OT - TDA1517 2x 6W amp

[Malc C]

Guys, bit OT but where else can a poor guy get some expert advice ;)

Been rumaging through some old PC cards and came across an old ISA 16bit soundcard all full of components, including a TDA1517. A quick google brought up lots of sources for the datasheets or suppliers in the far east, but I couldn't find any schematics for making a decent amp from this chip for use with my PC (as the current soundcard has no onboard amp and the speakers I'm using are passive bookshelf units -long story!)

The closest I found was from the datasheet, but the capacitor values are way off the values of the electrolytics surrounding the device on the soundcard.

Any suggestions:

[Chippie]

Mal,

I came across the same cct diags as you did, which suggests that the cap values are fairly typical.........

If you are using the device on a sound card, it would suggest small speakers therefore a lot of bass boost may be required.

What size speakers are you going to use?
This may dictate the value of caps needed.........

[Malc C]

Ok here's the story....

A while ago I asked for a set of replacement speakers for my PC as christmas was approaching. Now I'm not sure where the breakdown in communication happened, but I ended up with a pair of Acoustic solutions bookshelf speakers, rather than a set of powered PC speakers. ( http://www.acousticsolutions.net/product.asp?ID=1 ). These have a 100mm bass and 20mm dome tweeter, and handle 10-50w according to the specs. They work fine on my Abit N7-S motherboard, which has a decent soundchip on it (and full graphich eq etc), but the volume is a bit low.

I've been meaning to buy a small amp for some time, and then by chance my father gave my son a set of Awia speakers from an old midi system that gave up the ghost and we powered it from the small amp from inside a set of cheap active PC speakers. The small PCB had a DIL chip on it so I guess it was one of the LM range of chips that pumped out between 1 and 3w, but the volume that the speakers ran at (and with virtual no distortion at full volume) was amazing... so when I found this old card with a decent 6W + 6W amp I thought it would make an ideal way of driving the A.S.20's I have.

So there you have it... the long story :)

Now its hard to actually "reverse engineer" the soundcard to workout what capacitors go where, especially as there are some SMD's caps in the same area, but the electrolytics are 47uf, 470uf, 10uf, and 100uf. My guess is that the 470uf's replece the 1000uf shown in the datasheet

I'll try unsoldering it tomorrow, and breadboard the above circuit and power it from a 12v supply and see what I get out !!

[vintage1]

Well 470uf and 8ohm speakers is the same time constant as 1000uf and 4 ohm..most of these simple chips will do about 6W into 4ohm. from a 12-13v supply (car stereo stuff mainly)

The other bass roll off is the 220nF/60K time constant. You can use bigger capacitors here for more bass. But the dominant roll off is the output stage.

1000uF/4 Ohms is about -3db at 40Hz. Thats pretty hifi..for a pair of bookshelf speakers,. They don't do much below 100hz to be honest, and would probably be fine with 470uF.


All the rest is completely as non critical as well. The other caps are pure smoothing - low and high frequency.

ISTR I used this chip in bridge (mono) format for a small 15W guitar amp..you can run it to about 18v off load with luck..mine sagged a bit down to 12-14v on load IIRC.

[MatC]

All those caps look to be either power smoothing or AC-coupling caps, any value in the ballpark will be fine.
The power smoothing uses a large electrolytic for the low freq smoothing and a smaller one with low ESR for higher frequencies.
The output caps protect the speakers (and output stage) from the DC that is present - the speakers connect to ground but the output stage centres on 1/2 Vp.
So anything in the ballpark/carpark/refreshment-area is fine, but smaller capacitors (esp on output) will reduce your bass response as vintage1 says. Don't forget the polarity of the electrolytics :)

[flatfour]

I use this to power my pc speakers

http://www.yamaha.com/menuitems/panelviews/yec/RX-V800/RX-V800.htm

[Acetronics]

Hi, Malc

Why look for difficulties ??? ( as always ... )

as there are no links to internal circuitry ... there's nothing to add to this chip !!!

nothing to improve its sound nor ...

mmmmmhhhh, did you look at simple sound cards for PC ... Electricity to heat the iron is more than the price !!!

Alain

[Malc C]

Guys thanks for the input

flatfour - nice amp, I have a (now somewhat dated) Sherwood 5.1 AV amp for the TV/dvd/hi-fi, but don't have the space for somthing like that for use with the PC

Alain - yeah i could probably pick up a powered soundcard from somewhere... but where's the fun in that ;)

[Acetronics]

A good old SoundBlaster PCI 128 or Player 1024 could be more than enough ... and I saw a TDA dual amp. aboard :p !!!

Alain

[Malc C]

Well Alain you may well be right...

Maybe that's why I removed the card all those years ago... I hooked up one channel and tried it and got nothing out from the device... I would assume that the device doesn't need both channels hooked up to work, and the datasheet implies that its two amps in one package.

Oh well... it kept me busy for an hour !