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Old 27th Dec 2011, 12:06 pm   #1
Leon Crampin
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Default Which is the best performing 4 valve+rec. receiver?

I wonder, as a light hearted discussion topic whether contributors have a favourite - with reasons for its technical excellence.

Let's assume that it can be from any time period but limited to the valve compliment detailed in the title.

I'll kick off with the Murphy A24C.

Good: Band pass tuning (good second channel rejection), low IF (plenty of gain), DC amplified AGC (amazingly effective - pull the aerial out on LW198 and the noise comes up with a virtually unchanged output level), solid cabinet with a massive loudspeaker.

Bad: No SW, no AF feedback.

Any other contenders?

Leon.
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Old 27th Dec 2011, 3:29 pm   #2
Peter.N.
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Default Re: Which is the best performing 4 valve+rec. receiver?

I would without doubt say the pre war Philips mono knob with bowden cables especially as its four valves include the rectifier! Lots of gain, very good selectivity and variable bandwidth! Dreadful thing to work on though.

Philips always seem to have the knack of getting ther same or better performance with less valves, mainly due to their mastery of tuned circuits. When transistor car radios first appeared most manufacturers used seven or eight of the things, Philips brought out one with four.

Peter
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Old 27th Dec 2011, 11:31 pm   #3
mister valve
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Default Re: Which is the best performing 4 valve+rec. receiver?

AS Peter says, 'Philips' were very advanced (electrically) and got the best out of their sets. But also, as mentioned, they could be some of the worst to work on, when they needed any maintenance.
I still feel though, that the pre-war 'Gramophone Company' (EMI) products i.e. "HMV, MARCONI, COLUMBIA" etc. are lovely instruments and give a very good account of themselves. I still use an HMV 443 Radio in my lounge !!
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Old 28th Dec 2011, 12:43 pm   #4
Chris Parry
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Default Re: Which is the best performing 4 valve+rec. receiver?

This Ultra model 50 is prewar, using the very efficient Mazda AC/ series of valves. There are 4 of 'em plus the (indirect) rectifier. Here it is shown in my home office, which is where it lives every day. This radio works remarkably well and sounds very sweet. One valve functions as a fully-tuned RF amp on shortwave. Although only a short superhet, there's no shortage of gain. The reason I reckon this set qualifies as being unusually good, is RELIABILITY. This radio went through my workshop thirty years ago, and ever since then has run for about 5h daily during the working week with no problems at all. Chris.
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Old 28th Dec 2011, 2:33 pm   #5
Chris Parry
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Default Re: Which is the best performing 4 valve+rec. receiver?

Here's another contender. This is a Philips 735A/15, which lives in an inaccessible corner of my workshop. Frankly, I can't get near it at the moment, hence the poor photo showing all the dust. This is a typical stupid Philips design from the late 30s! When I first got this radio in 2002, I spent hours trying to extract the chassis from the cabinet. After finally realising that on this set, it is necessary to remove the wooden cabinet sleeve from the radio chassis in a complete reversal of normal procedure, the restoration work proved easy enough. So here we have a "Linodyne" pushbutton stack with a pointer which is optically projected onto the rear of the scaleplate. Works well. Until the bulb fails. The tuning gang is effectively a giant multi-section beehive trimmer which traverses axially by means of a hefty plunger. Here is one tuning gang which does not rotate at all, just to buck the trend. RF tuned circuits are bandpass coupled, complete with tracking notch filter made necessary because of the low IF frequency, 128kHz. Oh, and there are wirewound preset RF trimmer capacitors. Mustn't ever forget those confusing things... but performance is decidedly good because of them. Shortwave works well on this set. The EF9 IF amplifier provides AGC delay from its suppressor grid, an unusual arrangement which works well in practice. The front panel is a very massive bakelite moulding. So heavy in fact, that this radio will topple forwards onto its face at the slightest provocation. Detection & output come from a EBL1, but this sensible valve is forced to work around an EFM1 which performs the magic eye and 1st Audio voltage amplifier functions. Not to mention generating feed-forward as well as feed-backwards AGC. Early examples of the EFM1 had a bulb that was so heavily inked that little light reached the operator, even when new. (The EFM1 that is, not the operator!) There are 2 positions of IF selectivity, and the usual complicated Philips tone control. The awful CT8 side contact valves need cleaning occasionally to avoid intermittency. I view the 735A as justifiably rare. I deliberately chose the boring Ultra 50 over this Philips because its design is so much more intelligent overall. Chris.
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Old 28th Dec 2011, 3:58 pm   #6
Wellington
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Thumbs up Re: Which is the best performing 4 valve+rec. receiver?

