Valve Itch phono

[merlin el mago]

Good to know, thanks Salas.

 

[merlin el mago]

Salas could I use Vishay naked VAR for Rload 47K, RIAA 50K & 6K8?

 

[Salas]

For Rload surely yes, for those other positions measure the DC voltage across them and look up if the VAR will be within its max voltage spec.

 

[merlin el mago]

I'm uisng now Caddock MK132 0.75W without problems.

 

[stajo]

Riaa resistors has no DC over them

 

[fdegrove]

Hi,

Riaa resistors has no DC over them

Question is if you're going to hear any notable difference in that position.

I'd start with the MM loading resistor which in theory should be 50K, not 47K.
In theory.

I do hear a marked difference with MC cartridges with even a simple Vishay bulk foil resistor but MM ?

Cheers,

 

[stajo]

I would, unquestionable. Resistors measuring alike on a DMM can behave hugely different when it comes to AC signal surpressing. I dont know why but when rolling them in riaas aswell and in speaker filter networks, to me different brands, types etc of resistors affects more then dito capacitors. Roll some on the 50 K build out one and tell. Thats the noicebuilder.

 

[merlin el mago]

For Rload surely yes, for those other positions measure the DC voltage across them and look up if the VAR will be within its max voltage spec.

VAR max. voltage 200V, could I use?

 

[Salas]

From what I later saw there is no voltage drop across those positions so you can. But as I remembered that VAR were not especially high voltage resistors it was good to check before using them in a valve pre.

 

[fdegrove]

Hi,

A pity these VAR resistors don't come in values above 100K.

Cheers,

 

[stajo]

They sure do Audio (Through Hole)

 

[fdegrove]

Hi,

Ha, OK. Thanks for that Stajo.
I was going by the pdf file Felipe posted above.

Cheers,

 

[merlin el mago]

Salas could I use Vishay naked VAR for Rload 47K, RIAA 50K & 6K8?

Riaa resistors has no DC over them

From what I later saw there is no voltage drop across those positions so you can. But as I remembered that VAR were not especially high voltage resistors it was good to check before using them in a valve pre.

I measured the RIAA resistor and there is not DC across the resistors as stajo pointed.

 

[merlin el mago]

Salas could I use RIAA caps rated 200VDC?

 

[stajo]

Probably. Measure over your old. Should be 160 something.

 

[merlin el mago]

Yes Salas posted in the schematic 165VDC and I have teflon caps 15nF & 47nF.

 

[merlin el mago]

Both teflon caps are rated 200VDC, can be enough right?

 

[stajo]

It depends on how well speced they are, noone can really know. I usually have some more margin if I can. Theres only one way to find out.

 

[merlin el mago]

I will try.

 

[merlin el mago]

RIAA 200VDC teflon caps working near 1 day without problems.