DIY Purifi Amp builds

[Murray A]

Are you happy with the case? Do you recommend it?

The case is excellent. It's better than the Purifi eval case in my opinion!

 

[Murray A]

You mean by the power supply?

How so? The 4-wire sense point is in the DELRON sockets. Did you make any other adaptions in your build?

The sense points are in the same vicinity as the delron sockets. I was was unable to measure the output Z difference between the two connections.

 

[JimB]

The sense points are in the same vicinity as the delron sockets. I was was unable to measure the output Z difference between the two connections.

You appear to have done a really solid job of connecting your speakONs.

 

[Aardappel]

What is the reason for the pretty sizeable difference in Purifi output power measurements between their own measurement (top chart) and the soundstagehifi measurement (bottom chart)? In 8 Ohm its about a 100W difference - is it because of the input buffer being bypassed or not? And if so, why would one want to bypass the buffer if power output drops by 100W..?

 

[JimB]

What is the reason for the pretty sizeable difference in Purifi output power measurements between their own measurement (top chart) and the soundstagehifi measurement (bottom chart)? In 8 Ohm its about a 100W difference - is it because of the input buffer being bypassed or not? And if so, why would one want to bypass the buffer if power output drops by 100W..?

Those 8 ohm soundstage measurements are highly suspect. It's not 100W more, it's almost 175W more. This doesn't agree with Purifi, or the review here on ASR. 375W into 8 ohms corresponds to 54.8V RMS, and 77.5 peak. The max power supply rating for the EVAL1 is +70V and +75V for the 1ET400A. Output swing would be somewhat less than that, so it should take >80V supplies to get 375W (assuming the drive circuitry had the range).

 

[Aardappel]

Those 8 ohm soundstage measurements are highly suspect. They don't agree with Purifi, and they don't agree with the review here on ASR. 375W into 8 ohms corresponds to 54.8V RMS, and 77.5 peak. The max power supply rating for the EVAL1 is +70V and +75V for the 1ET400A. Output swing would be somewhat less than that, so it should take >80V supplies to get 375W.

@Murray A - how did your Purifi measurements compare?

 

[Murray A]

@Murray A - how did your Purifi measurements compare?

Don't know because I didn't measure it yet! Line voltage regulation is important when power measurements are done and I suspect the output regulation of the SMPS1200A400 is partially responsible for the discrepancy. The accuracy of the AP rms converter also may be a contributing factor when presented with a clipped waveform.

 

[JimB]

Don't know because I didn't measure it yet! Line voltage regulation is important when power measurements are done and I suspect the output regulation of the SMPS1200A400 is partially responsible for the discrepancy. The accuracy of the AP rms converter also may be a contributing factor when presented with a clipped waveform.

Per the SMPS1200A400 datasheet, output voltage is approximately proportional to input voltage, with 63VDC out being nominal for 230VAC in. Max out is 72VDC for max permitted input of 264VAC. But you only get 49VDC out at the Min of 180VAC in. These will definitely determine the max power from the amp modules, but they cannot get you to 375W into 8 ohms (1% distortion). At the EVAL1 max permitted supply voltage of 70V, the amps should not be able to reach above about 290W. This is significantly more than 200W, but who is running 260+VAC mains?

 

[Aardappel]

Per the SMPS1200A400 datasheet, output voltage is approximately proportional to input voltage, with 63VDC out being nominal for 230VAC in. Max out is 72VDC for max permitted input of 264VAC. But you only get 49VDC out at the Min of 180VAC in. These will definitely determine the max power from the amp modules, but they cannot get you to 375W into 8 ohms (1% distortion). At the EVAL1 max permitted supply voltage of 70V, the amps should not be able to reach above about 290W. This is significantly more than 200W, but who is running 260+VAC mains?

Very interesting. Well here in on the east coast of Australia we have an absolutely appalling grid with Voltages frequently over 250V, especially in summer when there is a lot of solar being injected into the grid. Lots of people are complaining about their solar inverters tripping frequently, which according to AS4777 should only happen at Voltages over 257V.

So I guess this 3rd world grid is good news for the Purifi Amp What would happen to the SMPS if the Voltage did briefly tip over 264V though..?

 

[JimB]

Very interesting. Well here in on the east coast of Australia we have an absolutely appalling grid with Voltages frequently over 250V, especially in summer when there is a lot of solar being injected into the grid. Lots of people are complaining about their solar inverters tripping frequently, which according to AS4777 should only happen at Voltages over 257V.

So I guess this 3rd world grid is good news for the Purifi Amp What would happen to the SMPS if the Voltage did briefly tip over 264V though..?

Maybe those power supplies with regulated primaries would be good there?

 

[LarsS]

Finally done ...

 

[LarsS]

Back & front

 

[JimB]

Finally done ...

How did you implement your split of the main DC outputs?

 

[LarsS]

How did you implement your split of the main DC outputs?

First tried with splicing & soldering, gave up and went for this, cut into 3*3 then grinded away all excessive material. Reasonably small bulb.

https://www.kjell.com/globalassets/...ef=1F1AE7F095&format=jpg&w=960&h=960&mode=pad

Edit: Isolated with butyl tape

 

[JimB]

@MicroAudio made a PCB for this:
https://www.audiosciencereview.com/...r-audio-applications.14307/page-2#post-463342

He also made a 3-out version that I might want to use soon. But, I might make a spliced cable, using ferrules, before inserting the crimps in the SMPS plug body. If I do, I'll share the technique.

