsets were more compact, and the carbon chamber was a different shape to facilitate use in different orientations.

The diaphragm is of thin aluminium, and presses on the front of the carbon button. A damping spring controls the motion of the diaphragm, and makes electrical contact. Insulation is provided by fibre washers and bushings, so that both the front and back of the carbon chamber are insulated from the frame and from each other. The carbon granules are from ground anthracite, passing a 60 per inch screen, but retained on an 80 per inch. They are carefully cleaned and heated in hydrogen to passivate the surfaces. The granules are held between carbon discs at front and back. This transmitter was sensitive between about 300 Hz and 3000 Hz, which determined the voice-signal bandwidth, and strongly peaked at about 1000 Hz. Later developments evened out the response considerably by 1927, with further smaller improvements continuing.

The carbon microphone is ideal for creating electrical noise, which appears as the "carbon hiss." The noise increases with the bias current, limiting the output of the transmitter. This noise is scarcely noticed in telephone applications, but is very disadvantageous in more critical ones, such as radio broadcasting and recording. In spite of this, carbon microphones were used until electronic amplification permitted the use of capacitor microphones and dynamic microphones, which are not plagued by noise. Crystal and electret microphones are used at the present time, but they are possible only because of electronic amplification by solid state devices. The sensitivity of the telephone carbon microphone was about -15 dB re 1 V/μbar, and its internal impedance was 30 to 100Ω"


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

which matches with what I've seen so far in that the audio range is 100 to 3000 and the carbon mics with lower impedance put out a lot more sound than a 500-600 ohm PC microphone (30-100 ohm stated). So, maybe I can put a small resistor in line to get the impedance up a bit so the output of a carbon mic is more similar to that of the PC test mic I am using. I don't need a lot of volume so this in a good box may turn out to be something good. I'll work on it this week end and let you know what happens. If this turns out to be useful, I will post it on the forum, and leave  myself open to criticism from a few pros who like to do that because it wasn't there idea or I did something wrong, if you know what I mean.

My only intent here was to create a simple system to test the quality of a transmitter. I found a weak T1 in a handset by just blowing into the transmitter so I know I have one poor one to test. This may turn out to be something better than just a quantitative test.

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

Ah, the stuff we learn on google while the tea is steeping (probably cold by now so off to the microwave). Bock to the box (and I glad I have one of those old progressive resistance boxes where you can dial in a resistance instead of searching for a handful of resistors to breadboard the project).

====================================
« Last Edit: March 18, 2017, 06:22:42 AM by TelePlay »
            John . . .

              

Offline TelePlay

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 6754
  • A Ringy-Dingy Thingy
    • . . . been good so far
Re: Test Post - No need to reply
« Reply #33 on: February 19, 2016, 07:33:06 AM »
Here's the . . . .
« Last Edit: April 08, 2017, 09:41:46 AM by TelePlay »
            John . . .

              

Offline TelePlay

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 6754
  • A Ringy-Dingy Thingy
    • . . . been good so far
Re: Test Post - No need to reply
« Reply #34 on: February 22, 2016, 10:01:20 PM »
Here's the . . . .
« Last Edit: January 27, 2017, 02:43:02 AM by TelePlay »
            John . . .

              

Offline TelePlay

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 6754
  • A Ringy-Dingy Thingy
    • . . . been good so far
Re: Test Post - No need to reply
« Reply #35 on: February 27, 2016, 12:05:56 AM »
Here's the . . .
« Last Edit: November 26, 2017, 10:37:36 AM by TelePlay »
            John . . .

              

Offline TelePlay

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 6754
  • A Ringy-Dingy Thingy
    • . . . been good so far
Re: Test Post - No need to reply
« Reply #36 on: March 06, 2016, 10:05:14 AM »
Here's the . . .

« Last Edit: September 05, 2017, 10:52:26 AM by TelePlay »
            John . . .

              

Offline TelePlay

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 6754
  • A Ringy-Dingy Thingy
    • . . . been good so far
Re: Test Post - No need to reply
« Reply #37 on: March 16, 2016, 08:54:06 AM »
Here's the . . .
« Last Edit: November 26, 2017, 10:47:15 AM by TelePlay »
            John . . .

              

Offline TelePlay

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 6754
  • A Ringy-Dingy Thingy
    • . . . been good so far
Re: Test Post - No need to reply
« Reply #38 on: April 30, 2016, 10:24:50 PM »
Here's the . . .
« Last Edit: April 29, 2017, 12:33:49 AM by TelePlay »
            John . . .

              

Offline TelePlay

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 6754
  • A Ringy-Dingy Thingy
    • . . . been good so far
Re: Test Post - No need to reply
« Reply #39 on: May 12, 2016, 07:44:33 PM »
Here's the . . .
« Last Edit: September 12, 2017, 04:38:02 AM by TelePlay »
            John . . .

              

Offline TelePlay

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 6754
  • A Ringy-Dingy Thingy
    • . . . been good so far
Re: Test Post - No need to reply
« Reply #40 on: May 28, 2016, 08:42:33 PM »
Here's the . . .
« Last Edit: December 25, 2016, 06:08:24 PM by TelePlay »
            John . . .

              

Offline TelePlay

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 6754
  • A Ringy-Dingy Thingy
    • . . . been good so far
Re: Test Post - No need to reply
« Reply #41 on: June 05, 2016, 08:51:09 AM »
Here's the . . .
« Last Edit: September 15, 2017, 07:41:30 AM by TelePlay »
            John . . .

              

Offline TelePlay

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 6754
  • A Ringy-Dingy Thingy
    • . . . been good so far
Re: Test Post - No need to reply
« Reply #42 on: June 05, 2016, 10:45:57 AM »
Test:  nested img in url

« Last Edit: September 12, 2017, 04:40:02 AM by TelePlay »
            John . . .

              

Offline TelePlay

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 6754
  • A Ringy-Dingy Thingy
    • . . . been good so far
Re: Test Post - No need to reply
« Reply #43 on: July 07, 2016, 08:20:12 PM »
Here's the  . . .

===============
« Last Edit: May 16, 2017, 01:43:36 PM by TelePlay »
            John . . .

              

Offline TelePlay

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 6754
  • A Ringy-Dingy Thingy
    • . . . been good so far
Re: Test Post - No need to reply
« Reply #44 on: August 06, 2016, 05:27:52 PM »
Here's the . . .
« Last Edit: June 08, 2017, 02:41:52 AM by TelePlay »
            John . . .