VTV Hypex NC1200 Tear Down and Recommendation

[goryu]

I'll definitely check this (I'm the OP) when I get a chance to open it up again. Either way, from that it would appear that the PS VTV is using in this build is not applicable/unsound in that configuration. I will say I've had no problems whatsoever with the unit in the time since this thread died down and I use the amp every day for home theater use, just two speakers L/R and bass performance is pretty incredible without a subwoofer. Don't notice any distortion, but with bass primarily in movies that would obviously be tricky. Sounds excellent with music too, though.

I think it certainly is worth checking though if you aren't noticing any issues maybe you got one properly wired.

 

[C. Cook]

I think it certainly is worth checking though if you aren't noticing any issues maybe you got one properly wired.

For sure. I just don't know when I'll be able to get around to it, and if you read the earlier part of this thread, things got pretty "heated" - pun intended - so I'm not sure I'll be in a rush to post my results, lol.

 

[goryu]

Well, it's either wired correctly or it isn't, not anything that can be argued about or disputed...

 

[C. Cook]

Well, it's either wired correctly or it isn't, not anything that can be argued about or disputed...

True, true. It's a binary. Either it is, or it isn't. I tend to think it is for the aforementioned reasons (works and sounds great), but I'll definitely let everyone know once I have a chance to take it apart again!

 

[windansea]

Just found this thread. I also have the VTV nc1200. Connected to big maggies. As with the OP, I noticed that the chassis got rather hot to the touch. Not very hot like my Class A forte amp, but relatively hot compared to another amp I had-- PS Audio S300 with ICEpower modules-- the S300 never even got warm.

After reading this thread, I'm going to peek inside the amp. Make sure I've got the right power supply, look around.

Important point: One of my nc1200 modules failed after about 20 months. I sent it back under the VTV warranty and got it back with a new module and it's been working fine. But I wonder if the heat was what caused the module to fail. For summer, maybe I should leave the faceplate open and put a quiet computer fan there.

 

[windansea]

Here are pics of the guts of my VTV nc1200 stereo amp. During August I'm going to leave the face plate open and put a computer fan in the front to draw heat out.

 

[kiwifi]

Here are pics of the guts of my VTV nc1200 stereo amp. During August I'm going to leave the face plate open and put a computer fan in the front to draw heat out.
View attachment 226104View attachment 226105View attachment 226106View attachment 226107View attachment 226108View attachment 226109

Firstly, I want to say that I have a pair of four channel VTV amps that use the same power supply and it arrived with two of the channels with their inputs & outputs (correctly) inverted for power supply load balancing.
In your case, I can see that both channels are wired the same, so there is no PS load balancing. Ideally one channel should have the polarity of it's signal input wires and output speaker wires swapped.

 

[goryu]

Firstly, I want to say that I have a pair of four channel VTV amps that use the same power supply and it arrived with two of the channels with their inputs & outputs (correctly) inverted for power supply load balancing.
In your case, I can see that both channels are wired the same, so there is no PS load balancing. Ideally one channel should have the polarity of it's signal input wires and output speaker wires swapped.

Doesn't look to me either like one channel has been inverted to avoid supply pumping issues as recommended by Hypex. This 3K supply is not to be used this way. I bought a used VTV nc1200 stereo amp and it was incorrectly wired like yours. I rewired it.

 

[windansea]

Firstly, I want to say that I have a pair of four channel VTV amps that use the same power supply and it arrived with two of the channels with their inputs & outputs (correctly) inverted for power supply load balancing.
In your case, I can see that both channels are wired the same, so there is no PS load balancing. Ideally one channel should have the polarity of it's signal input wires and output speaker wires swapped.

For the output wires, that simply means swapping the red and black, right? (for one channel)

For input signal, guess that would mean resoldering the XLR for the same channel. Or is there a simpler approach?

 

[windansea]

Doesn't look to me either like one channel has been inverted to avoid supply pumping issues as recommended by Hypex. This 3K supply is not to be used this way. I bought a used VTV nc1200 stereo amp and it was incorrectly wired like yours. I rewired it.

Thanks for the insight. How did you invert polarity for the input? Would an XLR phase inverter do the trick?:

https://www.amazon.com/Hosa-GXX-195-XLR3F-XLR3M-Reverser/dp/B000068O4L/ref=sr_1_2?crid=2CKEHA0U04AVP&keywords=xlr+polarity+reverse&qid=1661273674&sprefix=xlr+polarity+%2Caps%2C679&sr=8-2

 

[goryu]

Thanks for the insight. How did you invert polarity for the input? Would an XLR phase inverter do the trick?:

https://www.amazon.com/Hosa-GXX-195-XLR3F-XLR3M-Reverser/dp/B000068O4L/ref=sr_1_2?crid=2CKEHA0U04AVP&keywords=xlr+polarity+reverse&qid=1661273674&sprefix=xlr+polarity+%2Caps%2C679&sr=8-2

I just unsoldered the two input wires on one xlr, reversed them, and resoldered. Did the same with the speaker wiring on the same channel. I have seen photos of some VTV nc1200 stereo amps wired the correct way. I imagine he produced a certain quantity of these before finding out he was wiring them wrong. Would have been good to notify those who purchased them wired incorrectly and had a recall program.

