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DIY Purifi Amp builds

Rick Sykora

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Thank you all. So I guess even 5A fuse wouldn't blow too often with normal use. I'll get them.
I do know it uses Y caps. Though it doesn't seem to be a problem as I don't hear any ground noise, I'll replace it anyway as it's cheap and I want to add a fuse.
My NC500s have the IEC filters and they are my best measuring amps.

Looking harder at Bruno’s original Y cap comment, it was from 2004 and was in regard to the UcD design. The Ncore design may just route the grounds differently. I know the Ncore audio ground floats and so whether it would see any case noise is dependent on how you wire the grounds. Notably, the signal grounds for the XLR input connectors.
 

daniboun

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Hi guys,

A stupid question about the Purifi Neurochrome buffers, do you confirm they use a Pin to Pin connection with the Hypex 1200A400 PSU , like this ? :

 

Rick Sykora

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Hi guys,

A stupid question about the Purifi Neurochrome buffers, do you confirm they use a Pin to Pin connection with the Hypex 1200A400 PSU , like this ? :


Took me a minute to grok this. Gather you meant the Neurochrome buffer board?

In any case, try @tomchr as it is his product. :cool:
 

tomchr

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I received an email this morning with the exact same figures. I responded to it too...

Pin 1 should go to pin 1. Pin 2 to pin 2. 3 to 3 ... 6 to 6. Simple.

Tom
 

Madjalapeno

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Planning a new build. I know that class-D amps pump out less heat than class A, but heat is still a concern.

Is there any reason NOT to use a case that has heatsinks for sidewalls and mount the amplifier modules to them?

1640117615674.png


Means I can get them far away from the SMPS, and have relatively simple internal wiring. Going with a case with an internal height of maybe 100mm.
 

Rick Sykora

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Planning a new build. I know that class-D amps pump out less heat than class A, but heat is still a concern.

Is there any reason NOT to use a case that has heatsinks for sidewalls and mount the amplifier modules to them?

View attachment 173952

Means I can get them far away from the SMPS, and have relatively simple internal wiring. Going with a case with an internal height of maybe 100mm.

Have not found any details from Purifi on this, but if you want to be sure, this Hypex doc and spreadsheet are helpful:

 

Madjalapeno

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Have not found any details from Purifi on this, but if you want to be sure, this Hypex doc and spreadsheet are helpful:
Thanks. I'm working my way through all their application notes. This part always amuses me considering almost every amp I've seen has black heatsinks. It makes sense though.

1640120579709.png
 

boXem

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Planning a new build. I know that class-D amps pump out less heat than class A, but heat is still a concern.

Is there any reason NOT to use a case that has heatsinks for sidewalls and mount the amplifier modules to them?

View attachment 173952

Means I can get them far away from the SMPS, and have relatively simple internal wiring. Going with a case with an internal height of maybe 100mm.
If you look at idle losses and efficiency for both modules and power supply you may choose a different implementation.
 

daniboun

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Hi amigos,

Here my new Purifi DIY amp.
In a few words :

The Kayamb Audio Buffer is a DIY Buffer made by a friend of mine (thx to Teddy) and using :
- Susumu Japanese resistors
- Nichicon KZ Muse Audio grade caps
- DIP8 OP amps socket (OPA1656 here)
- Hypex HPR12 Voltage regulator

The enclosure is a Galaxy GX alu case made in Italy and the Speakers terminals are in Copper. (Viborg style)
There is also a soft start module to limit destructive inrush currents

The amp is absolutely dead silent even with my ears glued to the speakers.
I also added a copper film on the Hypex transformer.
The default Buffer gain is -14DB, these buffers sound awesome by the way !
Speakers cables are blue edition Studio serie (UPOFC)

I am still testing the OPA1692 / 1656 and 1622. In progress....





 
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fraa

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Hi all,
Since there have been some inquiries, here I document how I built the Purifi amp with big meters based on Purifi Eval1. Some of the below have already been mentioned, but it would be more convenient to put them all together in one place.

