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AIYIMA A07 TPA3255 Tear Down
- Thread starter amirm
- Start date
Interesting question. Thermal pad has lower conductivity than metal, but we have a whole chunk vs just some thin fins.
Or actually the question can be simplified if we just take the total volume of the fins. I think the heatsink still wins.
There's also the issue that by physically connecting to the chassis, you reduce the protection against impact.
I will be getting my A07 next week. At the beginning of this thread Amirm shows how hot the heatsink gets with just 20W @ 4ohms.
Your comments on the thermal pad being less conductive that metal makes me think that maybe a flat aluminum plated, to fill the space between heatsink and top cover, might improve the dissipation.
OTOS perhaps the heatsink has to be isolated from the case. Maybe a small fan on the side, blowing into the fins, might do a better job.
One thing I would like to change, besides the caps that contact the heatsink up front, and might be affected by the heat, is the frontal pot. I wonder why Aiyima used a linear pot instead of a logarithmic one, as the circuit works better with the latter. There's Hungarian video, with English subs, that explains how to do that.
There is simple trick that also works to make a linear pot behave as a log one: as this is a 100K pot, put a 47k resistor from the middle POT pin to ground.
Your comments on the thermal pad being less conductive that metal makes me think that maybe a flat aluminum plated, to fill the space between heatsink and top cover, might improve the dissipation.
OTOS perhaps the heatsink has to be isolated from the case. Maybe a small fan on the side, blowing into the fins, might do a better job.
One thing I would like to change, besides the caps that contact the heatsink up front, and might be affected by the heat, is the frontal pot. I wonder why Aiyima used a linear pot instead of a logarithmic one, as the circuit works better with the latter. There's Hungarian video, with English subs, that explains how to do that.
There is simple trick that also works to make a linear pot behave as a log one: as this is a 100K pot, put a 47k resistor from the middle POT pin to ground.
Based on what info?
Roland68
Major Contributor
You can be absolutely sure that this is not the case.
There are easily 6-10 ways you could have achieved 30-300% better heat dissipation on the A7 for well under $1 in production.
However, this should have been done in development.
But they have chosen the cheapest and simplest option.
Can you list some of those ways to 30-300% better heat dissipation. I named three: Increasing a bit the length of the HS, finding a HS with more fins, adding a small fan on the side blowing into the heatsink.
Would those work? Which others?
If you are really worried about heat and want to run at high power, IMO Fosi V3 is a better way to go, and you set the same great TI3255 chip. Nicer volume pot too - better control of lower volumes.
On the A07, my thermal pad addition was cut to be just the size of the fins of the heat sink. It is just wide enough to fit between the fins and the case top. No damage to the chip from too much pressure. So far so good. I don't run it very high/hot anyway because of the taper of the volume pot.
Next easiest thing to do would be to drill holes in the case top. Some members here have done that. I prefer not to mar the case and just let the heat dissipate via the case. The A07 design is not ideal, many caps are too close to the heat sink. Because of this, I'm not expecting it to last as long as some of my other amps, but we'll see.
Roland68
Major Contributor
As I said, the best solutions would have to be planned for during development, they cannot be integrated later.
If you don't have the skills, you can destroy the power chip and circuit board.
- Screw a 3x2cm copper or aluminum plate onto the floor. Choose thickness so that a 1-2mm thick thermal pad fits tautly but without too much pressure between the circuit board and the aluminum plate. Thermal paste to all transitions.
- When the housing is closed, more cooling fins can lead to heat build-up.
- Get a heatsink that runs the full width of the case and is at least as high as the case or higher. For this heatsink, make a full cutout in the case and drill 5-6mm holes on both sides just above the circuit board every 1-1.5cm for cooling.
In addition to these measures, a different housing would make more sense. However, from this point you should think about real DIY with another class D amplifier board with this chip, a reasonable power supply and a housing. There is now enough selection of such boards with Class D amplifiers.
Or, just get a Fosi V3 with the 48v power brick...and live life...!
Yes, I didn't pay enough attention to the Fossi V3. Perhaps I get one Fossi and keep the A07 for powering a sub, if possible with two sub drivers or a dual VC.
Anyone knows if the Fossi back 3.5mm output is dual?
I know you can't bridge the A07.
The Fosi V3 manual says the out jack ("pre-out") can be used for active SW or speakers or to a second amplifier. Other posts have confirmed that it is a pass-through, the V3 volume control does not affect output via the jack.
Which forums you know have modified the A07? Some drilled holes in the metal case (top, sides and bottom) to help ventilation and lower the heatsink hot temp.
daniboun
Major Contributor
Check here influence of the Op Amps upgrade with the 3R Audio TPA3255 finished amp. Stock op amps vs LM4562 measured :
audiosciencereview.com
3e Audio SY-DAP2002 Review (DSP Amplifier)
This is a review and detailed measurements of the 3e Audio SY-DAP2002 stereo desktop DSP amplifier with Bluetooth. It was kindly purchased new by a member and drop shipped to me. I will also do a teardown and test with upgraded op-amps. I went to look up the price just now and it says no...
audiosciencereview.com
Roland68
Major Contributor
Just look it up on diyaudio, there are a lot of modification threads for AIYIMA A7, TPA3255/3251, one even with 5000 entries.
A fan grill and just make time to make the hole
I wish they would make better cooling for the amps that has 2x100watt or more in 4 ohm at 1% thd
2x300 watt in 4 or 2 ohm 10% thd is still alot in in 8 and 4 ohm with 1% thd with no ventilation holes, just think of how much a normal sized amp has
The A07 was built with some compromises, which the Foxi avoids. But it's popularity and sales success seems to show that the design constraints can be dealt with. I am not seeing so many people complaining about in Amazon, for instance, or in forums.
Those of us that "foresee" a potential problem manage things in a different way. It might be a good idea, for those that know how to do it, to add a hot temp sensor, with an alarm blinking LED on the front plate. Can anyone do so?
Those of us that "foresee" a potential problem manage things in a different way. It might be a good idea, for those that know how to do it, to add a hot temp sensor, with an alarm blinking LED on the front plate. Can anyone do so?
to get a tube sound from this amplifier use an unregulated 32V adapter 30V .5 A would seem way to small but don't forget the 10:1 peak to average ratio of music I use a Jameco clarity can be improved by replacing the 6V reference for the opamps with a 5.6V low noise zener and using OPA32 TI opamps
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