Chipamp for computer - which one ?(need about 4W X 2)

[ash_dac]

Hi,

My pc speakers are nearly dead. (4W X 2 from 12V walwart)

Could I use the Lm3886 on a reduced powersupply ?

http://www.national.com/appinfo/audi...gn_Guide15.xls (The spreadsheet tells informs me that I can't use less that +-10V. However, the datasheet shows THD on 0.1, 1 watt with another graph showing that it may clip at reduced voltage).

Tdaxxxx chip amps have much worse poorer supply rejection ratio compared to the LMxxxx series so I would expect more distortion, layout problems, and oscillations.

I have ordered three Lm3886 for future projects but i'd like a recommendation of a chip amp for low power applications.

[ted]

Using a lm3886 or something within that family may be overkill. For simple, bullet proof amplifiers I use the lm4752 / lm4755. They have 2 channels, and few external parts. You are not going to win any sound quality awards with the 4752/4755 but I prefer them over some the tda options.

[joensd]

I wouldn´t say it´s overkill really.
You can get it almost anywhere (+PCBs), it´s simple to implement (say well behaved) and not that expensive likewise (see trade forum; just got some).
That said they indeed need 20V minimum.

A chip I often heard and seen implemented in PC amps is the TDA2030.
It´s also on the edge with 12V (AC or DC?) but should work and has a nice sound.
Better yet get the new version the TDA2040 (voltages from +-2.5V) or the TDA2052 (as TDA2030: +-6V)

[stelleg151]

if your not set on DIY you might want to consider an SI, although you will want to watch the voltages from that wall wart with any T amp.

[Irwin AR]

I think this might suit you just fine
http://translate.google.com/translat...lr%3D%26sa%3DG

[ash_dac]

Hi,

Lm3886- If I used a DC-DC convertor I could get -12V.

I'm not sure that there would be enough current for any output!

Any thoughts ?

edit: just looking at LM384

[joensd]

Lm3886- If I used a DC-DC convertor I could get -12V.

that depends on the wallwart and the circuit you wanna use.

Hmm, don´t know how much effort you´re willing to input
but I personally would rather keep it simple and go with a TDA2040
or alternatively getting another power supply/transformer for the LM´s.

One TDA2040 should cost ~ a quid, a little transformer for the LM´s from salvaged equipment (printer wallwarts, audio amps, lighting transformers..) can often be had for nothing.
The DC-DC converter will cost a bit and some nerves too to get it properly working and is nothing for a first time project anyway.
You decide.

just looking at LM384

uhh, had one of those and a LM386.
I remember they were a pain to get working noise-free.
They both have fixed gains so you´d have to lower the input signal quite a bit which is not very advantegeous in your application.

[ash_dac]

Originally posted by joensd

that depends on the wallwart and the circuit you wanna use.

Hmm, don´t know how much effort you´re willing to input
but I personally would rather keep it simple and go with a TDA2040
or alternatively getting another power supply/transformer for the LM´s.

One TDA2040 should cost ~ a quid, a little transformer for the LM´s from salvaged equipment (printer wallwarts, audio amps, lighting transformers..) can often be had for nothing.

Hi,

I've been digging around on the forum, and on the net this morning, and I have come to the conclusion that -

L165 = LM1875 = LM675 = tda20x0 (close)

I forgot that a speaker is really a motor

The only reason I'm a bit wary of making the psu is the fact that I see numerous examples on this forum, and on the web of DIY power supplies that look frankly leathal !

I will have a look on the web for a book on how to safely build power supplies.

[joensd]

If you don´t plan on further DIYing it can indeed be a bit involving reading about power supplies, safety issues, etc...

Another solution as already mentioned might be to find another wallwart with a bit more "juice" and voltage.
I used a HP printer wallwart for a PC amp once.
They usually have almost 30VDC at 1A. If you could find two:even better.

[ash_dac]

Lm3886 arrived yesterday.

I have gutted a NAD3130 (terrible insides) chassis to put the boards in.

I have been using the overture design guide (model) using 8 ohm load, and 18V secondaries with 40C ambient temperature.

The model recommended a heatsink of 5.94C / W for the TA package. This seems quite high to me but I guess this must reflect the 8 ohm load. Any thoughts on this ? It would certainly save on the heatsink costs.

I plan to have the heatsinks isolated form the case, and run them live.

I put the LM3886 onto stripboard (diagonally as recommended elsewhere on forum).