Salas congratulation for this super simple mc setup.With my Xerxes sme Dynavector 17d3 ortofon mc30 super mkii, cj pv12 pre it plays very clear,all organs it sounds with "air" full of body in classic music.sorry for my bad english iam not expert in technical but i know what i hear and this it is a exellent simple musical mc pre.Thanks
Hi, Salas
Thanks for the wonderful pre pre. I made one as per your schematic, it sounds much better to me than my pair of Lundhal 1678 SUT .
I have two questions,
Except improvement in noise level, will I benefit in sonic performance as well from paralleling 2 more 2SK170 ?
If I do parallel 2 more JFET , and I also want to increase the gain to 24db, do I need to change the 7809 to 7815 and increase the raw DC to 18V or 20V as you suggested in an early post? How do I calculate R2 if need 24db with 4 Jfet in parallel.
thanks
You made the two JFET pre-pre? More semiconductors also bring more junctions and more parasitic capacitance, not only extra transconductance. If your cartridge has so low output that you still have relatively weak signal with this circuit, and hiss is intrusive, then consider changes. Because subjectively everybody seems happy with it in this thread. Not to unbalance it with tweaks if avoidable. Link me the technical suggestions post please.
that what you suggested to make 28db gain in page 8 of this thread.
yes, I build the 2 Jfet pre-pre to replace my Lundhal 1678 SUT which has 24db.
I have a Denon DL-103R, and it has 0.25mv output. I feel I need a bit more gain from the pre-pre I build.
I don't have 250 ohm resistor, I replaced R1 with 270 ohm instead. It sounds all right, gain is increased a bit from what I can feel.
Voltage across R1 now is 4.6V, the other end of R1 is 7.4V. is the drain voltage 2.8V too low now?
Also, my MM tube phono stage has around 0.5mv noise level, now with the this pre-pre it is around 1.5mv. No hum, all I can hear is hiss. It's not too bad to me, but can this be improved by replacing eBay 2Sk170 with BF826?
Better to have 12V regulator now. For more VDS. Can you post a close up picture of those 2SK170s you used? I want to check their originality clues. BF862 isn't much better and usually has much IDSS in a little SMD package so bit difficult to use without degeneration resistors for best noise without heat. Except you must, in case the 2SK170s are fake so the gain is not as expected and the hiss higher. Do you have any 2SK369s by the way?
Try with four BF862 in parallel but with independent 10 Ohm resistors for each one's source pin. Those most possibly can't be fakes.
P.S. As kzeprf22 kindly noted in a message he sent to me, such a single stage common source pre-pre phase inverts the signal. It may be technically obvious to many members but its better to be stated as well.
P.S. As kzeprf22 kindly noted in a message he sent to me, such a single stage common source pre-pre phase inverts the signal. It may be technically obvious to many members but its better to be stated as well.
I replaced 9V reg with 12V one, it sounds much better now.
I will try 4X BF862 in parallel and see. But R1 still 250ohm if I need 24db gain? how about reg voltage ?
I have 50-100 BF862s and a test socket but I can't readily breadboard them as a pre-pre to answer you for sure. Because SMD I would need to make an etched test board for that. I'll see if I can simulate the whole configuration instead.
Will reply later. You put the thing together to see how it works. Even with the simplest circuits you never know before actually building them. Their gates may tune with the incoming signal wire and you could hear the AM radio for instance. They were originally designed for that.
Will reply later. You put the thing together to see how it works. Even with the simplest circuits you never know before actually building them. Their gates may tune with the incoming signal wire and you could hear the AM radio for instance. They were originally designed for that.
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I have powered this pre-amp with batteries. 5 x AA = 7.5V on top of R1 which i tried in different values. After some hum problems i got it almost silent. The only thing is that it sounds harsh. Capacitors 1000uF to 10000uF after the batteries do not really help. What can I do, or is this normal ?
Paralleled BF862's can sometimes oscillate at 100's of MHz without gate stoppers, depends on careful attention to layout.
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