679D9B07-503A-45B6-A99B-3224E6C50998.jpeg
CD2496C6-3E77-4503-A49F-D93D918AF791.jpeg
FED67D42-F29D-4893-9A3B-C28C04374CF6.jpeg



Case
The case is BZ3809H. It is available from Ali Express and Ebay. I got it from Ali. It's fairly cheap. I got it for 73USD including shipping (to Japan).
It is also available from Audiophonics. It may be cheaper if you are in Europe.

Sticker
To mark where to drill holes on the panels, I used transparent sticker films like this one. That is, I printed lifesize outlines of the holes using an inkjet printer and stuck it on the panel. The Purifi sticker was an afterthought when there were a few sheets of the films left. I just printed the logo from the Purifi website.

Tools
To cut the holes, I used mostly a handheld power drill I already had. For the big, non-round holes I used a jigsaw I bought a few years ago when I built the wooden amp rack you can see in the picture. With these tools, the precision is not that great. So I bored considerably smaller holes and filed away the rest. I started with the back panel so that I would get better by the time I tackled the big hole on the front panel. It was a pretty ardous process. For more effortless and cleaner machining, sattlermanufacturing.com and sendcutsend.com have been recommended by other members. I considered outsourcing the cutting to local machining shop, too; but the cost seemed too high relative to the price of the case. Besides, I already had the necessary tools.

Knobs
I made the three round knobs on the front panel from a solid aluminum rod with a diameter of 13mm. It was quite cheap with USD5 for 30cm length. I cut them to maybe 25mm long and put each in a drill (as if it were a drill bit, i.e., using the drill like a lathe) and filed it while rotating it. I also drilled a hole in the center of one of the cross sections so that the push switch and the VR could be screwed into it. (The left two knobs on the front panel are push switches. The one on the right is a VR/switch that changes the illumination of the meter and turns it off when it is rotated to the leftmost position.) This is however a tricky process and needed quite a bit of trial and error.

Meters
The meters are two of these. I took off the transparent plastic cover of the meter and also the blue meter panel (made of thin plastic, just attached by a tape). The remaining part is basically a white plastic board with a meter mechanism. I connected two of them side by side and made one big panel. I printed a new big meter panel on a plastic label that looks like a hairlined silver panel. I drove the meters using a control board called TS-VU001. I bought the meters and the driver from Ali Express. As the driver needs a DC power at 12V-16V, I used the switching regulator M78AR15-0.5 that happened to be available at the local shop I bought electronic parts from. I built the recommended circuit in its data sheet on a universal pcb to regulate 15VDC from the unregulated VAUX (at 19VDC when the main is 100VAC), available as J5.3 on the power supply Hypex SMPS1200A400. The signal input to the meter comes directly from the XLR input. For illumination, the meters came with white LEDs but I broke some of them experimenting. So I bought some more LEDs that are more diffuse and had more yellowish color. I concocted some light diffuser from some white plastic (the spine of a plastic paper file) that were around.

PS Standby
The Hypex SMPS1200A400 goes into standby when 3.3-5.5VDC is applied to J5.1. But the voltage has to come from some other source than the SMPS itself. I used an iPhone AC adapter (5V). The 5VDC is switched by the latching push-button (on the left on front panel.) I verified that the power consumption of the whole box is less than 1W when it is on standby.

Parts
I chose the necessary parts mostly by availability, trying to buy from as few shops as possible to minimize shipping. Because the parts are cheap, I didn't want to pay more for shipping than the price of the parts. I bought most of the electronic parts from a local (Tokyo) electronic parts shop (although I didn't actually go there, buying via web), but they are generic parts that can be had from any of e.g. Amazon, Ali Express, or Audiophonics.

