a bit confused with xfmrs wiring

[warpie]

ok, I know this is basic but I've got a LL1540 (line in transformer) and LL1517 (line out transformer), that I would like to connect as
an 2:1 (bal to unbal) and 1:2 (unbal to bal). Can somone give me some directions about the correct wiring?

http://www.lundahl.se/pdfs/datash/1540.pdf
http://www.lundahl.se/pdfs/datash/1517.pdf

Also, is there any info/threat describing diferent xfmr wiring configurations? I could find any...  ???

thanks
w.

 

[sodderboy]

I think that you can find similar transformers on the "transformers information" pages here at Dan Alexander Audio.  You can see how parallel and series configurations of windings change the actual impedance and gain.  Neve used the same transformers in different circuits and wired them to suit.  Sometimes they used a transformer as a 2 into 1 combiner.
And check with the manufacturer.  Are those Carnhill numbers?  They MUST have info.
Mike

 

[warpie]

Hi sodderboy ,

No, these are Lundahl transformers. Unfortunately the data sheet doesn't explain me much about different configurations.
I'm also unsure about the impedances. It looks to me like the input xfmr is 10K:10K while the output 600:600.
To be honest I'm not even sure if I can use the specific xfmrs as I described.
Well, I guess is the lack of knowledge...

 

[mitsos]

1540 as 2:1:  Put primaries in series and secondaries in parallel.  so tie pins 2+4 together on the primary, take your hot to pin 1, cold to pin 3.  On the secondary, connect 5 to 8 and 6 to 7, take your output from 5+8.

1517 as 1:2:  Put primaries in parallel and secondaries in series. Tie pins 1+6 and 3+4 together, signal in goes to 1+6. Do not connect the center taps (2 and 5) to anything.  Tie 8+12 together on the secondary and take hot from 7, cold from 11.

not sure how it will work for you, try it and see. I am pretty sure people have used the 1540 for 1176 builds as 2:1 on input IIRC?

 

[warpie]

hi mitsos, that's very helpful 

Just one last thing though...

1540 as 2:1: Can I connect pin 5 to hot and pin 8 to ground, in order to get an 'balanced to unbalanced' signal?

same for 1517, can I connect pin 6 to ground for 'unbalanced to balanced' conversion?

thanks for you help

 

[rodabod]

1517 as 1:2:  Put primaries in parallel and secondaries in series. Tie pins 1+6 and 3+4 together, signal in goes to 1+6. Do not connect the center taps (2 and 5) to anything.  Tie 8+12 together on the secondary and take hot from 7, cold from 11.

I maybe wouldn't do that actually, depending on what you are driving this with; the 1517 has very low primary inductance and naturally low series resistance. You might get better bottom-end/drive with just a single primary. If you are driving with an typically configured opamp with no feedback, then keep the lead-out resistance low, say 47R.

 

[mitsos]

I'd go with roddy on this.  ;D  Like I said, that should "work" but I have no idea how well.

 

[warpie]

thanks for the replies guys.

There are no opamps involved here. Only transistors.
Since you explained me the basic configurations I'll try them and see what gives me the best results

(in fact I just recalled another existing threat that might be more appropriate to ask )

 

[sodderboy]

You really should understand that Neve datasheet.  It shows different winding configs of one transformer and the resulting gains.  If you can grasp how changing the wiring of windings on a transformer from series to parallel, or just using one winding will affect impedance and gain through the transformer, then you will understand transformers 101.
Mike

 

[rodabod]

There are noopamps involved here. Only transistors.

Any hint as to what sort of circuit we are talking about here?

The 1517 is only suitable for driving from a low impedance.

 

[warpie]

You really should understand that Neve datasheet. It shows different winding configs of one transformer and the resulting gains. If you can grasp how changing the wiring of windings on a transformer from series to parallel, or just using one winding will affect impedance and gain through the transformer, then you will understand transformers 101.
Mike

thanks Mike, your link is very helpful indeed, and I think I understand the series/parallel wiring. What I don't really get is in which cases I need to connect a resistor and where...

There are noopamps involved here. Only transistors.

Any hint as to what sort of circuit we are talking about here?

The 1517 is only suitable for driving from a low impedance.

yes sorry you are right, TG-1

 

[sodderboy]

I think I understand the series/parallel wiring. What I don't really get is in which cases I need to connect a resistor and where...

Well, that would require a schematic and a goal to change the response.  Maybe you are talking about Zobel design?  Do a search.  When you are cloning things that do not come with schematics and a BOM on a gilded platter you have to be very specific and descriptive when asking questions.
Mike

 

[rodabod]

I'm not familiar with this TG circuit. And I can't reall go searching for it to determine whether or not the output impedance is suitable for this transformer.

You should be able to work this out though by looking at the specs of the original design (if they exist).

 

[Biasrocks]

The TG "calls for" a 10K:10K on the input and a 600:600 on the output, there are some other options for 2:1 and 1:2 which involve modifying the makeup gain stages.

It sounds just fine without any iron.

Mark