Apollon 1ET6525SA ST Amplifier Review

[JensA]

Good job and thanks for the test Amir.

1,190.00€ (USD $1,348) for an endgame amp. Great hifi times we live in.

Prices on www.apollonaudio.com are excluding VAT and shipping. On the other hand - at least until a couple of days ago - Apollon offered a 10% discount.
But even at around 1.275 € (plus shipping) this Stereo amp remains great value for money.

Just before Christmas, I ordered 9040 amps from Apollon's premium line.

To be perfectly honest, I doubt that
a) my deaf ears would hear any difference with this stereo amp
b) I will ever be able to use the power reserves of the 9040s

I was aware of all this beforehand, but I still opted for a slightly more expensive 9040 solution (which nevertheless replaces significantly more expensive amplifiers).

Never say never, but with these 9040 Purifi module amps, I won't be thinking about upgrading my amplifier in the foreseeable future...

And that's the great news:

- With the Purifi (and actually also Hypex) modules, there are undoubtedly sublime Class D amplifier modules with incredible performance at such affordable prices that were absolutely unimaginable just a few years ago.
- Manufacturers such as Apollon and Buckeye are turning the Purifi/Hypex modules into affordable and excellent amplifiers with excellend building quality.
- End users/buyers can choose from a wide range of enclosures (from spartan to very high quality) depending on their personal preferences.

It will be interesting to see whether these affordable Class D amplifiers will ultimately compete with suppliers of extremely expensive ‘high-end’ amplifiers like the recently introduced Linn Klimax Solo 800 which is being sold for abt 90.000 Euro a pair...
Even if I choose an extremely high-quality enclosure – such as Apollon in their premium line and check all the upgrade boxes – I can hardly manage to spend more than 5% of the Linn Klimax Solo 800 price
But of course, that's not how the target group for such high-priced monster amplifiers thinks...

 

[Apollon Audio]

@Apollon Audio two questions please :

1)Why do prices double for exports to the USA?

2)Why don't you update product pictures on your website?

Regarding pricing for exports to the USA:
There is no price doubling for shipments to the United States. The base (net) product price remains the same. However, shipping costs to the USA are higher than within Europe, which is expected due to overseas air transport. In addition, the United States has introduced a 15% import tariff, which is a government-imposed charge outside of our control. Even with this tariff included, U.S. customers typically pay less in total than EU customers, who are subject to 20–22% VAT on top of the net price.
Regarding product images:
Updated product photographs are currently in preparation and will be added to our website very soon.

 

[PristineSound]

I couldn't live with the Buckeye case.

I'm not a fan neither, to put it mildly.

I haven't checked Buckeye's recent pricing, but they are very competitive the last I checked, especially their MP amps. So a lot of the budget conscious customers flood over to Buckeye.

But for many of us, yeah, those cases, ah a, no way will that thing come into my house.

 

[Mort]

Is it time we let the buckeye case debate go?
On the other hand, I guess it's good marketing for buckeye.

 

[PristineSound]

Is it time we let the buckeye case debate go?
On the other hand, I guess it's good marketing for buckeye.

It's hard not to. I started with a praise of how good looking the Apollon cases are and unfortunately since the Buckeye was recently reviewed too, naturally others will draw a comparison, which is what happened.

Unfortunately, you can't have good looking when there isn't the opposite to compare with.

I get it some my not like the criticism, but unfortunately, these discussions do come up, on a public forum over the Internet nevertheless. This won't be the last time the topic of Buckeye's case comes up.

 

[Mort]

This won't be the last time the topic of Buckeye's case comes up.

Maybe you want to make your own thread.

 

[dan_uk]

For me, HiFi components should be a thing of beaty and ideally on display

That said, for a cinema room with hidden amps, buckeye would be a great choice as same performance but lower cost.

 

[David_M]

The gain is what the rest of the testing was at as that is the last test I run.

Because no one uses the amplifier with inputs shorted. AP's noise floor is quite a bit lower anyway:

See how it registers just 3 microvolts when the amp is off.

Regardless, this is not a noise test but power on/off glitch test. That it also shows the idle noise floor is a byproduct.

Ok, so that would be at the amplifier's maximum gain, then, correct? I find it odd that the amps tested so far, from different manufacturers, seem to have the same noise floors at idle, which is nonexistent with the Purifi modules with their inherent 12dB or 14dB of gain, based on their datasheets. Adding an extra 6dB to 12dB or so by the buffer should not raise the noise floor by that much, imho.

