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Old 6th Dec 2018, 6:56 pm   #21
Jonster
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Default Re: Hum and noise in BBC Sound Radio broadcasts?

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I think I started in 1978, so probably we just missed each other. It was a great place to work and was my first job after school. Lucky indeed.
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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Old 8th Dec 2018, 8:41 pm   #22
dryjoint
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Default 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?
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Old 9th Dec 2018, 4:12 pm   #23
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Default 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
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Old 9th Dec 2018, 4:41 pm   #24
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Default Re: Hum and noise in BBC Sound Radio broadcasts?

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....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. ....

Andy
Your story reminds me of one about the building of ITV's now deserted HQ in Central London. During the technical construction phase (for LWT as then) there was an awful lot of wiring going on as you can imagine and there was a great deal of thought applied to ensure the domestic and technical earths remained separate at all times. Apparently every half hour an electric bell would be rung across the construction site and all electrical installation work would stop and the isolation between the technical and domestic earthing measured. If any discrepancy was found any work carried out in the last half hour was simply de-installed and work started again. It meant you didn't have to waste time trying to find out where the problem lay - it was quicker to simply undo what was done and start again. Clever.

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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Old 9th Dec 2018, 10:57 pm   #25
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Default Re: Hum and noise in BBC Sound Radio broadcasts?

@ re16v

What's an 'LE' studio?

Regards,

Dave
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Old 9th Dec 2018, 11:15 pm   #26
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Default Re: Hum and noise in BBC Sound Radio broadcasts?

Light entertainment?
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Old 10th Dec 2018, 1:18 am   #27
red16v
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Default Re: Hum and noise in BBC Sound Radio broadcasts?

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Light entertainment?
Yes, Light entertainment.
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Old 10th Dec 2018, 10:51 am   #28
Amraduk
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Default Re: Hum and noise in BBC Sound Radio broadcasts?

@ red16v,

Thanks for the explanation.

Regards,

Dave.
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Old 10th Dec 2018, 11:35 am   #29
red16v
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Default Re: Hum and noise in BBC Sound Radio broadcasts?

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@ red16v,

Thanks for the explanation.

Regards,

Dave.
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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Old 10th Dec 2018, 11:50 am   #30
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Default 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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Old 11th Dec 2018, 11:10 am   #31
Alvin
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Default Re: Hum and noise in BBC Sound Radio broadcasts?

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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.
Ah yes I remember well being dispatched armed with a 'knocking chit' authorising the request to stop work.

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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Old 11th Dec 2018, 11:20 am   #32
Ted Kendall
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Default 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...
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