I run a maintenance company, on the tools half the time, behind a desk the other. So my hands are medium tough. Shall I attach a picture ;-)
Nelson Pass for many of his amps uses the general rule that if you can keep your fingers on the heatsink for five seconds, then it's probably ok. Not calibrated either, but a "good rule of thumb"... 😀
I run an electrical contracting firm, trying to find time for the desk part is the problem........your fingers will be pretty tough in the photo, I reckon about Gorilla Glass 3 hardness.......
Chuz,
Drew.
Wow! Thanks for the quick replies. What a great community!
I can possibly get a bigger trannie but I'm not sure how easy it is to replace the heatsink with a bigger one on the PCB. I don't have a chassis yet so chassis mounting is not an option now.
Any one know if it is okay to just parallel two 12V supplies for the required current output? Would there be undesirable interactions between the two regulators?
I am now planning the remaining items:
1. Just emailed Guido about the shunt regulators (16 pcs)
2. To order (at least) 8 pcs of 68 ohm 2W Shinkoh resistor
3. Order 4 (?) 22nF cap for reducing the quantization noise
For output I happened to have a pair of 1uF Duelund CAST Copper on hand so I'll try that. My amp input impedance is 1M ohm and I use a AVC preamp so I figured it should be fine bass-wise.
If I missed anything please let me know. Looking forward to building this DAC.
I can possibly get a bigger trannie but I'm not sure how easy it is to replace the heatsink with a bigger one on the PCB. I don't have a chassis yet so chassis mounting is not an option now.
Any one know if it is okay to just parallel two 12V supplies for the required current output? Would there be undesirable interactions between the two regulators?
I am now planning the remaining items:
1. Just emailed Guido about the shunt regulators (16 pcs)
2. To order (at least) 8 pcs of 68 ohm 2W Shinkoh resistor
3. Order 4 (?) 22nF cap for reducing the quantization noise
For output I happened to have a pair of 1uF Duelund CAST Copper on hand so I'll try that. My amp input impedance is 1M ohm and I use a AVC preamp so I figured it should be fine bass-wise.
If I missed anything please let me know. Looking forward to building this DAC.
If by AVC you mean TransformerVolumeControl or autoformer, you can probably run without any cap at all....I do...and I guess NO CAP is still better than ANY cap?
best
Leif
best
Leif
Hi Leif,
> If by AVC you mean TransformerVolumeControl or autoformer, you can probably run without any cap at all....I do...and I guess NO CAP is still better than ANY cap?
Thanks for the tip. Hopefully if the DC offset is sufficiently low then I can try that as well.
Jack
> If by AVC you mean TransformerVolumeControl or autoformer, you can probably run without any cap at all....I do...and I guess NO CAP is still better than ANY cap?
Thanks for the tip. Hopefully if the DC offset is sufficiently low then I can try that as well.
Jack
Hi Almeg, is there a reason why heatsinks are aluminium and not steel?
Just curious, nice welding by the way.
Just curious, nice welding by the way.
As I know alu has 3 times better heat conductivity than iron and 4 times than steel.
Plus lot lighter and heat conduction needs thick material.
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Ally is a very good heat conductor and as it has low mass compared to iron or steel will dissipate the heat better due to less heat soak.
Yes, but I want a self contained module that will be easy to swap for comparison duty 🙂
No cap is definitely better than cap! Also because you can use it balanced. the difference in sound quality is huge.
I expect most dddacs can be run without cap if measured dc on output is low enough (lower than 0,05v or so)
Note: this advice comes with NO guarantee!
Regards,
Guys, how critical are the I/V resistor values on the DAC output? 133ohm isn't always available in high quality resistors, would a 120ohm be close enough or is it very sensitive to being exactly as stated?
I can take this one 🙂
it depends.... higher is not good, as you will have the analog stage (the current source) in the PCM1794 clip against the positive rail, due to higher Bias voltage and also higher output voltage (I/V from Rload)
If you go lower, it is no problem, as your DC voltage goes lower, but the output AC signal voltage as well, so OK. no clipping...
Only back drop would be, that you have a bit lower output voltage. in your example only -1dB by the way.
it depends.... higher is not good, as you will have the analog stage (the current source) in the PCM1794 clip against the positive rail, due to higher Bias voltage and also higher output voltage (I/V from Rload)
If you go lower, it is no problem, as your DC voltage goes lower, but the output AC signal voltage as well, so OK. no clipping...
Only back drop would be, that you have a bit lower output voltage. in your example only -1dB by the way.
120 will work, just keep it as close as possible. This will draw a bit more current from the dac and that changes the sound. Just try it, I expect it will sound a tad bit thinner than using a larger value.
You can also use 2x 260 in parallel.
Quality of this resistor is important. I have best results with tantalum.
hi again
when hookling up for balanced out, no cap:
one load R for each leg, and I also need one 100K between each leg and gnd as well?
best
Leif
btw I use R load AN 2 watt tantalum as well
when hookling up for balanced out, no cap:
one load R for each leg, and I also need one 100K between each leg and gnd as well?
best
Leif
btw I use R load AN 2 watt tantalum as well