Simplistic NJFET RIAA

[buzzforb]

Gonna try a version of Joachims' prefilter with common mode choke after the transformer. This will fed Mur860 then KG 4.7mF, 1R Fukushima, then SSLV with another 4.7mF KG on board. What do you think. Should i throw a nother choke in and drop the R. How do i size the choke? Got boards done. May not get to mounting parts unitl after Christmas with the In-Laws

 

[Salas]

Nah, its enough filtering already.

 

[The Space Egg Corp]

Hi Buzz

Those CM f-cored inductors, could choke the sonics...
...The 1R Fukushima sounds cool !
What is it ?

Cheers.

Si.

 

[buzzforb]

Hi Buzz

Those CM f-cored inductors, could choke the sonics...
...The 1R Fukushima sounds cool !
What is it ?

Cheers.

Si.

From what I understand, just for Hf filtering of mains. Easily added or taken away. The Fukshima MPC 74 are high power resistors from famous nuclear island and have a bit of a following in the japanese audio world( you tihnk we got it bad)

 

[buzzforb]

Its good to break some EMI from the rectification. So drop 1 or 2 volts with an R before board's main C if with outboard bridge or by a small hack. Better still is choke input with some leftover speaker air coil.

Took the time to REALLY read you r post. SO you just suggesting a choke after transformer and before onboard cap. If so, Ill bump teh cap up to 10mF KG cap I have on hand and the only option will be the CM choke before rectifiers.

Just simmed a Hammond feeding the 10mF cap and it looks good and comes up pretty slow for electronic world.

 

[Salas]

What value AC secondary TX you got in Volt and VA?

 

[buzzforb]

Screwed up the sim. Need big inductor with low dc or I drop too much voltage......like you said! Looking at 50VA Hammond 36V sec. Duals wold be better, but just want to get it up and running.

 

[Salas]

Use this config. 2mH air coil plus 20 Ohm in series with it (included with its DCR in the sim).

 

[buzzforb]

sort of what I am playing with now. Quick question. What makes loading transformer directly with choke so difficult?

 

[Salas]

Loses too much voltage by having no capacitive storage at input. Choke input PSUs in tube audio use a high secondary Tx typically if you look in rectifier valves documents. They usually give choke input and max Cin curves.

 

[buzzforb]

gotcha. thanks.

 

[Salas]

They dip in the many volts there plus the chokes are in several Henry range. Here it can go off chart. But with a small input cap and a resistor to boost the DCR, the green VC2 output is just a smooth long ramp up/ramp down.

 

[buzzforb]

I sometimes am too lazy to think about how things actually function, sliding along the surface just building things. Had it working with big 158T, but dropped way too much V, as you said and was pushing its current rating. Ordering two of the hammond transformers and 155B chokes. Will pair with Kg caps that I have. Trying to get brother to bite on Ortofon Vienna cartridge that just went up in Swap No reason why i cant njoy it as well.

 

[The Space Egg Corp]

Hi Buzz

Dunno if you got me...
...I think the cored common-mode is a great GREAT idea...BEFORE the transformer...
...AFTER it you wanna air-core, like Capt. Salas says.

Salas...
...your screen-shot shows a CORED inductor.
( just keepin' you sharp Capt. ( wink )).

Cheers.

Si.

PS...Buzz...see if you can borrow a Geiger from the local high-school or somewhere...
...just a quick sweep of the audiophile 1R's when they arrive should ensure peace of mind.

 

[Salas]

That's what symbol the sim has in its bank. Its about Henry level tube PSUs sims. Still a cored 2A 6mH choke like H155B won't break a bead of sweat at circa 200mA CCS. And its compact.

 

[buzzforb]

Before ordering, what is the advantage of the air core over Hammond in this case. Dont mind getting an air core if it should help sonically.

As for the Fukushima, It is my understanding that the latest versions have an added energy to their sound.

 

[RCruz]

No coils here... not after and not before the TX.

I once experimented with some air coils before the TX (mains filter) and it totally killed the magic.

 

[Salas]

Before ordering, what is the advantage of the air core over Hammond in this case. Dont mind getting an air core if it should help sonically.

As for the Fukushima, It is my understanding that the latest versions have an added energy to their sound.

Air core will be more drastic in much higher frequencies than 120Hz.

 

[buzzforb]

that is a never before heard audio term. I love it

 

[Salas]

No coils here... not after and not before the TX.

I once experimented with some air coils before the TX (mains filter) and it totally killed the magic.

Was it big coils in value?