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Driving loads with MP3 player

Started by Bob Kindle October 25, 2011
I would like to use a pocket-size MP3 player to feed audio signals
direct (no added amp) to a solenoid type coil. The coil resistance
itself would be negligible. What is the minimum series resistance
required to avoid overloading the player's output? I am thinking maybe
32R? Any suggestions?

Bob Kindle
In article <4ea74028.3297437@news.tpg.com.au>,
Bob Kindle <bobkindle@terminox.com> wrote:

>I would like to use a pocket-size MP3 player to feed audio signals >direct (no added amp) to a solenoid type coil. The coil resistance >itself would be negligible. What is the minimum series resistance >required to avoid overloading the player's output? I am thinking maybe >32R? Any suggestions?
That's probably a good starting point, since 32R headphones are fairly common. A better MP3 player might be able to drive a set of 8R headphones to a reasonable volume level, although the power consumption might be higher. It'll depend a lot on the player. Suggestion: generate a few near-full-scale sinewave signals (say, 20 and 1000 and 10000 Hz) of a minute or so length each. MP3 encode them at a high quality setting. Load them onto your player. Play them, while loading the headphone output down through resistors of various values, and monitor the voltage across the resistors with an o'scope. Find the smallest-value resistor for which the output signal neither drops too much in amplitude, nor distorts. I used a cheap MP3/Ogg/FLAC player as an easy source of some low-frequency calibration tones, when I wanted to confirm the correctness of the CTCSS sub-audible access tones in ham radios belonging to some of my friends. My old service monitor doesn't have a CTCSS encoder/decoder... but by feeding a known-good 100 Hz tone into the horizontal input of its monitor scope, feeding the decoded CTCSS tone to the vertical, and looking at the resulting Lissajous oval on the screen, I could tell people just how much their tone frequency was off, or if it was distorted. -- Dave Platt <dplatt@radagast.org> AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads!
On Oct 26, 12:06=A0am, bobkin...@terminox.com (Bob Kindle) wrote:
> I would like to use a pocket-size MP3 player to feed audio signals > direct (no added amp) to a solenoid type coil. The coil resistance > itself would be negligible. What is the minimum series resistance > required to avoid overloading the player's output? I am thinking maybe > 32R? Any suggestions? > > Bob Kindle
sounds good. The solenoid will do very little of course. You can have speaker volume audio out if you use a 1920s style cork turntable amplifier :) NT
bobkindle@terminox.com (Bob Kindle) wrote in news:4ea74028.3297437
@news.tpg.com.au:

> I would like to use a pocket-size MP3 player to feed audio signals > direct (no added amp) to a solenoid type coil. The coil resistance > itself would be negligible. What is the minimum series resistance > required to avoid overloading the player's output? I am thinking maybe > 32R? Any suggestions? > > Bob Kindle >
Please stop abusing MP3 playerss.
On 10/26/2011 5:32 PM, Sjouke Burry wrote:
> bobkindle@terminox.com (Bob Kindle) wrote in news:4ea74028.3297437 > @news.tpg.com.au: > >> I would like to use a pocket-size MP3 player to feed audio signals >> direct (no added amp) to a solenoid type coil. The coil resistance >> itself would be negligible. What is the minimum series resistance >> required to avoid overloading the player's output? I am thinking maybe >> 32R? Any suggestions? >> >> Bob Kindle >> > Please stop abusing MP3 playerss.
When the unit is perfected, please let us know what type of music makes her twist and shout :-) I suspect she'll do a Tim Taylor and say, "more power". Mikek