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Review and Measurements of Purifi 1ET400A Amplifier
- Thread starter amirm
- Start date
Killingbeans
Major Contributor
I don't think maty is that bad. I like him in some weird masochistic way. Maybe I haven't had enough exposure 
From: https://hificompass.com/en/reviews/purifi-audio-ptt65w04-01a-midwoofer
This is from a recent article about the purifi woofer. I hope the amps will have a quantity discount for DIY.
Casey Leedom
Member
.. and I wonder just how stupid an idea it would be to consider a 7-channel amplifier using the Purifi 1ET400A modules? Lyngdorf is going to be coming out with an 8-channel amplifier based on the 1ET400A modules, the MXA-8400, but I have a nasty feeling that it'll be ... "fashion" expensive. It would be pretty cool to build a 7-channel 1ET400A-based beast. Trigger input would be a big plus. I just don't have the physical space for lots of mono blocks laying about ...
Casey
Casey
You couldn't power that conventionally and get full output on all channels. Even at 87% overall efficiency, at 400W/chan, x7 channels, that's 3.3KW power draw. But, I'd quite like to assembly a nice 3 channel unit!
Crossed over at 80 Hz, the AVR can handle the surrounds for me. In fact, I think I'd be okay with a single SMPS1200 for the job in my use. However, we are lead to believe the DIY kit will come as a pair of amp boards and a two channel input board, like in the unit as Amir tested, originally. And yes to some trigger scheme, though I have done it as an external, triggered power relay up to now...Casey Leedom
Member
So I'll admit right off the bat to not being an Electrical Engineer. I've taken some physics courses, and read generally everything, but I'm at best a "duffer" when it comes to Electrical Systems. (And if you want to know for background, I'm a Software Engineer working at the Hardware Layer.)
That said, I thought that the 7 Channels x 400W/Channel x 87% efficiency == 3.3KW would only be for trying to drive all channels at full power (400W). I thought that most surround channels have very little signal in them, and the vast majority of signal was in the front three channels. And yes, with aberrant inputs, you could over-drive the Power Mains (at least with a 120V 15A circuit) ... and probably lose your hearing at the same time ...
Mostly, I'm trying to solve an "ergonomic" problem in my own apartment. I need a single "box" that supplies 7 channels of amplification (space efficient), provides me with the best possible audio quality for my front three channels (stereo music + a stupidly over-the-top center channel[1]), and is power efficient. So yes, some form of Hybrid amplifier with 3 Purifi 1ET400A modules plus 4 cheaper, but still efficient, channels of some sort would "solve" the problem ... but now the design gets more complicated with different mixtures of equipment. So I figured 7 Purifi 1ET400A modules with a total cost of something on the order of $8,000-12,000 would just be "simpler" ...
And sure, go ahead and make it 240V capable so it could "potentially" be used in some crazy full on 400W x 7 usage ...
Can't I dream?
Casey
[1] Legacy Audio Focus SEs Left/Right; Legacy Audio Marquis XD Center.
That said, I thought that the 7 Channels x 400W/Channel x 87% efficiency == 3.3KW would only be for trying to drive all channels at full power (400W). I thought that most surround channels have very little signal in them, and the vast majority of signal was in the front three channels. And yes, with aberrant inputs, you could over-drive the Power Mains (at least with a 120V 15A circuit) ... and probably lose your hearing at the same time ...
Mostly, I'm trying to solve an "ergonomic" problem in my own apartment. I need a single "box" that supplies 7 channels of amplification (space efficient), provides me with the best possible audio quality for my front three channels (stereo music + a stupidly over-the-top center channel[1]), and is power efficient. So yes, some form of Hybrid amplifier with 3 Purifi 1ET400A modules plus 4 cheaper, but still efficient, channels of some sort would "solve" the problem ... but now the design gets more complicated with different mixtures of equipment. So I figured 7 Purifi 1ET400A modules with a total cost of something on the order of $8,000-12,000 would just be "simpler" ...
And sure, go ahead and make it 240V capable so it could "potentially" be used in some crazy full on 400W x 7 usage ...
Can't I dream?
Casey
[1] Legacy Audio Focus SEs Left/Right; Legacy Audio Marquis XD Center.
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Indeed, that is exactly the case, and even the full power situation won't last very long, so will be buffered by the capacitance in the power supplies.
Casey Leedom
Member
Hhrrrmmm, so here's where my lack of an Electrical Engineering Degree will really show ...
I thought that Switching Power Supplies (typically, but not always used in Class D amplifiers) have very little Capacitive Reserve Power. At least as compared with Classic "Linear Power Supplies" which spend all of their time trying to keep a massive Capacitor Bank charged?
Casey
I thought that Switching Power Supplies (typically, but not always used in Class D amplifiers) have very little Capacitive Reserve Power. At least as compared with Classic "Linear Power Supplies" which spend all of their time trying to keep a massive Capacitor Bank charged?
