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Amazing Troughline, first variant.

VHF FM is broadcast in mono with a [supra-aural] difference signal so that when the multiplex is decoded [added and subtracted from left and right] it gives a stereo output.

A remarkable 1950s system really, that still persists today so long after it was devised.

As discussed earlier in my Troughline threads, the mono version [un-decoded basic audible frequency send as sent on Frequency Modulation] has lower noise and distortion than the stereo multiplex decoded version. Jim Audiomisc has made posts that discuss this aspect, and those posts were new information to me. Thanks be ...

I remain committed to mono as the most suitable musical reproduction medium ...

Just two pennies' worth from George
 
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Tony L said:
Interesting, I need to read up on how FM stereo actually works as to be honest I’ve not got a clue! I’m curious as to what a mono signal is in a stereo age, i.e. is it broadcast simultaneously in mono and stereo?
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This may help:

http://www.audiomisc.co.uk/HFN/BandwidthBlues/page.html

Note also the links at the bottom of the page.

The 'mono' is simply (L+R)/2. i.e. as per pushing a 'mono button' on an old amp that actually has such a button. Equivalent to just listening to the 'horizontal' part of the modulation on a Stereo LP. (Yes, that also tends to give lower distortion than stereo.)

The (L+R)/2 is transmitted as 'mono' audio for stereo radio. The (L-R)/2 'difference' is sent as ultasonic modulation that a mono FM tuner ignores. But a stereo decoder can detect and use it to regenerate distinct L and R outputs. The 'mono' button on an FM tuner simply gets the (L+R)/2 'mono' and outputs that. That tends to lower the background noise level if you have a weak signal.

I also wish I'd had a QUAD AM tuner as they were really natty in terms of the filters, etc, available. However they are rare. Anyone interested in AM might note that an Armstrong 600 AM/FM receiver is likely to be more common, and much cheaper. It has the advantage of a 'double conversion superhet' front-end and can be tuned with presets across the entire MW and LW bands. Not 'Hi Fi' on AM as the bands are too congested. Even narrow filtering can't fix things like co-channel interference at night, etc.
 
Dear Jim,

Thank you for your various posts on the topic of VHF FM radio. I learned more from you in the last few weeks on the subject than I knew from the last fifty plus years!

What I still find amazing is that the set of compromises made in FM radio can still allow the quality I get from the old Troughline.

Best wishes from George

PS: Before knowing about VHF FM radio in the 1960s, I was certain that the quality of sounds from a TV were significantly finer than on the [Medium Wave] kitchen radio. That was one of those wonderful HMV kitchen radios, and in those day I suppose we all thought that HMV was among the best of normal radios and record players. I could not quite understand why a dedicated radio was less good than a TV where you might think that the sound quality might not be the first priority. Later I found out the TV worked on the VHF band! The old 405 line system.
 
There was a time when ye olde AM radio worked far better than it does now. e.g. back in the 1940s. The reason being that in those days many stations had a much wider transmission bandwidth than they are allowed to use now, and the bands were less crowded. So although it seems strange now, 'Hi Fidelity' (or 'quality') reception was possible given the right radio set, etc. Alas, now the allowed audio bandwidth is only about 4kHz, and the bands (at night in particular) are stuffed with people using the same channels.

FWIW Ted Rule at Armstrong did once modify an AM board for the 600 range to work as a short-wave radio. It did work quite well, but its unlikely any hi-fi enthusiast would have found the results to be 'hi fi'. Fun as a party trick, though. :)
 
IIRC 405 line TV used AM sound. Might still be potentially better than the AM radio of the day because of the greater bandwidth demand of the signal as a whole. 625 was FM audio. I think Armstrong (not that one) didn't invent FM until after 405 line TV was well into development.

