What can I do with these Telephone Transformers ?

[clintrubber]

[quote author="ciminosound"]I have to second the fact that sometimes "voice only" trannys perform better than spec (but not always!) I have an RCA that reads 300-4000Hz but performs in the 20-20,000 range as good as any UTC or Triad I have. On the other hand some voice only transformers suck.[/quote]

Hi,

Triggered by http://www.groupdiy.com/index.php?topic=158541#158541
but not wanting to abuse that thread I want to ask about these TXs,
which do come from some sort of military telephone/telegraph-converter.

From left to right (& sorry for the width):

#1
ADC (Audio Development Co.) A11538
600 Ohm - 10kOhm, 2.5mA DC
300 - 3500 Hz, +2dBm

#2
ADC A11537
1:1 (400mH - 400mH)
1225 - 1600 Hz, 'hipot 500Vrms'
This seems from the telegraph-side of the box,
so likely not usable at all ?

#3, yellow marking
UTRAD 2126
(200mH - 200mH)
1225 - 1600 Hz,
telegraph-side ?

#4, fully right
UTRAD 2125
460 Ohm : 7800 Ohm, so 1:4
(73mH - 1.24H)
1225 - 1600 Hz, +2dBm
telegraph-side ?

Stated frequency responses are indeed underwhelming, but for grins, could they still be usable for anything audio related @ modest levels ?

That #1 has already just a voiceband-spec, but those three others are really overwhelming with 1225 - 1600 Hz :wink: .
Some sort of signal-transformer ?

FWIW, last pic is the power-TX. It's tempting here in Europe
to enter that thing on its 220V secondary i.s.o. its 115V primary,
but I guess because of less 'screening' between the secondaries
that might be less safe...


Anyone heard btw of these ADC & UTRAD-brands ?

All suggestions (or laughter) welcomed...

Thanks,

Peter

 

[NewYorkDave]

The primary inductances on those transformers render them unsuitable for full-bandwidth audio except perhaps at really low impedances.

Sorry...

BUT, good telephone coupling transformers do come in handy eventually, especially if you work in broadcast or know someone who does.

 

[rafafredd]

yeah, those are very low inductance. Interestingly, they list the inductance in the specs. Never seen it. Or seen it once...

Try the bigger ones, and very low inductance as discreet opamp outputs. Might work, but will probably saturate too early.

If you can´t do anything with those, send the over to Brazil at my place. I love ****** transformers. :green:

 

[rodabod]

What can I do with these Telephone Transformers ?

Phone someone?

 

[clintrubber]

Thanks all,

The primary inductances on those transformers render them unsuitable for full-bandwidth audio except perhaps at really low impedances.

Sorry...

No problem, I was already afraid of this :wink:

I could try those 400mH ones, that'll be a source impedance of less than 50 Ohms for 20Hz if I'm not mistaken. But hmm, that's only a 1:1, so not much functionality in that one.
The 73mH one requires less than 10 Ohms for a f-3dB of 20Hz.

If I want to drive low mHs like this with an opamp it'd be probably be good to insert a cap to avoid DC-current, but cap needs to be large then. The yellow-print type seems fine with some DC-current though.

BUT, good telephone coupling transformers do come in handy eventually, especially if you work in broadcast or know someone who does.

Anyone ever heard of these ADC / UTRAD brands ?

As it seems there's only the small one that could do voice, those others with their 1225-1600Hz seem to be for the telegraph signal ? (Don't know anything about telegraph)

[quote author="rodabod"]

What can I do with these Telephone Transformers ?

Phone someone?[/quote]
That's actually not a bad idea ! I mean, why not do that (used-to-death) telephone-trick on voice not with an EQ but with something really telephone related for a change ? :wink:
Can try this one as an FX-thing, with variable drive. Uh, and in reverse it's
near the re*mp-byNYD-circuit (but I have already an Edcor for that).

[quote author="rafa"]Interestingly, they list the inductance in the specs. Never seen it. Or seen it once... [/quote]
I forgot to mention the most important spec of all: to which altitude these TXs can be used. :wink: They're all neatly sealed, probably to telephone/telegraph someone from a plane. Why it's still that olive green then is beyond me...


Finally, what are your thoughts on that power-TX ? Better not put the 230V mains on that secondary ? Will the safety of the 6.3V winding be compromised ?
Looks yummy, that big chunk of iron. A power TX with the word 'audio' on it should be put to use :razz:

Thanks,

Peter

 

[alk509]

[quote author="clintrubber"]why not do that (used-to-death) telephone-trick on voice not with an EQ but with something really telephone related for a change ?[/quote]

FYI, the process is called "phone futzing". A phone futz box, although of limited use, is one of the funnest things to have around.

Peace,
Al.

 

[clintrubber]

[quote author="alk509"][quote author="clintrubber"]why not do that (used-to-death) telephone-trick on voice not with an EQ but with something really telephone related for a change ?[/quote]

FYI, the process is called "phone futzing". A phone futz box, although of limited use, is one of the funnest things to have around.

Peace,
Al.[/quote]

This is funny - all of a sudden now I'm actually hoping that this TX will have limited bandwidth :wink:

But I don't know much of telephone-systems; I assume the BW-limiting is not just left to the various TXs, there will be some more defined filtering in the chain somewhere, right ?
In other words, I can't really imagine putting this TX in the chain will give enough BW-limiting already to give the telephone-sound.