Chris - a couple of interesting contributions, there! Thanks for posting 'em.

I think the Ultra is a most attractive set with its white plastic design highlights, and the nice contrast between the circular veneer inlay and a rectangular cabinet. Very pretty. The Philips possibly less so, but still a strange and curious beast. An EFM1 - a combined AF amplifier and tuning indicator? I had no idea such a thing existed .

Sorry - a bit off-topic, but I am unable to nominate a contender for best performing 4 valve + rec receiver because (gulp) none of my sets work!
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Old 28th Dec 2011, 4:12 pm   #7
Chris Parry
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Default Re: Which is the best performing 4 valve+rec. receiver?

Type EFM1 is strange. It led a short production life, being made only by the Philips companies and Tungsram. It drove its beam deflection electrodes from the screen grid of an integral AGC controlled audio pentode. The dynamic range of the display was slightly lower than a 6U5/6G5, and far below what was achieved only 2 years later by the EM4 which was the precursor to the famous EM34. The EFM1 was made in Germany in re-based form as the EFM11, and in Italy as type WE18. All are nowadays firmly in the "collectors" category. Chris.
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Old 28th Dec 2011, 4:23 pm   #8
jjl
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Default Re: Which is the best performing 4 valve+rec. receiver?

For its audio quality once the usual faults are sorted, how about the Pye P76.

John
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Old 18th Jan 2016, 9:41 am   #9
Jim Butterworth
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Default Re: Which is the best performing 4 valve+rec. receiver?

I see the rare Philips 735a is very well discussed above by Chris Parry who unfortunately is no longer a member but obviously knows these sets well. It is the only reference to the 735A I can find on the internet.

Typical Philips - and a rival to their weird Monoknob and Motor-tuned sets for mechanical complexity. As other manufacturers have discovered, it is not all that difficult to connect a knob, pointer and capacitor together - but Philips relegated a generation of Service Engineers to hours of frustration trying to repair the mechanical side of their otherwise excellent sets.

For my sins, I have one of these nightmares - it is complete, dusty and unrestored. Before I tackle the restoration:

1. Does anyone know what the special tuning tool (that should fit in the hole in the back) looks like?
2. Is there a source of circular rubber masks for the unique EFM1 magic eye to give a sporting chance of being able to see its display?
3. Should the tuning knob extend outward by spring so it stands well proud of the front of the set? It won't slide back in and lock so is very vulnerable.
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Old 18th Jan 2016, 11:59 am   #10
hansomcommon
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Default Re: Which is the best performing 4 valve+rec. receiver?

You cannot go far wrong with prewar Murphys, the A36 springs to mind, the bandpass tuning is superb
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Old 18th Jan 2016, 1:20 pm   #11
Jim Butterworth
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Default Re: Which is the best performing 4 valve+rec. receiver?

now you are talking Rolls-Royce
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Old 18th Jan 2016, 1:24 pm   #12
Peter.N.
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Default Re: Which is the best performing 4 valve+rec. receiver?

I once had a Philips 'Super inductance' set, a TRF with better selectivity and sensitivity than many superhets, it would work with no aerial plugged in! Don't know how they did it.

Peter
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