Can someone help identify this please?

[davemorris]

Hi Folks,

Can someone please tell me what this is and what it is used for?

PYE Stereo + 2 5550 is all I can glean from the back of it.

What is and what is it for?

I assume it is vintage?

Many thanks to you, Guy.

[Mooly]

I've no idea… although a picture of the connectivity on the back might give some clues.

[davemorris]

Originally Posted by Mooly

I've no idea… although a picture of the connectivity on the back might give some clues.

Will take a few pics now and post them.

[Paul_RK]

Any sockets at the back, or just leads coming out? From the name I'm expecting it's a unit to provide four-channel sound from a stereo amplifier, with "gain" probably adjusting the relative level of the two additional (rear) 'speakers.

Paul

[davemorris]

Hopefully these pics help a little more.

****************/mPSPy8

****************/dbZnJ8

[Mooly]

I get a 'doesn't exist' message. Try attaching the pictures directly, its dead easy using the 'go advanced' option.

[Paul_RK]

The first link just needed cutting in half. Yes, clearly an adaptor for "quadraphonic", from somewhere around the mid '70s I'd guess. Plug the leads into a stereo amplifier's output, using the DIN plugs that were very popular back then. and connect two pairs of 'speakers, front and rear, to the box. And, hey presto, you're surrounded by sound, though of course the box has nothing to work with except the audio information carried in the two channels.

Paul

[ms660]

Google "pye 5551"

Lawrence.

[Mooly]

Maybe I was too quick clicking or an edit was done. Works now

Yes, some kind of additional amplifier of some sorts to drive a second pair of speakers. I'm puzzled though as to the total lack of info on the panels. Quadraphonic and any other buzz words would be major selling points. It's all very anonymous.

Do we get to see inside at some point? That could be interesting. Maybe a couple of TBA820's lurking in there?

[davemorris]

I am not good with electronics and taking things apart..lol. Better not do that.
What are TBA820's and why are they important? Just curious...lol.

[Hartley118]

My guess is that it's a 'difference channel' simulated surround sound device, otherwise known as Hafler Surround. The attached diagram shows the principle in its simplest form.

The principle is that much of the reverberant signal in a stereo recording appears in the difference between the two channels. This is because the direct sound is pretty well correlated in the main left & right channels and tends to cancel in the difference signal. Reverberant sound, however, and mid and higher frequencies is by its random nature much less correlated and sees less cancellation in the difference signal. It can be very effective on classical recording made in a reverberant hall.

There was a Philips disc of the Last Night of the Proms conducted by Colin Davis in 1969 (SFM 23033) which I used for some public demonstrations back in the day, where the audience participation in 'Land of Hope and Glory' came clearly from the back of the hall whilst the orchestra remained out front

It's interesting that this Pye box is actually mains powered, implying that there's some electronics inside, perhaps some filtering on the difference signal to improve the effect.

Martin

[Edward Huggins]

Aha - well yes, I certainly remember this device. It is, as some of you have worked out, a rather basic add-on unit using the Hafler principle and with a modestly powered (c.4 watts) simple amp for the rear speakers. I actually think it was just single mono, not a pair of monos. it was positioned as a "Stereo Adaptor" never as "Quadrophonic".
This was designed by my colleague John Catchpole (Bless Him) in 1975/76. I have one somewhere. I played around with it but did not think much of it other than it offfered some "ambient". I was all too aware of some rather tiring (to listen too) cross-phasing going on.

[Mooly]

Originally Posted by davemorris

I am not good with electronics and taking things apart..lol. Better not do that.
What are TBA820's and why are they important? Just curious...lol.

TBA820 (was it TBA820 with the wings ? or TBA800) were a common early amplifier chip, everything needed to make a simple amplifier apart from a few passive parts. Often used in TV sound stages in the 70's.

All a long time ago

[G6Tanuki]

TBA820 was the baby of the SGS-ATES chipset; it didn't have wings or heatsink-connections and only did a couple of Watts.

TBA800 was the first of the 'power' series they did - the TBA810 was the higher-powered version [some had solder-to-big-areas-of-PCB wings, the TBA810AS had nice extensions to allow a proper heatsink: these were used in all sorts of 1980s amplifiers giving up to 10 Watts, and also in the Pye 'Olympic' two-way radios].

[Mooly]

Thanks, its coming back to me now. I remember burnt fingers replacing these on sets that had the little 'pressed tin' heatsinks. GEC TV ? where you could swap frame and sound boards over if you had a frame fault... as I recall being told.

So back to the item in question and it is just possible it does have something like these fitted. It would make a good little workshop test amplifier if so.

[jamesperrett]

I had one of these for a while - as Edward says, it is just a single channel amplifier feeding the difference signal to a pair of speakers. I seem to remember that the accompanying speakers were fairly small with something like a single 4 or 5" driver.