DIY ISO Variable Line Out Box Layout? (Suhr, CAE)

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Soulchief
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Post by Soulchief »

Does anybody have a Layout or Schematic for a DIY ISO Variable Line Out Box like the Suhr or CAE?


— Jensen JT-11-FCFL 1:1 600ohm Transformer ?
— Variable Potentiometer
— Ground Lift Switch
— Phase Reverse Switch
— Speaker In / Thru
— Line Out 1/4”
— Enclosure


I believe these would be the parts but I don’t know ‘Pot Size’, if any resistors are needed, or how to hookup..

The Suhr and CAE ones are really expensive and can’t be found currently so I though I’d make one but there is very little info out there that I could find at least…

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ppluis0
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Post by ppluis0 »

Hi Soulchief,

There is the diagram for a well reputed DI: Countryman model 85

Image

Take as a basis of your requirements as it already has speaker thru capability and is inherently ground isolated.

The other features you need can be implemented (IMHO):

- Phase reversal => A 2PDT switch to reverse the secondary of the transformer between pin 2 and 3 of the bal out.
- Variable potentiometer => Replace the switch S1 with a suitable pot.
- GND lift => open pin 1 of XLR from ground by means of a SPST switch

1/4" line out can be taken from the primary side of the transformer but there is always ground referenced :roll:

Cheers,
Jose

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Manfred
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Post by Manfred »

Do you know the transformer data?

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Soulchief
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Post by Soulchief »

Has anybody ever seen this layout?
Is this one close to the the Suhr or CAE?
line out w phase ground.jpg

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Post by ppluis0 »

Manfred wrote: 01 Sep 2021, 02:54 Do you know the transformer data?
Hi Manfred,

I have not even seen one of those boxes personally... :)

This is a diagram that I found a long time ago on the web and it seems that it is no longer available, so the exact characteristic of the transformer are unknown.

I think that a test can be done making a prototype with a bifilar winding as 1:1 turns ratio and a suitable air gap in the core.

600 ohms load can be driven (IMHO) with the couple of NPN transistors connected as in the diagram... :roll:

Cheers,
Jose

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Post by Manfred »

Hi Jose,
thanks for your suggestions.

Cheers
Manfred

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