Simplistic NJFET RIAA

Hi Salas-
I finished sorting jfets. Below are the best pairs of the pile, broken down into Idss sections, below.

Please advise which ones should be used where. I'd like to get as much gain as possible, as my cart has ~.4mV output.

Also, I saw on SGregory's circuit, you designed a B-1 style buffer. I have the jfets, would that be a better buffer?

10+mA-
10.19, 10.20
10.29, 10.30
10.64, 10.66

9 to 9.9mA-
9.83, 9.84
9.27, 9.28
9.59, 9.62

8.5-9 mA-
8.73, 8.74
8.93, 8.94
8.69, 8.70

8-8.5 mA-
8.01, 8.01
8.16, 8.17
8.10, 8.12

7.5-7.9mA-
7.69, 7.69
7.85, 7,85
7.83, 7.85

6.5-7.5mA-
7.42, 7.42
6.94, 7.02
6.74, 6.75

Thank you again for your help- Kent
 
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Use your fourth lot from the top on #5875 post 58.4dB adjusted CCT paradigm from the Greek builder with the same output Shelter cart. Has voltages and current measurements noted on it to know you are about right too. For using the B1 style output you just need a wee less IDSS than top JFET one replacing R7. G&S together and to ground. I am not sure it was really better or not because I have it in not completely the same gain and construction examples. Still I can't say that the builds differ strongly in general. See for your self. Listen as standard first. Resistor out, 2 legged (G+S as one) JFET in its place, listen again.
 
Thanks, Salas. Sorry, I have more questions. Still n00b to jfet understanding.

For the B1 style buffer, a "wee less IDSS" would a 0.01 mA difference suffice? Also, I remember somewhere earlier in the thread it was said lower IDSS for B1 buffer jfets is better.

I have 6.72/6.73mA pair and 6.74/6.75 pair. OK for B1 buffer? Or use 8.16/8.17 and 8.10/8.12 pairs for buffer?

For the rest of the Jfets-

Q1- 8.01/8.01 mA. They are my best matched pair. .634 & .633 mV for Vp.
Q2- 8.73/8.74 mA OK? They are also good Vp match (.624 & .628 mV Vp).
Q5- 7.42/7.42 mA pair OK?

Most of my 8.5-10mA matched pairs also had tighter Vp matching and I was hoping to use them.

Thank you- Kent
 
Resistor shopping for R14, R3&4

Hi folks-

Still gathering parts for my build. I'll be using either PRP or NOS mil-spec RN65 for most of the resistors except for the RIAA network and the Rload.

I assume RIAA precision is critical. So I tried to source 0.1% resistors. No luck for the values stated in the schematic (R14-43K & 2.7K series; and R3 1M & R4 6.8K in parallel).

So I've come up with other series/parallel combos and was wondering if the arrangements and values are good enough....

For R14- Target resistance= 45.7K

Option 1-
40K Vishay S102 0.01% (I have quantity of these)
in series with-
5K Vishay S102 0.01% (I have quantity of these)
in series with-
(2) 1.4K 0.1% Welwyn RC55Y-1K4BI (in parallel).

Option 2-
26.7K 0.1% IRC RC55LF-D-26K7-B-B
in series with-
19K 0.1% Vishay RN65E1902BB14

Option 3-
18.7K 0.1% IRC RC55LF-D-18K7-B-B
in series with-
27K 0.1% Vishay CMF5527K000BEBF

For R3 & R4, things get a bit more tricky. I came up with some other resistor combinations, below. They are not exactly at the target resistance, but within a few ohms.

R3, R4 target resistance- 6754.07 ohms (6K8 & 1M in parallel).

Option 1-

13.3K 0.1% IRC RC55LF-D-13K3-B-B
in parallel with-
13.7K 0.1% IRC RC55-D-13K7-B-B
Total Resistance- 6748.5 ohms.

Option 2-
562 ohms 0.1% IRC RC55LF-D-562R-B-B
on series with-
6190 ohms 0.1% IRC RC55LF-D-6K19-B-B
Total Resistance- 6752 ohms.

I would appreciate any feedback, even if I'm being too anal about this! :D

Thank you- Kent