Hypex NC400 - DIY Mods

[restorer-john]

Nice! where can I find this schematic? That's way better for me to do modifications on the nc400 board, could you please share this if possible?

NAD M22 service manual in the public domain.

 

[Killingbeans]

In the image below, I replaced the stock ceramic fuse (8A slow blow) in the SMPS600N400 power supplies with an equivalent one from HiFi-Tuning (in my case the Supreme 3 Silver Fuse). Note that this fuse is directional, meaning that the arrow on the body of the fuse needs to point in the direction of conventional current flow as shown below. If you place it the other way around, it just won't sound right (strange eh?).

Not sure whether I should ask you to share whatever you're smoking, or just plead you to stop smoking it

 

[littlepotato_as]

NAD M22 service manual in the public domain.

Thanks! but I think that one is for nc400 OEM, is there any released schematic for nc400 DIY module?

 

[littlepotato_as]

NAD M22 service manual in the public domain.

Appreciated! but I think that one is for nc400 OEM, is there any released schematic for nc400 DIY module?

 

[Feyire]

Nice! where can I find this schematic? That's way better for me to do modifications on the nc400 board, could you please share this if possible?

As @restorer-john pointed out, that section is an excerpt from the NAD M22 Service Manual. They use a custom made NC400 board, but the LC output filter is the same as the NC400 DIY board.

What modifications are you planning to do?

 

[sq225917]

Make it worse?

 

[littlepotato_as]

As @restorer-john pointed out, that section is an excerpt from the NAD M22 Service Manual. They use a custom made NC400 board, but the LC output filter is the same as the NC400 DIY board.

What modifications are you planning to do?

Thanks for the reply, not sure NC400 DIY and NC400 OEM are the same design, looks like NC400 DIY is smaller than the OEM version. Can't find the schematic of NC400 DIY on the internet..

 

[MCBowler]

- Removal/tweaking of SMD resistor R141 (Sort of optional - depends on your overall system configuration)
The goal of removing/tweaking R141 is to be able to adjust the gain of the amplifier module. Typically, you'll want to remove/tweak R141 in order to lower the gain. Full removal of R141 results in a 10dB reduction. This has a number of benefits:

• Higher feedback
• Higher signal-to-noise ratio

So given the list of mods I specified above, I personally was able to successfully implement the capacitor mod so far, with a very positive result on both of my Hypex NC400 DIY kits. I'd describe the perceived listening difference as a more pure and smoother sound with enhanced clarity. I find it most noticeable when I focus on listening to the vocals. My experience in this regard is very similar to others who implemented this mod and reported their experiences.

In the near future, I also plan on attempting the inductor mod and the gain resistor mod. I plan to report back to this thread with my experiences of both.

I'd appreciate it if anyone else on these forums, who has modified or attempted to modify their NC400 modules, share their experiences and thoughts.

DUDE... I did it.

I have an extremely simple setup, miniDSP SHD into these NC400 monsters into Tekton MOAB. Before removing the resistor I could only ever get to -20db on the miniDSP output without ruining my hearing. NOW I can push to 0db still being loud beyond any reasonable listening level. Chilling at -20db instead of -30db for normal listening, YES, it sounds better.. more dynamic. It works!

I suppose if I wanted to solve my problem another way I could have used a 10db or 20db XLR pad for 25$ a piece, but this way I get a little more performance out of the NC400 too while sacrificing maximum amplification. I'm guessing the most improvement was due to using the full output of the miniDSP SHD.

Even listening to Beat It on Spotify Connect is WAY more dynamic. If you have a digital volume control and want max dynamic performance, TRY an XLR pad OR this mod.

 

[HarmonicTHD]

DUDE... I did it.

I have an extremely simple setup, miniDSP SHD into these NC400 monsters into Tekton MOAB. Before removing the resistor I could only ever get to -20db on the miniDSP output without ruining my hearing. NOW I can push to 0db still being loud beyond any reasonable listening level. Chilling at -20db instead of -30db for normal listening, YES, it sounds better.. more dynamic. It works!

I suppose if I wanted to solve my problem another way I could have used a 10db or 20db XLR pad for 25$ a piece, but this way I get a little more performance out of the NC400 too while sacrificing maximum amplification. I'm guessing the most improvement was due to using the full output of the miniDSP SHD.

Even listening to Beat It on Spotify Connect is WAY more dynamic. If you have a digital volume control and want max dynamic performance, TRY an XLR pad OR this mod.

So you made it louder. What about the signal quality though? You did read the remarks on stability, right?

 

[MCBowler]

So you made it louder. What about the signal quality though? You did read the remarks on stability, right?

