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DIY Purifi Amp builds

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JimB

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I got my VTV build, and if it wasn't already confirmed, its 100% a Ghent case. I wanted my face plates to match and originally thought I would just order a second VTV one, but they wanted $50 so instead got a plain one from Ghent for $35 (including shipping).

I am new to amp building (and arm chair electrician'ism to boot) and curious why the Ghent / VTV boards are wired slightly differently. Both are using pins 1-3, but Ghent cable is also using pins 5 and 7 while VTV isn't. Having voltage regulation sounds like a good thing, is there any reason VTV might have excluded this, and should I add these wires?

View attachment 116032

Ps. As for build quality, it all looks fine. The faceplate was screwed on rather hard, almost stripped the screws getting them out and the cable positions have already been discussed. And it looks to be using a filtered IEC inlet which may need to be replaced
Yes - we confirmed that Ghent makes the VTV case. Ghent uses /AMPON and /FATAL because I advised them to do so. IMHO, they are desirable, but optional. This has been addressed in many posts LONG ago in this topic if you want to look for more.
 

nimar

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Yes - we confirmed that Ghent makes the VTV case. Ghent uses /AMPON and /FATAL because I advised them to do so. IMHO, they are desirable, but optional. This has been addressed in many posts LONG ago in this topic if you want to look for more.
Thanks for clarifying @JimB I have to admit I didn't read all 107 pages!, I think there was some mild uncertainty in another thread perhaps.

Do you have strong feelings about the orientation of the PSU? I'm tempted to take the best of both approaches and replace the IEC on the VTV build with a Ghent one, and flip the PSU around on my build to match the VTV approach. This should provide a little shielding between the chokes / buffer board.

I just need to figure out what the little metal clamps are called / what size I need, so I can buy some and extend my AC cables to reach.
 
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Thanks for clarifying @JimB I have to admit I didn't read all 107 pages!, I think there was some mild uncertainty in another thread perhaps.

Do you have strong feelings about the orientation of the PSU? I'm tempted to take the best of both approaches and replace the IEC on the VTV build with a Ghent one, and flip the PSU around on my build to match the VTV approach. This should provide a little shielding between the chokes / buffer board.

I just need to figure out what the little metal clamps are called / what size I need, so I can buy some and extend my AC cables to reach.
Orientation of the PSU? Not a big issue. @amirm tested the unit as built from Purifi to demonstrate their amp module and they had it oriented as Ghent does. It certainly does not degrade anything to a noticeable degree.
https://www.audiosciencereview.com/...easurements-of-purifi-1et400a-amplifier.7984/

What is your thinking on wanting to replace the VTV IEC filter with one from Ghent?
 

nimar

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Orientation of the PSU? Not a big issue. @amirm tested the unit as built from Purifi to demonstrate their amp module and they had it oriented as Ghent does. It certainly does not degrade anything to a noticeable degree.
https://www.audiosciencereview.com/...easurements-of-purifi-1et400a-amplifier.7984/

What is your thinking on wanting to replace the VTV IEC filter with one from Ghent?
Good point re orientation, though it is conceivable that the orientation was chosen at random by a manufacturer, unless we know the Purifi team was up late building them by hand. And while it measured great as is, maybe longer term it would be more stable the other way around? I don't have data to back this up, just the observation that VTV/Apollon chose to mount it the other way and Warrens reasoning was to shield the buffer from the chokes.

Re the IEC, as it has not been confirmed that they are using X capacitors, one is left to assume that they are using Y capacitors, and Bruno recommended against this as it pollutes the ground.

https://www.diyaudio.com/forums/class-d/38199-ucd180-questions-35.html#post466003
 
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Thread Starter #2,147
Good point re orientation, though it is conceivable that the orientation was chosen at random by a manufacturer, unless we know the Purifi team was up late building them by hand. And while it measured great as is, maybe longer term it would be more stable the other way around? I don't have data to back this up, just the observation that VTV/Apollon chose to mount it the other way and Warrens reasoning was to shield the buffer from the chokes.

Re the IEC, as it has not been confirmed that they are using X capacitors, one is left to assume that they are using Y capacitors, and Bruno recommended against this as it pollutes the ground.

https://www.diyaudio.com/forums/class-d/38199-ucd180-questions-35.html#post466003
No issue for stability, long term, just noise, constantly. I don't see that PSU orientation making a significant difference on internal shielding.

The Ghent unit has Y capacitors.
 

nimar

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No issue for stability, long term, just noise, constantly. I don't see that PSU orientation making a significant difference on internal shielding.

The Ghent unit has Y capacitors.
Perhaps originally but they switched to a bare unit at some point, as you can see in my side by side above.

