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DIY Purifi Amp builds

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JimB

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After having read @phoenixdogfan Purifi amplifier plight and sympathizing with the expense of shipping modules back and forth to Europe, I PM'd him and offered to help. I got the amp about 2 weeks ago and have been working with Hypex on it.

Initially I thought that it was a standby signal issue as the power supply would not hold maintain any voltage long enough to do much. After disconnecting the cables to the amp module, found the power supply would stay on. I checked the cabling and it was fine. However, as soon as any load was applied to the AUX power pins, it would shutdown. At this point as the power supply behavior was questionable, I contacted Hypex. Their previous repair was to the AUX power protection circuits and they shared some details with me. As mentioned, the SMPS was still in-warranty and so I was not tempted to do much, but they encouraged me to do some troubleshooting. Here is what I found that I thought might be useful to share...

R92 and R99 were open. These are 1 ohm SM resistors that are part of the SMPS AUX power protection circuit and are mounted on the bottom side of the board. As a quick test, shorted them out and the power supply started to behave normally. I hooked it back up to the amp and did a quick test on my QA401 and things were looking brighter. :)

I ordered some replacement resistors from Mouser and they arrived earlier this week. I got around to soldering them in and started re-assembling the amp to see if anything caused them to blow. The bad news is I did not find anything; the good news is that it continues to work! I have tested on my QA401 and did a quick listening test and all is well. Am packing it up today and preparing to ship it back to its owner.

Here is a pic of the amp with the LED shining just as @phoenixdogfan was hoping he would get to see someday…

View attachment 132450
YAY! So, as suspected, Hypex did NOT test with any load? Disappointing...
 

phoenixdogfan

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YAY! So, as suspected, Hypex did NOT test with any load? Disappointing...
Big up to Rick for finding this b/c it was way beyond my pay grade. Very disappointing that Hypex let something out that was not vetted under something approximating real world conditions.

Look forward to enjoying this amp for a very long time. I will open it up and share my no frills build when I get it back next week. and will pair it with the Octo Dac 8 Pro I have on order.

Probably one of the only builds ever done with Ghent's 300mm Hypex case with a custom fabricated back end (which I very poorly spray painted)--so it's unique. :) Should look just fine in my equipment cabinet, and I'll control on/off with a Gosund smart home plug via Alexa. (No 12 v trigger)

It was started well before Ghent did a case for Purifi, and way before VTV and others did their own builds. So now I'll finally get to hear it, so thanks again Rick.
 

Rick Sykora

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YAY! So, as suspected, Hypex did NOT test with any load? Disappointing...

I really do not know, but maybe. Hypex support was very helpful in pointing me towards the problem. They had replaced the resistors previously, so maybe a stray metal shaving or some other metal part? It has to be something that I could not reproduce and would have changed since.

As I replaced the resistors, I cleaned up the internals with air and did a wipe down.
 
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Any opinions on if there are any notable benefits to getting a different input buffer, like the neurochrome, over the Eval ones?
The Nord even appears to measure worse than the original...
 
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Any opinions on if there are any notable benefits to getting a different input buffer, like the neurochrome, over the Eval ones?
The Nord even appears to measure worse than the original...
For "better sound"? Not really. But there are many posts in this topic about the Neurochrome, which does have different features that can make it preferable to some. The EVAL1 is the 'value' leader for DIY.
 

phoenixdogfan

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After three trips to Hypex for the SMPS. a return trip to Purifi for the Eval 1 (it was fine, btw), a repurchase of the wiring harnesses from Ghent, and finally a trip to Mr Rick Sykora for the fully assembled amp:

IT WORKS
 

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phoenixdogfan

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And here's a shot of the internals:

https://www.audiosciencereview.com/...1742-1cdf-4332-8bd0-4179a063e65f-jpeg.132576/

Sorry but that image file was too large to copy and paste.

And how does it sound? Absolutely terrific. It's smooth and its powerful and does it ever sound clean. Beyond that, I don't know what else can be said. I know it will power my LS 50 Metas and probably anything I could ever want to upgrade to. Whether it's the best amp I've ever heard, or whether I could pick it out in a blind level matched listening test against any other amp is something I neither know nor feel I need to find out. I'm happy to just have a really nice powerful amp at a price I can afford (just barely!)

