Simplistic NJFET RIAA - Page 259

RCruz · 30th October 2009, 05:01 PM

Now you tell me !

massimo · 30th October 2009, 05:22 PM

Yes, Nicoh, I know. For low pw application EI Xfrm is my favourite, while split bobbins and R core ones follow closely. The problem is: if I must have it made, I can only get some toroids. Selectronic in France sells some nice R core made in China, but even if not cheap and not considering how expensive is to get them in Italy, they don't carry the V I would need.

disco · 30th October 2009, 06:41 PM

Quote:

Originally Posted by le´flu

Hi Disco,
could you please send farnell ordering number for cmc?
I can´t find them in german....

Sorry, can't help you with that. See attached picture for examples. The more milli Henry you use, the lower the filter frequency will be. Anything from 10 to hundreds mH helps, mind the suitability for at least 500mA of current passing. Connection to ground at the last capacitor. Besides, you can roll one of your own.

Quote:

Originally Posted by massimo

... tell us more. Possibly even the diode type.

There's a lot of info on the forum already on Schottky, hexfred and other diodes. Making a PSU is not hard, be aware of the consequences of ringing and select your components with care. No need to make it expensive though.

Quote:

Originally Posted by nicoch46

guys remember that Joh curl, Ayre and Jocko Homo don't use ring trafo because don't filter the dirty AC as wide band device.....!!!
The hammond in my phono sound better then talema ring, and peter daniel as quite critic in the component selection use the hammond split coil in the Dac....

Both EI-core and toroid have their strong points. For the sake of a small electromagnetical field I would opt for a toroid if placed nearby the amplifier circuit. For a separate box I'd take the EI-core for better filtering mains pollution.

Pity you guys don't have access to redundant equipment like an old Hifi amp. The larger units often contain a 2x30V tranny, some of Japanese origin are good quality. Forget anything under 2x25W.

disco · 30th October 2009, 06:53 PM

Quote:

Originally Posted by massimo

... I can only get some toroids

Try this manufacturer.

nicoch58 · 30th October 2009, 07:05 PM

Quote:

Originally Posted by RCruz

Now you tell me !

Ricarco

I told you five month ago ......

RCruz · 30th October 2009, 10:53 PM

I remember that

But in that time I was "focused" on low electro field because of using 6 tx inside the CDP box and I wanted to close one tx inside the riaa box.
At the time I did not get your idea... why are EI better in some cases ?

Now I am starting to get a picture:
" Both EI-core and toroid have their strong points. For the sake of a small electromagnetical field I would opt for a toroid if placed nearby the amplifier circuit. For a separate box I'd take the EI-core for better filtering mains pollution. " (Thank you disco)

RCruz · 11:05 PM

Just got the jensen caps from denmark !!!

Now I will be able to compare this riaa with the initial one on an equal base

nicoch58 · 31st October 2009, 12:01 AM

in teory the R-core have all the two pro , but not all have the primary and secondary in the separate coil......

Massimo I have the selectronic 500va r-core, very fine , works like a dead , but the small one 30va have little unbalance on sec...

RCruz · 11:19 AM

Just received the Block RK 100/30

It looks very good and the inscriptions in the TX reveal:
I have two independent secondary windings, each for 30vout and 1,66A so I got a 2x50VA TX.

It is smaller than spec but that is very good.

Hi Salas
I believe I will have between 42 and 45v output after rectification and smoothing.

I need to drop between 6 and 8 volts.... what resistor value should I use in series with the 15000uF cap ?

Ricardo

massimo · 12:16 PM

R ? = V (6 or 8 volts drop as you wrote) devided by I (you know how the CCS is set).
I must be in A, not mA, thus if you have set it for 400 mA, you use 0.4 in the formula

Then how big the resistor should be? Again, the Ohm's law says: P = V x I
(current always in A, not mA)
The result (in Watt), x 2,5 or better x 3 in order to get the right wattage for the required resistor.

P.S. if the Xfrm is smaller is not a very good sign..... high fluz maybe... BTW, how "square" its shape is? I mean, is the height the same at the ourter edge and at the inner edge of the "doughnut"?

30th October 2009, 10:54 PM	#2587
RCruz diyAudio Member Join Date: Sep 2006 Location: Saxon Blog Entries: 1	Just got the jensen caps from denmark !!! Now I will be able to compare this riaa with the initial one on an equal base Last edited by RCruz; 30th October 2009 at 11:05 PM.

2nd November 2009, 11:16 AM	#2589
RCruz diyAudio Member Join Date: Sep 2006 Location: Saxon Blog Entries: 1	Just received the Block RK 100/30 It looks very good and the inscriptions in the TX reveal: I have two independent secondary windings, each for 30vout and 1,66A so I got a 2x50VA TX. It is smaller than spec but that is very good. Hi Salas I believe I will have between 42 and 45v output after rectification and smoothing. I need to drop between 6 and 8 volts.... what resistor value should I use in series with the 15000uF cap ? Ricardo Last edited by RCruz; 2nd November 2009 at 11:19 AM.

2nd November 2009, 12:09 PM	#2590
massimo diyAudio Member Join Date: Dec 2002 Location: Milan, Italy	R ? = V (6 or 8 volts drop as you wrote) devided by I (you know how the CCS is set). I must be in A, not mA, thus if you have set it for 400 mA, you use 0.4 in the formula Then how big the resistor should be? Again, the Ohm's law says: P = V x I (current always in A, not mA) The result (in Watt), x 2,5 or better x 3 in order to get the right wattage for the required resistor. P.S. if the Xfrm is smaller is not a very good sign..... high fluz maybe... BTW, how "square" its shape is? I mean, is the height the same at the ourter edge and at the inner edge of the "doughnut"? Last edited by massimo; 2nd November 2009 at 12:16 PM.

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30th October 2009, 05:01 PM	#2581
RCruz diyAudio Member Join Date: Sep 2006 Location: Saxon Blog Entries: 1	Now you tell me !

30th October 2009, 05:22 PM	#2582
massimo diyAudio Member Join Date: Dec 2002 Location: Milan, Italy	Yes, Nicoh, I know. For low pw application EI Xfrm is my favourite, while split bobbins and R core ones follow closely. The problem is: if I must have it made, I can only get some toroids. Selectronic in France sells some nice R core made in China, but even if not cheap and not considering how expensive is to get them in Italy, they don't carry the V I would need.

30th October 2009, 10:53 PM	#2586
RCruz diyAudio Member Join Date: Sep 2006 Location: Saxon Blog Entries: 1	I remember that But in that time I was "focused" on low electro field because of using 6 tx inside the CDP box and I wanted to close one tx inside the riaa box. At the time I did not get your idea... why are EI better in some cases ? Now I am starting to get a picture: " Both EI-core and toroid have their strong points. For the sake of a small electromagnetical field I would opt for a toroid if placed nearby the amplifier circuit. For a separate box I'd take the EI-core for better filtering mains pollution. " (Thank you disco)

31st October 2009, 12:01 AM	#2588
nicoch58 diyAudio Member Join Date: Oct 2004	in teory the R-core have all the two pro , but not all have the primary and secondary in the separate coil...... Massimo I have the selectronic 500va r-core, very fine , works like a dead , but the small one 30va have little unbalance on sec...

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