As for the shorted input test, it would be helpful and instructive to add it to your repertoire of tests to highlight the output noise levels of the amp itself.

 

[David_M]

In real world conditions, what downsides would there be to having a SMPS power supply having “unregulated (or loosely regulated) high-voltage DC bus whose voltage varies with mains input voltage and load conditions” potentially have for a listener?

What are the practical benefits (if any) to having a Hypex SMPS1200A400 power supply instead?

On a practical note, the speakers I happen to currently have in rotation are the KEF LS50 Meta’s, KEF R3 Meta’s and Magnepan 2.7’s (terribly inefficient but relatively benign resistive load).

Thank you,
Lumi

I would say that living in an area having poorly regulated AC mains, like many do in some parts of the US, will cause your amp to be underpowered if the AC mains are on the lower side (~ 90VAC). Depending on the impedance of the load, it could cause clipping distortion as the amp struggles to deliver current to the load. But on other days, when the AC mains are nominal, even overpowered (but within spec'd range), that same piece of music at the same time in the song will not be clipped, since the amp would be able to deliver the required current.

One benefit of the two supplies is that the MA power supply can deliver 1400W or more to the amp, enabling you to reach the full specs of the 9040BA module into 2 ohms. The Hypex will deliver under 1200W, with 1100W typical based on some amp tests. You decide if that's important to you or not.

Inefficient speakers will require lot of power, especially the 4-ohm magnepans, if you want to crank things up. You decide whether 1100W or 1400W-plus will suffice.

 

[PristineSound]

Maybe you want to make your own thread.

This comment really isn't necessary, other people have their own opinion, and they are free to express them, you don't need to go around starting beef with other people. I have even defended Buckeye's case as part of their business model and how smart it is, despite I'm not fan. I am on a Apollon review praising their casework, someone else made a comment on Buckeye's case and I agreed to it. If you like to go around policing people, apply to become an ASR moderator.

 

[NTK]

Ok, so that would be at the amplifier's maximum gain, then, correct? I find it odd that the amps tested so far, from different manufacturers, seem to have the same noise floors at idle, which is nonexistent with the Purifi modules with their inherent 12dB or 14dB of gain, based on their datasheets. Adding an extra 6dB to 12dB or so by the buffer should not raise the noise floor by that much, imho.

As for the shorted input test, it would be helpful and instructive to add it to your repertoire of tests to highlight the output noise levels of the amp itself.

Which is certainly not the case, for example from a recent review (source):

The best measuring amplifiers do, however, show similar idle noise levels.

The Purifi 1ET6525SA datasheet specs a typical unbuffered idle noise of 6.6 µV, A-weighted, with S/N ratio of 137 dB. When Amir tested with the front buffer to raise the gain, the SNR went down by 8 dB to 129 dB, which is 2.5× (and would increase the A-weighted noise to 16.5 µV). Therefore, a measured unweighted idle noise of 30 µV is a reasonable number.

 

[JeremyFife]

I have a question about the Gain settings - specifically mentioned in this review, but it's a generic question really. Performance is more that good enough at any Gain setting, so my question is about achieving maximum rated power.

Quoting from the review: "20 dB gain is good enough to push the amp to max power with nominal 4 volt input over XLR connection"

Does this suggest / mean that in order to get max power, and if I want the "best" signal (lower gain), people like me should be adding a pre-amp that actually amplifies the signal to give higher voltage output?

 

[Mort]

starting beef

You can take it personally and call it that but my initial comment was not directed at you specifically was it? No it was not. But you took it that way.

Nor was it beef. It's been criticized multiple times by multiple people, who are entitled to their opinion as well. It's a legitimate response. This isn't even the buckeye thread.

 

[delta76]

one click away. I don't need a new amp. I don't need a new amp

 

[welwynnick]

Another phenomenal amp for roughly a grand. Thanks for the review @amirm. Did you get data for the reactive load presentation as you did for the boXem A 4216/E2? Does the Apollon perform the same?

View attachment 503418

That test of the 1ET6525 in the Boxem A4216E2 stuck in my mind, as Purifi claim similar power for 4Ω (450W) and 2Ω (510W).
Although it didn't double down like the 1ET9040 did, it still produced A LOT more power into 2Ω than 4Ω .
This Apollon 1ET6525SA ST on the other hand, produces very little more - Amir said 367W @ 2Ω @ 110dB SINAD, and I estimate 420W @ 1% THD+N.

