Hi! I have traced the Naim NA322/4 MM phono board PCB layout from some photos that I found online. I didn’t find any schematic, but there were enough pictures and some descriptions so that I could identify the parts.
Anyway I have some questions left:
1. Can anybody tell me if I have identified the transistors correctly? I am not absolutely sure which of the 10 transistors are ZTX384 and which are ZTX214.
It was hard to tell this from the pictures. Unfortunately I don’t understand the circuit enough and don’t have enough background knowledge to really be able to figure this out logically.
2. Is the polarity of the tantalum caps correct?
3. I can use BC560 instead of ZTX214 and BC550 instead of ZTX384, right?
4. Do the transistors have to be matched? And which have to be matched?
Thanks so much in advance!
Anyway I have some questions left:
1. Can anybody tell me if I have identified the transistors correctly? I am not absolutely sure which of the 10 transistors are ZTX384 and which are ZTX214.
It was hard to tell this from the pictures. Unfortunately I don’t understand the circuit enough and don’t have enough background knowledge to really be able to figure this out logically.
2. Is the polarity of the tantalum caps correct?
3. I can use BC560 instead of ZTX214 and BC550 instead of ZTX384, right?
4. Do the transistors have to be matched? And which have to be matched?
Thanks so much in advance!
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Have not checked it in detail, but looks fine to me, if drawn a bit unusually. The two CCSs can be made easier on the eye by mirroring T3 and T9 and positioning T3 similarly to T9.
Good job!
Good job!
Polarity of the caps is fine an i see no need to match the transistors as there is sufficient NFB to take care of gain mismatches.
Great, thanks very much! And thanks for the advice about the transistors in the schematic – I’m not used to drawing schematics, so I was aware that it might look bit unusual. But I’m glad it’s not completely unreadable. 🙂
I have drawn the schematic once again. It should look better now and more friendly to the eye 🙂 Just in case anybody else wants to use it.
Nice! One important thing to notice is that the transistor orientation in my layout is for ZTX834 and ZTX214. The pinout of the BC550C and BC560C is reversed. Just put them in the other way around!
JimSalabim - Thank You ! I started making the circuit Board . About Pinout 550/560 I know . About a result work - I write on this forum ... I like vintage schematics . And I have some preamps built from the old schematics . They sound great .
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An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
.....Very good sound !
JimSalabim - Thanks for the scheme ! I applied a gain of 40 dB . I also want to add switching capacitance and resistance input . It will soon .
And yes I do know how close it is and why i is slightly different -with added power rail decoupling and more modern component selections, this is actually superior to the Naim circuit.
Your execution looks great - I assume it sounds as good as it looks
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Hello everybody! Almost a year has passed . I changed the design of the preamp . I made a motherboard with star grounding . Made the input capacity switch ( 100, 150, 200, 250 pf ). Made the input resistance switch ( 22k, 33k, 47k , 62k, 75k, 100k). Installed gold-plated pins on the preamp Board . Now the Board is easily removed-if necessary . I still like the sound of that .
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Hello vsmusic,
your amp looks great and the possibility to adjust input capacity and input resistance make it very flexible. Short question regarding the input capacity.
@all,
is it sufficient enough to just replace the 470pF polystyrene cap? There are any side effectsto be expected by replacing this cap with f.e. 100pF cap?
your amp looks great and the possibility to adjust input capacity and input resistance make it very flexible. Short question regarding the input capacity.
@all,
is it sufficient enough to just replace the 470pF polystyrene cap? There are any side effectsto be expected by replacing this cap with f.e. 100pF cap?
Hello! I changed the 470 pf capacity on the board to a 100 pf rating . Additional capacity ratings are connected via a switch on the front panel . No negative consequences were identified .Signal paths to the capacitance and resistance setting switches pass through the motherboard .
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