Back in the old days if you had a cheap 625 line monochrome TV you could often see the colour subcarrier in the picture. Old FM radios are similar, the whole 64kHz bandwidth signal comes spraying out the back, the only problematic bit is the 19kHz pilot tone which can cause havoc with a tape machine by interacting with the bias frequency when recording. So I think most domestic tape machines have 'MPX filters' to cut the bandwidth. Some notionally stereo tuners also leave significant amount of 19kHz in their output. We had a virtual bakeoff on here years ago of tuners and looking at the outputs it was quite obvious in a spectrum analysis.
 
The Troughline continues to give the greatest pleasure. So much so that I would call it the most enjoyable source component that I have ever used.

Currently my poor MDAC is out of service, so that my collections of recordings on CD [replayed with iTunes, in AIFF files] is not useful, but there is so much fantastic music on Radio Three that even if I never have the MDAC repaired it would hardly matter.

Since the service - restoration and complete rebuild would be a better description - it has settled down nicely. On music it always sounded well, but occasionally the spoken announcer voice would be somewhat sibilant. That has gone now. Only the most dire microphone technique is horrid.

Tuning is a precise art. Out by only a few degrees of highly geared turning of the knob is far from grand, but in exact tune it is sublime. It simply does not drift once warm, and if in tune when turned off, give it ten minutes or so and it is back nicely in tune ten minutes after starting up. For a seven thirty concert simply start the tuner [on minimum volume] and let it settle for half an hour. it does drift about for the first few minutes as the chassis warms up. But it gets back to where it should be very nicely. It seems to draw a steady 38 Watts, so not worse than the MDAC [40 Watts] or my computer, Monitor which draws about 45 watts.

I have listened to many evening concerts on R3, and can only wait till the Proms start for nightly fix of music!

The set is very simple. Troughline -> Quad II Forty -> ESL. ..., and yet not in its subtlety.

Best wishes from George
 
Lovely.

I completely concur, BTW, on using mono tuners as designed - the S:N achievable is wonderful, and so that is how I use my 1955 Acoustical FM1. Infinitely preferable to the effects of add-on decoders... even when such fettled to suit the FM1's 'Foster-Seeley discriminator' output loading specification..


In fact I subsequently added-in a selectable flat-blend to my Onix BDW1 simply becasue the S:N improvement, potentially approaching 20dB, can make joy out of a noisy or distant signal.
(this was rather easy with a two-position switch, centre off for full stereo and a couple of resistors otherwise offering a choice of 10 or just 3dB channel separation. And yes, just 10dB is enough to provide a quiet, but near 'full-width' perspective. The concomitant noise reduction of c.10dB is utterly worth it.)
 
Dear Martin,

I am no enthusiast for stereo - at least as it is used in mainstream recordings and broadcasts. It is usually too wide, too precise about positioning of instruments in aural terms, too obviously unlike what is to be heard live in a good seat in a concert hall or venue. I realise that mono is not exactly right either but is less unlike real than stereo in my opinion. It is useful that a mono tuner can perform so well relative to a stereo one in noise terms as well. It means that a veteran like mine probably is not that much less good than anything made since - albeit delivering stereo.

I think of it like this. From my seat my ESL forms a similar arc to the stage at a concert hall, less than fifteen degrees of arc in reality from a good seat.

So not exactly a point source in the more modern sense of speaker design, but quite similar to real life in its width.

It seems that the Troughline [on a good broadcast] happily gives a real sense of the scale of the hall without this ever being at the expense of balance and lucidity. ... Something the ESL also does rather well on Radio or recordings in mono. There is so much that is right that the monaural thing is not anything that sticks out and gets in the way.

The trouble with mono on a modern speaker "designed as a point source" [so that stereo becomes precise in width imaging] leads to a peculiarly narrow sense of the "stage" that can be quite odd.

So while I don't expect to start a mono-craze, I think before people write it off as being inherently inferior to stereo they really need to hear an ESL driven by a monaural chain such as the Troughline or other pure mono source.

Best wishes from George
 
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+1 a big-mono setup is something I've meant to try for a while, at least half a decade now.

