Simplistic NJFET RIAA

[vgeorge]

I mean percentage deviation from nominal value(+-%), not resolution. Look at his manual or specifications.

 

[Salas]

Hi Salas,

i have built your phono stage to fet. For the riaa i have used:
Resistor metal film 1% 47K,
Resistor metal film 1% 6.8K,
N°2 Cap 47n + 1.5n to 5% (i measured 46500),
N°3 Cap 15n + 330p + 100p (i measured 15300).
This value are correctly for accurate riaa?

Many thanks

If those values are close to real, they are fine. Waiting for pictures of finalized build.

 

[atupi]

Why my shunt output voltage is not steady and it going up in the first few minutes after start ? Is that normal ?

 

[Salas]

Yes, its the Tc of its K170. A bit more than others because GR. Set it for after say half an hour.

 

[Marinos]

Since I didn't catch up the latest BIB GB I'm proceeding with Shunt 1.0.5 from pdf P2P.
Here is my PRELIMIARY layout... (Don't use it without care !!!)
Board will be mounted vertically with Q1&4 bolted to case bottom.
The only thing that bothers me is that C4 is too close to Q4 (heat..) or it shouldn't.
Comments please

 

[Salas]

Use 105 C part, mount it underneath board if you got space to stick out the other way, or mount the MOSFETS parallel like in power amps or many DCB1.

 

[Milos P.]

Hi
could I use smaller coupling cap for C7 (V1102F0), it is looking into R8=1M parallel to 47k on the input of my line preamp (grid to ground). I think 0.47uF will give me around 7.5 Hz corner freq. which should be low enough.
Cheers

 

[Salas]

Give it 1uF because C3 does some pre roll off between stages, and 0.47u cuts too early in that situation.

 

[Milos P.]

OK, thank you.

 

[Salas]

If you make any, don't forget to show it and discuss it here. See ya.

 

[Djinn]

Minimum current and size of R101?

In the BIB guide rev. 2 it says that minimum current drawn is 100ma and I am going to use two regulator in driving the Salas minimalistic NFET Riaa. I have to be certain, is this so or can the current use be lower like 25mA/20% over load consumption?

With regards

Martin

 

[Salas]

Set each at 150mA and supply channels individually. To keep the power output impedance low.

 

[atupi]

Can you tell me a source where to buy teflon capacitors other that ebay ?

 

[vgeorge]

https://www.siberian-shop.com/capacitors-c-80.html

But I would recommend ebay.

 

[atupi]

And what would be the next choice for the interstage capacitor after teflon ? PIO ?

 

[Salas]

I did not like non bypassed pio there, sounds thick. Get a 47n-100n Mundorf that is cheap enough because small value.

 

[Salas]

Obbligato Gold Premium and Mundorf no oil simple Supreme seem down to earth priced in 0.1u value.

 

[atupi]

If you recommend it i will order some.

 

[merlin el mago]

For MKP I recommend 1st choice Auricap, now 40% off PartsConnexion (no commission) 0,1uF 400V or 600Vcapacitor_film_auricap.html

 

[atupi]

Do you think if i connect by mistake the input of amplifier to the input of RIAA preamp can i destroy something ?
After i did this mistake my preamp is very quiet. On Q1 i have 0.6v on the gate and 6,8v on the drain.