Maybe not a ZTX but an MPSA06 in E-line package. Ian Finch may have more to say on what Naim uses here in different variants. The BC part is fine here, a BC550C better for noise.
I agree, I recently opened up my original NAP 200 and it has MPSA06 installed. I have them in my drawer, which transistor should I substitute in schematic for MPSA06 ?
thanks
Go authentic! MPSA06.
It's great that you own a NAP 200 so you can compare directly.
The NAP200 looks like it uses a single rectifier bridge and centre-tapped transformer output per channel. That's fine too of course. I happen to use two separate transformers with my amplifier, each with dual secondaries which I feed to two bridges and then the smoothing caps.
Attachments
so just to confirm BC546 should be replaced with MPSA06 ?
I am sorry I am asking to omany questions, but I am a novice and I love playing with things as long as there is no smoke
On an unrelated note, for Ian and Gareth and all, I just came across this: Online Tone Generator - generate pure tones of any frequency
It is a simple online tone generator whose frequency can be adjusted with a slider. You can change the L R balance too. I was just feeding this through my audio system, which is attached to a PC, and found it very simple and effective for finding resonances in the room and speakers too. I found a rattle at 218Hz that I'm now working on. I also found I had to open a cabinet door to stop it "singing along".
Little things like this can affect your musical enjoyment and are cheap to remedy.
It is a simple online tone generator whose frequency can be adjusted with a slider. You can change the L R balance too. I was just feeding this through my audio system, which is attached to a PC, and found it very simple and effective for finding resonances in the room and speakers too. I found a rattle at 218Hz that I'm now working on. I also found I had to open a cabinet door to stop it "singing along".
Little things like this can affect your musical enjoyment and are cheap to remedy.
+1
I still have a bryston 4B that I love and some C-Audio are muscular versions of these English amps so musical
Here's a UK seller of esoteric capacitors and other goodies. I've bought one or two things from here such as Mundorf caps. Mostly I use Farnell and Mouser.
Amplifier valve kits, HIFI pre-amplifiers, speaker kits, AMP Parts, upgrade components | Hifi Collective
Amplifier valve kits, HIFI pre-amplifiers, speaker kits, AMP Parts, upgrade components | Hifi Collective
The NAP 200 is actually dual mono - well, electrically dual mono at least. There are 2 sets of 28-0-28V windings, two bridge rectifiers and 2 pairs of electrolytics plus a 12-0-12V winding and electrolytic for the 24V preamp supply. It's quite a breath of fresh air and a more practical, modern and advanced PCB design approach to previous ones which were not exactly the latest tech. It's also by far the best clone to build provided you build it right in a suitably heavy case and provide for extra heat dissipation with a 25 x 6mm section heat spreader bar. I found the rubber isolation board mounting unnecessary but if you work your audio system hard, it could be quite beneficial.
As said earlier, the Zerozone kit is a poor show - it needs a comprehensive review of the parts types with a schematic in hand, which you can find at #1825 in this thread - a great reverse-engineering effort by member Algar-emi.
NAP-140 Clone Amp Kit on Ebay
As said earlier, the Zerozone kit is a poor show - it needs a comprehensive review of the parts types with a schematic in hand, which you can find at #1825 in this thread - a great reverse-engineering effort by member Algar-emi.
NAP-140 Clone Amp Kit on Ebay
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I do believe the earlier DACs that were expensive were far better than the lower cost ones. There have been a lot of advances in DAC chip engineering since then and some companies have done much to take advantage of this e.g. Schitt. Their stuff looks good although I haven't auditioned it.
I've marked up the amplifier schematic with what I would do.
--> No warranty implied <--
You may get conflicting advice here (very rare in DiyAudio) and I am not always going to explain things because I am secretive. But you may want to assemble one board this way as a comparison.
Also, your transistors are not the Naim choices and not matched so this will cause an unpredictably worse result. Unless you use Naim's build process it will not sound as good as a Naim. It is up to you whether you decide to spend extra money on these parts.
Schematic changes
- Remove crossed out parts. Replace with wire as appropriate.
- Use 35V tantalums for C7 & C10. DOn't use lower voltage ones as they may not like being reverse biased during half the music signal. IF YOU ARE NOT EXPERIENCED building these then use electrolytics for power-on and once you are sure the dc offsets are ok then change to tantalums.
- the base networks on the darlingtons will not be correct for these transistors. I am not going to explain how to correct them but you stand a better chance if you use MJE243/253 drivers like Naim does.
- Inputs better with BC550C low noise.
- Adjust R26 (Q8 emitter resistor) to get the dc offset small. The BC546 is ok but it is different from the ZTX part Naim uses and the Vbe will be different.
- Remove output coil, replace 15ohm with 0.22.
Power Supply
The supply should be transformer with separate winding for each rail, two bridges & two smoothing caps per channel. Use good caps as I mentioned earlier. Don't wire lots of caps together. You need to be careful with your grounding paths. This is very important and there is lots of advice around here about that already.
I can't comment on the regulated supply yet. I need to find time to study it. But use the board unregulated to start with anyway. See how it sounds.
I'm not sure if I'm missing something but even with the suggested changes there seem to be quite a few resistors the values of which are wildly different from those in many schematics of the NAP140/200/250 /ncc200 that I've seen.
eg R001 71R Should be 100k ?
R026 92R " " 620R ?
R28 51R " " 8R2 ?
The most recently fitted electrolytics are standard Kemet ALT22A type, if I recall correctly. For a very short period I fitted Kendeil KO5 but I was uneasy about it - probably because of the idea as much as the perception of change from a past audio experience.
You are quite right. Some of the resistor values are backwards. So the 100R is shown as R001 and the 620R is R026 and the 8.2R is R2.8.
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I'm sure you are right. It goes beyond the DAC chip of course...clock quality, noise, component quality, power supply.
But I am willing to follow your advice and modernize; would you please buy me one of these for my birthday this month? Alpha DAC Reference Series 2 MQA — Berkeley Audio Design
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I spent an hour looking at detailed pictures of that beast ... IMHO each channel is a stereo bridged 200W : 4 cells are + and - (2 NPN and 2 PNP) output branchs, 2 cells are the drivers ... So : 800W @ 8ohms , i.e. theoritically 1600W 4 ohms, 3200W 2 ohms and 6400 at 1 ohm
...if power cord is bigger than the genuine one
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Yes each of the four power amp boards contain the same type of transistor. 2 boards are NPN and two are PNP. Steve Sells states they use "positive feedback error cancellation" and there is no global NFB around the voltage gain stage.I spent an hour looking at detailed pictures of that beast ... IMHO each channel is a stereo bridged 200W : 4 cells are + and - (2 NPN and 2 PNP) output branchs, 2 cells are the drivers ... So : 800W @ 8ohms , i.e. theoritically 1600W 4 ohms, 3200W 2 ohms and 6400 at 1 ohm
...if power cord is bigger than the genuine one
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