Gain switch
When I basically finished the build, I used the amp for a while and found out that the meters hardly moved at the audio level I usually listen to music. Since the meters show the input level from the DAC (Topping Dx7pro), and the gain of the Purifi is fixed, I could turn up the digital volume on the DAC to see the meters moving, but that was too loud. Then I realized I could bypass the buffer of Purifi EVAL1. I bypassed it by changing the jumpers J14 and J15 as instructed in Purifi EVAL1 User's Guide and was mostly satisfied by the result: now that the gain is about 14dB, compared to 27dB when the buffer was not bypassed, I could turn up the DAC volume for another 13dB for the same level of speaker output, and the meters moved much more. However, for some sources, especially classical music with a large dynamic range, I found that the 14dB was not quite enough gain. So I wanted a handy way to change the gain without opening up the case and changing the jumper setting. So I concocted a circuit to use a few relays to simulate the jumper change. I used another universal pcb, which can be seen over the Purifi buffer board at the back of the case. The relays are controlled by the second push switch from the left on the front panel. They are latching relays that only need current when changing the switch position, which is not very often. I was worried about adverse effect on the sound quality of the longer circuit that the signal goes through, but I can't tell the difference. Only after I made this addition did I realize I could use the signal after the buffer for the meter input.

That's it. Have a nice holiday!
 
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k525

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Hi all

I have a PURIFI EVAL1 kit build using Ghentaudio case and cables, it is very good apart for the fact very often I have a BUMP (sometime very loud) into the speakers when I switch on (take into account my dog is worried as soon he understands I am going to switch the amp on! :D ).

Tho amp is normally off and I switch on using an external wifi socket using an Logitech Harmony automation

Can someone suggest me how to fix?

Regards
 

boXem

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Hi all

I have a PURIFI EVAL1 kit build using Ghentaudio case and cables, it is very good apart for the fact very often I have a BUMP (sometime very loud) into the speakers when I switch on (take into account my dog is worried as soon he understands I am going to switch the amp on! :D ).

Tho amp is normally off and I switch on using an external wifi socket using an Logitech Harmony automation

Can someone suggest me how to fix?

Regards
Did you already contact Purifi?
 
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tomchr

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I have a PURIFI EVAL1 kit build using Ghentaudio case and cables, it is very good apart for the fact very often I have a BUMP (sometime very loud) into the speakers when I switch on (take into account my dog is worried as soon he understands I am going to switch the amp on! :D ).
If you aren't already, make sure that you turn everything on in the direction from the source to the speaker and turn it off from the speaker to the source. Some turn everything on/off at the power strip or using a switched outlet, and that can sometimes lead to pops.

I recently worked on one of the "sporadic pop issues" with a reasonably savvy DIYer in Norway. I think he participates here as well. Maybe he'll chime in. We tried various things but never found something that worked reliably in his setup. I believe he asked Purifi as well but didn't get much traction there. He ended up adding a pair of Neurochrome Guardian-86 to his amp and that eliminated the pops.

Interestingly, I've never had issues with pops in my Purifi amp. I power the amp with a Hypex SMPS1200A400 and turn the mains power to the SMPS on/off using one of my Intelligent Soft Start boards. That works–at least for me. I do get the occasional very slight 'tick' when the Purifi wakes up (happens a bit after the power supply is turned on), but I have to jam my ear into the speaker to hear it. I don't use the Guardian-86 in my build. I basically figured that the Purifi modules would take care of the clicks and pops, and they seem to do so in all but a small percentage of cases.

Tom
 

k525

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If you aren't already, make sure that you turn everything on in the direction from the source to the speaker and turn it off from the speaker to the source. Some turn everything on/off at the power strip or using a switched outlet, and that can sometimes lead to pops.
Yes Tom, it is exactly what I do but I pretty sure the bump occur also without any source connected

I recently worked on one of the "sporadic pop issues" with a reasonably savvy DIYer in Norway. I think he participates here as well. Maybe he'll chime in. We tried various things but never found something that worked reliably in his setup. I believe he asked Purifi as well but didn't get much traction there. He ended up adding a pair of Neurochrome Guardian-86 to his amp and that eliminated the pops.
This guardian-86 seem interesting, unfortunately I am using EVAL1 build-in soldered speaker connectors, use this Guardian-86 will require som work (I see these board need power supply.. do you know where to find some instruction?)
Interestingly, I've never had issues with pops in my Purifi amp. I power the amp with a Hypex SMPS1200A400 and turn the mains power to the SMPS on/off using one of my Intelligent Soft Start boards. That works–at least for me. I do get the occasional very slight 'tick' when the Purifi wakes up (happens a bit after the power supply is turned on), but I have to jam my ear into the speaker to hear it. I don't use the Guardian-86 in my build. I basically figured that the Purifi modules would take care of the clicks and pops, and they seem to do so in all but a small percentage of cases.

