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What the current Aiyima A07 actually needs.

abdo123

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Yes, but voltage stress can break a chip too. You don't have much margin when constantly using it at the maximum allowed voltage. Any voltage spike will be a risk for the chips involved. What does your power supply do at startup? Does it ramp up slowly or does it come on suddenly with a small/large overshoot?
And safe operation at maximum allowed voltage is not always guaranteed for prolonged time. Sometimes there a time limit involved too.
It’s a medical grade regulated powersupply.

Twice as expensive as the amp itself.
 
D

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What about this for an idea? Design this cheap piece of junk properly in the first place! It's not hard.
An overheating amplifier is a consumer recall waiting to happen. No excuses. This Chinese chit needs to lift its game.

I agree and I said so in my Amazon Review of the A07...

I had one of mine come back because it kept shutting down... (lord knows how hard my client was pushing it)

Removing the heat sink I discovered they are using two silicon spacers on the bolts between the sink and the board. This is a good thing in that it stabilized the sink but it's also a bad thing because the edge of one of the spacers lands right on top of an SMT part. This may (not necessarily "will") cause the heatsink to sit imperfectly on the top of the chip. What I did was to make a small notch in the spacer to clear the part and hold it in place with a drop of stickum. Then I cleaned away the crappy thermal compound they used and put in some high quality stuff (Loctite 175-125) and re-assembled it using just a bit of extra pressure on the screws (contact +3/4 turn). So far so good.

Extra cooling could be added by inducing convection with a machined slot at the case joints about 2" long and 1/4" tall, on each side and a 1" long slot about 1/4" deep cut on the top centre at front and back... getting rid of the shiny aluminum is a matter for a quick swipe with a magic marker. I've done this on other amps but haven't tested this on the A07 yet... but then I haven't had to.

As others have commented 36 to 38 volts seems to be it's sweet spot for good power and longivity.
 
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RHO

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<rant>OK, maybe it is just me -- but I can't buy that last comment at all. Correlating lifespan of the product with price shouldn't be necessary from my perspective, especially in the light of growing global cognizance of the rolled-up costs of waste. A disposable electronic component is waste of the worst and most egregious (and inexcusable) kind, from my perspective.
</rant>
It's not only you. :)
 

RHO

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It’s a medical grade regulated powersupply.

Twice as expensive as the amp itself.
So, does it slowly ramp up or does it generate an overshoot?
Price or medical grade or not does not say anything about the behavior at startup.
 

abdo123

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So, does it slowly ramp up or does it generate an overshoot?
Price or medical grade or not does not say anything about the behavior at startup.
I'm not sure, here is the specification sheet incase you're interested

 
D

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So, does it slowly ramp up or does it generate an overshoot?
Price or medical grade or not does not say anything about the behavior at startup.

The simple answer to this problem is to leave the power supply on all the time and use the standby switch on the amplifier to turn it on and off. That way the big bulk capacitors are charged once and then stay forever charged and ready to go with no big current inrush and no spikes while things are settling down. In fact, the repeated inrush of current is what drastically shortens the lifetime of a lot of the "brick" styled external supplies. In standby mode (front panel switch off) there's only a few milliamps of current drawn.

(I'm fully aware that a "proper" power supply is designed to deal with current inrush... but these cheap bricks aren't.)
 
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RHO

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I'm not sure, here is the specification sheet incase you're interested

Looking at the specs there can be a spike at startup (but I would expect it to be small). Nominal output voltage is 48V but can be higher (up to 49V). Looking at the TPA3250 specs the absolute maximum voltage that can be applied is 50V. Maximum recommended voltage is 38V (typical 32V)
Looking at the remarks that come with the absolute maximum ratings:
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. (2) These voltages represents the DC voltage + peak AC waveform measured at the terminal of the device in all conditions.
I think your pushing it a bit with the 48V supply.
 

restorer-john

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When the Chinese work out amplifiers need externally vented heatsinks on the output devices, the world will be a better place.

Until then, we'll just watch with absolute glee as their poorly designed products self destruct due to poor thermal dissipation considerations.
 
D

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When the Chinese work out amplifiers need externally vented heatsinks on the output devices, the world will be a better place.
Until then, we'll just watch with absolute glee as their poorly designed products self destruct due to poor thermal dissipation considerations.

That and counterfeit parts ...
 
