RCD's - why 30mA?

[Derek Geldard]

Piece of piss.

[Ron Lowe]

Do you mean 'easy', ( which it mostly was ) , or 'what a load of bollocks'?

I dismantled the original 250, which had 4 PCBs: 2 amps, and 2 regulators.

I traced out the schematic of both ( which I can probably find here! ). I made measurements of the critical values ( constnt current source for the input long-tail pair, quiescent curent in the voltage gain stage, quiescent current in the quasi-complimentary class AB output stage, etc, etc )

I photocopies the PCB onto acetate, and used marker pen to increase the density of the image. I then etched and drilled PCBs.

All the parts were off-the-shelf, with the exception of the O/P transistors, which were Naim's own brand. A bit of digging at the local Naim dealer revealed that they were in fact re-badged BDY-58 ( older 250s had plain BDY

58s. ) No doubt the naim ones were hand-matched by virgins in Havanna. I did pop my batch or devices into a tester, and matched the hfe, but since the o/p stage was single transistor, I didn't have to worry about current-hogging and thermal run-away of individual devices. Even them, the emitter resistor would help provide some NFB around each device to help equalise current sharing.

Post-assembly set-up was trivial. All the constant-current stages ( input LT-pair, voltage gain ) came in right on spec. The O/P quiescent current was tweeked using the bias pot in the driver stage.

I'll take some pics tomorrow just for fun.

[BigWallop]

Ah now. I can hear a difference in the audio, but the video looks to be the same on all the equipment I have plugged into. We have a 48'' HD Screen hanging on the wall, and the DVD looks great on it. It also looks exactly the same when the Blue Ray is connected up with up. I don't really see a huge difference in video quality, but the audio does appear to be clearer and crisper.

anywhoo. I love getting more stuff on the discs than a standard disc, so it'll do for me. :-)

BTW. The Blue laser burner takes a bit more power to burn discs than the old ones as well. Just thought I'd mention that too.

[Andy Burns]

What connection do you have between the DVD and the TV?

You are talking about playing BluRay disks not standard DVDs?

If it's just a SCART cable you're not seeing HD video at all, if you have HDMI (or less likely YPbPr, DVI or DisplayPort) sockets use them instead.

[The Natural Philosopher]

so, you didn't bother to use FETS or even complementary transistors, just a load of old NPNs eh?

Well at least they weren't 2N3055's ;-)

[BigWallop]

Ah now, there ye go. I connected the blue ray with the RCA phono plugs. There are five of them on the TV and the blue ray player. All different colours of course. The DVD is plugged in with SCART (EURO) but the blue ray was connected by those RCA Phono.

Please tell me, oh wise ones, how to mend the error of ways. What should I be connecting them with. I know the Monitor has a load sockets on them, DIN DIMM and HDMIP, or whatever it is, labeled stuff, but the Blue Ray came with those RCA phono leads, so I thought they were the correct things to use.

All help appreciated.

[Andy Burns]

The phono plugs sound like they *are* YPbPr component plus L/R audio, but you may need to configure the BluRay (note no 'E') player to output a 1080p signal (or 720p or 1080i if your TV can't handle 1080i) for the TV, it may default to lower resolution, and it can't detect what your TV is capable of via the phono leads.

Alternatively (assuming player and TV both have connectors) an HDMI cable is cheap (i.e. about a fiver, don't pay £50 for a rip-off one) and will allow the player to detect what resolution the TV is capable of and use the maximum resolution.

[BigWallop]

Yes Yes. That could be what I'm not doing properly. I haven't touched any settings on the TV at all. I am actually allowing the TV to detect what is being pumped into it. Maybe if I play around inside the menu bits and pieces, I might find something that will do the changes of resolution on the TV. That should keep me going for a night. And it's Sunday, so no other major working stuff to contend with.

Thank you Andy, I'm off to play with my toys. :-)

[Andy Burns]

You're more likley to need to change settings on the BluRay player than on the TV, it'll help if you know what the maximum resolution of your TV is though ...

[John Rumm]

Its not the TV settings you need to worry about, but the BluRay players settings. The BluRay player probably has a setup menu, where you will be able to tell the player what the capabilities of your TV are.

