BBC modified 303 help

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21-Nov-2018 03:49 PM

bluegrass

bluegrass

Posts: 66

Hi,

I have what i think is a BBC (British Broadcasting Corporation) modified 303.

 Can anyone work out what it has been modified to do....I have created a youtube video of images to help.

 Many thanks for any thoughts

 www.youtube.com/watch?v=2N^LjljAtzE

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21-Nov-2018 04:02 PM

bluegrass

bluegrass

Posts: 66

Sorry , link should be:

https://www.youtube.com/watch?v=2N6LjljAtzE

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21-Nov-2018 04:10 PM

bluegrass

bluegrass

Posts: 66

Third time lucky on the link

www.youtube.com/watch?v=2N6LjIjAtzE

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21-Nov-2018 07:09 PM

Fabian

Fabian

Posts: 60

Looks like transducer to me. Possibly to create a symmetrical input. Just shooting into the blue.
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21-Nov-2018 07:19 PM

Iang

Iang

Posts: 4

They are balanced line transformers. Looks like it has been set up to be used as a two balanced line input mixer judging by the two pots and XLRs

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21-Nov-2018 07:23 PM

Iang

Iang

Posts: 4

My bad just modified to be balanced line input on either TRS jack or XLR and the pots are just left and right input controls

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21-Nov-2018 07:38 PM

bluegrass

bluegrass

Posts: 66

Brilliant, thanks.

How would they be used, what would be the purpose?

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21-Nov-2018 08:23 PM

Fabian

Fabian

Posts: 60

Have a look at the datasheets of some of these Jensen input transformers. They show a basic application schema:

http://www.jensen-transformers.com/transformers/line-input/

Hope the URL is correct and the forum will allow it. Can't copy/paste anything.

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21-Nov-2018 09:04 PM

bluegrass

bluegrass

Posts: 66

Thats a great link.....thanks for that.

I'm assuming that one or other of the xlr or 1/4 jacks are outputs to monitor speakers.

 I wonder in a hifi setting if there is any advantage/didsadvantage to keeping or removing this modified arrangement compared to a standard 303 amp.

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22-Nov-2018 05:56 PM

Margus

Margus

Posts: 7

hi

Just a shot in the dark,but i would guess that XLR-s are inputs for balanced audio, TRS-s (or more probably TS-s) are speaker outputs. XLR female is by standard input connector.

Balanced input has it's advantages if you have long cable runs, which is usually not a case in home hifi setups. Basically, you can feed unbalanced signal to balanced input, if you wish to reserve BBC touch to equipment.

Not sure if TS/TRS connectors are the best choice for speakers, though.

wb, Margus


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22-Nov-2018 11:35 PM

bluegrass

bluegrass

Posts: 66

Thanks. Yes, that sounds like it could be correct.

I'm going to try and rebuild this unit on new pcb's as the old ones are in bad condition, but keep everything else in its bbc modified state.

I'll then comnpare it to my non moddified 303 and see how it sounds


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