The case is unique. It's the Ghent case used to accommodate a Stereo Hypex NC 400 amp, and it's wider than the case he released last September for the Eval 1. I had a local company in Nashville, Sattler Machinery, fabricate a new case back to allow me to use the existing I/O's on the Eval 1 board. I thought about having it annodized, but was told it would cost as much as the custom case back, so I decided to just spray paint it with flat black. That yielded a terrible paint job which will be well out of sight, fortunately. I think the case looks really sharp. I opted for an orange light because I'm sick of blue light on amps. It has NCore embossed on the front panel, a reminder of the amp it was originally designed to house.

Finally, a big shout out to Rick Sykora who finally got this thing to work. I was pulling other parts of my system together (new speakers (LS 50 Metas), new DAC (Octo DAC 8 Pro), new headphone processor (Smyth Research A16), and I had this project waayyy on the back burner when I got an PM from Rick. After some discussion about what I had done, how often I tried to get it fixed, and my lack of results he agreed to do something no one else out there did: Take a look at the entire amp, diagnose its problems, and try to get it fixed. He succeeded totally and finally after almost a year I'm enjoying this amp right now. So many thanks to Rick who runs Sykora Sound. If anyone has a problem with their amplifiers, particularly Hypex or Purifi amps, I can tell you he would be the guy to get it fixed. Thanks again, Rick.

i'm sorry if this is a longwinded post, but, then again, I've had to wait a long time to post this. :p
 
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phoenixdogfan

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Oh, one last thing. This is a strictly no frills, plain vanilla build. No custom input buffer (sorry, Neurochrome), no 12v trigger, no front panel power switch--nothing. Only thing in the box is an SMPS. the Eval 1, and Ghent's power light. I will use a Gosund smart plug to power the unit on/off and at some point when the Octo DAC 8 arrives, I'll reset the input buffer for the lower voltage b/c the Octo will have two of its outputs set to 10 VRMS, enabling it to drive the Purifi to clipping even set to the lower gain.

It's been a long road, I'm glad I'm at the end of it.
 
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Is anyone aware what difference is between the two Hypex voltage regulators? The HPR and HNR
 
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ABall

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Is anyone aware what the purpose of adding a voltage regulator to the Purifi would be? I see Purifi says it doesn't need one - but at the same time there is the ability to add one... which sort of puzzles me.
I think it was probably designed at an early stage before the performance of the Hypex power supplies were realised. Tom from Neurochrome makes a regulator available for people who like to tweak and admits it measures no better but he also says people have made positive subjective comments that infer the amps sound better, of course we all know if something measures inaudible it's not going to make a difference. :p
 
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I think it was probably designed at an early stage before the performance of the Hypex power supplies were realised. Tom from Neurochrome makes a regulator available for people who like to tweak and admits it measures no better but he also says people have made positive subjective comments that infer the amps sound better, of course we all know if something measures inaudible it's not going to make a difference. :p
Fair enough - well, it makes a difference, its just a personal case of mental loopty-loops, which gets the job done for some people ;)
I did find an explanation earlier in the thread, that it remedies some issue with the Hypex SMPS, which is why the EVAL1 board apparently has a discrete regulator built in as well.

I'm currently just trying to discern which input board to go with - I'd like to customize my amp, to make it "my own", but I'd also like it to actually make some difference... The nord input boards are expensive, and somehow measure worse iirc? And the Neurochrome I can't seem to find much clear info on the purpose of.
I live in the EU so most of the alternate boards would have to be imported... So I'd like there to be a point.
 

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And here's a shot of the internals:

https://www.audiosciencereview.com/...1742-1cdf-4332-8bd0-4179a063e65f-jpeg.132576/

Sorry but that image file was too large to copy and paste.

And how does it sound? Absolutely terrific. It's smooth and its powerful and does it ever sound clean. Beyond that, I don't know what else can be said. I know it will power my LS 50 Metas and probably anything I could ever want to upgrade to. Whether it's the best amp I've ever heard, or whether I could pick it out in a blind level matched listening test against any other amp is something I neither know nor feel I need to find out. I'm happy to just have a really nice powerful amp at a price I can afford (just barely!)

The case is unique. It's the Ghent case used to accommodate a Stereo Hypex NC 400 amp, and it's wider than the case he released last September for the Eval 1. I had a local company in Nashville, Sattler Machinery, fabricate a new case back to allow me to use the existing I/O's on the Eval 1 board. I thought about having it annodized, but was told it would cost as much as the custom case back, so I decided to just spray paint it with flat black. That yielded a terrible paint job which will be well out of sight, fortunately. I think the case looks really sharp. I opted for an orange light because I'm sick of blue light on amps. It has NCore embossed on the front panel, a reminder of the amp it was originally designed to house.