I meant, I can push the output on the miniDSP to 0db (0 being the highest output it can make) if I want to without blowing anything up. The total gain of the AMP is reduced probably 10db. No, I missed stability remarks.

edit: I don't believe there is a stability issue. I think it just lowers the gain when removing the resistor. I kinda wish I just got an inline xlr passive volume control instead... that way I can peg out the miniDSP at 0db and control volume passively. I can still do that! , but I'll never get full gain out of the amp, not that I need to.


Something like this could replace the volume control on miniDSP SHD if I hard set it at max volume... https://www.sweetwater.com/store/de...tereo-audio-attenuator-and-monitor-controller

 

[boXem]

I meant, I can push the output on the miniDSP to 0db (0 being the highest output it can make) if I want to without blowing anything up. The total gain of the AMP is reduced probably 10db. No, I missed stability remarks.

edit: I don't believe there is a stability issue. I think it just lowers the gain when removing the resistor. I kinda wish I just got an inline xlr passive volume control instead... that way I can peg out the miniDSP at 0db and control volume passively. I can still do that! , but I'll never get full gain out of the amp, not that I need to.


Something like this could replace the volume control on miniDSP SHD if I hard set it at max volume... https://www.sweetwater.com/store/de...tereo-audio-attenuator-and-monitor-controller

Actually, you change the buffer gain to 0 dB when removing the resistor.

 

[Feyire]

DUDE... I did it.

Even listening to Beat It on Spotify Connect is WAY more dynamic. If you have a digital volume control and want max dynamic performance, TRY an XLR pad OR this mod.

Removing the small resistor can be tricky, and you want to be especially careful that you don't accidentally remove one of the solder pads in case you want to be able to solder the resistor back on at some later stage, or if you intend to do try further resistor value swapping.

As such, I'm glad to hear it all worked out well for you and that you perceived an audible improvement.

 

[clanon]

With the new air core inductor installed (yeah, that's right, it's absolutely massive and no, I haven't experienced any EMI issues):

View attachment 132442

GREAT JOB!
PS: is that 10uH...? copper width , turns length...(could it be made with copper tape...?)

 

[Killingbeans]

Please don't.... I beg you.

 

[Feyire]

GREAT JOB!
PS: is that 10uH...? copper width , turns length...(could it be made with copper tape...?)

Thanks, and yes, it is a 10 μH inductor - 12 AWG 44mm copper foil height.

Note that I didn't make the inductor myself, but I ordered one that fits this specification. The available space for a replacement inductor on the NC400 PCB is also very limited, so you'll need to be sure it can fit.

Are you actually serious about trying this mod? If so, I'm happy to share the exact inductor I used, as I can't be as confident of success/improvement from a homemade inductor.

 

[clanon]

Are you actually serious about trying this mod? If so, I'm happy to share the exact inductor I used, as I can't be as confident of success/improvement from a homemade inductor.

Thankz , trying to collect data for class D best designs...

 

[littlepotato_as]

I don't have any before and after measurements, simply because I don't have any analyser/measurement equipment. When I did the capacitor mod, I was relying on the positive feedback of others who have implemented it - basically a leap of faith. If there is anyone in the Netherlands who has a high precision analyser, and is curious and willing to come by and measure the effect of the mods, I'd be happy to invite them over for a chat and measurement session.


I believe Bruno stated a long time ago on another forum that removing R141 would increase the feedback loop and therefore also increase the measured performance. Whether that performance improvement is significant, I don't know, perhaps not, but I'd consider any improvement most welcome. My positive subjective experience of the mod is backed up by others who did the same. If you asked me if I'd want to go back to the un-modded sound of the module? I'd give that a definitive no thanks.


This is a good question. As far I as can tell, it still looks like a similar type of iron core litz wire inductor is used in the Purifi 1ET400A module - so no? Maybe this issue will be addressed in the more powerful Purifi module that is coming soon. Perhaps @Bruno Putzeys could shed some light on this.

Below on the left is the NC400 inductor and on the right is the Purifi 1ET400A one (The stickers seem to suggest something has changed, but physically they look very similar):
View attachment 124738

Just curious what's the name of these fancy inductor? I just can't find them on the web, is this something that's being customized?

 

[yodog]

This thread makes me want to buy a pair of these diy kits from madisound.

 

[clanon]

Just curious what's the name of these fancy inductor? I just can't find them on the web, is this something that's being customized?

i think they are custom made...Litz wire high power ...

 

[Feyire]

- Removal/tweaking of SMD resistor R141 (Sort of optional - depends on your overall system configuration)
The goal of removing/tweaking R141 is to be able to adjust the gain of the amplifier module. Typically, you'll want to remove/tweak R141 in order to lower the gain. Full removal of R141 results in a 10dB reduction. This has a number of benefits:

• Higher feedback
• Higher signal-to-noise ratio

A curious fellow on the Klipsch forums implemented this tweak (complete removal of the resistor) and was also kind enough to provide before and after measurements in this thread for those interested.

Some excerpts are shown below.

Before mod:

After: