Little cheapo 10W stereo amp modules

[Yorkie]

Visited Joe yesterday afternoon and spent a pleasant hour or two with him, where among other things, he showed me a neat little stereo amp that he'd built using a surplus module bought from Bardwell's on Abbeydale Rd Sheff. The modules are based on a pair of Thompson (French outfit) TCA940 ICs. On the way home, at just £3.99 each I couldn't resist a punt! (Worth more than that just as a donor for the pots).

They supposedly need 24V to power them, but Joe discovered that they'll work down to about 6 Volts, and at 9V they'll blow your socks off! I sorted through them in the box to pick a couple of good 'uns as some had rusty pots etc. (Vol/on-off switch, balance, treble, bass). Tested them when I got home - no probs. Just an impulse buy, and why not, I tell myself?

Quite handy as a bench amp, signal tracer, MP3 player amp etc.

The TCA940 has its 40th Birthday this year. (Ironic that some restorers say things like "I only play with valves - I don't touch 'modern stuff'"!)

http://www.radiomuseum.org/tubes/tube_tca940.html

[AlanBeckett]

I must get Joe to pick me up a couple of those when he's passing.

Where I used to work an old Product used the smaller and somewhat later TDA1011/1015. When it was declared Obsolete we scoured the World for them. We even recovered them from scrap Units until there were none left anywhere as far as we could tell. Unfortunately the Product, which was Certified, used all the facilities of the Device in a very specific manner, and there was no way of replacing it. A big pile of 'Surplus' Units like these would have kept it going for a bit longer. Very sad.

Ala

[Refugee]

What street number are they located at?
I have been to Abbeydale Rd a couple of times over recent years and may be interested.

[camallison]

288 Abbeydale Road

Colin

PS - they have an ebay shop too:

http://stores.ebay.co.uk/bardwellselectronics/

[Refugee]

Cheers.
I will have a look next time I am down that way.

[Joe]

Here it is on their own web-site: http://www.bardwells.co.uk/product/stere...r-channel/

- Joe

[Refugee]

Cheers for the web link.

[Yorkie]

A bit more info on these modules which might be of help:

I see from the TCA940 datasheet that Joe kindly sent me, that it's quite a capable IC. It features supply overvoltage protection, output short-circuit protection, and protection from overheating. The frequency response is from 40Hz - 20 kHz, and distortion is stated as 0.3%. The supply voltage can range from 6V - 24V DC. The volume control on the module has a double pole mains rated switch (which has no connections to it), which could be used to switch a mains PSU, to provide a DC supply from 9V - 20V, well within the stated voltage range, built into an amplifier cabinet.

As supplied, it's intended for use with 8 Ohm speakers, but by changing the two caps shown on the attached pic, (which also shows the connections), from 500uF 15V to 1,000 uF 15V the amp is suitable for 4 Ohm speakers, but given tht the IC is fairly well bomb-proof, I doubt it would come to any harm if the caps aren't changed.

Though Bardwell's website says the amp is 10Watts per channel, and the datasheet on the TCA940 states that it is capable of 'up to' 10Watts, the data and graphs on the characteristics indicate and output of 5 Watts.(More than enough to fill an average room!).

I've no idea what's happened to these little modules in their long storage life, but the underside of the PCB has stains that almost suggests that they've spent some time in water! I've tried to clean the underside with flux remover/PCB cleaner, which has had no effect whatsoever, so I've left it alone, given that it works fine.

(The TCA940 IC is pin-compatible with the more familiar TBA810 of the same era, which often featured in magazine projects as the output stage of receivers, or in such things as intercoms, baby alarms, guitar practice amps etc).

Hope these extra notes might be of interest and use to someone.

[camallison]

I have just received mine, and that "mucky" underside is possibly a poor (and dirty) application of a conformal coating David. Purely looks and not detrimental to operation, I think you will agree. You are correct - it did all but blow my socks off at 24 volts and with a couple of 8 ohm speakers. What a wonderful find. The man cave is now equipped with its own "music centre" built from my bits box and that module.

Thank you for the heads up David.

Colin

[Yorkie]

Thank you for the heads up David.

Colin

Glad you're happy with it Colin.

As you say, the shabby underside has no bearing on the performance.

As to the 'heads up' - it's Joe we both have to thank - he tipped me off about them and gave me a demo of his, resplendent in the cabinet he made for it.

All sorts of uses for them - an ideal bench test amp/signal tracer, but a nice stereo amp in its own right.