Rockbox Technical Forums

Support and General Use => Recording => Topic started by: FranciscoB on December 04, 2012, 12:36:28 PM

Title: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: FranciscoB on December 04, 2012, 12:36:28 PM
I've been using a Rockboxed Sansa Clip+ for a couple of years and it's just great. Recently I made a set of binaural mics using some old Koss Plugs and Panasonic electret mics which I'd like to use to make some field recordings.

I'd like to ask you if it's (would be) possible to use the headphone out as a mic-in, given some proper changes in the firmware.

Thank you.
Title: Re: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: saratoga on December 04, 2012, 12:44:23 PM
No. 
Title: Re: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: Reece on January 16, 2013, 06:12:24 PM
      "No." Doesn't exactly help.
Can you tell us why? Is it not compatible, or just not yet implemented?
Title: Re: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: saratoga on January 16, 2013, 06:35:12 PM
Quote
Would the hardware of a Sansa Clip allow Mic recording through headphone out?

Quote
No.

What is unclear about that?
Title: Re: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: Reece on January 16, 2013, 06:55:10 PM
nvm... I just told you...
In other words, can you elaborate a little?
Title: Re: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: saratoga on January 16, 2013, 07:13:21 PM
nvm... I just told you...
In other words, can you elaborate a little?

If you have a specific question, feel free to ask it. 
Title: Re: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: Reece on January 16, 2013, 08:08:12 PM
    I already did! up top.
I said: Can you tell us why? Is it not compatible, or just not yet implemented?
Title: Re: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: saratoga on January 16, 2013, 08:16:14 PM
See above!
Title: Re: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: Reece on January 16, 2013, 09:21:05 PM
Sir. All you said was "No."
I am asking, if you could please elaborate.
So that there is no more confusion, here is what I would like to know.
1: Why not? Is it because it has not been implemented yet? Or because it can't.
2: Is it available on other devices besides Clip+
etc...
Or whatever pertains to this topic.

     From what I have experienced, when someone gives a reply to a question, they usually say more than just "no" or "yes." They explain why, and direct them to some source of information, or something like that.
So that the person can learn, and not have to ask a question like that again, and become self sufficient in that area.
    And I am sure, sense you are a developer, that you can give a better answer than "No."  ;)
And I mean this with all due respect, and hope I did not come off as rude.
Title: Re: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: saratoga on January 16, 2013, 09:43:59 PM
1: Why not? Is it because it has not been implemented yet? Or because it can't.

See above.

2: Is it available on other devices besides Clip+

Is what available?  Recording?  Yes.  Recording through the headphone jack specifically?  I have no idea.  You need to look at each port and see what it supports.

And I mean this with all due respect, and hope I did not come off as rude.

Not rude, just really annoying.  You tend to waste everyone's time asking the same questions over and over because you ignore people's replies and ask really dumb questions that you could easily have figured out on your own.  Stop doing that.   
Title: Re: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: Reece on January 17, 2013, 12:55:53 AM
  Thank you for alerting me. I know I tend to not be self sufficient some times. But I do read the replies, but just don't always read-read them, if you know what I mean. Its like hearing someone vs. actually listening, and understanding. I will try harder to research something before I ask about it.
Title: Re: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: AlexP on January 17, 2013, 01:13:55 PM
Quote
Would the hardware of a Sansa Clip allow Mic recording through headphone out?

Quote
No.

What is unclear about that?

This indicates quite clearly that the hardware does not allow it.
Title: Re: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: rocksnoc on April 04, 2013, 10:38:56 AM
with the original jack it won't work - but you can mod the Sansa Clip+ :)

But first: Hi community, I'm a ROCKbox newbie.

I was searching after a small device that features triggered recording.
I found: ROCKbox & Sansa Clip+ & this website: http://jimlaurwilliams.org/wordpress/?p=1748

I ordered some cheep 3.5mm SMD jacks from china: http://www.ebay.com/itm/140848016663

and after some work I had this:

(http://rockbox.peils.net/2013-04-04_sansa-mod/sansa_09.jpg)

Features:
 - 3.5 earphones work as usual
 - with an special 3.5-to-3.5-adapter you can connect a mic or line out device to the sansa
 - with an special 3.5-splitt-cabel you can use mic and earphones (stereo) simultaneously!



