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DIY Purifi Amp builds

dronepunk

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Is anyone else having issues with cell phone RF noise and Purifi with Hypex buffers?
I’ve done some searching and reading for a few days and have found some issues but nothing definitive.. I am using quality sheilded though single ended with Nuetrick adapters.
Problem occurs on all sources ....
Thanks f this has been covered I apologize but I cannot find much usable info.
I’m thinking a low pass filter is needed for bandwidth limiting from what i understand.
 

boXem

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Is anyone else having issues with cell phone RF noise and Purifi with Hypex buffers?
I’ve done some searching and reading for a few days and have found some issues but nothing definitive.. I am using quality sheilded though single ended with Nuetrick adapters.
Problem occurs on all sources ....
Thanks f this has been covered I apologize but I cannot find much usable info.
I’m thinking a low pass filter is needed for bandwidth limiting from what i understand.
Hypex buffers are not designed for home use, they have no filtering. So nothing surprising.
 

ABall

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Is anyone else having issues with cell phone RF noise and Purifi with Hypex buffers?
I’ve done some searching and reading for a few days and have found some issues but nothing definitive.. I am using quality sheilded though single ended with Nuetrick adapters.
Problem occurs on all sources ....
Thanks f this has been covered I apologize but I cannot find much usable info.
I’m thinking a low pass filter is needed for bandwidth limiting from what i understand.
https://www.audiosciencereview.com/forum/index.php?threads/diy-purifi-amp-builds.10478/post-291842
Read on from post 43, ignore the idiot.
 
Last edited:

Naturlig

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Your AC connection/ground wiring looks weird. Is that top connector IEC middle pin i.e. ground tap? Looks like it goes to PSU.
No, the ground cable is bended backward (invisible) and down to the ground connection on the bottom.
 

lealoureiro

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Have you read the Hypex SMPS1200 data sheet? I've attached the relevant connector pinouts here (from page 10 of the data sheet).

Personally I prefer to use J4 for the connections to the Buffer. Why run many cables when you can run one?

Tom

Thanks @tomchr !

Indeed I've printed the datasheet to start analyse and understand the pin outs. I just want to make sure I understand well the connections before i start doing the connections etc. So basically the power output of J4 when select Unregulated is the same as J5 I believe.
 

lealoureiro

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Here is an example of my test build with the Modushop GX288 cabinet. The cabling is my first try and NOT yet finished, I could not wait to hear the sound of the Neurochrome buffer together with the 1ET400A amp module. And the sound from this build is indeed excellent. TomC knows how to it!
The next will be to insert the splitter card from Neurochrome and redo the cabling.
View attachment 123341

What are the dimensions of that one? I want to go with same model but that one from the picture seems a bit to small/compact.

How did you made the grounding? Does the case has some kind of coating make the contact more difficult or something?

Thanks!
 

TimoJ

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Does the case has some kind of coating make the contact more difficult or something?
Width 230mm, inner useful 210mm, Height: 80mm, Depth: 280mm.

To make all panels grounded you have to remove coating from the panel contact edges or remove coating inside the screw cap holes (not sure how well that works and it needs screws that conduct electricity, black ones may not) or use separate ground wires to each panel. Pretty easy job with Dremel sanding drum, just remove edge coating around all screw areas. Just did that to my GX388 case (3ch with EVAL1 & EVAL2 amps).
 

tomchr

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So basically the power output of J4 when select Unregulated is the same as J5 I believe.
That is my understanding as well. It would have been nice if Hypex had over-communicated a bit and added "unregulated" in the pinout table for J5. You can always just measure it.

Tom
 
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JimB

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That is my understanding as well. It would have been nice if Hypex had over-communicated a bit and added "unregulated" in the pinout table for J5. You can always just measure it.

Tom
Agreed. But their consistent convention is that they provide Vaux, or Vaux,reg. There is no Vaux,unreg. We users have been calling it Vaux "unregulated". J5 has only Vaux, while J4 offers the choice of Vaux, or Vaux,reg.
 

Naturlig

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What are the dimensions of that one? I want to go with same model but that one from the picture seems a bit to small/compact.

How did you made the grounding? Does the case has some kind of coating make the contact more difficult or something?

Thanks!
Dimensions are covered in recent post. The yellow/green cable is the grounding, from ground IEC inlet to the bottom screw (black coating removed) and then to the SMP1200. The GX288 is compact, I like that, but be aware of the minimum 3 mm distance between each unit as commented earlier also.
I designed the back panel and Modushop produced it perfectly, the XLR and IEC wholes is not easy to drill.

I still love the sound of this power amp. I have also done one Eigentakt EVAL1 amp with the same GX288 cabinet. The Neurochrome buffer solution from TomC is then the only difference. Sound: more details and better voice/instrument definition, better/vider soundstage, more dynamic.
 

TimoJ

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I have also done one Eigentakt EVAL1 amp with the same GX288 cabinet. The Neurochrome buffer solution from TomC is then the only difference. Sound: more details and better voice/instrument definition, better/vider soundstage, more dynamic.
How do you explain such big differences? There is nothing "magical" in TomC's buffer that could cause this and EVAL1 already measured very well.
 

lealoureiro

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Dimensions are covered in recent post. The yellow/green cable is the grounding, from ground IEC inlet to the bottom screw (black coating removed) and then to the SMP1200. The GX288 is compact, I like that, but be aware of the minimum 3 mm distance between each unit as commented earlier also.
I designed the back panel and Modushop produced it perfectly, the XLR and IEC wholes is not easy to drill.

I still love the sound of this power amp. I have also done one Eigentakt EVAL1 amp with the same GX288 cabinet. The Neurochrome buffer solution from TomC is then the only difference. Sound: more details and better voice/instrument definition, better/vider soundstage, more dynamic.


Thanks for your reply!

Which XLR input sockets you used? do you mind to share? Regarding the grounding cable, you made it yourself or you bought it?
 

Naturlig

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How do you explain such big differences? There is nothing "magical" in TomC's buffer that could cause this and EVAL1 already measured very well.
Differences: This is just what I hear. The «magic« is what comes out of the speakers? May be because it drives the amp module balanced and handles the input also balanced. To me the overall sound is also cleaner. I am not a technical expert.
 

tomchr

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@Naturlig thanks for sharing your experience.

One key difference is that the EVAL1 will produce a single-ended output if provided with a single-ended source. The EVAL1 also has no common-mode rejection (it relies on the CMRR of the amplifier module for that). The Neurochrome Purifi/Hypex Buffer will provide a differential and balanced output even if driven by a single-ended source.

Tom
 

TimoJ

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Differences: This is just what I hear. The «magic« is what comes out of the speakers? May be because it drives the amp module balanced and handles the input also balanced. To me the overall sound is also cleaner. I am not a technical expert.
Are you using unbalanced input signal?
 

boXem

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One key difference is that the EVAL1 will produce a single-ended output if provided with a single-ended source. The EVAL1 also has no common-mode rejection (it relies on the CMRR of the amplifier module for that). The Neurochrome Purifi/Hypex Buffer will provide a differential and balanced output even if driven by a single-ended source.

Tom
Hi Tom, could you please demonstrate these two assertions?
While I agree with your reasoning on the CMRR when the EVAL1 input stage is bypassed, I have to admit that I have hard time to follow your reasoning in the other cases.
As a reminder, EVAL1 input stage looks like this:
1618416226226.png
 
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