New P482 Stereo Power Amplifier

Below is the power v THD+N curve for an 8 ohm load

1% THD+N = 246 watts

0.1% THD+N = 211 watts

Hey Alan,

I thought it was time to join the community, it's Bobby here.

Looking good, anxiously waiting for this release 🙂

I had noticed the Gain stage was initially noted as 23dB & 29dB but now corrected to 21dB & 27dB, was that inadvertently copied from the P801's Ultra Buffer specifications?

Below is the power v THD+N curve for an 4 ohm load.

1% THD+N = 497 watts

0.1% THD+N = 397 watts

Oniiz86 wrote:
Hey Alan,

I thought it was time to join the community, it's Bobby here.

Looking good, anxiously waiting for this release 🙂

I had noticed the Gain stage was initially noted as 23dB & 29dB but now corrected to 21dB & 27dB, was that inadvertently copied from the P801's Ultra Buffer specifications?

Welcome!

Yep, my bad. Brain fart, I was thinking of the P801 amps.

Hello Alan
I have a question if that's OK? I have been discussing your test results on Audio Science Review. One of your competitors has posted a plot showing their equivalent to the P482 having more noise, distortion and lower power. He says the difference in performance isn't statistically significant and seems to be saying the Purifi modules vary significantly in power 210 to 230 watts. Have you found this?
Thanks

@james dyson I believe the difference regarding power output is because most competitors are using Hypex's SMPS1200A400 which is only 63V so cannot achieve full rated output, I believe BoXem did touch upon this but Alan's custom SMPS solution is closer to the 1ET6525SA module's rated voltage of 65V, somewhere between 64V-65V & it is the only one touted to have Active Synchronous Rectification. 😉

james dyson wrote:
Hello Alan
I have a question if that's OK? I have been discussing your test results on Audio Science Review. One of your competitors has posted a plot showing their equivalent to the P482 having more noise, distortion and lower power. He says the difference in performance isn't statistically significant and seems to be saying the Purifi modules vary significantly in power 210 to 230 watts. Have you found this?
Thanks

Hi James

I tend not to pay any attention to ASR, and I certainly don't want to get into an argument with another manufacturer. However, I will say that this doesn't correlate with our experience.

We have built thousands of Purifi based amps and each one is tested at production. This means we have a large database of performance results. Whilst it's true to say the modules are not identical in performance, the differences are small, very small.

Ok, we havent tested a large number of 6525 modules yet, but I see no reason why the 6525 module would be any different to the other modules. To assert that the module is varying 10% in power output is pretty out there and wrong in my experience.

@Oniiz86 hit the nail on the head. If this manufacturer is using a Hypex power supply then it is too low a voltage. 65volts is required, the Hypex is only 63volts at the nominal mains supply voltage of 230v (110v). It has very poor voltage regulation and will wander all over the place depending on the incoming mains voltage. The Hypex spec sheet says 49 volts to 72 volts! 49volts will significantly limit the power output. 72 volts actually goes above the modules recommended supply range. Bus pumping with reactive speaker loads could easily make the voltage rise to 75v which would trip its protection mechanism shutting it down. Alternatively, when heavily loaded this psu will drop in output voltage reducing power output.

So, 210 watts is about what I would expect at the nominal 63 volts. It's the psu causing the power output variations, not the module.

Our power supplies have very tight voltage regulation WRT the incoming mains voltage and output load, hence we dont see these problems. The amp performance remains consistent regardless.

Hope that helps.

Alan

Thanks Alan, that all makes sense.

Below is the power v THD+N curve for an 4 ohm load.

1% THD+N = 528watts

0.1% THD+N = 492watts

@james dyson @Oniiz86 The question about power supply voltage prompted me to perform a bit more testing. I have set-up the PSU for 63volts and ran power curves on the 1ET6525 modules.

8ohm 1% THD+N = 203 watts

8ohm 0.1% THD+N = 165watts

4ohm 1% THD+N=405watts

4ohm 0.1%THD+N = 311 watts

So my estimate of 210 watts at 1% THD+N into 8 ohms was about right. So thats all you will get out of a Hypex PSU running at nominal mains input voltage (230v/110v). This is just one reason why we dont use them and have our own custom PSU.

@Alan March A curious observation I noticed of when the Award-Winning P422 was reviewed by Australian Hifi, is that it also achieved 246 watts at 8 Ohms with the Hypex SMPS1200A400, perhaps the difference of 230V/240V plays a part in the final output power too, I believe this review took place before the transition to the custom PSU in late 2021.

Oniiz86 wrote:
@Alan March A curious observation I noticed of when the Award-Winning P422 was reviewed by Australian Hifi, is that it also achieved 246 watts at 8 Ohms with the Hypex SMPS1200A400, perhaps the difference of 230V/240V plays a part in the final output power too, I believe this review took place before the transition to the custom PSU in late 2021.
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Yes, the P452 did utilise a Hypex PSU. Note the mains voltage during the test - up to 253 volts! As mentioned, the Hypex supply varies its output voltage proportionally with the incoming mains voltage because its unregulated. So its a bit of a lottery depending on the mains voltage at your house as to whether the amp will reach its power output spec or not.

Taking into account voltage drop due to load, you would need over 240v (120v) for the Hypex to output enough voltage to make the 1et6525 reach full power output.

Alan March wrote:
Yes, the P452 did utilise a Hypex PSU. Note the mains voltage during the test - up to 253 volts! As mentioned, the Hypex supply varies its output voltage proportionally with the incoming mains voltage because its unregulated. So its a bit of a lottery depending on the mains voltage at your house as to whether the amp will reach its power output spec or not.

Taking into account voltage drop due to load, you would need over 240v (120v) for the Hypex to output enough voltage to make the 1et6525 reach full power output.

Thanks for that Alan, silly me for not picking up on that, I also didn't realise that Australia is officially a 230V country from way back in 2000, I thought we were 240V, I believe WA is still 240V & Queensland only recently transitioned to 230V back in 2020, I need to educate myself with Australia's current electrical power standards. 😉

237v here in WA as I write. Remember there is a tolerance its allowed to operate within. For example, whilst the UK is formally 230v and was supposed to drop to there from 240v to harmonise with Europe, it never did because 240v is still within the allowed tolerance.