JTT

Oooops! The above device is L200, not LM200! JohnT

A very useful regulator for this sort of thing is the LM200. It's very easy to make a fully variable supply based on an 18v transformer which will cover 3 - 22v, and it's a doddle to add selectable current limiting: very useful if you want it to charge batteries in its spare time. The voltage range is limited by the 32v max with which the device may be fed, and the reduction in voltage on the unregulated side of the supply as load is applied. There are ways to increase this, but but it does lead to more complex circuitry. You can make a pos/neg supply using two LM200 and a twin gang pot for setting the outputs. It won't have auto balance tracking, but dual linear pots seem to track each other very well these days. JohnT

You're right, and I s'ppose we could go on forever discussing the merits of one view vs another. None the less, the LM380 is so cheap and easy to implement that it would be interesting if some headphone-owning enthusiast would try it, and comment on the result. JohnT

The qualifying arrangement was bad enough last year, and this years change makes it just too god awful for words. Hopefully, Bernie Ecclestone means it when he says he wants it back to the 12 lap free-for-all that applied until a couple of years ago. Ditto the single engine rule. I sympathise with the Minardis and Jordans of this world, but if the whole thing gets dragged down to their level, then I for one will not for much longer regard the Grand Prix as must-have viewing. Let's get up a petition lads! (but ... well ... no ... , I don't think I'd like to organise it .......). JohnT

Sorry, but .............. I didn't note that you have had the USB setup working with an alternative 20Gb disk. JohnT

This sounds very much like a windows driver problem. You do need a special, albeit generic, driver to support external USB memory devices. To find out if you've got it (and if your system is detecting the disk), go to 'Control Panel', 'System Manager', and scroll down to the USB Controller section at the bottom of the list. Do this without the disk plugged in. Now plug in the disk, and within a few seconds you should see 'USB Mass Storage Device' added to the list. If you don't have the (correct) driver, then it won't be. The drivers for Win98SE, and possibly other Win versions, come as a set of 4 files which will enable support for USB HDDs and USB card readers eg: Compact Flash etc. They are: genedisk.inf genestor.pdr geneuide.inf geneuide.sys Hope this helps JohnT

Ah .......... well .. 1&2 ... If you think you will detect 0.1 - 0.2% distortion, then fair enough. 3&4 ... This IC has quiescant current of only 10 - 12 mA, and is the most useable un-bridged low power amp I know of, which is probably why it's been in production for 15 - 20 yrs. I use it as a battery powered amp, in conjunction with a laptop, for loudspeaker freq resonse testing. I use it with both 12v (lead acid) and18v (12 x AAA) rechargeables with no component changes required, and there is no requirement for external heatsinking with output powers below 1W rms. 5 ........ The (relatively) high fixed gain does offend my sense of proportion, and there seems to be no way to add additional external feedback without causing instability (I've tried). So you have to attenuate at the input if you don't need that much gain. However, for audio listening you would be using a LOG law pot, and a bog standard single turn job, with a series resistor to provide the adjustment range you want, would be fine. 6 ........ I don't use headphones, so I'm not really qualified to comment, but I'm a bit doubtful about your contention. JohnT

But the amplifier is not required. So little gain is required for this application that a buffer amp with reasonable current drive capability will be more than capable of doing the job. And, incidentally, the 637 spec warns of instabilty for gains less than 5. I could stoop so low as to suggest that the venerable LM380 would adequately do this job - and don't rubbish it if you haven't tried it. JohnT

S'cuse me butting in late in this thread, but it's not clear to me what you're trying to achieve. Why are you using 2 opamps? I am doubtful about the wisdom of using either the 634 or the 637 as a power amp, even for the low powers you are probably after, and there is nothing useful to be gained by cascading two of them in the way you are trying. And including them in a single feedback loop is definitely asking for for oscillatory trouble. Even if it would be stable, the gain would be 10 (R2/R1), and with only 18v to play about with, 2v rms input from your CD player would drive it into immediate clipping on peaks. 2v rms is approx 6v pk-pk, so to accomodate the max signal with an 18v supply you can't afford a gain greater than 2 - 2.5. I would try using a single opamp, with R1=2k2 and R2=4k7. JohnT

Hi I have had a DCD910 for some years, which seems to be little different to the 810. The 910 has one or two additional features, and slightly different styling, but the transport and main PCB are the same. The transport is a simple, solid, and dependable piece of work; the data and servo control chipset is the Sony 118x series, which seems to have been well regarded; conversion is via a pair of Burr Brown DACs, which are definitely good. Performance has been consistently satisfying. I have had no problem with the 910, except in recent weeks, when it started occasional mistracking. Changing the laser read-head (Sony KSS150A) with the current equivelent item (KSS210A) has given a complete cure. The new laser gives 50% greater output, so I'm pretty sure the original had had its day. A new laser is cheap, and is an absolute doddle to change. I did buy a current model DCD485 as a potential replacement, but I have to say I've winced at each playing and am truly grateful to get my 910 back in harness. The 485 is the bottom-of-the-range model; that'll teach me! I can't remember how much the 910 cost me when new, but I seem to remember it was at the upper end of the moderately priced ranges at the time. Regards JohnT