Mystery radio - Charles Amplifiers

[Synchrodyne]

There was an entry for Charles Amplifiers in the Jonathan Hill book Audio! Audio!, see pages 24 and 25.

There were several small and relatively obscure companies who engaged in the high quality radio and audio markets in the late 1940s, and for the most part, which did not appear to survive all that long. Two others were Coulphone and Ruco, who like Charles, advertised in Wireless World 1949 November:





Another was Peerless, whose products were discussed in the UK Export Models thread of some time back, see: https://www.vintage-radio.net/forum/...=111407&page=5.

Industrial, metal-cased versions of what were essentially domestic radio receivers were not unknown. As well as Chapman, as mentioned by turretslug, amongst others, Armstrong, Dynatron and GEC all engaged in this market.

Back in the 1940s, it was thought easier to obtain very wide AM receiver bandwidth with TRF circuitry than with the superhet type. By the early 1950s, when superhets with ±12 kHz IF bandwidth were available, the TRF was probably of less utility, although still perhaps used where simplicity was paramount. Before then, tuners and receivers that could be switched between the TRF and superhet mode were sometimes offered in order to obtain the best of both worlds, namely high quality local listening on the one hand and distant station reception on the other. The Lowther DT-series tuners were of this type, DT meaning dual-tuner. The DT/5 survived until c.1959. I think that typically the superhet configuration offered two or more bandwidths, with the widest thereof reaching the high-quality level, perhaps even with the same nominal bandwidth as the TRF mode. To some extent the TRF option may have been offered less because it was non-negligibly better than the widest superhet position, but more because some customers associated TRF with ultimate quality, and so expected it to be available.

With its three rotary control knobs, I’d say that the unit at interest is more likely to be a tuner, probably with a power supply unit in the same casing, and possibly some kind of small line output amplifier, perhaps to supply a 500R or 600R output. The three controls could well be waverange, tuning and bandwidth/selectivity. The last-mentioned would also switch to the TRF position, and switch in the 9 kHz notch filter if there was one.


Cheers,

[Frank.Keane]

What an amazing response! Thank you so much to everyone who has contributed. I understand very little of the technical pointers (so far anyway - I'll have to do some reading up on what all the terms mean) but I love the thrill of the chase and it has been a real buzz tracking down the history of the mystery radio in question.

I don't actually own it. Not yet anyway. I saw it at a viewing day for a General Sale Auction and will be returning later this week to see if I can put in a winning bid. If I bring it home with me I'll have the back off and take some pics of the chassis.

In the meantime I agree it looks very much like the Charles Amplifiers RA Tuning Unit. It's going to be exciting to find out what else is inside though to be honest I am disappointed to realise the lack of knobs indicates it probably won't be a Charles Amplifiers Concerto amp.

By the way I have only very recently been bitten by the vintage wireless bug but I can see how it can get hold of a person!

[duncanlowe]

It does look to me like some recasing has been done. The tuning scale panel seems to have quite a lot of very neatly applied tape around the edges, and doesn't quite fit properly to my eyes. That could also explain the lack of labelling on the knobs.

[Frank.Keane]

Well I went to the auction but sadly had to drop out of the bidding. I thought I was pushing the boat out plenty far enough when I hit £120 but the lot eventually sold for £344. That's way out of my league!

I'm curious to know why the lot went for so much. I have attached a pic from the auction catalogue. The speaker on top of the tuning unit is a Stentorian. The tuning unit as has already been discussed was an RA unit made by Charles Amplifiers. The amplifier does not appear to be either of the models made by Charles Amplifiers, although the casing suggests it was once mated to the tuning unit. The Leak record player case still contained an old Bakelite record deck but the amplifier was missing. And the box of valves contained amongst others a couple of KT66 valves still in their boxes.

Perhaps I was being a bit hopeful thinking I might get the lot for £120 but £344? Did someone get carried away or was that a reasonable price to pay?

[PJL]

Auction prices are a mystery and rarely a bargain. Buy some 18c furniture, it goes for peanuts (actually much less than peanuts by weight).

[Frank.Keane]

Good call PJL !!

One other detail I've remembered is that the smaller of the two transformers that can be seen in the amp was a Wharfedale W12 - I hardly think that solves the mystery though.

[Herald1360]

A couple of NOS KT66s together with any old amplifier fitted with a couple more would get serious bids. Any other "interesting" audio valves would only fan the flames. Just the boxed pair could get around £300

The radio tuner will probably just be scrapped, though it might just appear on Ebay later.