Tom
Thank you for all TOM!
 

tomchr

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This guardian-86 seem interesting, unfortunately I am using EVAL1 build-in soldered speaker connectors, use this Guardian-86 will require som work (I see these board need power supply.. do you know where to find some instruction?)
The power supply needs to be fished out of the EVAL1 as well. You can solder a couple of wires to the bottom of the board at the 6-pin power connector. It may also be possible to use the AUX supply (available on the ribbon cable) to power the Guardian-86. My only concern with using the AUX supply is that it may stay up longer than the main supply. In that case the Guardian-86 could possibly let a power-down pop through. It would still be effective against power-up pops, though.

I provide the design documentation in the form of a download link that's sent via email when your order ships. I should probably add some installation instructions or video on my website.

Speaking of... I get questions like these pretty regularly. Specifically, questions around using my products to modify VTV, Ghent, and EVAL1-based amps. I have no desire to buy any of these amps just so I can make a "how to hack" video, but if any of you have an amp that you would like me to modify for you, I could be open to that. You pay parts and shipping. I do the work for free. We'd just coordinate such that your amp arrives when I'm ready to shoot the video. That way you don't have to wait too long for me to get around to it. Contact me by PM/email if interested.

Tom
 

Madjalapeno

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I provide the design documentation in the form of a download link that's sent via email when your order ships.
I will say as someone who has now made a number of Tom's designs, his documentation is superb, and he's very helpful and patient.

I have no hesitation recommending any of his products.
 

Naturlig

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Yes Tom, it is exactly what I do but I pretty sure the bump occur also without any source connected


This guardian-86 seem interesting, unfortunately I am using EVAL1 build-in soldered speaker connectors, use this Guardian-86 will require som work (I see these board need power supply.. do you know where to find some instruction?)

Thank you for all TOM!
I have built two Purify amps, one EVAL1 and one with the Neurochrome buffers, both with the Hypex SMPS1200A400 psu. In the amp with Neurochrome buffers I mounted the psu with the aluminium "wall" towards the 1ET400A components. Before the installation of Guardian-86 I turned the psu with the alu "wall" against the front plate (shorter power cables). The bump sound almost disappeared, still a small tick from the psu. Measured lower voltage values on the speaker terminals and a cleaner graph with the Picoscope. Why? For me it looks like that the psu rectifiers are mounted on the alu "wall"?
 

tomchr

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I doubt the orientation of the SMPS1200 plays into the magnitude of any thump. I could see how it could impact the mains hum, though. Rectifiers should generally be kept at a comfortable distance away from amplifier inputs and other sensitive circuitry.

I'm obviously not denying your data or experience, but I wonder if the difference is actually from better electrical connections to the SMPS. Maybe there's lower strain on the connectors (especially on the 6-pin power connectors) with the new orientation. Just a thought.

Tom
 

Naturlig

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I doubt the orientation of the SMPS1200 plays into the magnitude of any thump. I could see how it could impact the mains hum, though. Rectifiers should generally be kept at a comfortable distance away from amplifier inputs and other sensitive circuitry.

I'm obviously not denying your data or experience, but I wonder if the difference is actually from better electrical connections to the SMPS. Maybe there's lower strain on the connectors (especially on the 6-pin power connectors) with the new orientation. Just a thought.

Tom
Could be the case if you have a chassis design with short distance (a few mm) between the components.
But I have seen that it is the rectifiers on the SMPS and the "230V side" that make the most noise.
 

tomchr

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But I have seen that it is the rectifiers on the SMPS and the "230V side" that make the most noise.
That's been my experience as well.

Tom
 
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