DAC basics

The minister's wife has been showing videos off the net with a laptop PC. She has been using the laptop speaker as relayed by a wireless mike, which is rather vile & picks up the blower on the video projector. The mike started using up batteries rapidly, so it is time to move on. New wireless mikes are $400 up unless you buy one with patented single use batteries stupidly expensive. I'm not interested. I repaired a $30 PV8 mixer with a stereo 1/8" phone plug cable to get away from wireless mikes, only to find her computer has no earphone jack. It has about 6 USB ports. The mixer works great on the condensor cardioid lavalier mike I bought the minister. The lavalier mike howls out in front of the speakers where the projector has to be, and I can control it with a graphic equalizer, but don't want to spend my time up front riding the slider pots.
So I look up DAC, and find the $349 cambridge audio dacmagic and a $299 something else, both with USB input and a line cord.
I look up DAC at newark and I get $5-12 IC's.
Isn't there some sort of gadget costing under $50 that will plug in the usb, be powered by the usb, and drive a stereo earphone jack?
BTW, what do you do to Windows 10 to tell it to put audio out the USB? She has no clue, and I use Lubuntu 14 which will run on a US assembled computer, hideously obsolete according to Microsoft. The great advantage, nobody writes viruses for lubuntu 14. Also It doesn't want to update in the middle of the service like windows 10 requested to do last week.
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There are cheapie Bluetooth audio receivers for a few bucks (from China); mine calls itself "H-163 Bluetooth Music Receiver". It run on 5V USB power, has a 3.5 mm (1/8") stereo socket. It might also be possible to turn Bluetooth headphones into a receiver with line outputs.

If you prefer wired USB, a cheap and immediately available option could be a junk USB headset from a thrift store (or e-waste bin). Just check that the headphone transducers aren't being driven in bridged mode by a class-D amplifier by checking for continuity between USB ground and one terminal of the headphone drivers.

There's a possibility of finding an actual USB audio interface box at a thrift store; I've picked up a number of the "ADS Technologies RDX-150 Instant Music" boxes for under $10; I like them because line-level and S/PDIF Toslink input and output; the codec is a name brand Burr-Brown/TI chip and the design is a pretty close copy of the chip's reference design.
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Thanks guys.
Learning the language of digital is part of the deal.
Ordered a $9 180-163 usb dac from parts-express.com USB Sound Adapter w/Mic and Headphone Jacks which might work.
Afraid of using bluetooth, we are next to a busy freeway and somebody's cell phone might mix into the video the lady is playing, unless I totally misunderstand how bluetooth works. She doesn't know how to enable bluetooth in windows 10, anyway. I don't either.
Needed some cables & a speaker driver from parts-express anyway, so freight was free.
Never seen the "USB headphone" or a "RDX-150 instant music" in a thrift store, this is a flyover state.
Trying to keep purchases of new stuff from a certain dictatorship down to < $20 but they are the sole source of almost everything anymore.
Found a used "PV8 USB" mixer online, bought that, but unspecified if the USB is for input or for output. If input, I could replace the ordinary PV8 I am using with a 25' USB cable to the laptop running the video, if there is such a thing. If an output, I could mix down several inputs to 2 track for Audacity as I have been doing with the line level input jack on PC's with ubuntu studio op sys. Such PC's with line input jack are now dying of old age (& dried capacitors). Windows 10 comes with warnings about *****y latency for using as digital recorders anyway.
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Afraid of using bluetooth, we are next to a busy freeway and somebody's cell phone might mix into the video the lady is playing, unless I totally misunderstand how bluetooth works.

Bluetooth is addressed, much like TCP/IP networking and breakins like that are vanishingly rare. There is a pairing sequence that must be completed before any two devices can communicate. Once two devices are paired, nothing else gets in there.

As far as enabling bluetooth in Windows 10 ... See THIS If she can use the WiFi she can use bluetooth.
Thanks. With the $8 parts-express usb-3.5 mm devices, came a $19 bluetooth to 3.5 mm phone jack gadget. Will try to pair the blue tooth gadget to the laptop PC tomorrow. If lap top has bluetooth, I have 3.5 mm stereo to dual mono 1/4 phone plug cables to plug signal into the mixer.
Advantage of parts-express, I don't have to send my debit card number overseas out of the jurisdiction of the FBI.
Last week discovered the horrid rattling the minister's wife was creating was caused by the wireless mike rattling on the cart to the projector blower vibration. Installed a piece of bubble wrap. Amazing what amateurs will put up with. Wouldn't take a very special bluetooth or soundcard device to sound better than PC speaker to wireless mike rattling on cart.
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