 

[windansea]

I did a LITTLE reading on this pumping issue, and much of what I've seen suggests that reversing polarity is not necessary for a Hypex system. Perhaps this was a problem in previous Class D amps but Hypex addressed it?

1) [found this on ASR:] Hypex's answer:

The NCxxxMP each have synchronous rectification on the main output rails, which will feedback any supply pumping in the supply voltage.
So this means it isn’t necessary to invert the second channel, but you are free to do so if you like.

2) [also on ASR]
Purifi's very kind reply:

Some power supplies have active rectifiers and do not have issues with supply pumping, like the HYPEX SMPS1200A400, where as the SMPS3KA400 can have issues.
We use the SMPS1200A400 in our demo amp, and do not invert the phase on one channel.

With other power supplies that do not have active rectifiers the phase inversion is highly recommended.

3) from another forum:
Bus pumping isn’t an issue with Hypex supplies due to the Mosfet outputs

These supplies are designed to power single ended class D amps. (Like all the Hypex amplifiers). Because the supply was designed this way, they designed it to tolerate supply pumping. And they did so by using mosfets that can sink current, rather than a rectifier like most supplies use. So adding caps will only worsen the supply quality, and potentially damage it like the Hypex engineer told you.

Hypex SMPS400A400 and Bus Pumping

Hi, I wrote to Hypex to determine the maximum capacitance that can be applied to the output of the Hypex SMPS400A400 power supply to reduce bus pumping. Their response was that : "It is unsupported to apply extra capacitance on the output of the supply. The surge current could damage the...

www.diyaudio.com

 

[KMO]

I did a LITTLE reading on this pumping issue, and much of what I've seen suggests that reversing polarity is not necessary for a Hypex system.

(Hypex's reply you found seems irrelevant as it's talking about modules with integrated supplies).

Purifi's very kind reply:

Some power supplies have active rectifiers and do not have issues with supply pumping, like the HYPEX SMPS1200A400, where as the SMPS3KA400 can have issues.
We use the SMPS1200A400 in our demo amp, and do not invert the phase on one channel.

With other power supplies that do not have active rectifiers the phase inversion is highly recommended.

Did you fully read Purifi's reply?

The answer is different for different Hypex supplies. You do want the swap for the 3K supply.

The SMPS3KA400 datasheet specifically spells it out:

2.1 Half-bridge amplifiers (UcD400/UcD700/NC500/NC1200)

The SMPS3K is intended to power our range of high power amplifier modules, such as UcD2K and NC2K. As a
result, this SMPS product does not feature the 2-quadrant operation as most of our other SMPS products do.
Therefore, they are unable to handle large reverse currents generated by half-bridge amplifiers operated at
low frequencies. For this reason, it is not advisable to use this SMPS to power half bridge amplifiers like our
UcD700 and UcD400 modules when used in the frequency range below 100Hz. A workaround for this could be
using the UcD700/UcD400 in bridge mode, or reversing phase for half of the modules.

 

[windansea]

(Hypex's reply you found seems irrelevant as it's talking about modules with integrated supplies).



Did you fully read Purifi's reply?

The answer is different for different Hypex supplies. You do want the swap for the 3K supply.

The SMPS3KA400 datasheet specifically spells it out:

Thank you for highlighting the relevant section.

Hmmm, OK guess I need to do the polarity inversion.

 

[KMO]

Thank you for highlighting the relevant section.

My NC1200 amp uses the SMPS1200A700, not the SMPS3KA400.

An SMPS1200 looks different:

You've got an SMPS3KA700. (I was wrong about the voltage, which isn't visibly obvious, but I checked VTV's specs).

I think you're getting muddled with VTV's mono NC1200 amp.

An SMPS1200 is only enough power for one NC1200. (As the name implies).

 

[windansea]

An SMPS1200 looks different:

You've got an SMPS3KA700. (I was wrong about the voltage, which isn't visibly obvious, but I checked VTV's specs).

I think you're getting muddled with the VTV's mono NC1200 amp.

An SMPS1200 is only enough power for one NC1200. (As the name implies).

I appreciate the clarification. You are correct, I've got the 3K. So I'll invert the polarity on one channel.
I better scribble a diagram-- my preamp is polarity-inverting (like many tube pres, apparently), so I was already reversing the speaker cables to re-invert polarity. Now I'll invert one side yet again, and buy an XLR hot pin inverter for the input on that side.

I wonder if I'll even hear any difference given the music I listen to. No deep bass stuff, just classical on this system.

 

[KMO]

Just to reassure you, not having the reversal isn't the end of the world, but it does increase the chance that the power supply gives up before the amp does under heavy load, reducing maximum output.

