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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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6th Dec 2018, 6:56 pm | #21 |
Heptode
Join Date: Apr 2008
Location: Eastbourne, East Sussex, UK.
Posts: 671
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Re: Hum and noise in BBC Sound Radio broadcasts?
I was there from 1983 to 1987. The banks of C9 amplifiers in the control room with their stabilised power supplies were still there then.
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8th Dec 2018, 8:41 pm | #22 |
Tetrode
Join Date: Nov 2009
Location: Southend-on-Sea, Essex, UK.
Posts: 60
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Re: Hum and noise in BBC Sound Radio broadcasts?
The amplifiers in general were practically bomb-proof. Very forgiving particularly the ones used on the Outside Broadcast section (OBs) which occasionally had ringing volts shoved into the inputs if incorrectly plugged into the telelphone control line instead of the music circuit or the "other end " connected their equipment incorrectly.
Was the old EMX still there? |
9th Dec 2018, 4:12 pm | #23 |
Nonode
Join Date: Dec 2002
Location: Coulsdon, Surrey, UK.
Posts: 2,135
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Re: Hum and noise in BBC Sound Radio broadcasts?
The BBC took great care on all engineering matters back in the day. There were very few places hum could intrude in reality, as all external connections of any length were always done transformer balanced and at line level. Low-level signals like pickup cartridges and microphones were duly amplified within a unit before leaving for any form of rating and processing.Low level mic signals would be routed direct to an amplifier ( balanced, of course ) which in valve days would have likely been an AMC/5 of which there were many per studio.This remarkable 2 valve amplifier (ECC8x) had a noise floor within 1 db of theoretical maximum, even in the 50s !
Most HT units had some form of stabilisation ( usually neon ) and the later transistor ones had fully regulated split rail PSU's .In these, even the mains transformers were mu metal shielded as they were generally mounted in closer proximity to their amplifiers than in valve days. The BBC were also very scrupulous about earthing. Mains and 'program' earth kept separate and large copper earth busbars would be found in the back of equipment racks. Studios were well isolated, and had massive dual doors and double glazing. Acoustically, they nearly always seem to get the treatment just right for general purpose studios. Drama studios often had 'live and 'dead' areas within the same studio. I recall several incidents where the relatively starchy continuity announcers in R3 and R4 had to apologise on air for a noisy amount of drilling which was taking place somewhere in the building at the vital moment. It took ages to find out exactly where and get it stopped. Happy days indeed ! Andy |
9th Dec 2018, 4:41 pm | #24 | |
Heptode
Join Date: Jul 2006
Location: Winchester, Hampshire, UK.
Posts: 639
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Re: Hum and noise in BBC Sound Radio broadcasts?
Quote:
In TV terms, I think the average viewer would be quite surprised at the amount of air-conditioning noise there is in a large LE sized studio. It's not as quiet as you might think! |
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9th Dec 2018, 10:57 pm | #25 |
Hexode
Join Date: Jan 2007
Location: Welwyn Garden City, Hertfordshire, UK.
Posts: 453
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Re: Hum and noise in BBC Sound Radio broadcasts?
@ re16v
What's an 'LE' studio? Regards, Dave |
9th Dec 2018, 11:15 pm | #26 |
Dekatron
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,433
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Re: Hum and noise in BBC Sound Radio broadcasts?
Light entertainment?
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Frank |
10th Dec 2018, 1:18 am | #27 |
Heptode
Join Date: Jul 2006
Location: Winchester, Hampshire, UK.
Posts: 639
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Re: Hum and noise in BBC Sound Radio broadcasts?
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10th Dec 2018, 10:51 am | #28 |
Hexode
Join Date: Jan 2007
Location: Welwyn Garden City, Hertfordshire, UK.
Posts: 453
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Re: Hum and noise in BBC Sound Radio broadcasts?
@ red16v,
Thanks for the explanation. Regards, Dave. |
10th Dec 2018, 11:35 am | #29 |
Heptode
Join Date: Jul 2006
Location: Winchester, Hampshire, UK.
Posts: 639
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Re: Hum and noise in BBC Sound Radio broadcasts?
LWT also had a very large studio at Stonebridge Park (down the road from their Wembley studios). The studio didn't have 'proper' air conditioning but had some very, very large fans at ceiling height in the side walls. It was effective enough, but were so noisy they had to be turned off during actual recordings. It got very hot indeed.
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10th Dec 2018, 11:50 am | #30 |
Dekatron
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,433
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Re: Hum and noise in BBC Sound Radio broadcasts?
I found this BBC research paper on a source of acoustic noise I hadn’t thought of.
http://downloads.bbc.co.uk/rd/pubs/reports/1967-01.pdf
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Frank |
11th Dec 2018, 11:10 am | #31 | |
Heptode
Join Date: Nov 2003
Location: East London, UK.
Posts: 761
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Re: Hum and noise in BBC Sound Radio broadcasts?
Quote:
There was one source of rumble on R3 that didn't require such intervention as it was dealt with personally by the announcer - the very delightful and far from starchy Tricia Hughes had her lunch delivered to the studio and ate it just prior to the long read of the lunchtime news as her hungry tummy rumbles could sometimes be heard on air!! |
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11th Dec 2018, 11:20 am | #32 |
Dekatron
Join Date: Jul 2008
Location: Kington, Herefordshire, UK.
Posts: 3,675
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Re: Hum and noise in BBC Sound Radio broadcasts?
Hum from continuities was a perennial theme of the FM column in Hi Fi News, both under Austin Uden and Angus McKenzie. I think it was finally nailed about 1974.
We issued a cod "stop knocking chit" to our unit secretary once about her typewriter. Her response was to issue another chit embargoing typing of expenses. Whoops... |