Simplistic NJFET RIAA

[nicoch58]

I have own two citroen CX in the past ...steering wheel with Hydro Guide

R-core have two separate secondary and one primary work fine no hum/buzz, C° like dead

[Salas]

So you use the French store ones (China made?) and work OK, plus they have the configuration on the PDF, not that in some product pictures on their website? Where you use it?

[nicoch58]

The 500VA 30V in two amp, trupath and after in erno mosfet (franky)

and small 30Va 12V in the truepath for driver chip

the pdf (my pic) is in all trafo on line , see riccardo link......

[Salas]

Cool, we should try them out in single box build then. In phono they have to really show how low field they are.

[RCruz]

It would be much easyer if I could place the boards and the tx flat in the case due to the sizes.... The perpendicular position is mandatory ? What is the reasoning behind it ?

[Salas]

If there is some field it reduces affecting the boards if at right angles. But if the cancellation in those transformers is near perfect in the actual product, then by a simple rotation test you can determine if so good that they can lay in the same plane or not without any rudimentary buzz penalty.

[RCruz]

[Joao@AltheaMusica]

Hello Ricardo,
some news from the "Vinyl" show in Portugal?

Hello Salas,
what about using following RIAA amp design:

1st stage > discrete op-amp with variable gain, i.e. from 20 to 40db, with an transformer coupled, single ended, output stage of 600 Ohm

following into an LCR-RIAA

2nd stage > same as 1st. stage

Or whaz's your opinion to use an LCR-RIAA in your design instead of the RC-RIAA?

Regards
Joao

[Salas]

I would not do that in a simple and relatively cheap to make concept like this one. The quality of core and value precision needed for LCR plus the anti hum measures that are going to come up are putting me off.

[Joao@AltheaMusica]

Originally Posted by Salas

I would not do that in a simple and relatively cheap to make concept like this one. The quality of core and value precision needed for LCR plus the anti hum measures that are going to come up are putting me off.

Salas I agree. It was just some idea out of topic.

An op-amp is complicated to handle getting it stable... maybe this is the point because it's preferable to use a simple - single ended -cascoded stage. You can do this with RC coupling / resistive load or with a transformer.

I like to experiment with the second version. Any idea? I think we can do this with PM first :-)