Simplistic NJFET RIAA

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the BOM shows two R1.
I think one of them should be R11.

Yes, there is a typo there indeed. Thanks for picking that up. I am arranging for the print on solder mask to have a Q3Y and Q3Z in the main circuit not to confuse with the Q3X in the regs also. So I will be editing a final refresh of the text when all is ready. I will let people know then.
 
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Update

Minor details fixed.

PCB
There are Q3Y and Q3Z designations on the PCB print now.
(Q3X, Q3Y previously for the alternative cascode transistor types).
So to avoid any possible confusion with the Q3x JFET in the regs when populating the board. (Tnx Rush).

Guide
Q3Y, Q3Z designations correspondingly listed and explained in notes.
R11 was R1 BOM typo fixed. (Tnx Andrew).
"Gain" topic in notes got better detailed.
R6x in the reg's schema went to its correct position (I only saw that bug :D).

So its recommended you discard the previous guide downloads to keep this one which is up to date. #9980
 
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Is it possible to switch the gain somehow?

No. You build with a certain gain in mind. Its possible to modify for using another output level cartridge by changing a couple of things as described in the guide but not on the fly. Its not a loop feedback design to flick some op amp gain resistor, its open loop SE so its about about re-fixing it.
 
Many thanks to Salas for making his Folded NJfet RIAA design compatible with MM cartridges.

I'm still using his first version of the 'Simplistic' for my Nagaoka MP20 and I'm happy with it. But I am heavily tempted to try the new folded simplistic pcb, so I would like to ask a few (newbie) questions.

I suppose R1 is the cartridge load impedance. This is specified as 47K. Is it OK to increase this value to make it compatible with a different cartridge load, say 68K?

If in future I opt for a low o/p MC, does this necessitate a change in the values of Rx1-Rx4?

Regarding the Elcap, is this the bi-polar type or will the usual 105 deg. aluminium electrolytic type do?

Thanks for any clarification to my newbie questions.
 
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The input load R1 is arbitrary, your choice in other words. The use of JFETS with their very high natural input impedance allows that.

Rx1-Rx4 can be high like 3.3k 10k 20k 33k to achieve intermediate values for evaluating MM and high MC carts or left unpopulated when you are sure of just one optimum value that you can use for R1. Or just put capacitor loads in some of those positions to select.

Later if with MC cart you can populate/replace with what is best load range for that cart.

Elcap for regs termination can be your choice electrolytic either polar or bipolar 50V-100V, any type not characterized as "Low ESR".
 
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That is a well done & filtered main PSU which may be of benefit and I don't see any negatives in principle for using it as a 45 to 47VDC source for each folded channel DCin.
But is it easy to convert it for two positive polarities when it is a symmetrical originally? Else, will it be using half of it for no double mono? Unless you mean just its positive polarity schematic doubled up and not using the actual board.
 
jfet follower

Hi Salas,

first of all thank you for your time and effort to make all these designs available for the community!!!

I am just starting to mess around with jfets, I have build a line preamp (not the DCB1, that I would like to try) and is sounds fine, but.... I was expecting something more. My experience is mainly with valve design, just to better focus what I mean.
So I started to look around the diyaudio forum (great source!!!!) and I have found out that, when developing and testing the DCB1, you pointed out the weakness, sonically speaking, of the 100% local feedback of the buffer and the lack of transparency versus tubes designs, and this matches with my considerations.
Since you are using a similar configuration in this riaa preamp, I was wondering then if a different buffer could give some improvements.

Ciao

P.S.: I am collecting the parts to try this riaa preamp too :)
 
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Hi Salas

Finally got the time to read the pcb building guide with care. Wonderfull job.

Now I understand how you can propose fixed values for R13 and R12 with such a wide range of Idss in the 369. (You suggest a range of Vin from 33 to 37v :))

In the 63dB build, using two 11mA 369 biased at 9mA, somehow I calculated that looking for 3.6v on R4 and 8v on Q3 emitter I can not go higher than 33Vin otherwise Vr1 should be negative.

But if I use R12 = 75 ohm, I can set Vr1 to 131 ohm and use Vin = 35V

Am I missing something ?
 
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Hi Salas

Finally got the time to read the pcb building guide with care. Wonderfull job.

Now I understand how you can propose fixed values for R13 and R12 with such a wide range of Idss in the 369. (You suggest a range of Vin from 33 to 37v :))

In the 63dB build, using two 11mA 369 biased at 9mA, somehow I calculated that looking for 3.6v on R4 and 8v on Q3 emitter I can not go higher than 33Vin otherwise Vr1 should be negative.

But if I use R12 = 75 ohm, I can set Vr1 to 131 ohm and use Vin = 35V

Am I missing something ?

I tried to give it a range of answers for Idss by examining many JFETS, took me a couple of nights just for that over the breadboard.:D
You know, to prepare such a device practical enough for people to make takes a lot of details to arrange. Open loop, high gain, and naturally ranging JFETS can be a nightmare to a newcomer if without a road map. Especially for a range of cartridges spanning from LMC to MM.
Its an easier directive to vary the rail first with VR2, the VR1 pot left to middle with single value across the sensitivity versions so not to perplex people, then use it for fine tuning only. TP1 is different in the board, its at the LEDS. So just one Vdif to mind for. But you are veteran in this and you change values in places by knowing more. Still the bias outcome is the same.

Vinyl is so alive

3D printing has a long way to go for cutting grooves, it sounds like an AM radio dying in a bucket of water in that video.:smash:

Was listening to Herb Alpert & Hugh Masekela on original A & M vinyl just before. Awesome lifelike sound, and as Sketches of Spain was spinning in the Pioneer DVD through the DAC I flipped forth and back, letdown, the digital came across flat. Where do they compress the vitality I don't know. One was like eating at a favorite Italian restaurant the other was like eating at NASA.
 
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Hi Salas

Finally got the time to read the pcb building guide with care. Wonderfull job.

Now I understand how you can propose fixed values for R13 and R12 with such a wide range of Idss in the 369. (You suggest a range of Vin from 33 to 37v :))

In the 63dB build, using two 11mA 369 biased at 9mA, somehow I calculated that looking for 3.6v on R4 and 8v on Q3 emitter I can not go higher than 33Vin otherwise Vr1 should be negative.
Correction

But if I use R12 = 275 ohm, I can set Vr1 to 107 ohm and use Vin = 35V

Anyway it is good to know we can fiddle quite a bit with Vin without compromising performance :)

PS: What I see from the 3D printing is that Young people is really beguinning to apreciate vinyl recording media.