Modifying a NAD 302

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#182
Hotep said:
I added a couple more of 2.8 mF PEH227 to the PSU. The noise floor is perhaps a little lower and a lot smoother, but it persists. Other than that the sound seems to have become even more enjoyable and powerful and serious and detailed. Well, detail didn't change, but everything's more effortless, more musical so it may be perceived as higher resolution. Or I still can't get over how amazing my headphones sound with this amp truly awesome. For sure the noise floor has improved (smoother, less audible) and overall enjoyableness factor has raised or at the very least hasn't become reduced.
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The housings of my PEG227s are not insulated. The negative pol/voltage is applied to these. I would insulate each individual capacitor. The simplest thing would be adhesive tape.
 
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#184
Hotep said:
#92

I've been meaning to do this. Removed J425, J412 and put in bridges at C440, C439. Put the driver transistors back in one more time.

I've heard too many different configurations today to be able to tell if there's any difference. Plays great. Perhaps even better, but also likely I'm still not used to how amazing my headphones play with this amplifier. Truly awesome.
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There was still a mistake here. The asymmetrical representation of the circuit diagram initially made me realize that Q413/Q414 was connected to the separate regulated voltage. Otherwise, as recommended: no separate power supply, instead remove the capacitor on the NAD 302 case and insert a bridge. As described.
 
#185
Hotep said:
I'll have to run this through AI a few times to understand, but are you saying the 302 has a PP input? If I have a balanced DAC, could I use advantage of this instead of using the RCA inputs?

Just yesterday reworked my RCA cables - sound like a dream. Six silver cores per pole in teflon tubes. Short as that greatly reduces noise floor in unbalanced cables. Much more effective than any screen! The silver is from Latvian folk named Lavricables. Not the best (some OCC silver is on another level) but it's great for the price. And it's as good or better than any copper I've heard regardless of price!
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For stranded wires, I recommend lacquer-insulated ones. This is because the single leads, if they are not individually insulated, touch each other, move in relation to each other and recharges occur, which are sometimes clearly audible. As crackling or hissing, for example. In addition, the signal is "smeared" with uninsulated strands. Through undefined paths. But it is also smeared with insulated strands: e.g. due to minimal length differences between the individual leads. But much less;-)
 
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#187
cumbb said:
There was still a mistake here. The asymmetrical representation of the circuit diagram initially made me realize that Q413/Q414 was connected to the separate regulated voltage. Otherwise, as recommended: no separate power supply, instead remove the capacitor on the NAD 302 case and insert a bridge. As described.
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Pardon me, what was the mistake? Did I do everything correctly? I have successfully avoided the regulated PSU here I believe. Running everything on common PSU should create more homogeneity than otherwise, which was the reason to do it. I know I can be slow to get things but thank you for your patience 🙏🏻

I would insulate each individual capacitor.
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Yeah one of the positive leads looks pretty dangerously close to the other channels casings, but this is temporary and still pretty safe despite looking quite close. But it is noted, isolating the housings is a fair idea.
 
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#191
#24
Hotep said:
Edit: C 429, C 430 replaced with 100uF and what I'm hearing is a more powerful sound, more powerful low end as far as I can tell.
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Hey guys,

I'm going through the same modifications on a new NAD 302 amplifier I got and this time I'm comparing and listening with my headphones.

So far so good, but C 429 and 430 film cap of 100nF replaced by electrolytic 100 uF was a mistake. I hear less clarity, more mightyness, softer and rounder bass. I put the C 301 and C 302 in their place (about the same value) and the sound improved again, clarity, bass tightness! So this one was a mistake in my opinion and as far as I can hear.

On with the other modifications now.
 
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