Say "Hello!" to boXem Arthur series, Hypex and Purifi based power amplifiers

[boXem]

Development tests are done on the buffer only and by measuring noise and distorsion independently (quicker and more accurate). QC is quick and dirty stuff.
At the end, nothing publishable.
As soon as things go back to normal on the 1ET940BA front, I will have publishable stuff.

 

[jamesdyson]

Development tests are done on the buffer only and by measuring noise and distorsion independently (quicker and more accurate). QC is quick and dirty stuff.
At the end, nothing publishable.
As soon as things go back to normal on the 1ET940BA front, I will have publishable stuff.

So you are saying you dont have developments tests data of a full amp build? You only test bits in isolation. Seems very odd.

 

[blackiridium]

Purifi sent us improperly calibrated modules. We had to ship back our entire stock and are waiting the parts back. At the moment we are stuck, not only on the measurement side.
Before the subject comes, amplifiers sent to customers are not impacted by this calibration issue.

So 1ET6525SA are shipping?

 

[boXem]

So 1ET6525SA are shipping?

Subject here is 1ET9040BA, sorry for the confusion. 1ET6525SA still planned for mid October.

 

[LETRA]

Hello @boXem. I have been on hold for almost two months for the Arthur 4516/2 and I have received an email that the order is already being processed, I guess it will be shipped very soon. I went to the website and I thought I saw in the description of the Arthur 4516/2 a new detail that was not there before: "Input and gain stage with exclusive boXem stage III composite topology". Could you explain what it is and what other changes you have made in this new 4516 with respect to the 4515 apart from Purifi module?

Best regards.

 

[boXem]

Hello @LETRA . Your order has actually been shipped. I hope that you did receive our emails informing about the additional delays and didn't worry too much whether you would receive your amp or not.
The product description has not changed (apart some typo) since we started selling the Arthur 4216/E2. The composite topology consist in splitting the tasks between opamps, one supplying the current, the other controlling the noise and distortion.
The input stage was completely redesigned. 4 layers PCB and ultra low noise regulators are the main changes - in addition to the composite opamp - compared to the previous generation.

 

[amper42]

Hello @LETRA . Your order has actually been shipped. I hope that you did receive our emails informing about the additional delays and didn't worry too much whether you would receive your amp or not.
The product description has not changed (apart some typo) since we started selling the Arthur 4216/E2. The composite topology consist in splitting the tasks between opamps, one supplying the current, the other controlling the noise and distortion.
The input stage was completely redesigned. 4 layers PCB and ultra low noise regulators are the main changes - in addition to the composite opamp - compared to the previous generation.

Fred,
Can you hear or measure a difference between the composite topology in the 4216/E2 versus the 4215/E2 input stage?
Thank you!

 

[LETRA]

Hello @LETRA . Your order has actually been shipped. I hope that you did receive our emails informing about the additional delays and didn't worry too much whether you would receive your amp or not.
The product description has not changed (apart some typo) since we started selling the Arthur 4216/E2. The composite topology consist in splitting the tasks between opamps, one supplying the current, the other controlling the noise and distortion.
The input stage was completely redesigned. 4 layers PCB and ultra low noise regulators are the main changes - in addition to the composite opamp - compared to the previous generation.

Hi @boXem. Yes, I have received the e-mails and shipping notification that the package will be delivered to me on Monday. The wait all this time yes it has been harder. Hopefully now customers will be able to get it very quickly from now on. I have been an early adopter and have had to be very patient.

Thanks for the explanations on the changes from Arthur 4215, I will follow with interest any discussion you have here on how this affects in terms of sound quality improvement.

Best regards.

 

[boXem]

Fred,
Can you hear or measure a difference between the composite topology in the 4216/E2 versus the 4215/E2 input stage?
Thank you!

Hear: well we are on ASR... I have the feeling that having the channels running out of phase (another difference with the previous generation) improved the bass. For the rest, if there is an audible difference, it is extremely subtle.
Measure: I never measured the old buffer with the new measurement system. The only data I have are with the Motu M2 as DAC/ADC, so the difference would not be realistic, the chain Su9n - A70Pro - Cosmos ADC being much lower noise and distortion by itself. But that's a good idea, in the to do list once all orders will be fulfilled.