Finally, a big shout out to Rick Sykora who finally got this thing to work. I was pulling other parts of my system together (new speakers (LS 50 Metas), new DAC (Octo DAC 8 Pro), new headphone processor (Smyth Research A16), and I had this project waayyy on the back burner when I got an PM from Rick. After some discussion about what I had done, how often I tried to get it fixed, and my lack of results he agreed to do something no one else out there did: Take a look at the entire amp, diagnose its problems, and try to get it fixed. He succeeded totally and finally after almost a year I'm enjoying this amp right now. So many thanks to Rick who runs Sykora Sound. If anyone has a problem with their amplifiers, particularly Hypex or Purifi amps, I can tell you he would be the guy to get it fixed. Thanks again, Rick.

i'm sorry if this is a longwinded post, but, then again, I've had to wait a long time to post this. :p
Glad you got it sorted. I see you're near Nashville. Love my VTV Eval 1. You're gonna love it.
 
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So far it seems rather unclear what input board would be ideal to go with, or if there is any point to any of them... If any of them perform better than the original Eval boards, or whether any of them affect the sound in some way of note - other than the NuTube ones which apparently sound a bit odd... some of them at least.
 
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So far it seems rather unclear what input board would be ideal to go with, or if there is any point to any of them... If any of them perform better than the original Eval boards, or whether any of them affect the sound in some way of note - other than the NuTube ones which apparently sound a bit odd... some of them at least.
I think the value/performance leader is the EVAL1, especially for a two-channel amp. It is generally accepted as being "transparent". The Neurochrome does have some different features that could be more desirable, depending on what you want, exactly. It does NOT require use of independent voltage regulation. I believe @tomchr has said that he personally would be satisfied with just running with the regulated outputs of the SMPS1200. He can answer more if he sees this.
 
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Oh, I see - that Guess I'd have to look closer at the Neurochrome board to see, but I assume I'd need one of each then to populate that board correctly if I were to use it.
Yes. All of these buffers are "bipolar" - they need both positive and negative supplies. So, if you are adding regulation, you should do both polarities.
 

ABall

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So far it seems rather unclear what input board would be ideal to go with, or if there is any point to any of them... If any of them perform better than the original Eval boards, or whether any of them affect the sound in some way of note - other than the NuTube ones which apparently sound a bit odd... some of them at least.

Its only unclear if you believe the hype from people who's only goal is to dupe people into spending more money than they need to. As far as I see it there's only 2 choices, Neurochrome or Eval, what I dont know is what type of amplifiers could be a problem when been used with the Eval. Its been mentioned a few times but nothing specific. Amir has already shown that expensive discreate opamps are a waste of money, at least that was my take from the reviews.
 
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Its only unclear if you believe the hype from people who's only goal is to dupe people into spending more money than they need to. As far as I see it there's only 2 choices, Neurochrome or Eval, what I dont know is what type of amplifiers could be a problem when been used with the Eval. Its been mentioned a few times but nothing specific. Amir has already shown that expensive discreate opamps are a waste of money, at least that was my take from the reviews.
It sort of depends on the application, the AES paper showed that op-amps can be audible, and also that people tend to prefer the ones that add distortion. Don't really know or care about the relative pricing of them, since that has nothing to do with their performance necessarily... Sort of similar to the cable debate in that sense; it shouldn't be a question of 'are expensive cables' but rather 'do any cables make any difference' - which some do, but usually only through some severely flawed construction, that makes them not 'transparent'... Which sounds like lunacy when we're talking about something as rudimentary as a cable or an op-amp.

But I digress... different can of worms. I think the only 'problematic' thing about amplifier matching with the Eval if if you bypass the buffer to get maximum performance, that would put some unusual demands on the pre-amp.
 
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I think the value/performance leader is the EVAL1, especially for a two-channel amp. It is generally accepted as being "transparent". The Neurochrome does have some different features that could be more desirable, depending on what you want, exactly. It does NOT require use of independent voltage regulation. I believe @tomchr has said that he personally would be satisfied with just running with the regulated outputs of the SMPS1200. He can answer more if he sees this.
In this case I'm trying to discern what the best performing one would be, regardless of price - and since I know someone who has the Eval1 based one, I'd like to try something different, just for the sake of curiosity...
I do also intend to make monoblocks... mainly just because I like it aesthetically. A shame purifi discourages bridging the amps even though its apparently possible. Would be interesting to know why/how it performs.

But yea, I'm sort of just trying to figure out how to add a different twist, for the fun of it, and hopefully get equal or better performance if possible.
 
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