Simplistic NJFET RIAA

[Salas]

Woo hoo! Whoops, what a doozy. 43 volts is good yes!!
Thanks Nick, spot on.

Yep, "that's good enough for Australia"

 

[Salas]

BTW that Tenma DMM in your picture should be the UNI-T UT139C. I have one. Pretty good features for the price and a big read out. Reliable measuring vs my Fluke 87V and Brymen BM257s. Little slow auto-ranging in resistance mode, but not too slow, in all other modes fast enough. But I don't like the short 15sec back-light auto off, the small print blue letters around the switch, and all those function signaling beep sounds.

 

[Bix]

242 v ac from the wall most of the time where I live. Yes the Tenma I thought it was good value, much nicer than my old one, oscilloscope is next on my shopping list.

 

[Salas]

For entry level, either a four channel Rigol or a two channel Siglent. Keysight's economic 1000 series is nicer though, fast updating & better made, does response plots and better FFT, has onboard function generator versions too.

 

[Bix]

Siglent 1072 is on sale at the moment for $300. Seems pretty good for the money. I’ll definitely check out your recommendation though, I haven’t seen it before. Thanks for the tip.

 

[Salas]

Nah.. save a bit more and get the new Siglent SDS1202X-E

 

[Bix]

Yeah... Alright then I’ll wait a little longer and get the better one.

1 M point FFT math function, that’s gotta be nice!

 

[Salas]

Look well into such models including the Rigol DS1054Z, check their reviews and options costs, also think in terms of a signal generator's cost too. All those mentioned are smoother displaying faster capturing newer gen "economic" category scopes. You will keep this tool for many years to come and it will teach you a ton because you will be able to actually see and analyze your signals now, wow! Try make a balanced long term standing buy.

 

[Pars]

Any recommendations for semi orientation in an FSP? This is how I have it laid out right now:

Ch1: Q1 12.41 Q3Z 657.1 Q4 8.37 Q5 7.77 Q6 8.37 Q7 5.69
Ch2: Q1 12.41 Q3Z 655.6 Q4 8.37 Q5 7.78 Q6 8.56 Q7 5.71

This is for a 40 or possibly a 43dB configuration.

 

[Salas]

Good IDSS & HFE choices

 

[Pars]

Thanks Salas, though I had a mistake on the Q4s:

Ch1: Q1 12.41 Q3Z 657.1 Q4 8.37 Q5 7.77 Q6 8.37 Q7 5.69
Ch2: Q1 12.41 Q3Z 655.6 Q4 8.34 Q5 7.78 Q6 8.56 Q7 5.71

 

[Bix]

Well I’ve had a long think about it and decided on this one EDUX1002G
Haven’t pulled the trigger yet, what do you think? 2 channel enough for my audio hobby, function gen.. quite a bit more expensive but hey.

 

[Salas]

Good choice. It includes a 20MHz function generator with frequency response plotting. Good FFT app also. The gen alone would cost high enough if a separate unit. 50MHz OK for audio work.

 

[Bix]

Pretty exciting stuff, just ordered it. Big investment towards my hobby but I love it. Thanks for your advice Nick you’re a champ. Stand by for many more questions...

 

[Salas]

Congrats on buying your first scope. A Keysight one nonetheless

 

[Bix]

In other news, things are coming along nicely. I’ll get the last bits of the puzzle installed and wait for my new scope to arrive.

 

[Bix]

One channel lit up. No smoke!! So I’ve cranked up vr2x to max and I’m getting 30.83 vdc. Looking at the schematic... do I need to adjust R3x to 10k?

 

[Salas]

More R3x value will do, you are near. If you now got 9.1k replace with one 11k resistor or two 22k resistors in parallel for 11k. Can hide one at the bottom side. That should give useful 30.5V to 35.7V adjust range with the 2.56mA current you probably now got in the Vref.

 

[Bix]

Time to order more resistors all good though. Can’t wait to crank it up!

 

[Salas]

Do try 10k R3x that you got in hand for now. It will maybe suffice for your TP1-TP2 adjust needs. I can't be sure of the exact JFET current you now got in the Vref. I am speculating it from your results but there is some tolerance. The other channel might not need something else even, depends on what Q3x JFET IDSS it chanced.