Simplistic NJFET RIAA

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Salas

Salas

diyAudio Chief Moderator
Joined 2002
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Siberia said:
Guys, just found out that KWTUBES ebay seller has lots of NOS russian stuff, moreover he's in my city. If you could recommend any parts to tryout from his shop for Simplistic RIAA, I would be glad to try'em out. Alas, no FT Caps:

kwtubes | eBay
Click to expand...

You could use MGBOs for output. Those are interesting in tone. He has got 1uF so you could parallel 2-3. He has also got S mica that you could build your HF Riaa cap by paralleling some. There he has PETP too (mylar) in small size and some correct single values that are very good for what they are, but not among the best dielectric available. The tolerances mean you got to use a meter if combining for Riaa. Meantime have a look in what Altek from Russia made: RIAA Dual mono Phono preamplifier - My Photo Gallery A very original simplistic phono and shunt regs construction. It looks he recycled a (satellite receiver?) case and put inside everything, even a VU meter circuit! I hope that he will tell you more in this thread also.
 
Siberia

Siberia

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Joined 2011
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Salas, thanks a lot!

If only I had a cap meter. Otherwise it could be a wild adventure with these tolerances. Not that I don't like those... But already with p2p it's daring for me.

For the time bein , in my cart I've got resistors all takman carbon, Obligato Gold for output, muse lytics, MKP1837 for 0.047UF and 0.1UF, silver micas 330pF, and I've just realized I'm missing something 15nF, damn. Are those choices reasonable?

Also I miss heatsinks for shunts. Excuse me for calculating their values in this thread.

R-core 2x15, from experience will provide ±2x17VAC, thus 34AC, which after rectification (x1.4) will turn in 47.6 DC (is that acceptable?)

Thus:
DCin 47.6V
DCout 28V
LOAD 0.07A

Q101 dissipation = (DCin-DCout) * CCS current setting
47.6 - 28 = 19.6 x 0.2A = 3.92W
25º : 3.92W = 6.38 ºC/W

Q106 dissipation = DCout * (CCS-LoadCurrent)
28 x (0.2A-0.07A= 0.13A) = 3.64W
25º : 3.64W = 6.87ºC/W

Correct? Does tha lend to metal floor enclosure sinking?


PS. Altek sat. receiver makeover – wow, crafty!
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
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Calculations are alright. Since you get +13% than nominal from those Tx on your mains from experience, get the 12+12V model to avoid useless dissipation. Floor will do if with 4mm aluminum medium size box. With diodes Vf drop and other losses a 1.33X than 1.41X AC to DC multiplier of Tx secondary is rather more realistic at that voltage range.
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
Siberia said:
Unfortunately, knowing slow selectronic service, I've already ordered 2x15 Tx and it's underway. I'll have to cope with what I've got now. Other stuff seems reasonable enough?
Click to expand...

Yes, nice warm choices. MKP1837 15nF has good tolerance from enough I measured, keep in mind since you miss that one. The 0.047u-0.1u interstage is very influential, maybe you would like not to repeat MKP1837 there, although compact for layout. One small enough 0.047u for interstage I have got but not chanced to had applied yet is a wax Jensen one, but expensive.
 
Siberia

Siberia

Member
Joined 2011
Paid Member
Ooof, them Jupiter caps are pricey indeed at my shop. I try to limit ordering locations to two: farnell and hificollective. Mainly because of lower shipping costs and faster delivery. And with some luck I might be able to hear Simplistic by Xmass.

Alright then MKP1837 for 15nF. I've seen Ampohms being used for interstage in this thread too. If you could take a peek here: Capacitors - Hifi Collective for another quick middle ground suggestion, I would appreciate that.

Thanks.
 
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