This is offset to some extent by you having more than enough power - 3000W power with total of 2400W amplifiers, so there's a bit of margin.

And the reversal isn't totally fool-proof anyway - in theory some track could send out of phase bass signals!

I wonder if I'll even hear any difference given the music I listen to. No deep bass stuff, just classical on this system.

Then I would say you're a long way away from the SMPS even beginning to sweat. I don't think there would be any issues at low level, only when approaching current limits. (Correct me if I'm wrong, anyone)

 

[windansea]

Back to the OP. I got this pair of silent cooling fans for $15 and removed the faceplate. I'd like the unit to last longer and hopefully this cheap solution will help.

Now it sounds more airy and open, ha just kidding. But the chassis is completely cool to the touch now.

 

[ilan5555]

Figured I'd put up a post on the matter after exchanging pics with another member. Bought the VTV Hypex NC1200 build using on-board buffers before Christmas and just had the chance to take the lid off and get some pics this evening. As always, if this goes against any forum rules, please let me know and I'll do what's necessary to comply. Not sure if this counts as a plug for this product or whether plugs are allowed. Couple of notes in no particular order...

* I didn't know this prior, but it looks like the NC1200s have the buffer on the same board, unlike the NC400s and 500s which require a second (Hypex stock or custom) buffer board. Here I opted for stock rather than any fancy op-amps (unsure what was even on offer in that regard) because I've got a lot of experience with the NC500s w/ stock everything and they sounded just fine. No 'house' sound to speak of. Just flat and clean.

* This amp tends to heat up A LOT on the bottom in the back on each side, so it would appear that it's the n-core modules that are responsible and not the big 3-channel-capable SMPS. In the past using NC500s it's been the SMPS that generates the most heat and it the larger XFMR seems to be the primary source, pun intended. I did purchase a set of 4 box fans to place underneath and wired up a little control knob to keep it cool because the temps were getting up to about 130-150F. That's a lot hotter than NC500s run in my experience. The fans aren't audible since I've got the amp in an enclosed built-in cabinet under the TV, which also contributes to heat build up over time. I drilled holes in the wood for all the various wires that go in and out, primarily to keep the aesthetics to my wife's liking.

* As far as sound goes, the thing is a beast. I'm particularly impressed by the dynamics coupled with the JBL speakers I'm using. Even at very low volume, most of the dynamics and details are still there. It can go from VERY soft to VERY loud in the same track and I hear no distortion at discotheque levels. I've also created an EQ setting on the RME ADI-2 v.2 for stereo home theater where I've boosted the bass and adjusted the midrange according to Amir's T&M report on the JBLs. No subwoofer needed, it's that good. I'm not sure what the general ASR consensus on damping factor is, or whether an 'official' test has been done on NC1200s, but it's gotta be very high. Extremely good control of the woofers. As cliche as it may be, it's a blast cueing up some old favorites and hearing new life breathed into them - at all volume levels. It's amazing what high power can do even if we only use the first few watts in most listening. It doesn't hurt that the speakers are very efficient. The closest thing I've heard in my own (admittedly limited) listening in terms of raw power is the IcePower 1200AS2, which I think might have more distortion than the Hypex. Both can rock the house with ease. NC500s are great, NC1200s are a real step up. I had a very nice Krell for a number of years that I never thought I'd part with, but after listening side by side with the NC500 build I decided to sell it. This ups the bar even further.

* Build quality is good by me. The XLR input lead cables use what looks like an extra layer of shielding which has been soldered to the back of the cabinet. In my past experience, these signal cables only used the 3 pins on the back of the XLR connector, but here there are 4 'conductors' including the extra (?) shielding. EDIT: I was wrong and after inspecting more closely it looks like the cables have the normal shielding which is soldered to the cabinet. For what looks like Pin 2 on the back of the XLR inputs, that too is soldered to the case. I'm going to do some more research on this.

I suppose the speaker leads could've been twisted a bit more tightly, but the wires he used are very nice and I doubt it makes a bit of difference in my application. He's using a standard Ghent Audio case, which are among the highest quality pre-fab cases you can get, and the front plate is customized with the VTV logo in the center as we've seen on their other amps. All the soldering is about as good as I tend to do myself, so no complaints there.

All in all, I'd definitely recommend this particular amp configuration from VTV, especially at the price - and I'm sure it measures very well.

P.S. I also recently acquired a Nord Acoustics Nord Three SE Purifi-based integrated which I'll take apart and post separately. I'm using that one in a smaller office setting and it sounds great too and is highly recommended if you can get a decent price.

Attached are some internal pictures which I've taken no particular care in framing or making look pretty (for example, the dust particles come right off with compressed air).

Hi,
Which amplifier do you prefer, the NC1200 or the Purifi?

 

[C. Cook]

Hi,
Which amplifier do you prefer, the NC1200 or the Purifi?

Sorry only just saw this. Since I have them in totally different systems I couldn't tell you much more than that the 1200 has incredible bass in my living room, but it's also connected to much bigger speakers, so....