The fan must be triggered by TH_WAR on pin28 of STA-516BE. There is a pull up resistor connected to this pin and 3.3V. I think you can look into this part of the circuit.
I hope the fan is not being triggered by the TH_WAR pin on the STA516BE. That is the "thermal shutdown is imminent" warning that comes on when the IC die temperature exceeds 130C. It is probably too late to turn on the fan and start cooling the IC by that time.
My fan is coming on intermittently at relatively low volume levels. The heatsink is only slightly warm. I'll remove the heatsink and check the thermal interface between STA516BEs and the heatsink. I have some Arctic Silver leftover, I might try that one.
Well, this is all I can think of for now. I will receive my amp in few days. Will check it out.
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I took off my heatsink and fan off today. There was heatsink compound between the chips and the heatsink. I wiped it off and put some Ceramique there, which is made by the same manufacturer as Artic Cool. Seems a little better, but the fan still power cycles at idle. I will be looking into quieter fans when I get back in town.
I do like the amp, though. Sounds great.
I do like the amp, though. Sounds great.
You may use a LM317T as current limiter. By adding a VR, current can be adjusted. This is how I control the fan speed on my computer.
Got my Sure AA-AB32971s this week, and been listening them for a day now (one module per speaker on my FAST). I can understand why someone said they have "deeper blacks". Very, very low background noise, even when run by a 24V 10A SMPS brick. Overall, they are a nice upgrade to Sanwu TDA7498.
My mini tweak amplifier AA-AB32313:
- Removed schottky diodes D5-D12
- Replace power capacitors on Nichicon PM 2200x50V (supply voltage 32V)
- Replace the input ceramic capacitors on Elna Silmic II 10x16V
- Replace the fan on low noise - Noctua NF-A6x25 FLX
Attachments
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What is the function of those Schottky diodes? They are not present in the ST reference circuit. Are they to prevent the outputs of one STA516BE from the other one during power-on?
Which ones are the input ceramic capacitors?
Most of the difference between the two graphs appear to be the lower frequency range (below 300Hz), what do you think was the main culprit?
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The diodes are connected from the output connector speaker to VCC and GND.
Yes, on the reference circuit, these diodes are not present, so I removed them.
Hmm ... do you think it is protection for STA516BE when paired?
C1 and C2
This effect it only on the replacement of ceramic capacitors. It is easy to check. SW1 switch disables the effect of these capacitors.
This is normal for signal ac caps (high pass). Large cap is better for LF, but it will affect the HF as signal is going through longer path on a capacitor. So, an adequate value is essential. On the other hand, does the distortion on LF really matter? Despite of those modding tips, I'd also try upgrading the LM317s (if any).
These amps are back ordered for 2 weeks. The seller will start to ship this week (hopefully).
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Ceramic сapacitors increase distortion due to this effect.
Ceramic Capacitors FAQ | Murata Manufacturing Co., Ltd.
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For subjective evaluations I did not have enough time.
I noticed a change only by replacing the ceramic capacitors.
By the way! The stock fan when his work adds electrical interference.
Fan Noctua NF-A6x25 FLX work without interference.
No. I use a different volume control.
Sure Volume Control Module is not enough quality.