The idea of things like the Paul Voigt Corner horn loom-large in 'things so simply right from first analysis to reputation in hindsight, they are worth re-visiting' that I'd love to try.

I do have the makings and enough spare equipment I really ought to try ( ...might just be one Impulse H2 pushed into a corner pro tempore.)
 
I always liked Gilbert Briggs’ ideas for a huge brick corner speaker built as part of the room itself. Audiophiles seemed somewhat more adventurous back then!
 
Tony L said:
I always liked Gilbert Briggs’ ideas for a huge brick corner speaker built as part of the room itself. Audiophiles seemed somewhat more adventurous back then!
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There was someone who had a horn speaker with the horn part underneath the floor boards. There was also someone who had drive units on the wall so that the adjoining room became the cabinet.
 
Stunsworth said:
There was someone who had a horn speaker with the horn part underneath the floor boards. There was also someone who had drive units on the wall so that the adjoining room became the cabinet.
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I have in a non-serious manner considered both! I live in a typical 3 bed Victorian terrace, the type with two living rooms and a cellar. Mounting the Tannoy drivers in the wall between the living rooms might work rather well, the logical equivalent of a brick-built wall-sized open baffle! The temptation to turn the cellar into a sub exists too, i.e. just mount a couple of upward-firing 15” drivers in baffles mounted into the floorboards! It would be rather interesting to see what could be achieved in that direction for the JR149s, but I won’t ever try it as I don’t intended staying here forever so don’t want to be doing unnecessary things I’d need to put right again.
 
Dear Matin,

Let me only encourage you in the assembling of a first quality monaural system. If you fancied a day out one weekend, you would be welcome to have a listen to my replay if it would help.

Dear Tony,

I used to have a friend - someone with real skill and scientific understanding, who after the peace in 1945 built his own oscilloscope for example - who had a mono speaker in his very old house built into the wall where an internal window was before he did it. The baffle was an eighteen inch stone wall, and the cabinet as such was the back kitchen or as it was called, the pantry. It was used as a piano restoration workshop rather than domestic uses when I knew the house! He used to make concert recordings, and replay them on this as a monitor. It had that amazing sense of clarity and scale when using the whole of a room as the baffle box! My friend has passed away now, but he had some fascinating ideas on pianos. He was very keen on the old John Broadwood and Sons straight strung pianos from the nineteenth century. These were from before the time of steel frames, and amazingly he built his own hand made steel frames into several of these. You might wonder what would be the reason to do this, but it takes all the opposition of the string tension away from the sound-board, so that the piano became much clearer and capable of being louder, while retaining its old abilities at the quiet end of the dynamic. Okay Steinway did this at the end of the nineteenth century, but the Broadwood has many qualities the Steinway does not, not least being the voicing of the various register voices, so that bass is different to tenor, and these different to the upper voicing, giving a delightful effect on Beethoven, Schubert and Chopin where such voicing characteristics were absolutely part of the compositional technique.

We had long talks about recording and replay. He was an original thinker on the subject, who had the skill and time to implement some of his ideas. The BBC made a series of recordings of his modified Broadwood pianos, which were broadcast. Many years ago now, but I remember him as being a fascinating fellow.

His wife was a lovely retired professional violinist. In London she had been in the Goldborough Orchestra, which is what the English Chamber Orchestra was called in its early days. Apparently they were playing a Bach Concert in the Festival Hall, when a good looking middle aged man turned up with his violin. She went over and said hello. She said, "You're new aren't you?" He replied, "I am the soloists." She still had no idea who he was. It was Yehudi Menuhin!

Best wishes from George
 
PS: My last playing on the 'bass [1999-2002] was with this wonderful violinist leading a small group of strings - between twelve and nineteen according to the space of the hall we were to perform in. It was was the best playing I ever did, after I gave up my professional involvements. We used to rehearse in the front room, and my friend, the piano restorer, would have a tape running so that we could gauge our efforts during rehearsal in the kitchen afterwards. It is startling to actually hear the effect of our own performance from a proper perspective. I am sure that this was good for the music making. It often led to a slightly slower tempo so as to get maximum clarity and articulation, which are vital elements in expression.
 
