Simplistic NJFET RIAA

[andyr]

The shunts need some voltage difference between input and output in order to regulate properly.

For example, if you set the shunt to output 35V, it needs at least 40V input to regulate properly but if you feed it 50v you can get better SQ.

Aaah, OK. thanks.

Andy

 

[stajo]

Somehow I get the idea that damping ressonances in the secondaries reduces the ability for the psu to radiate hum into other circuits.

As I am using "soft" diodes, ringing might not be so evident and as I am using a separate PSU that is physically far from the amp, it might be really difficult for me to detect improvements.

In this case (zobels on secondary) its not the diode noice that your after to kill but the trannys own ringing.

 

[bucurb]

Stajo,
I completely agree with you. You did mark precisely the subject.
Quasimodo jig helps making snubber's design extremely simple an efficient.
Mark Johnson did great job, congrats!
Happy auditions my friends!

 

[merlin el mago]

Where from ?

Please post pics when they arrive

 

[Salas]

Tx array he, he. Merlin, do post Quasimodo assisted snubber values for those FSP compatible standard models if you may. For other possible users to know.

 

[merlin el mago]

Of course let me measure and come back with the information

 

[Salas]

Before and after snubber oscilloscope ringing photos will be persuading too.

 

[merlin el mago]

R-Core 230V 30VA two 0-15VAC secondaries wired in series to have 0-30VAC, attached pics. It's also very important to know o measure wich are the real phase at primary and secondary. As 3rd pic shows our necessary Rs is 357 ohms (use the more aproximate standard value)

Asap I will give value for R-Core 230V 30A two 0-18VAC secondaries wired in series to have 0-36VAC.

 

[merlin el mago]

R-Core 230V 30A two 0-18VAC secondaries wired in series to have 0-36VAC needs 450 ohms.

 

[Salas]

Merlin, very nice. Thanks. For members to see it full, is this the correct total snubber circuit?

 

[merlin el mago]

Yes, mine Rs is your Rx

 

[Salas]

 

[alexkosha]

I also can do measurements with Quasimodo for all US located guys who use Antek toroids, the same tranys that I have in my builds:
AS-0515 - 50VA - 15V
AS-1236 - 100VA - 36V
AN-8412 - 800VA - 4x12V

 

[nezbleu]

R-Core 230V 30VA two 0-15VAC secondaries wired in series to have 0-30VAC, attached pics... As 3rd pic shows our necessary Rs is 357 ohms (use the more aproximate standard value).

I am curious how much the ringing varies with different R. So if 357 is "ideal", what does it look like with 330R? 220R? 500R? At what point above or below "ideal" does the ringing become significant? (And how do we define "significant"?)

 

[nezbleu]

Alex I would love to see your results.

 

[Salas]

I also can do measurements with Quasimodo for all US located guys who use Antek toroids, the same tranys that I have in my builds:
AS-0515 - 50VA - 15V
AS-1236 - 100VA - 36V
AN-8412 - 800VA - 4x12V

AS-1236 I think some had used in FSP. They could benefit. And let us know if they could hear an improvement too.

 

[Golana]

AS-1236 I think some had used in FSP. They could benefit. And let us know if they could hear an improvement too.

Yes, this one please.

 

[alexkosha]

Please allow me to do it over the weekend (Saturday). I'll let you know ASAP.

 

[merlin el mago]

I am curious how much the ringing varies with different R. So if 357 is "ideal", what does it look like with 330R? 220R? 500R? At what point above or below "ideal" does the ringing become significant? (And how do we define "significant"?)

I posted the target snubber pic, if you use 500R the tx will be over damped and scope will show a large tail wave, if you use 220R you possibly see in the scope more than one wave or at least the second inversed wave. Attached Mark Johnson PDF, link diyA thread http://www.diyaudio.com/forums/power-supplies/243100-simple-no-math-transformer-snubber-using-quasimodo-test-jig.html

 

[merlin el mago]

Please allow me to do it over the weekend (Saturday). I'll let you know ASAP.

Have a nice weekend Alex