Simplistic NJFET RIAA

[kstlfido]

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

[kstlfido]

I had the good fortune to find some Vishay S102 resistors at a local ham-radio swap meet.

I have 50R, 3.3k, 5k, 40K, 70K, and 300K. All 0.01%. Unfortunately, none will combine to R14's required 45.7K. Oh well, looks like I need a 700R.

I can at least use some of the S102's for Rload.

[Salas]

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.

[kstlfido]

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

[Salas]

Q5 7.69-7.69. Q1 8.01/8.01. Q2 8.16/8.17. The 7.42-7.42 for (R7) 7.85-7,85 Q3 are OK for B1 type buffer and right B+ Vdrops in that schema.

[kstlfido]

Roger. Thanks!

[kstlfido]

Quick question-

I spotted a small heatsink on one of the small TO92 devices on SGregory's 1.2R shunt. I tried searching but could not find it.

Was there a sink on one of the TO92's? If so, which one?

Thank you- Kent

[Salas]

He uses higher B+ and he helped the BC546. You will probably not need it.

[Tea-Bag]

Can someone post a link to the 'teflon caps, from Texas' that was raved about?
I remember seeing this, possibly not on this thread. T

[merlin el mago]

Originally Posted by Tea-Bag

Can someone post a link to the 'teflon caps, from Texas' that was raved about?
I remember seeing this, possibly not on this thread. T

Surplus USA Film Capacitors Teflon Polycarbonate Polyester Polypropylene

Ask Markus matched pairs, his e-mail: mailto: marko@33audio.com

Cheers

Felipe