freestompboxes.org

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…

Hi Soulchief,

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



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

Cheers,
Jose

Do you know the transformer data?

Has anybody ever seen this layout?
Is this one close to the the Suhr or CAE?

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...

Cheers,
Jose

Hi Jose,
thanks for your suggestions.

Cheers
Manfred