here are some pics
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and here is the schematic
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Not sure I understand you totally. The xformer has 2x24V and 50 Watts like suggested from ebay.
I know its not wired good, but does it matter in that experimental phase?
I never had this hum problems in my other (JLH) headphone amp either. Also a power filter didnt change the hum...
what is Iq you set per channel ?
I see that parts values are suggesting Iq in range of 0A65/channel as maximum , while you're having 50VA xformer
2x24x0A65 means 31,2VA per channel , without losses
double that , with possibility that 50VA xformer is sissy one , and there is problem
connect just one channel to xformer (if possible ) and observe - if hum is still there , then wiring is culprit
I see that parts values are suggesting Iq in range of 0A65/channel as maximum , while you're having 50VA xformer
2x24x0A65 means 31,2VA per channel , without losses
double that , with possibility that 50VA xformer is sissy one , and there is problem
connect just one channel to xformer (if possible ) and observe - if hum is still there , then wiring is culprit
Sometime ago I measured how much power the transformers sucks. It was around 32W.
Connected also one channel only to the xformer, nothing changed. And I wonder how it should change, cause if the xformer provides 2x24V with 50W means its 25W per secondary, right?
So I will look at my wiring again. Thanks for your input
Connected also one channel only to the xformer, nothing changed. And I wonder how it should change, cause if the xformer provides 2x24V with 50W means its 25W per secondary, right?
So I will look at my wiring again. Thanks for your input
sorry - I made a mixup , assuming bipolar supply .......
I simply forgot that Zen amp is having unipolar one , without even looking for that "detail" on schm
however , that means power draw of some 24Vacx0A65 per channel ( roughly , without translating from AC to DC domain)
more important is that you tried with just one channel connected ; take care of signal grounding , then report here
input RCA need to be isolated from chassis , PSU grn must be connected to safety gnd-ed chassis in one point via NTC , signal routing strictly grounded on pcb input location
what's happening when you short inputs ditto on pcb ?
I simply forgot that Zen amp is having unipolar one , without even looking for that "detail" on schm
however , that means power draw of some 24Vacx0A65 per channel ( roughly , without translating from AC to DC domain)
more important is that you tried with just one channel connected ; take care of signal grounding , then report here
input RCA need to be isolated from chassis , PSU grn must be connected to safety gnd-ed chassis in one point via NTC , signal routing strictly grounded on pcb input location
what's happening when you short inputs ditto on pcb ?
I set the Voltage according to what the ebay seller wrote:
adjust the side 100K adjustable*resistor*and test the*voltage on 1 ohm resistor"a2" "a3" for 380mV
This was done very easily
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only on my Macbook…
Also what I dont understand: If i take my multimeter I measure no AC or DC
on the output of the amp. How is this possibel if there is audible hum?
Slowly I start to get the feeling that my xformer might be too small. Also it meets the suggestions of the ebay seller. I had an AC Power supply with 24V and 1A lying around
which I connected to only one channel of the amp and the hum got even worse (it has no toroidal core)
I remember from the JLH headphone amp when I had hum. After fiddling around with cables and grounding I put in a bigger xformer and the hum was gone.
which I connected to only one channel of the amp and the hum got even worse (it has no toroidal core)
I remember from the JLH headphone amp when I had hum. After fiddling around with cables and grounding I put in a bigger xformer and the hum was gone.
My build went pretty smooth and the amp works. BUT:
I do have hum
The Transformer is about 20 cm away from the amp sitting on my desk, as I am still waiting for the case...
Connecting the case to signal ground didnt make any difference.
Any help is apprechiated
"Dress" all those wires and specially the one for the power switch (AC) that goes next to the potentiometer. Keep those wires as far as possible to the inputs.
I did already dress them. I also tried different grounding schemes.
What I didnt try so far was this thing with the thermistor.
Nothing of my schemes made any difference to the hum.
On an cheap iPhone inear the hum is the worst. On an Audio Technica Headphone with 70 Ohm its much better, but its still more noticeable then
on my JLH headphone amp.
I think I will give up on this. Thanks for all your support
What I didnt try so far was this thing with the thermistor.
Nothing of my schemes made any difference to the hum.
On an cheap iPhone inear the hum is the worst. On an Audio Technica Headphone with 70 Ohm its much better, but its still more noticeable then
on my JLH headphone amp.
I think I will give up on this. Thanks for all your support
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