 

[Oniiz86]

Hear: well we are on ASR... I have the feeling that having the channels running out of phase (another difference with the previous generation) improved the bass. For the rest, if there is an audible difference, it is extremely subtle.
Measure: I never measured the old buffer with the new measurement system. The only data I have are with the Motu M2 as DAC/ADC, so the difference would not be realistic, the chain Su9n - A70Pro - Cosmos ADC being much lower noise and distortion by itself. But that's a good idea, in the to do list once all orders will be fulfilled.

@boXem I was just curious why having the channels out of phase for the 2 Ch variant of the 4216 was necessary as I thought the Hypex SMPS1200A400 is a 2 Quadrant design thus will not suffer from power supply bus pumping effects, I thought it was only deemed necessary with the SMPS3kA400 as that is not a 2 Quadrant design?

 

[boXem]

@boXem I was just curious why having the channels out of phase for the 2 Ch variant of the 4216 was necessary as I thought the Hypex SMPS1200A400 is a 2 Quadrant design thus will not suffer from power supply bus pumping effects, I thought it was only deemed necessary with the SMPS3kA400 as that is not a 2 Quadrant design?

You are perfectly right, mapping the channels out of phase is not necessary with the SMPS1200 since it is a 4 quadrant PS. As a matter of fact, many amplifiers (including our own previous generation) work perfectly with channels running in phase.
But since the SMPS1200 is not regulated, when it starts to be loaded, the rails voltage decreases. This impacts the max amplifier power.
When the channels are running out of phase, and the signal to be amplified is the same on both channels, the load on the power supply is much lighter since the currents from each channel are in opposite direction, so they kind of feed each other.
Result is higher available power due to higher rails voltages for mono signals, like the bass frequencies in many mixes. And since most speakers happen to be current hogs in the bass frequencies, it's a nice improvement.

 

[Oniiz86]

You are perfectly right, mapping the channels out of phase is not necessary with the SMPS1200 since it is a 4 quadrant PS. As a matter of fact, many amplifiers (including our own previous generation) work perfectly with channels running in phase.
But since the SMPS1200 is not regulated, when it starts to be loaded, the rails voltage decreases. This impacts the max amplifier power.
When the channels are running out of phase, and the signal to be amplified is the same on both channels, the load on the power supply is much lighter since the currents from each channel are in opposite direction, so they kind of feed each other.
Result is higher available power due to higher rails voltages for mono signals, like the bass frequencies in many mixes. And since most speakers happen to be current hogs in the bass frequencies, it's a nice improvement.

Thanks for that, I believe it is actually advised by Purifi as I forgot these are half-bridge amplifiers, I thought the SMPS1200 was a 2 Quadrant design not 4 Quadrant?

 

[boXem]

Thanks for that, I believe it is actually advised by Purifi as I forgot these are half-bridge amplifiers, I thought the SMPS1200 was a 2 Quadrant design not 4 Quadrant?
View attachment 409041

The SMPS3k was designed with bridged amplifiers (especially the NC2k) in mind, thus is 2 quadrants.
The SMPS1200 was designed to be easily integrated with most Hypex modules that happen to be single ended. So it is a 4 quadrants PS

 

[Oniiz86]

The SMPS3k was designed with bridged amplifiers (especially the NC2k) in mind, thus is 2 quadrants.
The SMPS1200 was designed to be easily integrated with most Hypex modules that happen to be single ended. So it is a 4 quadrants PS

@boXem Oh I thought the SMPS3k was not a 2 Quadrant design, this was your post from some time ago https://www.audiosciencereview.com/...-purifi-amp-builds.10478/page-125#post-983596 where you had mentioned this regarding the SMPS3k, "Are you sure that they are *that* easy to integrate? Unlike the SMPS1200, the SMPS3k is not a 2 quadrant SMPS...", it seems you suggest the SMPS1200 is in fact a 2 Quadrant design.

