[ltp] Q further2: sound recording, A21m, Caldera 2.4

[Richard Neill]

Can you make line-in work? (Use, for example, the output from a hi-fi 
intended for a tape deck, or the headphone output from a radio as a 
source).

That will eliminate a few sources of error:
	- Mic gain insufficiently high
	- mic not powered
	- internal mic not working (as is the case on my A22p)
	- phantom power needed.

Phantom power: some microphones, particularly older, heavier, more 
expensive ones are "moving coil". They actually output a voltage. Others 
- the more modern (usually smaller) type are "electret" - this is a 
capacitor + field-effect transistor and requires that a DC supply 
voltage is present on the microphone signal line (known as phantom 
power). If I remember correctly, many "soundblaster compatible" cards 
provide this, but thinkpads do not.
A quick test: try using a pair of ordinary headphones plugged into the 
mic input. These will work like a poor quality moving-coil mic.

Does it work in Windows, or did you obliterate Windows as I did?

Richard






Robert Hueckstedt wrote:
> Thank you for the help and suggestions. I will try to respond to all your suggestions together. 
> 
> First, the external microphone I want to use is not powered.Erik, is the external mike you use powered? Maybe the solution is here. But if not . . .
> 
> In addition to the files /dev/dsp and /dev/mixer, I also have /dev/dsp1 and /dev/mixer1. I checked the permissions for all four of those. They are:
> 
> dsp crw------
> dsp1 crw-rw-rw-
> mixer crw------
> mixer1 crw-rw-rw-
> 
> My handy-handy kfm gui popup tells me that that means:
> 
> dsp: Bob is the owner and the user has rw access; group and others do not
> 
> dsp1: root is the owner and user, group, and owner all have read/write access
> 
> The same holds, respectively, for mixer and mixer1.
> 
> I do not know what hardware dsp refers to as opposed to dsp1. Likewise for mixer and mixer1.
> 
> I also see that none of those files have been accessed since May 23, 2000, which may have been the date of installation by linuxcare.
> 
> I decided that I probably need to have executable rights to those files, so I made that change in all of them. I then jacked in my non-powered, external microphone, ran the mixer program and tried the three jacks, called in that program line, line1, and line2, as record sources and again tried to record. Nada for all three. 
> 
> As Erik suggested, I tried the command cat /dev/dsp, in an effort to test the built-in mike. That gave me a blank console with the cursor running all over the place, but it gave me no garbage as if it were picking up sound from that mike. (Where is that mike?)
> 
> So, is the next and only possible solution getting a power thingee to go between the mike and the computer? Any other suggestions?
> 
> Gratefully,
> Bob Hueckstedt

-- 
rn214@hermes.cam.ac.uk  **  http://www.richardneill.org
Richard Neill, Trinity College, Cambridge, CB21TQ, U.K.