Casey
Yes, that is totally true - traditional linear (unregulated) power supplies have huge capacitors, partially because that is their only way to deal with high load situations. A SMPS still has capacitance, but the real factor limiting power output in a SMPS is usually heat dissipation, so they are typically capable of short time peak loads exceeding the nominal specification.
You couldn't power that conventionally and get full output on all channels. Even at 87% overall efficiency, at 400W/chan, x7 channels, that's 3.3KW power draw. But, I'd quite like to assembly a nice 3 channel unit!
According to the test results, the Purifi 1ET400A and the NC400 are not 400wpc amps. 7 channels would be are @ 1,800 watts of peak (non-clipped) power plus loss.
As for a total power remedy, multiple power cords could be an option. 1 power cord drives 4 channels and one drives 3 channels so it can be plugged into separate circuits if desired.
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Depends on where you call the limit, and your load impedance Yes, it's 'only' 257 at 0.0003%. But almost 400W at 1%. The Purifi datasheet claims upto 425W at 1% in 4 ohms (this is a cue for John to jump inAccording to the test results, the Purifi 1ET400A and the NC400 are not 400wpc amps. 7 channels would be are @ 1,800 watts plus loss.
As for a total power remedy, multiple power cords could be an option. I have a 7 channel amp that has 2 power cords. 1 power cord drives 4 channels and one drives 3 channels so it can be plugged into separate circuits if desired.
!). It will source 25 amps.Depends on where you call the limit, and your load impedance Yes, it's 'only' 257 at 0.0003%. But almost 400W at 1%. The Purifi datasheet claims upto 425W at 1% in 4 ohms (this is a cue for John to jump in
Running the amps at clipping is not a normal use case (excluding torture tests). I think the tests have proven the manufacturer's power specs are a bit generous. The 400w rating for the NC400 requires 240V power, not attainable in 120V.
So I'll admit right off the bat to not being an Electrical Engineer. I've taken some physics courses, and read generally everything, but I'm at best a "duffer" when it comes to Electrical Systems. (And if you want to know for background, I'm a Software Engineer working at the Hardware Layer.)
That said, I thought that the 7 Channels x 400W/Channel x 87% efficiency == 3.3KW would only be for trying to drive all channels at full power (400W). I thought that most surround channels have very little signal in them, and the vast majority of signal was in the front three channels. And yes, with aberrant inputs, you could over-drive the Power Mains (at least with a 120V 15A circuit) ... and probably lose your hearing at the same time ...
Mostly, I'm trying to solve an "ergonomic" problem in my own apartment. I need a single "box" that supplies 7 channels of amplification (space efficient), provides me with the best possible audio quality for my front three channels (stereo music + a stupidly over-the-top center channel[1]), and is power efficient. So yes, some form of Hybrid amplifier with 3 Purifi 1ET400A modules plus 4 cheaper, but still efficient, channels of some sort would "solve" the problem ... but now the design gets more complicated with different mixtures of equipment. So I figured 7 Purifi 1ET400A modules with a total cost of something on the order of $8,000-12,000 would just be "simpler" ...
And sure, go ahead and make it 240V capable so it could "potentially" be used in some crazy full on 400W x 7 usage ...
Can't I dream?
Casey
[1] Legacy Audio Focus SEs Left/Right; Legacy Audio Marquis XD Center.
Here you go:
https://www.nordacoustics.co.uk/nord-one-hypex-mp-multichannel
I specially like playing with the options of this one here:
https://www.nordacoustics.co.uk/pro...w-custom-configurable-channel-amplifier-black
Personally I would choose a black faced, 5 channel power amp with the front channels having 3 x 500W at 4 ohms and the surround channels 2 x 250W at 4 ohms for 1.5k pounds.
NCore MP series measures quite well, check their datasheets.
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Cheap!
Handwaving: A conventional full-wave bridge applies charge pulses at 120 Hz (120 times a second) in the US (other countries may run at 50 Hz so recharge the caps at 100 Hz). Big capacitors are needed to store and maintain the voltage during heavy current demands since they get "recharged" relatively slowly (120 Hz). Switch-mode power supplies (SMPS) typically operate at several hundred kHz, say 500 kHz, so recharge the capacitors 500,000 times a second. That means much smaller capacitors are needed since they are recharged so much faster (more often). You really cannot compare performance based on the size of the capacitors.
HTH - Don
HTH - Don
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Amir tested 1 NC400 channel running off of a 600watt PS and it still did not produce the manufacturer's specs.
A believe they can only charge the caps during the times the mains is a bit above the required output voltage (assumes they do not up-convert). For a 64V output, I'd estimate that to be about 1.5mS at 115 VAC, 60 Hz, full wave rectified, and about 1.0mS if 230VAC, 50 Hz, full wave rectified.
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