At first I thought the difference must be down to power supplies, with the Apollon 1ET6525SA ST having to share one SMPS1200A400 between two amp modules.
But no, that appears to be the same configuration for the boXem as well.
So now I'm at a loss as to whether the load tolerance of the 1ET6525 is merely good, or very good?

 

[Whiskey the Cat]

I have a question about the Gain settings - specifically mentioned in this review, but it's a generic question really. Performance is more that good enough at any Gain setting, so my question is about achieving maximum rated power.

Quoting from the review: "20 dB gain is good enough to push the amp to max power with nominal 4 volt input over XLR connection"

Does this suggest / mean that in order to get max power, and if I want the "best" signal (lower gain), people like me should be adding a pre-amp that actually amplifies the signal to give higher voltage output?

I believe most power amps have too much gain. I have a Moon 330A which, according to specs is about 31dB gain. I use a Benchmark DAC 3 HGC as the pre-amp. The latter is a professional level device and it will produce (at the factory setting) such a high output signal that the volume control has almost no range, i.e. very loud at the '7-8 am' position. However, the Benchmark has internal jumpers which I have set to reduce the output by 20 dB, but if I was using this Apollon I would have it's gain at the lowest setting and my Benchmark at the highest (factory) setting. That way I would get very low noise and also high volume. The only reason I can think of for most power amps having such high gains is that it impresses the non-educated user, who thinks that the amp being very loud at the '9-10 am' setting means they have a high power amp. (Wrongly of course). I think all high end power amps should have a variable gain setting for these reasons.

 

[GS430man]

@JeremyFife

26db input gain for the amp at full power roughly corresponds to 2v input. 20db gain is roughly 4v input to the amp. Lower gain at the amp requires more output voltage at the upstream device (AVR, preamp, etc).

If your amp gain is set to 20db but your preamp maxes out at 2v output, you cannot drive the amp to full power. Conversely, if your amp gain is set to 20db but your preamp can do 6v (like a Trinnov Altitude for example), you will not be able to use all of the volume control range on your preamp without overdriving the amp into clipping.

Gain optimization is a whole subset of knowledge. Pro audio folks live it every day, those of us doing audio as a home hobby only deal with gain on the rare occasion when we set up new amps and preamps.

I think of a car's gearbox as a rough analogy when thinking of audio gain. If you set the gear too low, your car engine 'redlines' early and your top speed is limited.

 

[JeremyFife]

@JeremyFife

26db input gain for the amp at full power roughly corresponds to 2v input. 20db gain is roughly 4v input to the amp. Lower gain at the amp requires more output voltage at the upstream device (AVR, preamp, etc).

If your amp gain is set to 20db but your preamp maxes out at 2v output, you cannot drive the amp to full power. Conversely, if your amp gain is set to 20db but your preamp can do 6v (like a Trinnov for example), you will not be able to use all of the volume control range on your preamp without overdriving the amp into clipping.

Gain optimization is a whole subset of knowledge. Pro audio folks live it every day, those of us doing audio as a home hobby only deal with gain on the rare occasion when we set up new amps and preamps.

Thanks, I get that. I'm wondering if the option of lower gain settings should lead to a takeup of pre-amplification

 

[amirm]

Thanks, I get that. I'm wondering if the option of lower gain settings should lead to a takeup of pre-amplification

Only if that preamp has lower noise than the power amp buffer.

 

[David_M]

Which is certainly not the case, for example from a recent review (source):

The best measuring amplifiers do, however, show similar idle noise levels.

The Purifi 1ET6525SA datasheet specs a typical unbuffered idle noise of 6.6 µV, A-weighted, with S/N ratio of 137 dB. When Amir tested with the front buffer to raise the gain, the SNR went down by 8 dB to 129 dB, which is 2.5× (and would increase the A-weighted noise to 16.5 µV). Therefore, a measured unweighted idle noise of 30 µV is a reasonable number.

View attachment 503627

You are correct ... I should have qualified my statement by limiting my observations to Purifi-based amplifiers, especially Gen 2 types, which is what I meant. Whether it's the higher-powered 9040BA or the 6525A module, I see the 30uV of noise at idle.