Hi, I have two schematic for naim nap250. One is from my kit. 470pf cap series with 680ohm resistor or series with 390ohm resistor. Which is correct?
In my kit, 680ohm&470pf series and looks like amp is working.
In my kit, 680ohm&470pf series and looks like amp is working.
680 on top / 390 on bottom is correct.
The Sziklai pair does not act identically to the emitter follower pair.
The Sziklai pair does not act identically to the emitter follower pair.
Now, I read my post. It's really not clear 🙂 Sorry,
JeffYoung, 470pf capacitor series with 680 on top / 390 on bottom are correct you mean?
JeffYoung, 470pf capacitor series with 680 on top / 390 on bottom are correct you mean?
Thank you for your answer!
I bought a kit with schematic. In that kit resistors opposite. I made the kit like that. Now, I changed resistors places.
I have a question as, I only find that, idle current changed with changing that resistors. I don't hear any change in sound? Is this normal?
I bought a kit with schematic. In that kit resistors opposite. I made the kit like that. Now, I changed resistors places.
I have a question as, I only find that, idle current changed with changing that resistors. I don't hear any change in sound? Is this normal?
Julian Vereker (the founder of Naim and the original designer of their amps) supposedly adjusted those values by ear. Lore has it that it was to make the top and bottom phase-consistent.
So if you drink the Kool Aid, at least he could hear the difference. Or, maybe he did it just to even out the idle current.
Hard to know as cancer took him before he gave away many of his secrets....
So if you drink the Kool Aid, at least he could hear the difference. Or, maybe he did it just to even out the idle current.
Hard to know as cancer took him before he gave away many of his secrets....
Hi again,
I tested a few different kind of caps with the same value in my chinese kit. My decision is that;
C7 (in my diagram) is tantal 10uf (they send 10uf elect.),
C10, tantal 100uf (they send 100uf elect.)
C5, elect. 47uf (I'm not satisfied from tantal.They send 47uf elect. I used it)
Diagram is which was send to me, values are mirror 🙂
If you comment I will be gratefull.
View attachment NCC250.pdf
I tested a few different kind of caps with the same value in my chinese kit. My decision is that;
C7 (in my diagram) is tantal 10uf (they send 10uf elect.),
C10, tantal 100uf (they send 100uf elect.)
C5, elect. 47uf (I'm not satisfied from tantal.They send 47uf elect. I used it)
Diagram is which was send to me, values are mirror 🙂
If you comment I will be gratefull.
View attachment NCC250.pdf
I don't think C5 will affect the sound, so any will do.
Electrolytics in C7 and C10 would probably result in lower distortion, but they won't have the characteristic Naim sound.
Electrolytics in C7 and C10 would probably result in lower distortion, but they won't have the characteristic Naim sound.
I find a note for C3, 47pf cap, "Start with 100 pF VAS cap and work down ( scope required ) . Use COG/MPO ceramic or silver mica ( all sound good although other ceramics usually not ) .Never use polystyrene although sonically excellent .It will let go eventually and take your speakers out . Surface mount 1205 types can be excellent ." nigel pearson nap140 comments
I disagree with using silvered mica. They corrupt the signal.
I have never had a polystyrene “let go” in 40 years.
Capacitor construction is really important. You’ll notice that the Naims use a lot of solid tantalums and polystyrenes in the signal path. They do not use electrolytics paralleled with ceramics.
There are a lot of well-intentioned enthusiasts out there who think they can improve the Naim by making circuit changes that seem sensible to them. Vereker was not a naive man. On the contrary, his understanding of complex systems led to this deceptively simple design.
There are a lot of well-intentioned enthusiasts out there who think they can improve the Naim by making circuit changes that seem sensible to them. Vereker was not a naive man. On the contrary, his understanding of complex systems led to this deceptively simple design.
True. Making something simple is very very more difficult than complex doing. Much more knowledge necessary to make things simple.
NAP250 tr5
Some schematic for TR5 shows ZTX108 or ZTX384 or 2N5551.
Ok! I have used 2N5551 and changed with ZTX108, then bias doubled. If they are similar transistors, how the bias doubled?
Some schematic for TR5 shows ZTX108 or ZTX384 or 2N5551.
Ok! I have used 2N5551 and changed with ZTX108, then bias doubled. If they are similar transistors, how the bias doubled?
A pair of 2N5551s could easily be different enough to double the bias, and that's the same transistor. That's why there's a pot to adjust the bias.
