Simplistic NJFET RIAA

[RCruz]

I found this one : SELECTRONIC ::: L'univers électronique :::

But in this case I will not have one winding per channel (both psu will be connected in parallel to the TX)....

Maybe this is like overkill : http://www.selectronic.fr/article.asp?article_ref_entier=10.3263-9999

 

[Salas]

Its 18+18 I think, not 18-0-18. I see 2 wires per secondary there, right?

 

[massimo]

Yes, they all have dual secs

 

[Salas]

But their product picture in Ricardo's link looks like 115+115/V-0-V. Risk? Who knows French to email them?

 

[RCruz]

They all very large.... Do you plan to place the boards vertically and the tx laying down ?

Should I aim for two 2x18v 80va or one 2x18v 120va ?

 

[Salas]

Yes, plan Tx down, boards on their side. I am looking to get the 2X21 120VA and series the secondaries, or just use the outer taps if they are actually V-0-V configured. I will possibly need 50V reg out.

120 is not significantly more expensive Ricardo, but from their photos VS their pdf maybe you are in 50% risk of them being V-0-V and not V+V for using double bridges ''OR'' that you do. You should email them about what stands true of their current stock.

 

[RCruz]

I meant usin two 80va so to get real double mono setup versus one 120va where the two bridges should be connected in parallel... this setup (my initial one) needs special care in the gnd connections (both smoothers must be connected together before going to star gnd)...

Meanwhile I will e-mail the supplier. (Je peux ecrire en Français aussi !)

 

[Salas]

I have to answer you...Citroen. There my French skills end.

 

[RCruz]

I just e-mailed them.

Nevertheless the picture shows four wires in the secondary so probably I will get lucky.

I believe I will need a big case this time so I can put two TX inside to benefit from true double mono.... or do you believe sharing the same winding is as good ?

Ricardo

 

[Salas]

I don't have a clue of how it will be with those trafos, and what will be perceived preferable, but must have low primary to secondary capacitive coupling in the high ranges.

 

[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]

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