Ultrasimple mm/mc RIAA preamp 2

[Magura]

Well, could you correct this one

Magura

[Mad_K]

That looks horrible, but correct. You forgot the G-D-S on the second JFet Maybe I'll have to make a real schematic for you

[Magura]

Considering its made in MS-Paint....its ugly but readable. The second fet is left out intetionally, since theyre identical.

Im fine with the "back o' napkin" solution, thats how i do schematics as well. I dont even have software for making schematics or simulation for that kind of matter.

Anyhow, its a great RIAA you made there....ill make a clone right away


Magura

[Magura]

What about substitutes for the SK170GR mosfets??

Any IR or On semi equalents (an ON semi cross ref. search didnt suggest any)???

Magura

[Mad_K]

Originally posted by Magura


Anyhow, its a great RIAA you made there....ill make a clone right away

-I know, I'm going through my record collection like a Mad_Kman

-Good for you.

BTW, have you read this? http://www.audionote.co.uk/anp2.htm

And this ? http://www.audionote.co.uk/anp1.htm (which I think is even better)

edit:
2SK147 and 2SK117GR are drop-ins. Don't really know about any IR or ON parts. Many JFETs can be used, but I believe the Toshiba parts are particulary good sounding units.

One other thing; you need to check the recommended load capacitance for you pickup and plan accordingly. I don't need any extra load C because my ClearAudio Virtouso Wood likes about 100pF and my cable is about 50pF and the Ciss of the 2SK170 is about 30pF pluss you can add a little to those numbers.

edit2: and don't even consider not to use batteries with this circuit... SLA's are recommended I think (and do get 3 of them so you can have more fun with cascoding etc later )

[Magura]

Thanks Mads

Ill make a PCB for this in the nearest future, then it will be a little easier to experiment with values without ending up with a bird nest


Magura

[Mad_K]

Nice! Then make room for a load C... I don't agree with you on the "easier to experiment" part, but we all do it the way we prefer.. We prototype HF circuits up to several GHz on gnd-planes and Mini MountTM at work, but it's obviously not for everyone. -A resistor change can be done in seconds

[Magura]

I like to experiment on a PCB cause the risk that i get confused by something is smaller since the basic circuit is there. I usually CNC cut my PCB's so its no big deal to make such a proto board.

I know your way of doing prototyping is the RF way, and not bad, but it is confusing me to have such a mess of wires and components hanging on to a board in selected spots.

Magura

[PaulH]

Just a question is this schematic for use with MM or MC cartridges?

[Mad_K]

This setup is for MM, but you can use medium output MC provided you make the load R suitable for your pickup. If you need more gain, you could just insert one more JFet stage before the first one for about 90dB gain (it's about 54dB as drawn). Or use a stepup trafo.

edit: if you insert a third stage, the amp inverts the absolute phase.