Toslink to RCA converter.

My TV only has a toslink audio output. To feed an external Hi-Fi. Or rather it does also have a headphone socket, but the quality from that isn't Hi-Fi.

I already had a 'universal' D to A converter lying around which I've been using but it has several minus points - it's a not new 'pro' unit.

It is large. Comes up on the wrong input when powered up which has to be selected manually - or left on. The PS induces hum on other things, so it can't be positioned where I'd like it.

There are lots on Ebay - all at a pretty low price and look much the same as each other, so I bought one. Quoted spec is minimal.

It works ok except that the analogue output is low. Compared to everything else feeding the power amp. The TV does have a preset in software for the output level and it's now on max.

Been looking through the ones on Ebay, and none seem to quote the actual output. They are all also too small to add an amp inside easily - even if there was room.

Ideally, I'd like one with adjustable output level.

Reply to
Dave Plowman (News)
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I find the output level quite low anyway if I link the Toslink output of my TV straight to the Toslink on the amp - maybe it's intentional.

I did try one of the cheap converters, basically a Toslink reciever and a cmos chip, not much scope to do much there.

Using ARC over hdmi cures all the problems anyway, so that's the connection of choice here now :)

Reply to
Lee

The older unit is fine.

If toslink to toslink was low, there's no reason to assume HDMI to HDMI is going to be any better.

Reply to
Dave Plowman (News)

"Pro" 0 dBu v "domestic", -10 dBu, line levels?

Assuming 0 dBu = -18 dBFS.

0 dBFS "Pro" RMS 6.1 V, peak to peak of 17.4 V. 0 dBFS "Domestic" RMS 1.9 V, peak to peak 5.5 V.

What are the power rail(s) of the cheapy convertor? You can do "Domestic" with a single rail PP3. "Pro" levels are right on the edge with two PP3's as a +/- 9 V supply.

Maplin have a kit for a stereo amp board. £5.99, adjustable output levels. I have one to level raise the analogue out of the telly to "Pro" levels to feed a stereo PPM. This power rail issue bit me when just fiddling and running the amp from a PP3, two series PP3s is better but it still clips.

Currently waiting for a 5 V to +/- 15 V DC-DC convertor to arrive. The PPM wants +/- 9 to 18 V. The amp kit is single rail up to 25 V on the kits spec sheet but the chip (NE5532) spec has a typical supply of +/- 15 V.

Reply to
Dave Liquorice

The pro convertor I hsve has both balanced and unbalanced outputs.

It uses a 5v supply. And I did wonder if this was why the output was low. I'd always assumed you needed at least 12v for domestic line level - unless you do clever things.

Yes - I could just add an amp. The idea was to make things on the Hi-Fi unit as neat as possible, as it's glass and you can see everything. ;-)

I've got an (old) circuit for a PPM driver that uses a single 24v supply. It's probably not to the very best PPM spec, but adequate for most things. The sort of thing you'd find on many devices with a PPM other than a full BBC spec studio sound desk.

Reply to
Dave Plowman (News)

5 V can't do 0 dBFS at domestic levels... at least if I've got the maths right. 9 V ought to be safe for domestic line level.

The maplin thingy is very small, 35 x 49 x 15 mm. That includes fixing holes in each corner and about 7 mm each end for the connections, the actual important bit of board could be cut down to

35 mm square. Connections made to component lands.

supply

This is a proper red/green twin needle movement and Alice 704 card, "new old stock" on eBay for £30 ish delivered. DC-DC convertor arrived earlier, about to start playing. B-)

Reply to
Dave Liquorice

Crikey. Those stereo meter movements cost a fortune new. ;-)

Reply to
Dave Plowman (News)

Oh - if it hasn't got any illumination, 9 x 5mm diffused white LEDs on vero board spaced 3 holes apart gives a near perfectly even spread. Got a bag of 50 off Ebay for a couple of quid. 10 mA drive current seems right here. Site them towards the back of the PPM to reduce the light on the shelf at the bottom of the PPM needle window.

Reply to
Dave Plowman (News)

What's a PPM?

Reply to
Capitol

Peak Programme Meter, I imagine.

Reply to
Huge

Peak Power Meter I thought

Reply to
Chris French

It's a peak programme meter. Clever electronics so it shows the peak of any signal rather than a sort of average like a VU meter. Used for many many years by UK broadcast companies to monitor audio levels. Now being replaced by some fancy software based device which is oh so much more easy to use that even an unskilled work experience type understands it.

That's why you never now get commercials/trails which are too loud, or variations of levels between different programmes, as before. It's all perfect. Or that's what the suits say.

Reply to
Dave Plowman (News)

Thanks. How I wish it were true about volume levels between channels and programs. Having designed voice operated gain activating devices (VOGADS) in the past, I am not convinced that any of them work satisfactorily in the real world. You can do a better job digitally now using memory time shift, but it is almost impossible to prevent distortion.

Reply to
Capitol

The only easy way to balance sound levels is by using a trained human being.

However, this never really has been economical to do across the entire output of a channel or station. Then or now.

But the suits decided it was all down to not having a device which measured 'loudness' correctly, so have spent millions on equipping with one which is said to.

Snag is, of course, it still needs action to implement what it reads and adjust accordingly. Not something they are interested in paying for.

Reply to
Dave Plowman (News)

No, I think it was programme - anyway VU meters ;-)

Reply to
The Natural Philosopher

And you claim to know about electronics. ;-)

Reply to
Dave Plowman (News)

It hasn't. IIRC that used to be a 5 W festoon bulb mounted above the movement shining through the window on the top.

Ahead of you, four 3 mm 36 degree clear white LEDs will be mounted above somehow. I was thinking of drilled block but vero and a few mm of lead length allows them to be tweaked directionally.

Bit greedy, the LEDs I intend to use are taking 1.32 mA on the bread board, they are just at the "too bright to look at" level.

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They glow slighly with leakage currents through dry fingers...

Have to be sort of towards the back of the illumination window as there as a flag along the top of the PPM window. A case of AOT for both position and brightness.

And yes the movements cost several hundred quid a couple of decades ago.

Reply to
Dave Liquorice

Tut, tut, Dave you should know better. A PPM is quasi peak, it has a

10 ms rise time IIRC. The relatively slow rise time is why you don't peak harpsichords above PPM 4, the short sharp pluck of each note isn't properly registered by a PPM. A true peak reading meter will register all the pluck.

It's a lot better now than it was a couple of years ago. How much of that is down to R128 (Loudness metering) or not I don't know.

Reply to
Dave Liquorice

It's better on ITV 1 as regards commercials, but many of the minority channels a bad joke.

My guess is everything is simply transferred into the server exactly as is from the play in device.

Reply to
Dave Plowman (News)

No mechanical movement can possibly show a true peak.

Luckily, harpsichords don't feature much in TV these days. ;-)

But that's the beauty of a PPM. It gives a good indication of both peak level and average - if you know how to read it.

Reply to
Dave Plowman (News)

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