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Old 2nd September 2008, 09:33 AM   #1
Salas is offline Salas  Greece
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Default Simplistic NJFET RIAA

Hello people.

I want to make an easy RIAA with NJFETS switchable for mm and mc. I thought of that no feedback simplistic circuit in the attached picture.
I am not asking for very good performance. Just to work and don't sound harsh. Will it work at all?

Build guide MC & MM older version
Experts version MC only hardwired
Official PCB version guide MC & MM
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File Type: jpg salasriaa2sk170bl.jpg (76.8 KB, 27799 views)
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Old 2nd September 2008, 09:45 AM   #2
Bonsai is offline Bonsai  Taiwan
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Salas, if you want something simple and reliable with adequate performance, just use a good quality op-amp like a 5534.

If you want to use JFETS to improve your MC/MM listening expereince, I don't think this circuit is the best one - there are better JFET circuits - see JC-1, Dennis Collins et al.

Good luck
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Old 2nd September 2008, 09:47 AM   #3
h_a is offline h_a  Europe
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There's already some stuff using that concept, L'Pacific RIAA, since I cannot find a schematic for this one, I link you to Mad_K's variant of it

Ultrasimple mm/mc RIAA preamp 2

Have fun, Hannes

EDIT: oh and I almost forgot: the Pearl by Wayne Colburn (Pass Labs) is another example of a 2 stage Njfet-riaa pre.

EDIT2: bonsai, I cannot find a schematic for the Dennis Collins'pre - would you please point me to one? Thanks!
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Old 2nd September 2008, 09:54 AM   #4
Salas is offline Salas  Greece
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Nice link Hannes, cheers! Looks alike.
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Old 2nd September 2008, 10:05 AM   #5
Salas is offline Salas  Greece
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Quote:
Originally posted by Bonsai
Salas, if you want something simple and reliable with adequate performance, just use a good quality op-amp like a 5534. Good luck
Had 5534 2 stage with passive RIAA for many years when I was doing solid state. Very effective. Had original Signetics and synergistically sounding caps and resistors. Best I have heard is my mate's Steve Bench modded 12AY7 parallel & ECC88 cascoded. I just have 2SK170BL left overs from my recent DC coupled Pass B1 version and I am monkeying around a bit.
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Old 2nd September 2008, 12:04 PM   #6
Salas is offline Salas  Greece
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I saw in that link that some put the first stage to second stage coupling capacitor after the passive RIAA and say they got better subjective performance. I guess because they use mainly small ones and the response is linear after the RIAA stressing less. I will have to listen for that position exchange. They also had several other circuits made with highly endorsed op amps etc. but some prefer the ''Pacific'' class for better subjective musicality. I guess that my experiment to be, falls in that class. Interesting. Some cascoding mods that I saw are also good to test. I did not see Rsource bypassing for more gain as I do aspire though. Maybe sounds bad, or it is noisy. I have some Dynavector 20dB silver step up if things prove difficult. Nice pass time concept non the less.
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Old 2nd September 2008, 04:25 PM   #7
kevinkr is offline kevinkr  United States
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Take a look at Richard Sears JFET phono stage design, works well and sounds pretty good.

http://www.triodeguy.com/other_projects.htm

Note that you will need to match jfets regardless of what you decide to build.. Their transconductance varies all over the place.
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Old 2nd September 2008, 04:29 PM   #8
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I use a mad_k with ska optvol ,good sound for me

I will try at first stage 170bl with 33r to ground for lower the second armonic dist.

at 24v there is a possibility of battery and use small series caps...what I found that this simple phone are very sensitive to quality component for now I use :
all R dale rn55 non magnetic
riaa caps vishay MKP1837
for series caps c3 66nf I use clarity caps Sa 0,1mf
outcaps 1mf Sa //mundorf 0,47mf silver-oil without r parrallel 100k
psu caps near jfet mundorf 22000mf

I will order more exotic part and report

this circuit are not so good for mm because have higth input capacitance near 300pf and no more 3-4mv at input ,Iuse denon dl-160 mc 1,8 mv
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Old 2nd September 2008, 05:15 PM   #9
Salas is offline Salas  Greece
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Quote:
Originally posted by kevinkr
Take a look at Richard Sears JFET phono stage design, works well and sounds pretty good.

http://www.triodeguy.com/other_projects.htm

Note that you will need to match jfets regardless of what you decide to build.. Their transconductance varies all over the place.

Now that's a decent one. SRPP to drive the properly impedance sized RIAA, BJT follower for output. Kevin you dropped in here to remind me of glass...
How does it compare to decent vacuum?
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Old 2nd September 2008, 05:25 PM   #10
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very interesting 52db gain....are sufficent for dl103 ?
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