Now I need your help!

Triggered recording stops after creating 16 files (normaly) with the message: "The disk is full. Press OFF to continue."
The disk is not full... I think a buffer is limiting the filenumber?! Any idea?
(http://rockbox.peils.net/2013-04-04_sansa-mod/sansa_10.jpg)


modding...

1. removing the mic
(http://rockbox.peils.net/2013-04-04_sansa-mod/sansa_01.jpg)

2. test cables
(http://rockbox.peils.net/2013-04-04_sansa-mod/sansa_02.jpg)

3. removing earphone-jack
(http://rockbox.peils.net/2013-04-04_sansa-mod/sansa_03.jpg)

(http://rockbox.peils.net/2013-04-04_sansa-mod/sansa_04.jpg)

4. soldering new 4pin-jack and capacitor 22nF
(http://rockbox.peils.net/2013-04-04_sansa-mod/sansa_05.jpg)

(http://rockbox.peils.net/2013-04-04_sansa-mod/sansa_06.jpg)

(http://rockbox.peils.net/2013-04-04_sansa-mod/sansa_07.jpg)

(http://rockbox.peils.net/2013-04-04_sansa-mod/sansa_08.jpg)
Title: Re: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: FranciscoB on April 04, 2013, 01:34:36 PM
So you soldered the mic inputs to the earphone inputs? This way the earphone input can be used to plug in a microphone or the earphones (or both), right?

Very interesting, indeed. Could you share some of your recordings?

This mod also looks interesting but I haven't tried it yet:

http://o--o.se/doc/sansa-clip-audio-input-mod.html
Title: Re: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: saratoga on April 04, 2013, 01:45:53 PM
Thats a 4 pin jack:

http://en.wikipedia.org/wiki/File:3.5mm.jpg

Basically, it has pins for the line in and headphones.
Title: Re: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: FranciscoB on April 04, 2013, 01:54:41 PM
Oh, so that input now works as most mobile phone inputs do, correct?

What about the 22nf cap? Is it to block dc current? I dont see it in the photos, maybe the smd is part of the input jack?
Title: Re: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: rocksnoc on April 04, 2013, 04:51:20 PM
the cap:
(http://rockbox.peils.net/2013-04-04_sansa-mod/sansa_11.jpg)

(http://rockbox.peils.net/2013-04-04_sansa-mod/sansa_12.jpg)

the cap is to block DC

I measured:
- 1.5 V DC between battery negative terminal an jack "GND" (UNEXPECTED!)
- 0.0 V DC between battery negative terminal an mic GND
- AC voltage - I can't remember... (but about 2.5V AC ?!)


the 3.5-4pin-jack :
There are two different types of 3.5-4pin-jacks (A and B) on the market with a different pin assignment...
picture: german wikipedia: http://de.wikipedia.org/wiki/Klinkenstecker#Stereo-Stecker_mit_Zusatzfunktion_.284-polig.29

I tested a motorola 3.5-headset with mic (typ B) and it works fine: stereo + mic!


test recording:
If somebody sends me a licence free audiofile (provided from the RockBOX poject) I will share a test recording of it here.
Title: Re: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: FranciscoB on April 04, 2013, 07:16:07 PM
Oh, I was only thinking "smd" and didn't notice the ceramic capacitor  ;D

You could use something from Archive.org, for example:

http://archive.org/details/opensource_audio

You can only record in mono, correct?
Title: Re: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: rocksnoc on April 11, 2013, 05:16:48 PM
sound test:

I played a test-wave-file from 1-22kHz:
(http://rockbox.peils.net/2013-04-04_sansa-mod/sansa_14.jpg)

The frequency response:
- low frequencies are cut off because of the cap
- high frequencies are baffled

Ideal would be the same amplitude over all frequencies!


Zoom to low frequencies:
(http://rockbox.peils.net/2013-04-04_sansa-mod/sansa_13.jpg)

- there is a minor DC proportion on the input
Title: Re: Would the hardware of a Sansa Clip allow Mic recording through headphone out?
Post by: LADave on May 17, 2013, 11:36:17 AM
How do you explain the HF rolloff?  Is the Clip doing some kind of equalization, is it in your input source, or is it the mic you are using?