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Purifi 1ET400A / Hypex NC500 Input Buffer

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#81
stamper said:
Hi all.
I am new to this forum and at Tom's request, I come to present the project that I just finished 2 days ago. These are mono blocks based on Purifi 1ET400A modules and the Neurochrome buffer made by Tom.
I opted for a Hypex SMPS 1200A400 main power supply, and a more complex regulated power supply than the Hypex regulators.
It is composed of :
  • 1 THEL Audioworld NT-25HQ-18 for regulated for regulated 2x15VDC
  • 1 MPAudio ALD-HPULN PS Dual Rail 2x2,5A for ultra regulated symetrical 12VDC (+/- 12VDC)
All the wiring and connections were chosen based on my past experiences and tests (previous projects or improvements made on commercial devices).

I hope that my first intervention will be received with kindness because I am not used to the forum and I do not necessarily know the rules to be respected 😱 .

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Click to expand...
Hi

Has anyone compare the sound improvement of using the standard SMPS regulation against the better regulated version? I'm trying to work out if it's worth the additional complexity/space/cost?
 
#82
UK Dave said:
Hi

I'm looking to build a stereo power amp as detailed by Mello4 above. I've read some reviews on the NAD C296 power amp that uses the same Purifi 1Et400A modules and they say that NAD uses left positive and right negative terminals and therefore cautions against connecting subwoofers with common ground connections.

Does anyone know if that's NAD specific, or if the 1ET400A Purifi modules, Neurochrome Input Buffers, and SMPS1200A400 Power Supply will have the same issues? I assume this isn't an issue as I can't see anyone highlighting it on any 1ET400A builds.
Click to expand...

Is this about the way the modules are connected, I.e. one channel is reversed to partially defeat his pumping? On this case this is not due to the buffer, but to the way the inputs and outputs are wired. Also in my amplifier I wired one channel with inputs and outputs reversed.
 
#83
UK Dave said:
I'm looking to build a stereo power amp as detailed by Mello4 above. I've read some reviews on the NAD C296 power amp that uses the same Purifi 1Et400A modules and they say that NAD uses left positive and right negative terminals and therefore cautions against connecting subwoofers with common ground connections.
Click to expand...
The Purifi 1ET400A and Hypex NC500 are single-ended amps. The speaker ground is connected to power supply ground (says the 1ET400A data sheet).
Screen Shot 2022-01-02 at 10.16.56.png


Tom
 
#84
From the wording of the Stereophile article, it would appear that the NAD C298 has floated the two Purifi modules, and connected them with split supplies and differential input connections.

https://www.stereophile.com/content/nad-c-298-power-amplifier

"Standard bridging strategies are verboten with Purifi amp modules since neither output terminal is at ground potential and should never be connected to an external ground. Unlike regular bridged amplifiers, where the output is taken from the left and right positive terminals, NAD uses the left positive and right negative terminals and cautions against connecting subwoofers, switches, or headphone adapters with common ground connections. Safety is a good reason for the bridging switch to be inconvenient."

521nad.inside.jpg
 
#85
mocenigo said:
Is this about the way the modules are connected, I.e. one channel is reversed to partially defeat BUS pumping? IN this case this is not due to the buffer, but to the way the inputs and outputs are wired. Also in my amplifier I wired one channel with inputs and outputs reversed.
Click to expand...
Funny, I edited this message but I later discovered that the edit was not accepted. Of course is is about BUS pumping and “In this case”….
 
#86
Mello4 said:
From the wording of the Stereophile article, it would appear that the NAD C298 has floated the two Purifi modules, and connected them with split supplies and differential input connections.

https://www.stereophile.com/content/nad-c-298-power-amplifier

"Standard bridging strategies are verboten with Purifi amp modules since neither output terminal is at ground potential and should never be connected to an external ground. Unlike regular bridged amplifiers, where the output is taken from the left and right positive terminals, NAD uses the left positive and right negative terminals and cautions against connecting subwoofers, switches, or headphone adapters with common ground connections. Safety is a good reason for the bridging switch to be inconvenient."

View attachment 1011065
Click to expand...

The problem is not the floating; I mean, they cannot run with the negative not grounded, the two negatives have to ne connected - and through the ground. But if something bad happens that trips protections on one module, the other one has to be shut down immediately as well. So AFAIU this needs to run the modules in SW mode to monitor what is happening. It can probably be achieved by some clever circuit, with no need to use a MCU, but with the latter you can implement more features as well.
 
#92
Very cool. Looks like everything fit in the box nicely. I like the reuse of VTV's ribbon cable. I don't understand why they put 14-pin connectors on a 10-pin cable. #whatever...

You might want to take the XLR chassis connection directly to the chassis rather than via the long meandering green wire. Keystone #7311 is your friend in need. Just add one to the mounting hardware on the XLR connector and you get a chassis connection. Unless the green wire has a different purpose, that is.

Tom
 
#94
I now offer a custom machined chassis for a stereo Purifi 1ET400A or Hypex NC500 powered by a Hypex SMPS1200A400 power supply: https://neurochrome.com/collections/connectors-parts/products/purifi-chassis

The chassis is made by Takachi in Japan and is of incredible quality – better than that of many commercially available Purifi/Hypex amps – and that's reflected in the price tag. Sorry... Custom machined aluminum is expensive to start. Custom machined aluminum at this quality level is even more expensive.

I expect to have the chassis in stock towards the end of February. I won't have too many made as I hate having money tied up in aluminum. Also I'm approaching this as a bit of an experiment to see if I should offer a full Purifi/Hypex kit. Given that the DIY kit will be more expensive than a completed amp by [INSERT CHEAP BRAND NAME HERE] I see it as a bit of an uphill battle and will limit my risk until I see where it goes.

The chassis comes with all the mounting hardware; including the two custom made mounting plates for the amp modules and buffers. All the connectors, switches, circuit boards, etc. are available separately.

You can watch a previous iteration of the chassis in the video below. That version of the chassis did not support the Guardian-86 optional speaker protection. The current version of the chassis does.

Tom
 
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