Pin 1 wiring error again. Im afraid the Benchmark cables arent giving you any benefit because of he internal wiring error. BTW we also sell correctly wired XLR to RCA cables.
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VTV Hypex Ncore NC252MP (It's all Amir's fault)
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OP
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Thanks. Once I put on my strong magnifying goggles and got a flashlight I figured it out. The front is held in by screws and requires taking off the front faceplate first by backing out two 1.5mm hex heads (or Allens as they used to be called).
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Crap. How hard is it to desolder from the XLR side and fix?
Looked closer, I'm no expert at electrical assembly, but I am pretty sure that molex plugs shouldn't need duct tape!!!!
Attachments
The problem is not there on the IDC connector you picture, although they look like they have bodged the wrong type of connector into the socket and used tape to stop it falling out
The problem is at the XLR connector end. There is another thread here somewhere with details. Search "Pin1"
Duh! I had forgotten about Amirs review of the IOM NC252MP amp - thanks.
Thanks for popping in, Alan. We discussed headroom in an older thread here, and I mentioned my Classé Model Seventy with its huge PS capacitors, and I think it has a bit of headroom. I notice that you simply list the NC252MP power specs on your March Audio website without conditions or details, but Amir found that the power ratings by Hypex for the NC252MP were not seriously exaggerated.
As a non-engineer, I get frustrated as you can see from my above post, but now that I have been reminded that Amir tested the IOM version of an NC252MP amp, all of my questions have been answered. According to Amir, the IOM has very limited headroom due to its regulated power supply.
If you offer an NC252MP amp at March Audio, that's a big positive for me, because I know about your passion for high quality and good engineering. And I wouldn't hesitate to buy three of your ultra-low distortion Purifi 400 monoblocks if my budget were bigger.
While you are at it you can also correct the signal polarity error.
Pin 1 on the IDC header is inverting (-) input. Its wired to Pin 2 on the XLR (+)
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Duh! I had forgotten about Amirs review of the IOM NC252MP amp - thanks.
Thanks for popping in, Alan. We discussed headroom in an older thread here, and I mentioned my Classé Model Seventy with its huge PS capacitors, and I think it has a bit of headroom. I notice that you simply list the NC252MP power specs on your March Audio website without conditions or details, but Amir found that the power ratings by Hypex for the NC252MP were not seriously exaggerated.
As a non-engineer, I get frustrated as you can see from my above post, but now that I have been reminded that Amir tested the IOM version of an NC252MP amp, all of my questions have been answered. According to Amir, the IOM has very limited headroom due to its regulated power supply.
If you offer an NC252MP amp at March Audio, that's a big positive for me, because I know about your passion for high quality and good engineering. And I wouldn't hesitate to buy three of your ultra-low distortion Purifi 400 monoblocks if my budget were bigger.
Thanks for the kind words
We do indeed have a NC252MP, our P252 amp.
https://www.marchaudio.net.au/p252
Promit
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For a three hundred dollar premium over what VTV or Audiophonics are asking, yes.
I also got the impression, looking at VTV's photos on the eBay listing, that the wiring work was questionable. Apparently my instincts were not wrong. Audiophonics looks comparatively impeccable, although with a pretty substantial lead time.
Larger power supply capacitors, or anything else that "stiffens" a power supply, will generally decrease dynamic headroom but provide a bit more steady-state power. Class D amplifiers tend to use regulated power supplies.
However, headroom is just as often (if not more so) a decision made by engineering and marketing as they decide how to spec the device. Ditto things like the ability to "double down", doubling power into 4 ohms from 8 ohms. You can choose to spec higher wattage and less at 4 ohms, or lower 8-ohm wattage but show doubling in power at 4 ohms. Probably more marketing than engineering...
However, headroom is just as often (if not more so) a decision made by engineering and marketing as they decide how to spec the device. Ditto things like the ability to "double down", doubling power into 4 ohms from 8 ohms. You can choose to spec higher wattage and less at 4 ohms, or lower 8-ohm wattage but show doubling in power at 4 ohms. Probably more marketing than engineering...
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While you are at it you can also correct the signal polarity error.
View attachment 62596 View attachment 62597
10 pin, but it shows the issue
View attachment 62598
Pin 1 on the IDC header is inverting (-) input. Its wired to Pin 2 on the XLR (+)
While you are at it you can also correct the signal polarity error.
