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323N Schematic?

Yank

Yank

Bulbous Also Tapered
Has anyone got a NA323-N schematic?

I thought my 323 boards were S, but it turns out they're N, and I need the gain. With a schematic for the N I could see what components need to be changed, if possible. Thanks for any help.

robmill said:
Standard K boards will overload with a 2.5mV cartridge which is why they produced these:

323N MM phono boards, 2 mV, 47 KΩ
323E MC phono boards, 400 µV, 560 Ω
323K MC phono boards, 100 µV, 560 Ω
323S MC phono boards, 100 µV, 470 Ω
328 Variable boards, 75-300 mV, 47 kΩ
326 Line-level "blank" boards

The 323N was dropped for the 322 BUT both were manufactured together for years. The 323E and N were discontinued by Naim ages ago. The 323E is meant for high output MC.

Also the 20x has an output of nearer 3mV and prefers a load resistance of below 300ohms. The problem with Naim phonostages is that you cannot adjust or even tweak for optimum load. I had a XX1-L years back and it sounded quite 'loose' above 470ohms. It was the same with the XX2 Mk2, so I cannot image 560ohms on a 20X is actually the best thing. It needs to be about 100 - 220 ohms maximum IMHO... and many other users
Click to expand...
 
I've got S and K, but I think the changes for N must be more extensive, I was hoping someone would know so that I don't have to physically trace it out, which would require removing my preamp from service.

With any luck it's just a half-dozen resistors or so per channel? Without looking, I'd imagine the gain around the feedback loop would be different, and perhaps the bias for the input? If the stated 47K input load is correct then the bias for the parallel array of input transistors would have to have a higher-impedance voltage divider.
 
When I went looking for the 5xx MM board schematic I had no joy and had to trace it. I don't know the 323 but if it's like mine then it is quite different from the MC circuit - two very similar gain stages one after the other. If you just want to change the gain then you should be able to find the right resistors in relation to the two 47uF feedback caps. I did this when I decided to change my MM cartridge for an MC - I still have to whack the preamp vol up near max though
 
simonbrown said:
When I went looking for the 5xx MM board schematic I had no joy and had to trace it. I don't know the 323 but if it's like mine then it is quite different from the MC circuit - two very similar gain stages one after the other. If you just want to change the gain then you should be able to find the right resistors in relation to the two 47uF feedback caps. I did this when I decided to change my MM cartridge for an MC - I still have to whack the preamp vol up near max though
Click to expand...

What you describe sounds more like the 322/522 MM stage. The 323N has the MC topology with the five input transistors in parallel. It's a different kettle of fish altogether. I don't think trying to a convert a 322/522 to MC gain levels would meet with much success. But the 323N appears to use at least the same circuit board and semiconductors as the 323S and 323K. They all use the same RIAA so I don't have to worry about upsetting that.

If it's more than just changing a few resistors, I'll just have to look for a set of 323S boards.

It was just a bit startling to install my low-output MC Cartridge, swap out the old 322 boards for a set of 323s, and find myself having no gain or dynamics. That's when I noticed the "N" stickers on the caps...
 
BTW my 323N is new enough to be the /5 variant with the little ceramic cap tacked to the back of the output transistor.
 
Hi Yank

This is a curious phono-card, never heard of it before. As audioflyer says, if you could post some nice hi-res front and back pics of the board, we can quickly trace out the schematic.

Regards
Peter
 
Well, I pulled the preamp apart today to attempt to trace out the circuit, and as soon as I saw the 560-ohm input load I started feeling pangs of embarrassment. The 6.8nF load cap on the input confirmed it, this is a K board with the wrong sticker on it.

So anyway false alarm.

I feel like the boy who cried wolf.

So all I need to do is get a pair of 100 ohm resistors for my ZYX cartridge, and 1nF caps and be done with it.

Still, the gain is absurdly low, I don't think I could make the amp clip even with the volume up all the way, and anything resembling "average" listening level requires volume knob up past 3:00 o'clock for starters. At least it's quiet.
 
Don't worry about it. At 6 o'clock it'll blow yer socks off!

The volume pot is logarithmic and not linear. Just enjoy!

Cheers,

DV
 
If you know your way round Neil McB's site you'll also find instructions on how to increase the gain of the 323 circuit...

Note that the gain can easily be adjusted (I've tried changing it by a factor 2 with no problem) by changing out R13 (220R). For example putting in a 110R in its place will double the gain, which may be useful if you are trying to match the subjective output from LP and line inputs (particularly in combination with lowering of the line stage gain... see below). Personally I have found that doubling the gain can give the phono stage more 'grip' and slam with low output moving coils (eg, the original Linn Arkiv).
 
neiljadman said:
If you know your way round Neil McB's site you'll also find instructions on how to increase the gain of the 323 circuit...

Note that the gain can easily be adjusted (I've tried changing it by a factor 2 with no problem) by changing out R13 (220R). For example putting in a 110R in its place will double the gain, which may be useful if you are trying to match the subjective output from LP and line inputs (particularly in combination with lowering of the line stage gain... see below). Personally I have found that doubling the gain can give the phono stage more 'grip' and slam with low output moving coils (eg, the original Linn Arkiv).
Click to expand...

Grip and slam is exactly what it needs, it's all very "polite" right now. But then the cartridge is still new, but that doesn't seem like the kind of thing that would improve with break-in.

I've heard this same sort of "politeness" in systems with passive preamps, where the introduction of an extra gain stage, despite the necessary degradation, was deemed a net improvement.

So I think I'll give this a try.
 
Well, my order of resistors came today, along with TSHAs for HackerNAP gain stage supply, so I got busy with my phono cards. 110 ohms for input load and feedback resistors, and while I was in there I replaced the red Roderstein electrolytics with Nichicon Muse -- black ones for the Vbe, and green NP ones for the feedback cap.

After cleaning up the solder spills, all I can tell at the moment is that (1) they do pass signal and (B) there is a bit more gain. Doesn't seem to have done any harm anyway, but too soon to tell if it's much better.

And with my eyesight, not doing any harm is a major accomplishment. I had to put on two pairs of reading glasses to make the solder joints.
 
neiljadman said:
How do you like these? I have a big bag of them (47uF/35v?) and have never really used them.
Click to expand...

I can't say that I've done a scientific survey, since my only use for them so far was to replace the aging Roederstein cap on the 323 phono card. The phono does seem clearer and cleaner, but I changed too many things at once -- raised the gain a bit, corrected the cartridge load, and replaced both the feedback cap and the Vbe cap.

But they don't seem to have done any harm.
 
I will say that it sounds more "lively" than before. I was previously suffering from excessive "politeness" but after making the changes, and letting it break in for a couple of days, it's rockin' out pretty good right now on an old green-label WB pressing of Van Morrison's "His Band And The Street Choir".

Even though they're non-polar, I put the short lead on the "-" side, just for the sake of consistency.
 
One more question about 323 cards -- the 1nF/6.8nF input load capacitor, is it necessary for the stable operation of the preamp, or it it just for cartridge EQ? My cartridge doesn't specify an input capacitance value, so rather than try to find a pair of small 1nF caps I was wondering if I could just remove the 6.8uF ones and leave it open with just the resistive load?
 
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