12V DC to 9V DC

Well, I thought you were wanting advice, but clearly you know what you're doing so I'll let you get on with it!

OK, I'm kidding, but really, if you are so sure that the audio circuits in question are not capable of running at 12V then surely you are up to building a simple regulator circuit consisting of only three components?

I'll bet if you look at the datasheet for the audio IC in your equipment you'll find it is designed for at least automotive voltages, and I'll bet your Creative speakers use a circuit design fairly close to the manufacturer's recommended circuit on the datasheet.

Also, as Dave Plowman rightly points out, the adapter that came with your speakers will in all likelyhood be unregulated, and you'll probably find it puts out well over 9V off load, maybe as high as 16V!

Dave

Hi Michael

I hear what you're saying, and you are of course right in the core concepts of what you say. However, I think we have to be careful not too become too pedantic about the whole thing. The internet, including Usenet, evolves like everything else in the world, and the demographic of the users likewise changes. What was a hard and fast ' rule ' a few years ago, may not necessarily be quite so appropriate now. Although it's a bit of a contradiction in terms, sometimes a degree of devolution is part of the evolution process.

I would not condone lots of really off-topic posting on a group, but I really don't think that *some* constitutes a big problem. We all do it from time to time, and sometimes, some really interesting debates come out of it. You could say that this is nothing to do with repairing equipment, and you would be right, but it is about the repair community, who just occasionally, do take an interest in things other than picking up a meter and a soldering iron ...

I, and I'm sure most of the other regulars on here, don't object to questions being asked that, whilst not being strictly to do with repair, are never-the-less, electronics related. This is particularly so when the person posing the question is himself, a regular poster. I have hung around this group and others for a long time now, and I really can't say that I've seen this one degenerating as a result of some postings that are not, strictly speaking, charter specific. Rather, I think that in general, the group thrives as a result of the diversity of people and their electronics-related questions.

I wasn't actually implying that the other Michael was trying to " impose his will " as you say, merely that the way he brought attention to the other group to Bart, had a rather dismissive tone to it. OK, by your contention of how Usenet heirarchy works, then perhaps the question should, strictly speaking, have been posed on the 'basics' group, but I thought it was a bit sharp and unfriendly-sounding, the way it was put to him, and by dint of the way I see the group as having evolved, not necessarily a valid response, in that manner. Hence the reason that I said that it may have been nicer to point out the existence of the other group by saying "could also" rather than "should". This would then leave it open to the poster, and other lurkers, to determine for themselves whether they might be better off to post similar future questions there rather than here.

It's all a case of being friendly to one another as an electronics community really. Lets face it, there's enough hostility world-wide, as it is ...

Arfa

because your required voltage is so close to the supply voltage, there isn't much in the line for a common regulator circuit to maintain a stable regulated 9 volts don't get me wrong, you can make a PWM (pulsed width modulated) unit to drive a power FET with a very low on resistance to give you a nice regulated 9 volts. you can find DC to DC converters online, you just need to know your wattage/amp factor of the load. or use a dual op-amp, MOS powerfet witha few minor components and make your self a regulated PWM supply...

That isn't strictly true. Most manufacturers quote the dropout voltage for their range of standard 78XX regulators, to be 2v max. Even allowing for the vehicle engine to be off, there is an overhead of 3v, and with the engine running, asuming that the alternator is working correctly, there will be an overhead of 4.8v ( 13.8v - 9v ) so he should be fine with a '7809, providing he doesn't need more than an amp, although there are higher rated devices available. The LM317K adjustable could be used. This can source currents in excess of 1.5A and has a max dropout voltage of 2.5v.

Arfa

The data sheet for the L78D09CV 2 amp regulator gives the input voltage as

However, the app is for a car, where the running voltage is more like 14.