BBC transformers

Hi
I have a metal panel that contained 4 marinair T1442 transformers (two green and two black) and some other in and output transformers that I thought were sowters. I only saw them once refered to as Sowters and here on the forum as "BBC transformers". Does anybody has information on:
- "LL/76 msc": small (25mm dia)
- "LL/81 msc": small (25mm dia), only 4 leads come out, instead of the 5 of the others.
- "LG/96 asc": bigger (35mm dia)

Brian Sowter replied me these were not made by Sowter.
The output transformers are the same size as the Sowter replacement for the LO1166, and some very small logo that says VP(or MP??) in a circle (an oval)?
Thanks in advance,
Bram

Hi,

LL76 - 1:1 turns ratio, used with audio equipment with 600 Ohm input and output terminations for both input and output. Primary: Yellow+Blue , Secondary: Red+Green.

There is little I can say about the LL81 just now. I'm guessing 1:1, and know that the primary is Green+Red and the secondary is Yellow+Blue. I would have thought there would be a black wire for the shield though.

LG96 - 1:1.23 turns ratio, used in line amps with high input impedance (eg. 18K in the case of an AM7/13) from mic level up to line level for input. Zobel network = 12K + 560pF for that amp. Primary: Red+Green , Secondary: Yellow+Blue.

The panel possibly came from an old BBC desk or similar. Sowter made some of the BBC-designed transformers, but they are not the same thing. Other manufacturers made their designs too.

Thanks Rodabod!! Highly appreciate that information.
Is there any way how I can identify the output transformers? Is it wishfull thinking to try them on a 1272/1290 project? (just come to think of it looking at those marinairs)
(by the way that logo can also say: "CvP" or something like that)

Regards,
Bram

Do the otput transformers have any model numbers on them?

Possibly you could post a photo which may help.

Unfortunately, you can't assume that they will be great for pro audio as they could be "control line" output transformers which have not particularly good frequency response.

Roddy

[quote author="bram"] Is it wishfull thinking to try them on a 1272/1290 project?
[/quote]

For the output of the Neve you need transformers that can cope with d.c current. If your BBC transformer do not have this capability you will probably damage them.

FYI.

A range of Carnhill's inductors and transformers will soon be available via our on-line store.

Initally, the following types will be available (Expected availability from stock is approximately 2 weeks from now).

VTB1148 - £17.07 ea (Line Out - same as VTB9049 but narrow board)
VTB9045 - £37.22 ea (Mic In)
VTB9046 - £41.90 ea (Line In)
VTB9048 - £11.87 ea (Inductor)
VTB9047 - £11.87 ea (Inductor)
VTB9049 - £17.07 ea (Line Out)

VT31284 - £29.22 ea (Mains Transformer: 110-0-110 (Pri); 20.95v-0-20.95v @0.27A + 50v @ 0.023A (Sec) Toroid 1U)
[This is intended for use as a mains transformer for 1U mic amps].

Prices exclude freight and VAT [if applicable].

Colin
www.audiomaintenance.com

Thanks Rodabod, I'll try to upload a pic to my server next week.
No model number on any of those output trannies; except OPT-4, OPT-5; OPT-6 etc. Color scheme of the leads seems the same as those soldered on the marinair inputs: green, blue, brown, grey, black.

bram

These are the ones Canford sold after they took over the ex stock of the BBC spares depatment
If you do a search you can find some info ont he ( I bought a few - they were stupidly cheap)

Ok, I finally took some high-res pics of the output transformer. On the second photo you can see a small logo under the numbers '2' and '3' of the cable on the top.

http://web.usal.es/~neerlandes/xformer1.jpg
http://web.usal.es/~neerlandes/xformer2.jpg
http://web.usal.es/~neerlandes/xformer3.jpg

Anyone able to identify this one?

Bram

any low res?
top file took 5 minutes before i pulled the plug...

yea sorry for that, photos are 1,5 meg each. Have to find out how to handle my girlfriend's new camera. I'll post reduced-size pictures tomorrow.
Thank you,

Bram

just resize with infran, no need to re shoot

Done. I've overwritten the files on the ftp so just reload the pics and maybe refresh the cache of your browser if you had already watched them. The urls of my previous post still work, I just mixed up photo 1 and 2. File size now is 120kb.

bram

OPT12? That'll be "Output Transformer 12" then!

I'll have a look and see what I can find.

Roddy

looks like neve stuff, should work great, same core, so same turns approx, same sound
the resize works great thanks!

A small breakthrough : the panel comes from a BBC GP3, audix made. Maybe someone has schematics or can now determine the characteristics of the transformer?
thanks!

bram

hell I'll make a guess myself. The output trannies look like the Sowter 4127 trannies that user Greg used in his audix 35102 rack. Anyone cares to confirm?

regards,
Bram

Brian Sowter the good guy himself confirmed.
FYI: The core is a mixture of Mumetal and Radiometal and a rather complex winding structure with 5 electrostatic shields.
The part Mumetal used in the core would magnetise with a few micro-amps of dc offset and saturate with perhaps 0.5 mA.

I wonder if these are not similar to those bbc spec'ed marinair t.1801 found in Neve broadcast desks.

Thank you guys,
Bram

I have some new BBC transformes:
"LL/88 asc" is apparently the type.
Anyone knows about these, turns ratio, uses, etc.?

Thanks in advance!
Bram

Well LL is usually used by Lundahl. Pics?

Ruairi