The players default configuration will have to assume that the TV its connected to is not capable of displaying anything higher than normal PAL video - otherwise you would get no picture at all should it actually get connected to a normal non hi def TV. There are two ways it can learn of the capabilities of the TV. One is if it is connected via a bidirectional interface like HDMI, where the TV can tell the player what it supports. The other is by you telling it.

When you change the mode, you may find the player does the same as windows when you change screen settings - i.e. it will switch to the new mode and get you to confirm it is ok, then automatically revert to the previous mode if it does not get confirmation in a certain time.

It sounds rather like you have been watching all your HiDef content downscaled to look like ordinary video.

(this is the same situation where loads of people end up watching odd aspect ratio pictures because they have never bothered to tell the DVD player they have a widescreen TV etc)

[BigWallop]

I will look further into it all. As usual, I think the devices should do it all for me.

You mean I have to press buttons? Bugger that, take it back. It must be faulty. :-) lol

I knew I was doing something wrong, because everyone has said that I should see and hear a big difference.

[BigWallop]

Got ya. So it might actually be possible to tell both devices what each other is doing. Now I see why I am getting the same picture as anything else I playback. As I said earlier, the audio is surely clearer and crisper, and we get a more surround sound effect from the BluRay player (got it right that time). But the video was no different, where we were told we should see an improvement in the video quality, and see all the details in background scenes and things. It still looked pixelly and blurry like the DVD did.

So it's my fault again. :-(( I should learn to play with all the settings and things, so I get a better idea of how and why things should be. But I hardly watch anything on them really. A few movies I wanted to see, but that's it. It the rest of the family that like to bring mates round and watch and play games and things. SWMBO like to watch a weepy with her pals as well on occasion.

I get stuck in the shed, to fend for myself. :-(((

Thanks guys. This is a little learning curve for me to follow.

[Andy Burns]

With a HDMI cable instead of phono leads, they would ;-)

[Dave Plowman (News)]

Julian claimed to use US military spec devices. And to import them personally by flying to the States. But then he would...

[Dave Plowman (News)]

What's the spec? 'They' are allowed to claim HD for 720i whereas you really need 1028p for Blue Ray. In other words not all HD is the same.

The last bit makes no sense. Any difference in the audio (if any) would need specialised test equipment to measure.

[Dave Plowman (News)]

That's the snag with Y Pb Pr which is in many ways a retrograde move - SCART provides data circuits to control the TV as well as video and audio. HDMI is really the modern equivalent.

[BigWallop]

Looked at the TV and BluRay player and both have a connector for one of these

it has been ordered and paid for, so I'll have less hassle trying to find the correct settings. Aren't I the lazy barsteward? :-)

Thanks guys. Maybe now I'll get to see what everyone has been telling me for ages.

[John Rumm]

The player can do its best with audio without any fear of the result being incompatible with your other equipment.

Sounds like it was down scaling it to ordinary video then...

As is right and proper! (it is after all *our* domain) ;-)

[Dave Plowman (News)]

Musing about this I know SCART doesn't allow HD - but why not? There are so many versions why not just one more?

[The Natural Philosopher]

Well that's not exactly so. You can - if its nasty enough, hear distortion down to about 0.5%.

Now RCA (phono) connectors (or other sorts) can, if made with cheap nasty zinc(?) or indeed silver plating that is oxidised, make excellent rectifiers, and I have seen them do just that. There IS a justification for gold plating connectors to prevent that.

The problems tend to accrue when they are old, and often connected/disconnected. Chrome is also good for connectors.

So I don't discount the grain of truth in the hifi bullshit.

Nonlinearity of corroded metal to metal joints also appears in other arenas..the 'rusty fence' effect is well known in my hobby - RC model aircraft. Interference at certain sites between transmitters that normally work fine together is associated with rusty fences, which create intermodulation products that upset the receivers.

So if you can avoid analogue transmission through not very good metal (oxide) to metal joints that's a clear plus.

I dnt know whetherdigital audio signals are persented at these new fangled DVD players or not, but if they are, then another possibility exists, that you are using a different DtoA converter somewhere if ypu use digital sound streams.

D to A converter are also subject to their own issues, of filtering and of bit size errors.

Although to be fair the modern trend in design makes them all very good these days.