Simplistic NJFET RIAA

[Salas]

There is a big difference between to and too in english. Is that the problem you are having?

I have no problem with to & too. I am explaining why the 180R in this case and other options given the opportunity.

 

[AndrewT]

It won't be wise to run that ccs fet at full idss because it sees a high potential across and it will dissipate much.

then why the necessity to post this immediately after my post that refers to jFET+R17?

 

[Salas]

Because that's when I logged in and saw the posts.

 

[AndrewT]

posts 4735 and 4737 are the two relevant posts between your posts.

Why did you make that comment?

 

[Salas]

Again. To explain the 180R choice or other options given the opportunity it was discussed.

 

[merlin el mago]

@Salas @AndrewT
Hey guys, I'm not confort with discussions I only want help so:

between B+ & njfet 3k3 1W or 180R?

Peace

 

[Salas]

You can either use the 180R as it is and run the leds lower current, or delete it and put a 3k3 1W between B+ and the Led's Jfet to run them higher current. In any case you should test and match them with the jfet of choice feeding them with an 180R or without (fet g&s) if you are to use the 3k3. I would choose the configuration that takes me nearer to the voltage I seek with the particular leds. You use the trimmed down Idss already in your current build.

 

[merlin el mago]

For balanced I want to use this schematic gain 60dBs:

An externally hosted image should be here but it was not working when we last tested it.

How many volts will have to measure the LEDs string?

Of course 4 channels.

 

[AndrewT]

You can either use the 180R as it is and run the leds lower current, or delete it and put a 3k3 1W between B+ and the Led's Jfet to run them higher current.

For balanced I want to use this schematic gain 60dBs:

An externally hosted image should be here but it was not working when we last tested it.

How many volts

Merlin,
you have ignored Salas' advice and deleted R17 without doing anything else.
Why bother asking questions when you don't implement the recommendations?

What voltage, I cannot read your tiny sketch.
Crop it and repost at a sensible/legible size.

 

[merlin el mago]

Merlin,
you have ignored Salas' advice and deleted R17 without doing anything else.
Why bother asking questions when you don't implement the recommendations?

What voltage, I cannot read your tiny sketch.
Crop it and repost at a sensible/legible size.

You don't understand nothing, I'm not implemented nothing, just starting to measure the voltage LEDs string to matched them for 4 channels balanced NJFET RIAA using the last posted schematic.

First to do a bad answer read all posts & you can know that I asked to measure with mine bench psu because I don't have any 9V battery to match the leds, after I asked the current needed to fix mine bench & later I posted the schematic I want to use & I asked how many volts must measure the LEDs string in mine schematic?

 

[Salas]

Merlin just do that circuit. Test it with the specific jfets & specific leds or mix 3+diode on a breadboard. Try red leds if you have, first. Use 20V for testing without a 3k3 or 45V with a 3k3. After matched, just copy it in the final builds.

 

[merlin el mago]

You can either use the 180R as it is and run the leds lower current, or delete it and put a 3k3 1W between B+ and the Led's Jfet to run them higher current. In any case you should test and match them with the jfet of choice feeding them with an 180R or without (fet g&s) if you are to use the 3k3. I would choose the configuration that takes me nearer to the voltage I seek with the particular leds. You use the trimmed down Idss already in your current build.

Now measure 6.04V, it's corrected for the schematic I want to use?
sorry crossed your post with mine post

 

[Salas]

Its not bad but I would prefer around 7V.

 

[merlin el mago]

What about 7.56V using your last schematic?

 

[Salas]

Good.

 

[merlin el mago]

Thank you, now I will match the rest of LEDs for the 3 channels more🙂

 

[merlin el mago]

Done, I have 4 LEDs string matched each one 7.56V🙂

 

[merlin el mago]

BC550C Idss

@Salas
Wich will be the best Idss value for Q3 BC550C?

I have following Idss:

535
536

558
559

562
563
564
565
566
568

574
575
576
578
579

580
584
588
589

591
598

602
603
606
609

611
616
617
618

624
625

641
642
648

652
656
658

660
669

670
678

680
685
686

I need 4 transistors for 4 channels

 

[Joao@AltheaMusica]

Try low Rbb Toshiba etc.

Thanks a lot. Another question, didn't find the Rdson from the SK170 and SK359 in the data sheet, can you provide it to me.

 

[merlin el mago]

2SK170 Q6 Idss

@Salas
Wich will be the best Idss value for njfet don't matched Q6 2SK170?