View Full Version : 2.1 amp?
I was thinking about a portable MP3 boombox project, but with good power. It seems like a 2.1 configuration would make a nice package. Perhaps 10 to 20 watts per stereo channel and whatever might be requred for the subwoofer channel (20 to 40W??). Rechargable SLA for power. Sort of like the Boominator in the other post. Is it possible to offer/connect an amp in this configuration?
There's the amp9 which would do that. Just filter and parallel (not bridge) two of the channels for dedicated subwoofer use. Alternatively use a dual voice coil woofer and feed each vc with it's own amp channel.
That would give you a 2.1 amp that outputs exactly twice as much power into the sub-channel as in the stereo channels (depending on speaker impedance naturally).
quote:[i]That would give you a 2.1 amp that outputs exactly twice as much power into the sub-channel as in the stereo channels (depending on speaker impedance naturally).
I assume that you can adjust the gain separately for each channel ... ? (To make the volume from the sub fit the volume from the satellites.)
Sounds like a good idea. I assume through gain adjustments, speaker selection and crossover design, the volume could be matched. Good idea about the dual voice coil subwoofer. That would make the design simpler.
What about input impedance to the amp9? Most MP3 player outputs are designed for 8 to 16 Ohm impedance headphones. What does the amp9 like to see?
I think it is more efficient to design a crossover at the input to each amp9 instead of conventional crossovers at the speakers. Do you agree?
IIRC, the gain is set internally in the chip on the amp9 as well as the input impedance.
In the amp9 forum V-bro has written many posts about this, and also how to use an audio transformer in the input to fit mp3 player output, and PLLXO (passive line-level crossover). Instead of me repeating his excellent work, I'll just direct you there.
Dear 41hz, Tripath-AMP users.
Any Dual-voltage (not TA2020, TK2050, TAA4100A....) that can be bridged (TA2022, TA3020 etc) can be hooked up as a 2.1 system.
- set it to bridged mode (so 1 ch. has inverted input)-
- hook-up the two fron/satellites on the normal channels
- put the subwoofer on/over the bridge i.e. the two outputs.
- remember to hook-up the satellites reversed, to compensate the 180 phase shift induced by the inverting.
Yes, you will need to put in a cross-over. But you do not need an extra AMP !
So this can be done with AMP-1x, AMP-5, AMP-10, Truepath, AMP-7 etc...
It's in the Application Note 8 and 13.1, under Downloads in your Shop-acount.
Read them. Please.
They ARE helpful, just like many other articles under Documentation (which were (partly) on the Wiki before).
I'll put them on the CMS one day and make an article of this 2.1-item. Seems useful and unknown.
Yeah, I'm crazy, I know.
In theory it will work, but in practice it won't.
Bridging the amp causes each channel to see half the impedance of the subwoofer.
Assuming you are using 8 ohm satellite speakers for the sub and sats, the amp would see 4ohm and 8ohm load in parallel = 2.6 ohms.
That is a little too low for most amps here except maybe the AMP2 & 7.
There is a Tripath app note in the Downloads area:
Application Note 13 : TWO CHANNEL PLUS SUBWOOFER CONFIGURATION FOR TRIPATH BRIDGED AMPLIFIERS
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