Hello,
Hoping someone here might know.
Have been using a Radio Shack Mini Amplifier Model No. 277-1008 for many years to help out a person with a disability. Really important for them
As no longer a R/S, have been trying to find who might actually make/made this unit, and/or who might still be carrying them.
Anyone have any ideas where I can purchase a few.
Much hanks, Bob
It's still in the catalog:
Rumors of Radio Shack's demise have been greatly eggagerated. Many stores are still open as is their mail order business.
Online. See above URL.
Or eBay at outrageous prices:
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Oops. Looks like the mail order business isn't there any more. However, the store search found several stores that allegedly have it in stock.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I use these for simple hearing assist. No volume controls but nice.
Another alternative is an amplified PC speaker, if the input impedance is too low just add a JFET source follower. You can use the volume pot as rhe source resistor, then all you need is a gate-leak resistor and input coupling capacitor.
Most types run off a wall-wart, but you can get them with an internal battery compartment.
A couple of years back; a columnist in one of the hobby magazines mentioned
to say, all gone by the time I got there. Apparently the unit had a pair of small speakers driven by a TDA2822.
Ready made amplifiers aren't exactly rare, back in the 70s - 80s, any number of component stockists advertised small amplifiers (just a populated PCB) around the 250mW mark.
An old vest pocket transistor radio is a good candidate for the JFET modification - but those are often collectibles, such vandalism would horrify some people.
Search for Personal Amplifier on Amazon.com. There are several there that have builtin microphones, but use earphones instead of a builtin speaker. Prices are generally under $30.
My dad used one of those amplifiers for several years before his death. Sorry, but it's long gone now, else I'd be glad to send it to you.
If you're into electronics kits, you might check out the kit at
Cheers, Dave M
Bob wrote:
A stereo unit can be a PITA if you only want mono, but if its a common chip and not already BTL, most have a sample circuit for a BTL amp included in the appnote.
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And there's sort of a return to all this. In the old days, stereos were=20 big, now everyone with their Walkman, oops iPod, are throwing out their=20 stereo system and replacing it with a docking station, which is just an=20 amplifier with speakers in the same box, so stereo separation is virtually= =20 non-existent.
Oddly, there was a period when boomboxes included auxiliary inputs,=20 because they wanted to be "ready" for CD players that were either not yet= =20 out, or too expensive to build into the thing. So they also have=20 auxiliary inputs, if they are of the right vintage.
Anything with an amplifier should be useful, just find a way to feed the=20 audio into it. In the old days it was easy, the top of the volume control= =20 would be the place, a coupling capacitor would make sure all was safe.=20 But now, the volume control may not be a suitable marker, the control may= =20 not be attenuating the audio signal, but varying a DC voltage to control a= =20 stage that is controlling volume.
Michael
Or a rotary encoder going to the microprocessor.
may
I rather like my old JVC hi-fi in which the remote control (which unfortunately was stolen!) causes a motor to turn a nice large volume control knob, on which a flashing LED shows what setting it has reached. Much better than a digital display!
I have only recently given up using my Nikko TRM 40LA amplifier which I bought second hand from an ex-pat colleague on a business trip to NY City in the early 1970s. Although it was fairly heavy (with of course a large power transformer) it came back to the UK embedded in my dirty laundry in my suitcase. Since the instruction booklet included a schematic I tweaked some circuits as I saw fit...
Mike.
Most of the older shirt pocket items had about 4k7 volume pot, usually this is too low for most signal sources you might want to patch into it.
My solution is to build a JFET source follower onto the input, you can use the pot as the source resistor, in front of the JFET you only need a gate-leak resistor and coupling cap.
Bob,
There happens to be a new one on e-bay right now, for what I think is too much money:
If you watch e-bay and similar sites for a while you may find a few.
Regards, Tim
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