Screenshot 2021-03-04 at 1.23.53 PM.png
 
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Yes. That one has NO filter, and I think I prefer it, though the filtered unit also has a fuse. Please satisfy yourself that you can get it installed on the VTV panel, or you'll also need a new back panel to go with it.
 

nimar

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Yes. That one has NO filter, and I think I prefer it, though the filtered unit also has a fuse. Please satisfy yourself that you can get it installed on the VTV panel, or you'll also need a new back panel to go with it.
I would be very surprised if VTV bothered to get a custom back panel to use a specific unit, more likely they got one that fit the panel. Eitherway I have one on order though it may take some time to arrive. Will confirm once I get it. As for the fuse, its looks to be non replaceable (I don't see how it would be replaced), so perhaps more trouble than it is worth. I plug these into a decent surge protector which I assume will flip in a scenario where a fuse would have been useful.

Thanks for your feedback, I am still green at electronics. I've built breadboard things before like Arduino but not done much with "serious" electronics.
 
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I would be very surprised if VTV bothered to get a custom back panel to use a specific unit, more likely they got one that fit the panel. Eitherway I have one on order though it may take some time to arrive. Will confirm once I get it. As for the fuse, its looks to be non replaceable (I don't see how it would be replaced), so perhaps more trouble than it is worth. I plug these into a decent surge protector which I assume will flip in a scenario where a fuse would have been useful.

Thanks for your feedback, I am still green at electronics. I've built breadboard things before like Arduino but not done much with "serious" electronics.
The hole for the Ghent filtered mains entry is larger than for the simple switch. So, the is a gap if trying to go from a filtered unit to a switch. Had you wanted to go the other way, at least you could have filed out the hole.

The fuse on the Ghent version is certainly replaceable. I'd be surprised if the one that VTV uses was not. You could confirm with them.
 

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VTV puts the shield on the SMPS facing the Purifi amp modules. Now that I think about it, doesn't that make more sense than having it face the face plate?
I believe it's more for surface area to allow the chassis to function as a heatsink for it more effectively.
 

jae

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Sorry if this sounds like a stupid question. Just been reading and catching up on the purify stuff. The cost of a putting a DIY together seems to be $1000 for Eval1 1et400 Stereo + $250 for Ghent audio kit + SMPS $250; totally $1500 appx. Vendors like VTV and Marchaudio are already selling in the same price range. What am I missing? Is this purely a fun project with not necessarily a saving angle? Thanks in advance. Also not sure if I should post this as a new thread.
The EVAL1 is about $750-770 USD, so your estimate is off by about $200-250. But yes it's mostly just for fun if you're doing a stereo configuration scratch, but you can still possibly save money if ordering a premade one isn't feasible in your country (import taxes etc). Most people build them as-is, but if you're adventurous you can do things like add a DAC board and/or raspberry pi for an all-in-one integrated solution if you were so inclined, since there's no such product on the market that compares in terms of specs (except perhaps the NAD M33 which also uses these modules - but it's $5000 and NAD's implementation causes a loss in performance). Other situations where DIYing is beneficial is you you want something like a single channel ampllifier or need multiple channel (4, 8) amplification with this high performance, building active speakers etc. Many avid DIYers may already have a suitable power supply and the modules might be a drop in replacement to an already functioning/damaged amp.
 
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I believe it's more for surface area to allow the chassis to function as a heatsink for it more effectively.
With that Ghent/VTV case, ventilation effectiveness is actually quite good with the heatsink towards the front panel - that's to use the heatsink of the SMPS to get heat to the air, which is the ultimate goal. Heat transfer to, and from, the bottom chassis, is about the same, regardless of orientation. The chassis is 4mm thick. People usually cite electrical shielding as a presumed benefit of the orientation in the VTV
1614964425536.png
 

rony

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The EVAL1 is about $750-770 USD, so your estimate is off by about $200-250. But yes it's mostly just for fun if you're doing a stereo configuration scratch, but you can still possibly save money if ordering a premade one isn't feasible in your country (import taxes etc). Most people build them as-is, but if you're adventurous you can do things like add a DAC board and/or raspberry pi for an all-in-one integrated solution if you were so inclined, since there's no such product on the market that compares in terms of specs (except perhaps the NAD M33 which also uses these modules - but it's $5000 and NAD's implementation causes a loss in performance). Other situations where DIYing is beneficial is you you want something like a single channel ampllifier or need multiple channel (4, 8) amplification with this high performance, building active speakers etc. Many avid DIYers may already have a suitable power supply and the modules might be a drop in replacement to an already functioning/damaged amp.
@jae Thank you very much for replying to my thread. I am in the US and feasibility is not an issue. I am also fortunate enough to splurge a couple of hundred. I am aware of DIY raspberry kits and can probably work on a pi4. I did not know that even DAC's can be DIY. Can we put together a hi spec end game DAC board? Will look that stuff up too.
 

jae

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@jae Thank you very much for replying to my thread. I am in the US and feasibility is not an issue. I am also fortunate enough to splurge a couple of hundred. I am aware of DIY raspberry kits and can probably work on a pi4. I did not know that even DAC's can be DIY. Can we put together a hi spec end game DAC board? Will look that stuff up too.
It's been a very long time since I've done much DIY so I can't help much with that people are doing these days or what the best options are. As 'recently' as 5-10 years ago there was a fairly decent incentive to DIY even dacs as some of the best designs were relatively easy to make and some even came in kit form, and many outperformed commercial products whose retail exceeded 3x-5x the build cost. These days cheap commercial DACs perform so well that there is less of an incentive to do so and many of those projects are obsolete.

