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Old 13th January 2011, 08:04 PM   #1
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Default Lagato 2 with transformer S.E.

A few questions on a transformer SE on a Lagato 2.

Can a balanced to SE transformer have its + / - inputs be taken from before the C5-C8 caps (the Nichicon green Muse), where then caps can be removed, or after (keeping the caps in place)?

I do not plan on using the onboard balanced/s.e. on board silicon.

If the caps are to be kept in place, iirc in reading the other threads, that thay can be replace with film caps ( between 2.2uf and 10uf), but dependant on the impedence of the transformer.

I have a choice between low (600/600 1:1) or high (10K/10K 1:1) balanced to s.e. transformers...

Which transformer would be more appropriate for this application? and an appropriate value of capacitor for that transformer?


Up front will be dual mono Buff2's and from my reading of the threads the I/V values should be 75 ohm and 330 ohms ( to keep a good balance between output current and distorion), as the Buff2's would be wired to have 32ma each out to each channel of the single Legatto2.

JD
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Old 15th January 2011, 08:44 PM   #2
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Quote:
Originally Posted by Jeffrey Davison View Post
A few questions on a transformer SE on a Lagato 2.

Can a balanced to SE transformer have its + / - inputs be taken from before the C5-C8 caps (the Nichicon green Muse), where then caps can be removed, or after (keeping the caps in place)?

I do not plan on using the onboard balanced/s.e. on board silicon.

If the caps are to be kept in place, iirc in reading the other threads, that thay can be replace with film caps ( between 2.2uf and 10uf), but dependant on the impedence of the transformer.

I have a choice between low (600/600 1:1) or high (10K/10K 1:1) balanced to s.e. transformers...

Which transformer would be more appropriate for this application? and an appropriate value of capacitor for that transformer?


Up front will be dual mono Buff2's and from my reading of the threads the I/V values should be 75 ohm and 330 ohms ( to keep a good balance between output current and distorion), as the Buff2's would be wired to have 32ma each out to each channel of the single Legatto2.

JD
Hello Jeffrey,

The transformers can be placed wither before or after the caps, but if you take the signal from before the caps you'll have some DC offset. Trouble is, transformers saturate and produce much distortion if fed too much DC offset. How much offset can be tolerated depends on the particular transformer - ask the manufacturer for a guide here. Alternatively, just try both ways and see which you like the sound of best. If the tranny is distorting badly you'll get a fat and bloated bass, and general lack of clarity.

As for which type of transformer, 10K types are known as "input transformers" - they go on the input of the amplifier as they can't have much wire length after them, dues to capacitance. 600 ohms types are "output transformers" and can be placed in the DAC / preamp.

Hope this helps,
Dan
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Old 15th January 2011, 09:24 PM   #3
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I'll only have about 24" of interconnect between the DAC and the preamp I'm using. Decided on a pair of Cinemag CMLI-15/15B2 input transformers for the Balnced to S.E. duties. (even tho they will be used at the output and mounted in the case after the Lagato2). I'll use a 4PDT switch to manualy switch between S.E. and Balanced. Output caps will be 4.7uf Jupiter HT Beeswax.

JD

Quote:
Originally Posted by Spartacus View Post
Hello Jeffrey,

The transformers can be placed wither before or after the caps, but if you take the signal from before the caps you'll have some DC offset. Trouble is, transformers saturate and produce much distortion if fed too much DC offset. How much offset can be tolerated depends on the particular transformer - ask the manufacturer for a guide here. Alternatively, just try both ways and see which you like the sound of best. If the tranny is distorting badly you'll get a fat and bloated bass, and general lack of clarity.

As for which type of transformer, 10K types are known as "input transformers" - they go on the input of the amplifier as they can't have much wire length after them, dues to capacitance. 600 ohms types are "output transformers" and can be placed in the DAC / preamp.

Hope this helps,
Dan
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Old 15th January 2011, 10:40 PM   #4
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OK, you might get some peaking in the treble as the cable capacitance resonates with the transformer inductance. Keep the wires as short as possible, and use low capacitance stuff.
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Old 15th January 2011, 11:34 PM   #5
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Just found out that Nuetrik makes (what they call) a tiny XLR connector.
The panel mounting hole size is .44" (11.2mm), where as the RCA holes in my pre are .47".
A pair of the "tiny" XLR's can fit in the input panel one for one. Also, there is plenty of room inside my pre for a pair of the Cinemags. My pre is a self built S.E. tube jobbie.
Doing it this way will allow for a set of balanced cables from the Lagato2 to the pre, and the Cinemags will provide galvanic isolation to boot. The internal wiring in the pre from the traffos is about 3" of .5mm Mundorf silver/gold, so capacitance is nill.
I'll run the Lagato2 to Pre in Balanced, and I'll find a proper pair of output traffos for the S.E. duties.....
JD
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File Type: jpg preamp guts.JPG (679.2 KB, 303 views)

Last edited by Jeffrey Davison; 15th January 2011 at 11:44 PM.
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Old 16th January 2011, 01:25 AM   #6
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hmmmm..... Lundahl Ll1582 looks appropriate here
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Old 16th January 2011, 12:58 PM   #7
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Hi JD

You have really nice stuff there....!!

Seems You are dooing extensive reserch with realy pro aprouch....

Well I do not know what trafo would be the best but ..in thread about Legato, Russ mention that it would be good idea to put extra VR in parallel with one of CCSR of Legato and this should allow for canceling or at list geting really low with DC at Legato DIF OUT. There will be probably some thermall drift, but avoiding caps beffore trafo could to be worth trying this small mod.

Rosendorfer
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Old 17th January 2011, 04:41 AM   #8
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After a bit of leg work and some questions asked and answered by some key people..
I decided to go with, and ordered a pair of Lundahl Ll1684 transformers to do the balanced to S.E. duties immediately after the Legato 2.
Thanks all.

JD
Attached Files
File Type: pdf 1684.pdf (23.6 KB, 72 views)
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Old 20th January 2011, 03:06 PM   #9
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Default Transformers vs the on board conversion

Hello JD

Are you planning on implementing the Legato's onboard balanced to S.E conversion and compare between the two options? it would be interseting as I am in a similiar situation.

Thanks

Eitan
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Old 20th January 2011, 03:34 PM   #10
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I am using LL1570 Xl for balanced to S.E.

http://www.jacmusic.com/lundahl/appl...ymmetrical.htm
http://www.4tubes.com/SCHEMATICS/LUN...RCA-LL1570.jpg
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