D

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Oops.:oops:
Yeah, that makes quite a difference.:D 48V should be fine.
48 volts is electrically safe. But at 48 volts it's likely the chip will overwhelm the poor cooling solution and the chip will repeatedly go into over-temperature shutdowns.

The 32 volt supply delivered with the A07 is probably the best compromise between heat and performance.
I would not recommend going over 36 volts with a sealed case.
 

RHO

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48 volts is electrically safe. But at 48 volts it's likely the chip will overwhelm the poor cooling solution and the chip will repeatedly go into over-temperature shutdowns.
That could be. But We can't determine that from reading the technical documentation.
The 32 volt supply delivered with the A07 is probably the best compromise between heat and performance.
I would not recommend going over 36 volts with a sealed case.
I'm not planning on going over 36V
But we do not know what the actual reason for failure is on some of these amps. We don't even know what the failure rate on these is.
I suspect many are sold and we see more complaints than average from people that have one die on them.
 

restorer-john

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That and counterfeit parts ...

Yes, but let's give credit where credit is due. I see no evidence of fake components in Topping gear or even this Ayima stuff. I harp on about poor design, especially thermal considerations, because I am old school. Whatever the rating is, the device must be able to deliver/produce that power/output indefinitely. Not just a second or two at 10% THD before shutting down/exploding.

A power amplifier, regardless of its topology is going to produce heat. That heat needs get out of the device, out of the casework and dissipate into the air or else...

That's expensive. Expensive in thermal considerations, power supplies, construction etc. Our Chinese friends overrate their gear in terms of power output and underrate their ability to get rid of waste heat. That leads to failures, shutdowns and disappointment.

They will learn, just as the Japanese and the UK (English) learned. I would say the UK designed amps of the 1970s and even into the 1980s were simply terrible when it came to continuous power delivery, especially in hot climates like parts of the US and Australia. Quads for example just blew up. Sugdens cooked themselves.

Over engineering solved the problems people couldn't predict. Those dusty cupboards with no air. Those humid, seaside places where the "significant other" placed a potplant on the amplifier, etc.
 
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D

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Yes, but let's give credit where credit is due. I see no evidence of fake components in Topping gear or even this Ayima stuff.

I just pulled a couple of fake 5532s out of my A07. I have no idea what they may have actually been but they weren't 5532s. I subbed in RC4558s from my stock and all is good.
 
D

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That could be. But We can't determine that from reading the technical documentation.

Sure we can. We know how much power is lost to heat ... a little math with the case volume and voila!

I'm not planning on going over 36V

Many people are.

We don't even know what the failure rate on these is.
I suspect many are sold and we see more complaints than average from people that have one die on them.

Probably true. Failure rates are never published.
 

Moderate Dionysianism

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When the Chinese work out amplifiers need externally vented heatsinks on the output devices, the world will be a better place.

Until then, we'll just watch with absolute glee as their poorly designed products self destruct due to poor thermal dissipation considerations.

Ohh so you're gonna examine EE skills of all 900+ million working age Chinese ppl? Or is there a number of well designed devices they have to reach for you to give the nation a pass? lol

I don't see nation-level generalizations and references to the places of origin when discussing badly designed stuff or outright scams by Audioquest, PS Audio, Hegel, and soo many others who happen to be headquartered in other parts of the world ;)

ctrl+h -> replace the Chinese with Aiyima - I honestly don't see how this could hurt in a forum that prides itself in accuracy, precision, and scientific approach.
 
D

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Ohh so you're gonna examine EE skills of all 900+ million working age Chinese ppl? Or is there a number of well designed devices they have to reach for you to give the nation a pass? lol

There may not be a level of well designed products ... but there certainly is a level of poorly designed stuff that sticks out like a sore thumb.

For example ... when I get speakers in here for a client, I always check all the screws are tight, nothing is missing, etc. 9 out of 10 times when the speaker is made in China I will find half a dozen loose or missing screws. --and-- The same is true for amplifiers; bad solder, fake parts, loose screws you name it.

Another example... Some time ago, I did a bulk purchase with a ham radio club in my area and in pre-checking the equipment, I found potential problems in almost every one of them... mostly loose screws and bad solder ... the stuff that is done by hand.

It's not that China itself is bad, but between dirt cheap labour and zero quality control, the manufacturers there do crank out more than their share of sub standard product.

And @restorer-john is 100% correct when he points out that power amps need air. You can't just box them up air-tight and expect them to last very long, especially when used near their limits. Doesn't matter where they're made... they need air circulation to prevent over-heating.
 
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