Pepping up a Silicon Chip SC480 audio amplifier

** Not much praise in that remark.

** Close enough to my figure of " ... about 1MHz " - eh ?

..... Phil

I love my digital video recorder. I shall never watch another ad.

pretty darned good indeed. I cant sleep, so Im gonna do the load tests now. And test the input-voltage-to-secondary-current transfer function with my toroid driving a short.

Cheers Terry

Can you set that up so that it omits all adverts then? And does it work 100% (in the face of all the efforts of the advertisers?) How does it work?

I press the FF button, and with practice can go *very* fast and not overshoot (well at least not too often).

it would be lovely to have it eat the ads automagically, but I doubt we'll see commercial products that do that anytime soon.

Cheers Terry

You bet. They're as fast as slugs on mogadon.

Oh the email in my headers works fine.

Graham

Not even necessary with Toshiba bipolars.

Graham

May not actually be that fast. Remember gate capacitance. You need a beefy driver stage to get them moving quickly as Terry will surely already know.

Graham

any suitable part numbers?

and yeah, I knew the xx55's were slow as all hell.

I havent done my power-bandwidth tests yet, but my small signal bandwidth is now 0-10MHz, which is good enough for a lot of what I have to do.

If I can get 1W@1MHz I'll be doing well indeed.

I sent you a pretty picture, too.

Cheers Terry

** If you want wide power bandwidth, then lateral mosfets are the clear winners.

Eg, Hitachi 2SK176 / 2SJ56 or the similar Semelab BUZ 901/6 devices.

Main reason is lack of charge storage in the C-B junction means they turn off so much faster ( circa 50nS ) you avoid the cross conduction disaster at high slew rates.

Also, these mosfets self protect at high chip temperatures, " throttling back " instead of simply blowing up.

..... Phil

**As Phil has already stated, MOSFETs are MUCH better at HF than even the Toshiba BJTs.

--
Trevor Wilson
www.rageaudio.com.au

**I looked at doing just that a dozen or so years back. Back then, TV stations used to send a 200mS of black level, before and after ads. Trouble was, the system was not infallible, since some programmes go to black.

--
Trevor Wilson
www.rageaudio.com.au

you could almost do it looking solely at volume levels. ads are *always* louder, some channels more so than others. Still, 8x or 20x FF works pretty well, and requires little or no effort on my part.

Cheers Terry

LOL

yeah, but I'd want to be damned sure its not going to burst into oscillation at 200MHz. especially when I jam 200MHz up the input :)

mostly, this little amplifier was good enough to solve the immediate problem (needed 100kHz), and now I've vandalised it further, it'll probably do everything I want. it had the added advantage that I could buy it in one bag from Jaycar, and spent 1hr putting it together. it took longer to drill the heatsink than build the kit.

Cheers Terry

it's just a software problem as others have said there's a watermark that can be used, all that needs to be done is detect it and stop recording when it disappears and start a few seconds before it reappears, as it typically turns up late.

I'd not be surprised if there isn't already a non-commercial product that does that.

Bye. Jasen

Ah, how does it know when the logo is about to re-appear?

Dave.

one way would be to buffer a few seconds worth in RAM when it sees the logo it saves the buffer

recording doesn't have to happen in real-time, only playback.

Bye. Jasen

100%

MythTV uses the logo and a couple of other clues. It is conservative so it does miss some advertisements but mine has never lost any program content. Like any other PVR it always "records" a program so that it, and you, can skip backwards and forwards. My computer is not powerful enough to remove advertisements in real time so I have to wait about the same time as the length of the program before I can watch the advertisement-free version.

It is not a commercial program and it is totally free but not the faint hearted. You can build a MythTV PVR for a little less than a similar consumer product. Commercial programs do what the content providers want them to which resulted in some Microsoft Vista users missing not just one program but several days recording .