I had a 15V trafo and wanted to power XRKs DCA headphone amp with it but the cap multiplier in this amp drops the voltage too much to get 20V DC, I decided to use little ebay TPS7A4700 LDO regulator board to drop 21.4V to 20.2V, it worked well and might even sound better than the cap multiplier.
This regulator board has a small heatsink and it only got slightly warm after running for prolonged period.
But then after a few hours the regulator suddenly stopped working, the output drops to 0 when attached to the load and it gets very hot even with nothing connected to the output.
After cap multiplier is 8800uf of filter caps... could this be what killed it?
The TPS7A4700 has a 1A limit aswell ,The temperture was more than fine but I was thinking heat might not be an indicator of overcurrent when you are only dissipating less than 1V.
The amp has a 125mA class A bias and it was driving 300ohm headphone so it seemed ok.
This regulator board has a small heatsink and it only got slightly warm after running for prolonged period.
But then after a few hours the regulator suddenly stopped working, the output drops to 0 when attached to the load and it gets very hot even with nothing connected to the output.
After cap multiplier is 8800uf of filter caps... could this be what killed it?
The TPS7A4700 has a 1A limit aswell ,The temperture was more than fine but I was thinking heat might not be an indicator of overcurrent when you are only dissipating less than 1V.
The amp has a 125mA class A bias and it was driving 300ohm headphone so it seemed ok.
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there isnt, but they might be internal with this reg? the only external part aside from caps is a resistor connecting the output to some pin... there is no resistor shown in basic application in datasheet so not sure what it is edit:actually its on the input and connected to enable pin.
If its a short then it would have to be on the regulator board, there is no visible shorts on PCB, the only explanation would be a cap or the resistor shorted internally, if thats even possible.
For such an inexpensive board I could see them using under voltage rated caps
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I have never had a large capacitance kill a TPS7A before. I use mine to drive a CRCRC with 2200uF caps and it’s been running for months.
If you want higher voltage, I highly suggest using a DC-Step up followed by this board which does CLC filtering, capMx, and allows a TO220 78xx implementation of the TPS7A to be used for best of all worlds. It is very quiet and let’s you adjust to get any voltage you want, even 30v etc from only a 12v Class 2 wall wart.
GB for Simple Cap-Mx Regulated Low-Noise PSU
If you want higher voltage, I highly suggest using a DC-Step up followed by this board which does CLC filtering, capMx, and allows a TO220 78xx implementation of the TPS7A to be used for best of all worlds. It is very quiet and let’s you adjust to get any voltage you want, even 30v etc from only a 12v Class 2 wall wart.
GB for Simple Cap-Mx Regulated Low-Noise PSU
Hi xrk,
considering that, and also that it died with the power still connected, it was a probably a faulty part with a delayed failure.
I found the amp sounded best with a simple non switching supply, trafo rectifier and regulator is about as simple as you can manage with adjustable voltage, I even bypassed the CRCRC for that.
considering that, and also that it died with the power still connected, it was a probably a faulty part with a delayed failure.
I found the amp sounded best with a simple non switching supply, trafo rectifier and regulator is about as simple as you can manage with adjustable voltage, I even bypassed the CRCRC for that.
A well designed linear supply and regulator are very good in general - but I don’t understand why bypassing the CRCRc makes it better? There will probably be some residual 60Hz hum (most likely inaudible but measurable) on an all linear system. The DC-DC moves the 60Hz to 400kHz where it can be steeply filtered (and is not audible) plus lets you adjust the output voltage from the cap Mx.
Someone suggested output impedance of a power supply should be kept as low as possible, the result was good at least with a linear source
BTW out of curiousity I was comparing the DCA's Mx and a LM350 regulator set to same voltage (~17V), and I find that Mx sounds a lot better, the regulator has the cleaner precise sound but with a closed in and flat sound.
it is really a problem in the bass, the regulator just kills the powerful bassy sound of this amp.
Oh when I say bypassing CRCRC I just mean the resistance, those Cs are important for the Mx as you know.
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