Review and Measurements of Hypex NC400 DIY Amp

[ehabheikal]

Just keep in mind that one also needs to consider other factors - gain, intermodulation distortion, perhaps damping factor, and I'm sure others I'm forgetting about. But yes, while one cannot say for certain, I would say there's a good chance a 252 and a 400 are going to sound the same (when driven to volumes that are within the power handling capacity of each one, given that the 252 is less powerful).

Since you seem to know much more than me, here is my situation

I have bought used smg magnepans each with its own bass panel, sound is a huge upgrade from my old polks with a emotiva bassx a-300.

I was thinking of either upgrading the amp to a hypex/purify for 800 to 1200usd
or
get one of the great measuring revel speakers m105 or m106 for a bit over 1200usd i think

Which will make a bigger change in quality?

The thing is I am in Egypt and our selection is quite limited, i have to import a lot of stuff ( we have limited selection and even the few available do not have models on display to hear, they usually order for you ( audiophile grade, stuff like polk and yamaha entry level is available mostly ).

 

[tmtomh]

I'm actually not nearly as knowledgeable as a lot of other people here, so I hope others will weigh in.

Magnepans - cool!

I see their rated efficiency is 85dB. That's not high efficiency but it's not super-low either. I would say it's at the low end of average efficiency. I know planar speakers can be hard to drive, so if it were me I would go with the higher capacity amplifier - I would not go with a Hype 252 for example. I'd go with a Hypex 400, 500, 502, or Purifi - or heck, even a Hypex 1200 if you could afford it.

But beyond that I'm afraid I can't advise you. But I am sure others here can help.

 

[JimB]

We are measuring the distortion produced by a 10 k tone, so the first distortion product is at 20k.

Adding to this (piling on?), any normal undistorted music content will be lower at 10 KHz than average, so you'll be on a lower power curve when music starts to clip. If 28 watts (still high), the THD is about 0.005%. Next, as Julf implies, not all of that distortion will be the second harmonic - maybe half (the rest at the even higher frequencies of 30 KHz, 40 KHz, etc.). So, half of 0.005% (=0.0025%) of 28W is 0.00035% of 200W (-109 dB). Now, at any age, our hearing is less sensitive at such high frequencies - at least 10-20dB worse, so calling it -15dB would equal -124 dB perceived. What? You're not 20 years old? Maybe -30 dB more. -154 dB. I KNOW I can't "hear" that.

 

[lucadoc]

Hi all,

I've bought a second hand dual mono NC400 amp: do you know if I can connect in parallel a neutrik speakon cable for my BKelectronics subwoofer ?

 

[Julf]

I've bought a second hand dual mono NC400 amp: do you know if I can connect in parallel a neutrik speakon cable for my BKelectronics subwoofer ?

In parallel with the regular speaker? Can't see any reason why not.

 

[lucadoc]

Yes to catch high level signal for speakers and feed the subwoofer. I remember having read 'somewhere' that hypex module didn't like too much this kind of connection.

 

[Julf]

Yes to catch high level signal for speakers and feed the subwoofer. I remember having read 'somewhere' that hypex module didn't like too much this kind of connection.

Any long cables with a high-impedance termination are of course antennas for noise, but otherwise I can't see them having an effect.

 

[lucadoc]

Subsidiary question: I use SMSL M500 dac as preamp. Which would be the best gear to cut the signal below 80Hz (for exemple) for main speakers and use a subwoofer with calibration?

I cannot use calibration system at this moment because the dac has no inputs for the sweep tones

 

[lucadoc]

Any long cables with a high-impedance termination are of course antennas for noise, but otherwise I can't see them having an effect.

Thanks

 

[DonH56]

I do not know about the Hypex amps specifically, and high-level subwoofer inputs are typically isolated ("floating"), but any time you connect something other than a speaker to an amplifier output it is worth seeing what the manufacturer says and looking carefully at the topology. Bridged or "balanced" amplifier outputs generally float with respect to ground; think of the amplifier's (+) and (-) output terminals both being driven by separate amplifiers. In that case, connecting the (-) side to ground shorts the output of the amplifier. At best protection circuits shut it down; at worst, dead amp. Make sure neither side of the subwoofer's (or whatever -- an add-on output meter took out one guy's amp) input is grounded when you attach the cable.

I would double-check the sub's manual and/or check with BK just so you know it's not a problem. Just make sure neither side (+ or -) of the sub's high-level input is grounded.

Again, this may not be an issue with your specific amplifier, but is usually good to know and write in the sub's manual if not already there.

