Simplistic NJFET RIAA - Page 1874

SKA76 · 23rd January 2021, 08:24 AM

Quote:

Originally Posted by Salas

50VA Antek which is very much used by American builders has magnetic shield that their lesser VA models don't have is another reason why usually recommending 50VA

A Polish manufacturer of toroidal transformers offers shielded transformers starting from 20 VA. Which VA rating would be your primary choice for a pair of transformers (230V) for this project?

Thanks!

Salas · 23rd January 2021, 03:35 PM

30VA-50VA each

SKA76 · 25th January 2021, 05:05 PM

Thanks Salas!

How do I wire the 32 V primaries of the 2 transformers to one IEC (230 V)?
Usually one of the primaries is tagged with a tape at the end (indicating the inner winding?).

Thanks!

Salas · 25th January 2021, 07:15 PM

32V can't be primaries but secondaries. Primaries should be 115V each. Depends on each brand. Could be connecting two tagged or specifically colored ones together and the side ones to the mains. But better look it up at the manufacturer's website.

SKA76 · 26th January 2021, 08:23 AM

Thanks Salas!
Luckily, I did not mix up primaries and secondaries in real life

The background of my question was if it is necessary to use 2 fuses with 2 transformers as suggested in this thread: Wiring up two trafos to one IEC socket.

Which slow blow fuse(s) should I use (230 V), 1.25 A?

Thanks!

Salas · 26th January 2021, 11:27 AM

Its not necessary to use individual primary fuses by electrical safety code. In case you want to, you should not skip a central fuse. In other words 2.5A in the IEC socket and 1.25A before each 50VA transformer for USA. Cut those figures to nearest 1/2 available amperage values for Europe and other 230V countries. All such fuses should be time lag (T) type. What we call slow blow.

cygnus x1 · 27th January 2021, 09:58 PM

The ultra is using PF5102 fets? I can't find a data sheet that specifies the noise figure, any clues?

Salas · 28th January 2021, 12:02 AM

PF5102s are strongly related to the J11/112/113 family. Look in their datasheet page 5 figure 14: J/MMBF

cygnus x1 · 28th January 2021, 03:09 PM

Thanks!

elwood625 · 3rd February 2021, 01:07 AM

Hello Salas and Tea-Bag, I finished my preamp with BA2018 line stage boards stacked for Balanced operation with the UFSP with shunt regulators in the same chassis. The power supplies for the display/ relay input /volume control/remote, has a 250vac 30A relay to turn on the power supply for the BA2018 line stages.
The UFSP has a remote power supply with umbilical cord, the shunt regulators are mounted vertical with the home made heat sinks 10mm below the vents in the steel chassis. After 3 hours of operation, the inside of the enclosure stayed the same temperature. It is dead quite on all of the inputs, the UFSP I've adjusted and played HO MM, LO MC, HO MC. After a month of playing, time to move it into the main system.

Thank you both for all your help with this project!

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23rd January 2021, 03:35 PM	#18732
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	30VA-50VA each

25th January 2021, 05:05 PM	#18733
SKA76 diyAudio Member Join Date: Nov 2014	Thanks Salas! How do I wire the 32 V primaries of the 2 transformers to one IEC (230 V)? Usually one of the primaries is tagged with a tape at the end (indicating the inner winding?). Thanks!

25th January 2021, 07:15 PM	#18734
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	32V can't be primaries but secondaries. Primaries should be 115V each. Depends on each brand. Could be connecting two tagged or specifically colored ones together and the side ones to the mains. But better look it up at the manufacturer's website.

26th January 2021, 08:23 AM	#18735
SKA76 diyAudio Member Join Date: Nov 2014	Thanks Salas! Luckily, I did not mix up primaries and secondaries in real life The background of my question was if it is necessary to use 2 fuses with 2 transformers as suggested in this thread: Wiring up two trafos to one IEC socket. Which slow blow fuse(s) should I use (230 V), 1.25 A? Thanks!

26th January 2021, 11:27 AM	#18736
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Its not necessary to use individual primary fuses by electrical safety code. In case you want to, you should not skip a central fuse. In other words 2.5A in the IEC socket and 1.25A before each 50VA transformer for USA. Cut those figures to nearest 1/2 available amperage values for Europe and other 230V countries. All such fuses should be time lag (T) type. What we call slow blow.

27th January 2021, 09:58 PM	#18737
cygnus x1 diyAudio Member Join Date: Sep 2006	The ultra is using PF5102 fets? I can't find a data sheet that specifies the noise figure, any clues?

28th January 2021, 12:02 AM	#18738
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	PF5102s are strongly related to the J11/112/113 family. Look in their datasheet page 5 figure 14: J/MMBF

28th January 2021, 03:09 PM	#18739
cygnus x1 diyAudio Member Join Date: Sep 2006	Thanks!