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DIY Purifi Amp builds

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Just wondering, when connecting a 2V unbalanced DAC to a purifi based poweramp like the P452, the best way would be through the March Audio Pin1 XLR shield terminated at the RCA cables to minimise interference and to get some of the benefits of a balanced connection. Would you lose the benefit of that cable though if the DAC is not grounded (powered by a 5V DC mobile phone charger for example) or if you add a passive volume controller (or pre-amp) between the DAC and the amp using a regular RCA to RCA cable?
 
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Here's 2 pair of mono's built with a SMPS 1200A400 power supply, Neurochrome IET400A buffer and IET400A amp module grafted into a ghent NC400 amp case each. Mods to the ghent case were very light - drill off & csk 12 holes in the base. Got some 50mm longer 10pin ribbons coming to tidy the routing. They run so cool they're barely above room temp and the detail revealed from the lack of noise floor is striking.
 

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The Hypex has no EMI filtering at the input, the Purifi does, which makes it OK for home use.
The Hypex can't be sourced for DIY, but you find it in some pre-built.
Hi boXem, if you use the EVAL1 board but bypass the buffer (to reduce the gain), would the input signal still be EMI filtered or is that also bypassed?
 

boXem | audio

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Hi boXem, if you use the EVAL1 board but bypass the buffer (to reduce the gain), would the input signal still be EMI filtered or is that also bypassed?
Hi Aardappel, from EVAL1 documentation the filter seems to be bypassed.
 

phoenixdogfan

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Once again the SMPS is being returned repaired. The aux circuit was what needed repair. They said the 6 pole harness was good. They did not test the aux cable b/c they said it lacked crimps which it would b/c it was made with the 3m IDC cable. They did say it appeared to have been wired correctly. No matter. I will have the Ghent cable.

The Eval 1 arrived at Purifi yesterday. They will look at it beginning next week. Hopefully in two weeks I should have all the working components back in house and can start assembly anew.
 
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Aardappel said:
Hi boXem, if you use the EVAL1 board but bypass the buffer (to reduce the gain), would the input signal still be EMI filtered or is that also bypassed?
Hi Aardappel, from EVAL1 documentation the filter seems to be bypassed.
Hi,
Could it be a problem for a normal user (HiFi) ?
Or it's irrelevant because the signal we feed to the PURIFI modules is already "clean" (without any EMI or other hassles) ?
 

boXem | audio

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Hi,
Could it be a problem for a normal user (HiFi) ?
Or it's irrelevant because the signal we feed to the PURIFI modules is already "clean" (without any EMI or other hassles) ?
Hi zappa,
There is a risk to have the noise disturbing the modulator behavior. DACs are not always clean. Our home environment is full of EM crap.
While I consider that products sold by professionals have to include these protections, I do not want to spread FUD, we are talking about DIY here, so I would say that if you don't hear any noise out of your speakers when no music is playing, this is a non issue.
 

phoenixdogfan

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Well Purifi looked at the Eval1 and Kim said it was in perfect working order. Also liked Ghent's wiring harnesses, so I guess I'll be using them. The repaired SMPS arrives at my door tomorrow. Still no idea why the aux section blew out twice. Hypex said my six pole harness was perfect, and they didn't check the five connection b/c it wasn't crimped (It wouln't have been given I was using the 3M IDC connector) but said it appeared to be wired correctly, so I have no idea what the root cause for these failures.

I will check out the SMPS by trying Ghent's LED first, then when the Purifi arrives I'll connect it with Ghent's harneses. If all the Leds light up, only then will I reinstall it in the case, first with the back off. If it works that way, I'll reistall the back and cross my fingers.

I put thermal paste under the base of the SMPS, could that possibly have caused any issues? Anyone know?
 
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JimB

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I put thermal paste under the base of the SMPS, could that possibly have caused any issues? Anyone know?
Nope. If you use too much, too thick, it could be worse than none - meaning, it would overheat at a lower power output than without the paste. But, applied properly, it improves thermal margin. It should have nothing to do with SMPS failures unless it was conductive and you got it where it shouldn't be.
 
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JimB

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Well Purifi looked at the Eval1 and Kim said it was in perfect working order. Also liked Ghent's wiring harnesses, so I guess I'll be using them. The repaired SMPS arrives at my door tomorrow. Still no idea why the aux section blew out twice. Hypex said my six pole harness was perfect, and they didn't check the five connection b/c it wasn't crimped (It wouln't have been given I was using the 3M IDC connector) but said it appeared to be wired correctly, so I have no idea what the root cause for these failures.
Before connecting the two cables to the EVAL1, power up the SMPS and DOUBLE CHECK the voltages on each pin at the EVAL1 ends. If all good, power down the SMPS for at least several minutes before connecting them to the EVAL1.
 

phoenixdogfan

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Before connecting the two cables to the EVAL1, power up the SMPS and DOUBLE CHECK the voltages on each pin at the EVAL1 ends. If all good, power down the SMPS for at least several minutes before connecting them to the EVAL1.
To do that do I just put the hot lead on the pin and the neutral on the case. and record the voltage?
Do I find the correct voltages in the Hypex user guide?
 

phoenixdogfan

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Nope. If you use too much, too thick, it could be worse than none - meaning, it would overheat at a lower power output than without the paste. But, applied properly, it improves thermal margin. It should have nothing to do with SMPS failures unless it was conductive and you got it where it shouldn't be.
It was a super thin coat and it was under the base plate of the SMPS and nowhere else, so I don't think it should have caused any problems. That leaves me with the back shorting things out or some short in the IDC connector. If it's the IDC connector, that irrelevant going forward b/c I'm using Ghent's wiring harness which is crimped, and looks to be a nice job. I will on second thought get the back "ventilated" b/c I just don't like the idea of the Eval 1 circuit board touching the metallic case back, especially if everything works without the case back.
 
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To do that do I just put the hot lead on the pin and the neutral on the case. and record the voltage?
Do I find the correct voltages in the Hypex user guide?
Neutral lead on the ground pin(s) of each cable. Voltages per the Hypex datasheet (allowing for your mains AC voltage).
 

March Audio

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Hi,
Could it be a problem for a normal user (HiFi) ?
Or it's irrelevant because the signal we feed to the PURIFI modules is already "clean" (without any EMI or other hassles) ?
As @boXem | audio says if you hear no odd noises then its not a problem. Its just something that commercial products should take care of as a precaution.
 
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Been waiting for this but now Eval2 is online
I have been so lucky to actually use these for some weeks now.

Easy to implement, I think, and the sound combined with 1ET400's, is absolutely fantastic, in my setup.

The package I received contained everything I needed to hook them up to Hypex SMPS 1200A400's.

I can recommend them, no problem.
 
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I have been so lucky to actually use these for some weeks now.

Easy to implement, I think, and the sound combined with 1ET400's, is absolutely fantastic, in my setup.

The package I received contained everything I needed to hook them up to Hypex SMPS 1200A400's.

I can recommend them, no problem.
Very nice! Are you driving it with the XLR output of the NAD C658 to the EVAL2/1ET400 combination with the buffer bypassed or not bypassed?
 
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