BTW, if you are summing to mono for the sub, do not just tie the two amplifier outputs together with the cables to the sub. The sub should have separate, isolated, inputs for the L and R amplifiers. If not, use one side, or build or buy a passive summing circuit to create a mono output. This probably seems obvious, but prior experience tells me it is not obvious to everybody...

HTH - Don

 

[lucadoc]

Hi Don,

You're right it's not obvious, especially for me .

The manual of BKElectronics (as Rel subwoofer) says that for speakon stereo high out you have to connect the positive (red) output of each channel and one negative (black) of your choice. It's a three leads cable.

From the manual:

Please Note: It may not be possible or advisable to connect the high level input directly to an amplifier that has a class d digital output. Please check with the supplier of your amplifier that this form of connection is possible.

If you do have a class d amplifier and are unable to use the high level input, then BK have developed a sonicaly transparent isolator that overcomes this problem. Please contact us for further details.

 

[Julf]

From the manual:

Please Note: It may not be possible or advisable to connect the high level input directly to an amplifier that has a class d digital output. Please check with the supplier of your amplifier that this form of connection is possible.

That pretty much confirms the inputs are not isolated, and it won't work with a floating output.

 

[lucadoc]

I've sent a mail to BKelectronics

 

[March Audio]

The Hypex ncxxxmp modules are ground referenced so it wouldn't be a problem for them. As such I would expect so is the nc400. I will try and find out for sure.

However personally I think it makes much more sense to use the line level inputs on the sub, lower noise etc.

 

[boXem]

Subsidiary question: I use SMSL M500 dac as preamp. Which would be the best gear to cut the signal below 80Hz (for exemple) for main speakers and use a subwoofer with calibration?

I cannot use calibration system at this moment because the dac has no inputs for the sweep tones

Doesn't your sub have line level input?
This would make your life much easier, also for filtering.
M500 XLR -> filter -> NC400
M500 RCA -> sub
Unless you already use all M500 outputs, then a Y-splitter would do the job.

 

[DonH56]

Hi Don,

You're right it's not obvious, especially for me .

The manual of BKElectronics (as Rel subwoofer) says that for speakon stereo high out you have to connect the positive (red) output of each channel and one negative (black) of your choice. It's a three leads cable.

From the manual:

Please Note: It may not be possible or advisable to connect the high level input directly to an amplifier that has a class d digital output. Please check with the supplier of your amplifier that this form of connection is possible.

If you do have a class d amplifier and are unable to use the high level input, then BK have developed a sonicaly transparent isolator that overcomes this problem. Please contact us for further details.

Well, it's a problem with any bridged or balanced (differential) amplifier output, not just class D. Just to be safe, and for future use, I'd get the isolator from them for the sub(s).

The Hypex ncxxxmp are ground referenced so it wouldn't be a problem for them. As such I would expect so is the nc400. I will try and find out for sure.

There's service! I'd wait for confirmation from Alan. Actually, I'd get the isolator anyway so you don't have to worry.

For me, if at all possible, I would use line-level inputs to the sub instead, as noise and distortion is lower and you don't have to run the mains full-range. One of the big benefits of using a sub is taking the load off the main speakers, reducing amp power and speaker distortion; you cannot do that pulling the sub's input off the speakers' outputs.

 

[lucadoc]

The Hypex ncxxxmp modules are ground referenced so it wouldn't be a problem for them. As such I would expect so is the nc400. I will try and find out for sure.

However personally I think it makes much more sense to use the line level inputs on the sub, lower noise etc.

Thanks Alan!

By the way Tom @Bkelectronics answered me:

The problem with class d amplifier is that you cannot connect the black wire on the high level lead to the black speaker terminal, you need to find an alternative return 0V / Gnd. This can be picked up on the outer of a spare phono socket by soldering the black wire to the outer of a phono plug (picture Attached) or via the chassis please see video HERE

 

[lucadoc]

Doesn't your sub have line level input?
This would make your life much easier, also for filtering.
M500 XLR -> filter -> NC400
M500 RCA -> sub
Unless you already use all M500 outputs, then a Y-splitter would do the job.

I think it's my only viable option.

Which kind of filter doesn't affect the sound quality?

 

[Julf]

Thanks Alan!

By the way Tom @Bkelectronics answered me:

The problem with class d amplifier is that you cannot connect the black wire on the high level lead to the black speaker terminal, you need to find an alternative return 0V / Gnd. This can be picked up on the outer of a spare phono socket by soldering the black wire to the outer of a phono plug (picture Attached) or via the chassis please see video HERE

That answer is not entirely correct. It only applies to class D amps with floating/balanced outputs.

 

[Thomas savage]

Iv removed a post that seemed like a paid advertisement to me .