As far as DACs go I know that a few years ago some used to use the premade Khadas tone boards (the original barebones version without any case- not sure if they are going to sell an 'OEM' version of the new tone 2) and stick them in their projects as a cheap way to get USB input into their integrated projects. Another thing I have seen some people doing is using (and sometimes heavily modifying) manufacturer evaluation boards for some of the latest chips, but I think for the most part I think it's still too cumbersome and probably not going to measure as well as a well-engineered modern dac, even some of the cheap ones reviewed on ASR.

As recently as a few months ago one thing that caught my eye were the chinese dac boards/modules sold on aliexpress. Generally you can search for a chip name on there (like akm4499 or ess9038pro) and find some interesting boards that supposedly perform well, and you can buy them fully functional or in modules (so you can also pair them with your choice of USB chipset or wireless chipset boards, etc..), but I think the prices are high enough that it may not be worth it to risk on a mystery product. I think most of those boards find themselves in lesser known mid-fi or even luxury chinese products, but that doesn't mean they are necessarily bad. diyaudio.com might be a good place to get an idea of what people are doing with diy these days and may have more info on what's good and what to avoid.
 

Joe0429

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I am new to amp building (and arm chair electrician'ism to boot) and curious why the Ghent / VTV boards are wired slightly differently. Both are using pins 1-3, but Ghent cable is also using pins 5 and 7 while VTV isn't. Having voltage regulation sounds like a good thing, is there any reason VTV might have excluded this, and should I add these wires?
Hi nimar,
https://www.audiosciencereview.com/.../vtv-purifi-1et400a-updates.17564/post-665909
According to those photos shared by ironhorse128, the difference of pin connection between VTV and Ghent are Pin1 'AMPON' and Pin3 'FATAL'.
For safety reason, I think it will be better connect 'FATAL' to SMPS J4 pin10 'DC ERROR'.
It cuts off power supply quickly if there is fatal happened on 1et400a modules.

VTV didn't use "SMPS Stand-By" control of SMPS1200A400, therefore connecting the 'AMPON' pin might make no difference.
Maybe you could give it a try.
 
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Yes - we confirmed that Ghent makes the VTV case. Ghent uses /AMPON and /FATAL because I advised them to do so. IMHO, they are desirable, but optional. This has been addressed in many posts LONG ago in this topic if you want to look for more.
SO many pages in this topic now... It's hard to find things, even when you know they are there. From over a year ago, this was covered in several pages before and after here:
https://www.audiosciencereview.com/...y-purifi-amp-builds.10478/page-14#post-304137
 
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Hi nimar,
https://www.audiosciencereview.com/.../vtv-purifi-1et400a-updates.17564/post-665909
According to those photos shared by ironhorse128, the difference of pin connection between VTV and Ghent are Pin1 'AMPON' and Pin3 'FATAL'.
For safety reason, I think it will be better connect 'FATAL' to SMPS J4 pin10 'DC ERROR'.
It cuts off power supply quickly if there is fatal happened on 1et400a modules.

VTV didn't use "SMPS Stand-By" control of SMPS1200A400, therefore connecting the 'AMPON' pin might make no difference.
Maybe you could give it a try.
If you really want to go this way, the plug for the J3 connector on the Purifi input board is JST brand EHR-7. The corresponding crimps are JST SEH-001T-P0.6, though the exact part number can vary with wire gauge on your cable. For example, here they are on Digikey: https://www.digikey.com/en/products/detail/jst-sales-america-inc/SEH-001T-P0-6/527266
 
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I'm about to go ahead and cut off one end of a pair of balanced Canare 'StarQuad' XLR cables, as a member here who I'm selling my Purifi amplifier to wishes to use a single ended pre into the Eval1. So I'm converting the cable to have a phono plug at one end. Just wanted to triple check the following is OK to go ahead with for the Purifi cable, thanks.

"One half of the star-quad ties Pin 3 of the XLR to the shield of the RCA connector. The other half of the star-quad ties pin 2 of the XLR to the center pin on the RCA. The braided shield ties pin 1 of the XLR to the shield of the RCA."

The above taken from: https://benchmarkmedia.com/collections/cables/products/benchmark-rca-to-xlrm-adapter-cable
 
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