A couple of posts below the one you made above here https://www.audiosciencereview.com/...-purifi-amp-builds.10478/page-125#post-983672

 

[boXem]

@boXem Oh I thought the SMPS3k was not a 2 Quadrant design, this was your post from some time ago https://www.audiosciencereview.com/...-purifi-amp-builds.10478/page-125#post-983596 where you had mentioned this regarding the SMPS3k, "Are you sure that they are *that* easy to integrate? Unlike the SMPS1200, the SMPS3k is not a 2 quadrant SMPS...", it seems you suggest the SMPS1200 is in fact a 2 Quadrant design.

A couple of posts below the one you made above here https://www.audiosciencereview.com/...-purifi-amp-builds.10478/page-125#post-983672
View attachment 409166

Post on sunday, cry on monday...
My bad, 1 quadrant vs 2 quadrant. For each rail. Post corrected.

 

[amper42]

1. Does the Boxem A 4216/E2 also map the channels out of phase with the SMPS1200?

2. What causes the Arthur 4216/E2 to have 100k input impendance versus 10K for the A 4216/E2?
Will you be able to hear or measure a difference between these two models?

Thank you.

 

[boXem]

1. Does the Boxem A 4216/E2 also map the channels out of phase with the SMPS1200?

2. What causes the Arthur 4216/E2 to have 100k input impendance versus 10K for the A 4216/E2?
Will you be able to hear or measure a difference between these two models?

Thank you.

1. Yes
2. The OPA1612 has a quite high bias current that translate into non neglectible DC (pops at power up-front) when associated to high input impedance. So input impedance smneeds to be lowered (A series) of DC needs to be filtered out (Arthur).
Arthur has lower noise than A series.

 

[amper42]

1. Yes
2. The OPA1612 has a quite high bias current that translate into non neglectible DC (pops at power up-front) when associated to high input impedance. So input impedance smneeds to be lowered (A series) of DC needs to be filtered out (Arthur).
Arthur has lower noise than A series.

Fred,
If I am understanding you:
1. The Boxem A 4216/E2 will make a pop noise or crackle at power-up and that noise can be louder with a high impedance device feeding the amp? I am using the RME ADI-2 DAC FS which offers low impedance to feed the Purifi based amp which should not be an issue?

All three Purifi amps I have used in the past (March Audio, Buckeye and Arthur 4215/E2) typically produce a "tiny" crackle noise when first turned on if the RME is already powered. When I power up both the RME and the Purifi amp at the same time using a power strip the crackle is inaudible. Even so, the very tiny power-up noise was never an issue. Is that what we are talking about?

2. Is it possible to show a chart that compares measured noise differences between the A 4216/E2 and the Arthur 4216/E2. Is the difference enough that a highly trained ear could pick out which unit is playing?

I am thinking of purchasing one of these amps and trying to understand what the actual tangible difference would be in ownership/usage besides size and visual appearance. Thank you.

 

[boXem]

Fred,
If I am understanding you:
1. The Boxem A 4216/E2 will make a pop noise or crackle at power-up and that noise can be louder with a high impedance device feeding the amp? I am using the RME ADI-2 DAC FS which offers low impedance to feed the Purifi based amp which should not be an issue?

Nope. Bias current is contained within the amp and the few hundreds ohms from high output impedance devices would anyhow not change anything to the DC caused by the bias current. 100k causes a pop noise that is not nice, 10k makes the pop noise caused by DC almost inaudible.

All three Purifi amps I have used in the past (March Audio, Buckeye and Arthur 4215/E2) typically produce a "tiny" crackle noise when first turned on if the RME is already powered. When I power up both the RME and the Purifi amp at the same time using a power strip the crackle is inaudible. Even so, the very tiny power-up noise was never an issue. Is that what we are talking about?

Since you own an Arthur 4215/E2 with a tiny pop noise, the one caused by the A 4216/E2 is tinier, further reduced with the Arthur 4216/E2

2. Is it possible to show a chart that compares measured noise differences between the A 4216/E2 and the Arthur 4216/E2. Is the difference enough that a highly trained ear could pick out which unit is playing?

I will work on this once all backorder is cleared.

 

[PloddyPastard]

So if I connect A 4216/E2 to a BlueSound Icon and use trigger out - will there be an audible pop noise on startup?