Total Newbie Question: Powered Amp Connected to the Prop?
dfletch
Posts: 165
Hi all. I'd like to build something like this:
www.aaroncake.net/circuits/amp20w.asp
Is it safe to plug the output of a low pass filter connected to the prop into "Right In" or "Left In" in that diagram?
1 channel example:
Is it OK to connect the grounds as the linked diagram hints? Do I need additional circuitry between that LP filter and the amp for protection? If so, how hardcore does the protection need to be - e.g. could it just be a load resistor or would I need something like an optocoupler?
After frying a set of AA batteries so badly that they leaked the last time I tried to connect 2 independent power sources, I thought I'd ask for some help this time
One question unrelated to the power supply: Could I stick a 10K dual potentiometer in between the filters and the amp for volume control? If not, where would a better place be?
Thanks for the help and your patience with a newbie!
UPDATE: cleaned up original diagram.
Post Edited (dfletch) : 2/20/2008 2:31:33 AM GMT
www.aaroncake.net/circuits/amp20w.asp
Is it safe to plug the output of a low pass filter connected to the prop into "Right In" or "Left In" in that diagram?
1 channel example:
+3.3v +12v
| |
v v
[noparse][[/noparse]Propeller] p10 ---> [noparse][[/noparse]low pass filter] ---> [noparse][[/noparse]amp input]
| | |
+-----------------------+ |
| |
. .
- -
_ _
-3.3v -12v
Is it OK to connect the grounds as the linked diagram hints? Do I need additional circuitry between that LP filter and the amp for protection? If so, how hardcore does the protection need to be - e.g. could it just be a load resistor or would I need something like an optocoupler?
After frying a set of AA batteries so badly that they leaked the last time I tried to connect 2 independent power sources, I thought I'd ask for some help this time
One question unrelated to the power supply: Could I stick a 10K dual potentiometer in between the filters and the amp for volume control? If not, where would a better place be?
Thanks for the help and your patience with a newbie!
UPDATE: cleaned up original diagram.
Post Edited (dfletch) : 2/20/2008 2:31:33 AM GMT
Comments
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Paul Baker
Propeller Applications Engineer
Parallax, Inc.
an amp but DON'T connect the positive power together. The audio output from the low pass
filter and the ground can go to a "PHONO" plug which is also called RCA plug and it plugs into many
audio components AUX IN or AUDIO IN LEFT , AUDIO IN RIGHT on a stereo or video system.
(This type of connection seems to be the most common one in the USA)
For guitar amps the input is called a 1/4 inch diameter "PHONE" jack/plug for some reason.
You can connect a 5K or 10K pot if you know the right way to do it for a volume control... which is...
one side grounded, the other side connected to the audio output of the filter,
and the wiper (pot center pin) is connected to the audio input of the amplifier.
(a) a low pass filter, say 2.2k + 22 nF for audio
(b) decouple by a serial cap, say 10 µF
(c) a 10k volume control, the middle tap to the input of your amplifier. You can also add a fixed resistor to prevent blasting
+3.3v +12v / | 10k | / | | | /| v V 10uF v / | HEAVY METAL [noparse][[/noparse]Propeller] p10 --> [noparse][[/noparse]low pass filter] -->"right in" --vvvv->||--> [noparse][[/noparse]amp] | | OUT | | | \ | +-----------------------+-------------------------------------+ \| | | \ . . \ - - _ _Virand: Yep, I of course know about RCA jacks, and I've always known that you could take some low powered, un-amplified driving device and hook it up to an amp in a different device. What I didn't know was if this was some inherent property of amplifiers: that you can hook a lower powered device to a higher powered one, or if there was some special protection present in amps or sound generating devices to avoid power source meltdown (deSilva is leading me to believe that it's the series caps that are the protection) . In the macro world of plugging RCA plugs into case mounted jacks, this seems completely obvious. Not so much when actually building these devices though!
deSilva: Aha sounds good. The amp circuit I linked to seems to show those 10uF series caps.
Sounds great guys, now I just need to save up $50 to spend at mouser
Cheers,
--fletch
UPDATE: Cleaned up the diagram a bit more, added potentiometer and series cap.
UPDATE2: Moved the pot to the other side of "right in" because that was silly.
UPDATE3: Speaker. Ok now I'm just being silly. I need to find better circuit designing software than ASCII in the Parallax forum
UPDATE4: Ok this is going to rock hard: www.happcontrols.com/amusement/jukebox/50900700.htm + $20 = up to $70 now [noparse];)[/noparse] By the way check out the other amazing goodies on that site!
Post Edited (dfletch) : 2/20/2008 5:29:14 PM GMT
How my amplifier is wired up ...
3V3 ------. .---- +V | | .-----^-----. .-----^-----. /| | | ___ + | || | | .-|/ | | Propeller |---|___|---.-----| ||---> >-------| In Amp |====| | | | | __|__ | || .---| 0V | `-|\ | `-----.-----' --.-- | `-----.-----' \| | | | | 0V ------^-----------------^------------> >---' `---- -VPost Edited (hippy) : 2/20/2008 9:31:27 PM GMT
Both circuits are DC I believe (just looked again at the amp circuit, if it's AC, there's no hint). So I just removed the negative notation completely.
There appears to be a minor bug in the forum CSS. The "font-family" property in the .msgCode rule should probably read "monospace". It's currently set to "Lucida Console,Verdana,Tahoma,Arial,Helevetica,Sans-Serif". Some clients don't have those fonts, and Sans-Serif is not fixed width.
UPDATE: Yep, just firebugged this. Monospace works great.
Cheers,
--fletch
Cheers,
--fletch