I'll be searching for "phone futzing".

Bye,

Peter

 

[ciminosound]

Anyone heard btw of these ADC & UTRAD-brands ?

ADC=Audio Development Corp. The Collins 356 Vari-mu used ADC trannys for example.

http://waltzingbear.com/Schematics/Misc/Collins_356E-1.htm

UTRAD some connection with Triad.

Like there's some UTCs labled as TRW after TRW bought them.

 

[BradAvenson]

[quote author="ciminosound"]

Anyone heard btw of these ADC & UTRAD-brands ?

ADC=Audio Development Corp. The Collins 356 Vari-mu used ADC trannys for example.
[/quote]

They are still around, just not in that business any more:
http://www.adc.com/

 

[clintrubber]

[quote author="ciminosound"]

Anyone heard btw of these ADC & UTRAD-brands ?

ADC=Audio Development Corp. The Collins 356 Vari-mu used ADC trannys for example.

http://waltzingbear.com/Schematics/Misc/Collins_356E-1.htm

UTRAD some connection with Triad.

Like there's some UTCs labled as TRW after TRW bought them.[/quote]
Thanks, yes, it also said so on the big power-TX. Nice those Vari-mu's used several components that were 'close'/related...
...but since there were 6AL5's and some ADC-brand stuff in that box still doesn't mean you could convert this into a Vari-Mu, Peter !

I've 'de-populated' the chassis of this box, that chassis could come in handy one day for experimenting.
Will toy around with that 600:10k TX first. And then take it along on a plane - those max altitude 10,000 FT indications are all over these components. :wink:

Regards,

Peter

 

[clintrubber]

[quote author="BradAvenson"][quote author="ciminosound"]

Anyone heard btw of these ADC & UTRAD-brands ?

ADC=Audio Development Corp. The Collins 356 Vari-mu used ADC trannys for example.
[/quote]

They are still around, just not in that business any more:
http://www.adc.com/[/quote]
Thanks for the link. Interesting: http://www.adc.com/aboutadc/history/
From this it seems those TXs are roughly from somewhere between 1949 & 1961.

I'll refrain from asking them about these TXs. :wink:

 

[clintrubber]

FWIW, let's finish this for now with some irrelevant pron
('irrelevant' since its not really an audio-thing and because that chassis looks quite a bit different now - as in 'empty').

Nicely made though :thumb:

 

[clintrubber]

Just a bump w.r.t. the power-transformer above:
would it be unwise to use a secondary high voltage
winding for 'inserting' the mains voltage?

Would it give an increased safety risk ?

What I was thinking about was to connect mains (230V here)
to that 220V secondary winding and get my HT-AC at the
(previously primary) 115V winding.
That should be fine I think, but could there be a safety issue
for the 6.3 V winding ? Its CT is already grounded,
and I'll be connecting that to mains-ground.
(I won't use that remaining 570V winding).

Thanks,

Peter

 

[gyraf]

would it be unwise to use a secondary high voltage
winding for 'inserting' the mains voltage

Very unwise. There should be MUCH better isolation between pri/sec than between any two secondaries. Safety issue.

Jakob E.

 

[clintrubber]

[quote author="gyraf"]

would it be unwise to use a secondary high voltage
winding for 'inserting' the mains voltage

Very unwise. There should be MUCH better isolation between pri/sec than between any two secondaries. Safety issue.

Jakob E.[/quote]

Thanks Jakob for the warning. :thumb:

One last question (for my understanding, not for putting this TX
to service at all costs :wink: ):
would it still give a safety issue when using just that one secondary
winding (for mains-input) and then only the original primary for output ?

(That wouldn't be elegant since it'd require a separate heater-TX, but OK)

So in fact using the TX in reverse and ignoring (but safely isolating)
all other windings ?
Or is there then still the potential danger that the secondary has less
'safety margin' w.r.t. say the grounded core ?
(I should check how pow-TX's are usually being wound).

Or perhaps better phrased: so should power transformers with a
seemingly suited secondary voltage simply not be used in reverse
for direct connection to the mains ?

Regards,

Peter

 

[CJ]

:shock:
What are you going to do for your B+?

 

[clintrubber]

[quote author="CJ"]:shock:
What are you going to do for your B+?[/quote]

You mean what I'd be doing with only 115Vac after the TX ? (if it'd had been OK to reverse-use this TX )

Some doubling, or wait, some tube stuff I have could use a sym. supply, about +/-100V.

Bye,

Peter

 

[enthalpystudios]

interesting, this is all i could find while searching, in google actually, not just prod-pro, for adc transformers...

i've been finding time to work on my m79 tape machine, and reading the manual, discovered that some were transformer input, and some were transformerless. so of course i had to find out ;]

i got the back connection panel off, and discovered, contrary to the rumor i have heard all over, that not only do i have a transformer input machine ( ;] ), but all the i/o transformers are ADC.... look very similar to oep, but square and slightly larger.

i've always heard that these machines are full of beyers.... and there is one beyer on each channel card, but it is actually just for bridging the sync head to the sync preamp for cue monitoring. in repro or record, the beyer is out of circuit. looks to me like a 1:15 mic input type used backwards. so perhaps this machine will have a very different sound in cue.

anyway... just thought i'd add a blurb about my findings to the only info i could find on adc transformers... especially i've heard nothing but the word 'beyer' associated with m79's.