Maplin "50W HiFi" amplifier module instructions.

OK, Wagon of beer tokens;)..

Another very good English designed speaker:))..

There's a very interesting design in 'Elektor' magazine this month, for a power amplifier using lots of op-amps in parallel, by Douglas Self. Seems a very good idea, I haven't heard of it before, with advantages including no heatsinks and their asociated assembly difficulties, because the dissipation is divided among the chips, 32 of them in this case, fully protected against short circuits, due to the self-protecting nature of each op-amp, amplifiers can be paralleled to work into a lower load impedance, as each op-amp has a 1- ohm resistor at it's output, these are all effectively in parallel to give a very low source impedance.

Good for speech not quite so nice in music.

In what way?..

The voice is just another instrument, isn't it? What sort of music are you thinking of?

Bit "light" and don't go particulary loud, I liked LS5/8's.

Ah well, the voice is. Lots of voices aint.

Also lots of any instrument.

If one instrument sounds good, that means nothing.

If you can actually pick out individual voices or instruments in a chorus or orchestra,, you have bloody low intermodulation products in the speakers.

Best there are Quad ELS, then horn loudspeakers IME. I've heard some lovely PA style horns that serious money was spent on. JBL used to be very good.

Price you pay is tendency towards colouration. so the single instrument may sound tainted..

Actually rock music is easiest to get right. Few instruments - just needs decent bass, but no transmission lines please. They muddy bass drums awfully. IB or bass reflex better, or best 20 ft concrete horns.

Same for jazz. Nothing special required.

Hardest is really full orchestra or full chorus - not opera. There you want both low colouration and low distortion and those are hard to get together, especially at high volume.

I think if I were putting a serious setup together today, Id go for 12 or 15's in bass reflex cabs, crossing over to some serious 8" units about 300hz, then a mid range horn at 1.5kHz ad some bullet horn style tweeters at about 5khz.. be aiming for 97dB/W or so and spending a sodding fortune on the kit..

Any old amp though :-)

Well thats not a problem as such .. the LS3/5A is an excellent speaker let alone one for its size..

Yes.. wouldn't mind a pair of they for meself:)..

Are they seen that often outside BBC control rooms and similar places?..

I can't pick out the individual instruments in an orchestra when I'm listening to it in a concert hall. Should it be easier with amplifier/speakers? ;-)

really?

Should it be easier with

Sometimes..if they are multi-miked..

Remove positive supply fuse. Put meter across fuse holder on current setting. Turn preset fully clockwise. Turn on amp. Adjust preset for 20mA.

In message , snipped-for-privacy@talktalk.net writes

Is this the main supply fuse or possibly just for one stage where it is maybe a method of setting a bias current? No mention of an input signal, so this is presumably quiescent current?

I'd pick electrostatics or ribbon tweeters for the top end, both as sweet as it gets at high frequencies. Electrostatics for midrange too. Moving coil doesnt come close.

I hear bass reflex are better designed now, when I had some years ago the time-spread made a right mess.

NT

nah. no power from ES.

a good mid range horn is an utter joy.

You might be thinking of labyrinth. Bass reflex is not really noticeable delay wise.

...

I have a pair. They came in kit form and were only available to BBC staff. I was a "pre university trainee" at Research Dept at the time. I think only a couple of hundred were ever made to that specification.

John

there were at least 3 firms which had the licence to build LS3/5As. At least one firm was founded by a former BBC Research engineer. This probably explains the "kit" version which I hadn't come across before even though working in TV Centre at the time they were developed.

In article , charles scribeth thus

Dudley Harbeth?..

Theres a pair of LS5/8's on ebay BBC made c/w power amps at the moment..

David Stebbins was another.

I dont remember that being a problem with the Quads - but they did lack in the bass department.

Not sure I've ever encountered one, moving coils are inherently problematic in ways statics arent. Having had statics I think it would be very hard to convert me back to moving coil, for mid & tweet anyway.

Time-smearing is an issue with bass reflex, its a resonant system. How much of it there is depends on design. Unfortunately the first bass reflexes I ever had were terrible in this respect, and they do tend to be.

I only had labyrinth speakers once, not much experience with those.

NT