 

[LarsS]

@MicroAudio made a PCB for this:
https://www.audiosciencereview.com/...r-audio-applications.14307/page-2#post-463342

He also made a 3-out version that I might want to use soon.

Saw that, for the ribboncable I followed your proposal with one long cable, three connectors and using the strain relief as you adviced. Worked great.

 

[wineds]

Back & front

View attachment 95559 View attachment 95558

Looks good! Strongly recommend you add a fuse holder with a 5 amp fuse as well though. The soldered onboard SMPS fuse is 12amp!

 

[JohnM-73]

Hi folks!

First post here, though have visited often. It was Amir’s review of the Purifi amplifier plus positive word of mouth here that convinced me to order one, as I couldn’t stretch to a Benchmark AHB2. Ordered the EVAL1 ‘kit’ plus the Ghent case. Very pleased with it indeed, but now turning to getting the best out of it.

First question is, should the provided wiring between J1 on the smps and J1 on the EVAL1 board be twisted? I assume not as on pictures of the Purifi demonstration amps I don’t see this done.

Secondly; speaker cable. I’ve ordered some Canare 4S11 Star-quad speaker cable, but am unsure as to the best way to solder it up. Is there likely to be a performance difference between using either the 2 pole or 4 pole speakon connector and plugs?

The Ghent case I have came with the 4 pole Speakon connectors, so I assumed a 4 pole connector would be best, but then I came across this from the Benchmark website (I know the two amps are not the same, but assume if it was needed to use all four poles, Benchmark would have done so):

“The plug used on this cable is a two conductor Neutrik NL2 SpeakON™ connector. It is compatible with the four-conductor NL4 jacks on the back of the AHB2 power amplifier. The NL4 jacks provide two additional contacts (+2 and -2) but these extra contacts are only needed for some bi-amp applications. Use this 2-pole cable for stereo and bridged mono applications.”

Lastly, would I use the clear and clear red Star-quad wires for one banana plug, and the red and white for the other banana plug? Or should it be clear red & red, and clear & white on the other plug... or doesn’t it matter?

Cheers!

John

 

[JimB]

Hi folks!

First post here, though have visited often. It was Amir’s review of the Purifi amplifier plus positive word of mouth here that convinced me to order one, as I couldn’t stretch to a Benchmark AHB2. Ordered the EVAL1 ‘kit’ plus the Ghent case. Very pleased with it indeed, but now turning to getting the best out of it.

First question is, should the provided wiring between J1 on the smps and J1 on the EVAL1 board be twisted? I assume not as on pictures of the Purifi demonstration amps I don’t see this done.

Secondly; speaker cable. I’ve ordered some Canare 4S11 Star-quad speaker cable, but am unsure as to the best way to solder it up. Is there likely to be a performance difference between using either the 2 pole or 4 pole speakon connector and plugs?

The Ghent case I have came with the 4 pole Speakon connectors, so I assumed a 4 pole connector would be best, but then I came across this from the Benchmark website (I know the two amps are not the same, but assume if it was needed to use all four poles, Benchmark would have done so):

“The plug used on this cable is a two conductor Neutrik NL2 SpeakON™ connector. It is compatible with the four-conductor NL4 jacks on the back of the AHB2 power amplifier. The NL4 jacks provide two additional contacts (+2 and -2) but these extra contacts are only needed for some bi-amp applications. Use this 2-pole cable for stereo and bridged mono applications.”

Lastly, would I use the clear and clear red Star-quad wires for one banana plug, and the red and white for the other banana plug? Or should it be clear red & red, and clear & white on the other plug... or doesn’t it matter?

Cheers!

John

1. Not important, but not bad. I would. I did, but I 'wound' the wires together before inserting them into the second plug so there was little stress in the bundle. Ghent cable is (I think). Be careful not to insert the wires in the wrong positions!!!
2. For just a 2-wire cable, conductors on the opposing corners of a square go together, so that should mean the reds go together and the whites go together. As for the speakONs, it depends what you want to do. As noted here recently, there is a common pattern for wiring the 4-poles in the case for these Purifi amps. If you want to use your speaker cables for this amp only, I'd wire the four conductors to the four pins of four-pole plugs to match the wiring to the four poles in the case. That is, on the amp end, each conductor gets its own pin in the plug. Just don't use the cable with other amps without first confirming how they are wired. Otherwise, a more universal cable would be to use 2-pole plugs and double the wires (reds and whites) into the terminations on the speakONs.

 

[JohnM-73]

Thanks very much for your reply Jim. That clears up the wiring. I’ll be using the Neutrik SpeakON at the Purifi end (and only for that amp), and standard pair of banana plugs at each speaker end.

Just curious why the 4-pole version per channel of the Purifi modules seems to be the more popular option here? Is there a slight measured advantage (lower impedance?) over the 2 pole, or is it slightly more mechanically reliable?

I’m using a Quad Artera Play+, which is a combination dac/cd/pre-amp, bought to cut down on the clutter. It can output up to 8Vrms via it’s balanced outputs. I assume therefore it might be advantageous to bypass the input stage on the Purifi for a tad more transparency, by moving the pre-gain jumpers as detailed in the manual?