Quality of low voltage IC

[copynmail]

I am looking to power a couple 8ohm speakers I recently bought (typical shelf speakers from Circuit City, 5" woofer with 2" tweeter). My father has a hard time hearing the TV from the back of our living room, so I plan on putting speakers in the back. The TV has RCA audio outlets, which I plan on plugging into a lm386 amp.

My main concern here is I don't want to spend too much money, I just need a loud enough sound out of the speakers (I won't be using them myself at all). I am interested in the lm386 opamp because I already have plenty of DC power supplies I can use.

Is the lm386 descent enough to power speakers for TV shows? It will not be used for music, so the quality isn't too much of a concern. If the lm386 is really that bad, I guess I'll bite the bullet and use an lm3886 an build my own power supply.

Some googling has confused me, because some reviews say the lm386 is good enough for TV applications, but other reviews say it is only for really small speakers. I wouldn't mind ordering the parts and trying it out, but shipping takes time and I'd like an amp finished by Xmas in 3 weeks.

[pacificblue]

The LM386 has only 1/8 W. Which means you need very efficient speakers to achive decent sound pressure levels.

There are options between LM386 and LM3886. LM1875, LM1876 or TDA2030 are not too expensive and have enough power.
If sound quality is no issue and you want to use available DC supplies, car amplifier ICs could be interesting for you. They often need very few external components, e. g. TDA8563AQ works with only four capacitors and one resistor or TDA7374 with six capacitors and one resistor.

[danielwritesbac]

Originally posted by copynmail
. . .
My main concern here is I don't want to spend too much money, I just need a loud enough sound out of the speakers (I won't be using them myself at all). I am interested in the lm386 opamp because I already have plenty of DC power supplies I can use.

Is the lm386 descent enough to power speakers for TV shows? It will not be used for music, so the quality isn't too much of a concern. If the lm386 is really that bad, I guess I'll bite the bullet and use an lm3886 an build my own power supply.

. . . . I'd like an amp finished by Xmas in 3 weeks.

Given this timeframe, I'd suggest a Sanyo LM4628 and an inexpensive 2a regulated supply cord, or perhaps a supply from a salvaged obsolete computer. Either that chip amp or one of the little Tripath amplifiers will give a remarkably clear output, considering the short timeframe for development. These are both BTL and, therefore, may be able to control the woof on those boomy little mass market speakers so that you can get clarity of the voiceband for your television. This clarity will be partially reliant on the power supply, so I'd recommend a prebuilt "switching" style power supply so that you've a good chance at a lesser quantity of better quality bass (better as determined by the purpose of clarity in the voiceband).

The original T-amp, here at $49.99 with free shipping: http://www.parts-express.com/pe/show...number=309-952 has a lot of threads here on "how to's" However, given that its response is approximately similar to the speakers you've purchased, all you'd really need to add is a "12v regulated" wall plug supply. The regulated part is important for both clarity and longevity of the Tripath. Switching is another option, but unnecessary with that particular unit. Tip: Don't replace the potentiometer. The one that's already installed is better than most of the attempted upgrade projects.

Because of the wide media coverage of the Tripath, you'd have no reason to believe me when I say that the Sanyo will outperform it. Even if you think so too, the Tripath is still yet a wiser choice for your family, because of its low power consumption. Television amplifiers are often forgotten and left switched on. I think the T-amp will do fine.

[pacificblue]

Originally posted by danielwritesbac
I'd suggest a Sanyo LM4628

Did you mean LA4628?

[danielwritesbac]

Originally posted by pacificblue


Did you mean LA4628?

Yes I do!

Thanks for catching that typo.

[danielwritesbac]

Also check out Audiovox VR1 http://www.amazon.com/Terk-VR1-Autom...8304598&sr=8-1
as this is very helpful to cope with the bizarre volume variations from the television. Connect direct to the cable/dish box.

The VR1 also helps protect from receiving further hearing damage from the television. In this example, the television is already loud during a movie, and then a commercial frequently plays at much more volume, causing irreversible, albeit incremental hearing damage. The VR1 prevents this scenario of hearing damage.

The "garage band" quality equalizer at the local Radio Shack, albeit not as durable as its appearance suggests, does have many bands and a clear rendering. It can help to match up the differences between room, equipment, speakers, and ears.

I have used this equipment (VR1+EQ) to help my real-estate agent, who was suffering both Sony's roaring muffled TV sound and a slight hearing impairment. His television-related injury has not worsened. Actually, he reports that his hearing has improved, although I suspect that the report has no basis in fact. Perhaps its just better that his ears aren't ringing every day, as they had been prior to installing the protection equipment.

Quality matters
It may be unnecessary to increase the output of the television, but rather it could be more healthwise to provide a more suitable audio signal to the listeners.

[valleyman]

I would probably go with a ta2024. Have a look for ads from a member named Arjen China/ArjenShenzen in the Vendor's bazaar. He can supply ready made boards that perform very well for around $10 and it only took around 4 days for me to receive mine in the UK.
It will run happily off a modest 12V wall wart and delivers 2x15W which should be enough. It's very easy to get up and running too, just connect power, inputs and outputs and you're set

[lineup]

I would use LM1875.
http://cache.national.com/ds/LM/LM1875.pdf

You can use either single voltage supply, or dual.

Works from +-8 V (16V) to +-30 V (60V).

You have one LM1875 project description here:
http://sound.westhost.com/project72.htm

With +-10 V dual (20V) you get like 5 Watt into 8 Ohm speakers. This they may survive?
With +-15 V dual (30V) you get like 10 Watt into 8 Ohm.

One transformer 2x12 VAC would supply stereo.
One separate winding used for each channel.
The rectified voltage would be like 16-18 VDC. Two single supplies.
(Make sure the transformer has 4 wires output on the secondary!)

[pacificblue]

Why would you use a 2 x 12 V transformer to make two single supplies?

One split supply for the stereo amplifier avoids the need for virtual ground and big electrolytics in the signal path.

[danielwritesbac]

Well, there's this: http://www.parts-express.com/pe/show...887218#reviews

And, given that its going for a television, you don't need a potentiometer. Simply stick 20k metal film resistors parallel to the inputs (its like a 20k pot at full blast). Then you can either increase or lower the negative feedback gain for appropriate results with the TV.
The 20k was a guess. Simply use exactly the same value as the potentiometer that's recommended on the parts list (that I couldn't find).

Parts:
Input jacks
Speaker terminals
Ventilated box
12-0-12 transformer
pair of metal film resistors (input load)
cables
power switch

Well, that's simple and cheap.

P.S. Instead of the murky sounds of mass market speakers, howabout a pair of these instead: http://www.parts-express.com/pe/show...number=264-819