I have improved the antenna connection. When the old radio was rebuilt, I was clear that nothing that did not need to be altered should be altered, except for replacing worn out electronic parts and accepting a modern RCA phono socket for output to replace the original 1950s nickel one which was in so small a rebate that no modern interconnect would ever fit ...

I retained the original socket for the antenna which left me a problem of not having a suitable two pin plug for the intended dipole style aerial.

So I stuck in the bare wires and put small wood screws in finger tight to secure the antenna!

Well I looked at this and with a little bit of experimenting I found the perfect pin size is the middle [signal] pin of an RCA phone plug. So I sacrificed an RCA terminated interconnect, and got the two signal pins out - preserving the solder and original ends of the interconnect wire. I soldered the pins to the antenna wires without a soldering iron!

Using the hotplate of my hob! I pulled out the interconnect wires having completely heated the pins on the plate, and then warmed up the ends of the antenna and inserted them in the hot solder left. Okay that is the kind of thing you would do post armageddon! I really need to borrow a soldering iron and remake the joints to looks nice though the actual job works well. A useful improvement in connection has already been achieved.

Best wishes from George
 
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Tomorrow sees the start of the new season of BBC Proms. This is why I decided to get a fine radio the week before Christmas last year. Tomorrow the eight month journey will be consummated with this seasons First Night Of The Proms.

I'll report back afterwards. But going on current performance, it will be an enjoyable listen.

Best wishes from George
 
Well that went well. Fantastic performances!

I am more than glad I got the Troughlines and had it restored. The best component I ever bought for replay is my ESL. I had to have a suitable amp of course.

But to complete the arch has been the Leak. As good as the ESL on this showing. Perhaps a surprise is quite how well this set conveyed the monumental scale of the Janacek Mass.

Thanks for all the marvellous replies on this thread. I think I can retire from hifi now, and just enjoy what I have.

Best wishes from George
 
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It is time for new VHF/FM tuners to be developed!

The BBC have surpassed themselves with the quality of the first two nights of the the Proms on VHF. Tonight was right down my street [in terms of massive Romantic music] because the concert contained Ma Vlast by Smetana.I find this about my favourite late nineteenth century opus.

The scale wass wonderfully presented by my modest radio set. Quite a surprise really. But that is only a small fraction of how well it works ...

Best wishes from George
 
I also enjoyed the Dvorak/Smetana Prom. However in my case not via FM but HDTV and the iPlayer from R3. :) One nice thing about the iPlayer is that I can get the R3 file and play it on my portable unit via headphones. I've also enjoyed the Barber Violin con and the VOCE8 prom. Seems a good season thus far. But I do wish the BBC would start including some more British composers from the 'forgotten decades' in the circa 1900-1950 period.

Your mention of the Goldborough Orc. reminded me: Back c 1970-ish I and friend were on one of our shopping trips into London and I bought an LP of them playing some of the Bach Keyboard Concerti. Alas, I could only afford one disc so didn't get the set. I've wished ever since that I'd been able to get them all as I like their performances very much.

However I have recently found the others on YouTube! Alas, only modest-rate lossy files, and played on indeterminate record playing equipment, but better than nothing I guess!
 
Well the point of home replay is to bring something of a great - unique - performance into your own space.

I have just listened to the Prom first half half with the CBSO in Elgar's Cello Concerto.

That alone is worth the effort of getting this veteran old radio going on the top-line!

The last really significant performance I had on it was the Goldberg Variations from the Wigmore Hall a couple of months ago in the arrangement by the Polish Koeffler. [See the thread on that in the Classical section of the music room].

That is why we have replay!

Best wishes from George
 
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