View attachment 62596 View attachment 62597
View attachment 62599
Pin 1 on the IDC header is inverting (-) input. Its wired to Pin 2 on the XLR (+)
So making sure I am understanding correctly pins 2 and 3 need to be swapped on the XLR side.
I appreciate your help with this. Honestly, I would have bought one of your amps, but couldn't swing the extra cost right now. I know that selling from Australia to the US has high transactions and exchange costs.
Hi
I have to pop out for a few hours, I will check back in later
alan
I have to pop out for a few hours, I will check back in later
alan
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If I am understanding correctly, Pin 1 should go to the case, not to the the idc connector. Pins 1 and 14 on the board should also go to ground (which here is also the case as the case is connected to the ground). The board should not be directly connected to pin 1. Finally, here the guy also flipped the positive and negative legs (pins 2 and 3).
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That 75-80W is 0.5dB...
My euphoria over VTV has just been lowered a couple of notches. That is sloppy assembly technique replete with outright errors.
CDMC - you should be able to fix this - and Alan is a true gentleman in trying to help you.
Although he doesn't reveal his identity at his websites, the owner of VTV is Warren Coleman, and he participates at tube audio forums where he seems to have a good reputation.
I really like the VTV/Ghent case, we know that the NC252MP is a good module, and VTV prices are excellent. Warren apparently didn't have a correct plug, and his sloppy cobbled-in substitution and miswiring of the XLR connections bothers me.
CDMC - I suggest you contact Warren, describe your problems, ask him to fix them, and and invite him to ASR. Tell him it might be rough at first, but some of us still like his amplifiers, and we will work with him to make things right.
I really want VTV to get it right, and will buy a mono 250 and stereo 252 from him if he works with us to correct these issues and assemble the amps properly. If he doesn't work with us, I may still buy from him, purchase a wiring kit from Ghent and rewire the amp myself. We can buy cases and wiring harnesses ourselves from, but the NCxxxMP modules are an OEM product line, and not generally sold to DIY'ers.
[Edit: I already own a Ghent case for similar rated ICEpower modules - the same ones that were used by Cary, Bel Canto and Jeff Rowland. I will finish that project to and not spend another $500 to get the VTV Hypex amplifiers instead.)
CDMC - you should be able to fix this - and Alan is a true gentleman in trying to help you.
Although he doesn't reveal his identity at his websites, the owner of VTV is Warren Coleman, and he participates at tube audio forums where he seems to have a good reputation.
I really like the VTV/Ghent case, we know that the NC252MP is a good module, and VTV prices are excellent. Warren apparently didn't have a correct plug, and his sloppy cobbled-in substitution and miswiring of the XLR connections bothers me.
CDMC - I suggest you contact Warren, describe your problems, ask him to fix them, and and invite him to ASR. Tell him it might be rough at first, but some of us still like his amplifiers, and we will work with him to make things right.
I really want VTV to get it right, and will buy a mono 250 and stereo 252 from him if he works with us to correct these issues and assemble the amps properly. If he doesn't work with us, I may still buy from him, purchase a wiring kit from Ghent and rewire the amp myself. We can buy cases and wiring harnesses ourselves from, but the NCxxxMP modules are an OEM product line, and not generally sold to DIY'ers.
[Edit: I already own a Ghent case for similar rated ICEpower modules - the same ones that were used by Cary, Bel Canto and Jeff Rowland. I will finish that project to and not spend another $500 to get the VTV Hypex amplifiers instead.)
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I really love/hate how all these module sellers only produce power amps...
"Oh, these amp modules have a low input impedance and a varying impedance vs frequency, and hence needs an active preamp stage if you want a volume control? No volume control, problem solved."
Love how they avoid the problem (as opposed to putting a passive volume knob), hate how they avoid the problem.
"Oh, these amp modules have a low input impedance and a varying impedance vs frequency, and hence needs an active preamp stage if you want a volume control? No volume control, problem solved."
Love how they avoid the problem (as opposed to putting a passive volume knob), hate how they avoid the problem.
It's 155 watts over its 500 watt rating. 1.2dB
The NCxxxMP modules have high input impedance, 47kohms SE 94kohms diff.
Correct
Pin 1 to case as close as possible to the xlr socket.
The idc grounds (pins 3 and 14 - the cable braids) to case somewhere else but not the same place as the pin 1 connection.
You might also want to re solder that blue speaker neg wire shown in the picture.
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