Stacking HA5033s and thermal consideration?
Sep 19, 2002 at 1:27 PM Thread Starter Post #1 of 3


100+ Head-Fier
Aug 6, 2002
Dear Headfi DIYers,

I've tried stacking six HA3-5033s per channel for my meta42 like amp, and sonically quite preferred it to my former 3 Buf634s per channel version. Unfortunately, running this amp for more than 30-60min, buffers start to malfunction. They stop all operation and only make a hum-like lower frequency noise regardless volume nor source. After cutting off the power for a while, the amp works but it starts to malfunction again soon. And I'm suspecting the heat. 5033s are going quite hot while they're running.

I've prepared places for 3 chips per channel, so 2 chips are stacked per socket. Only upper chips are heatsinked. My suspicions are
1. Anyway I have to prepare all the six sockets to eliminate stacking and heatsink all chips,
2. Maybe chips are damaged soldering pins directely, so I have to buy new chips and improve my soldering skill, ...

Would anyone experienced this buffer inform me about your experiences regarding the heat? Thank you in advance for any help.
Sep 19, 2002 at 2:40 PM Post #2 of 3


Top Mall-Fi poster. The T in META42.
Formerly with Tangentsoft Parts Store
Sep 27, 2001
First thing to know about heat: if you can't leave your finger on it for more than 5 seconds, it's too hot.

What you're hearing is probably the internal shutdown circuitry kicking into action to prevent the chips from frying themselves.

It's possible to damage the chips while soldering them, but if they work for a while and then fail, chances are good that it's a thermal problem.

Each 5033 has 8 Ohms of output impedance, so with 6 in parallel the impedance drops to just over 1 Ohm. Perhaps the chips are fighting each other; if you added some current-sharing resistors this might go away. This will bring your output impedance back up, which may help with the overheating problem, but it will work against one of the advantages of stacking buffers.

You might critically listen and see if the 6 buffers sound better than just 3. You might find that you'd be best off just removing the extra buffers and using them in another project.
Sep 20, 2002 at 7:28 AM Post #3 of 3


Building amps and assuring water resistance.
Jun 21, 2001
3 5033's in a dip will have to be heavaly heatsinked since evean just one of these devices will overheat at no signal from just the Bias current. Use a large Heatsink and use thermal grese on top and bottom of stacked chip assembly so heat can get transfered from one dip to another and then the heatsink. the perfered method is not to stack these and use separate sinks on each device

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