I don't thing it has something to do with a passive I/V, because active I/V can provide much lower impedance (and load) than a passive resistor (unless 10R or so was used).
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Yes, C31/C36 and R8/R9 are vacant.
Perfect! I’ll increase R4 to 2K4. Curious about if/how the sound changed? Must wait until morning to get some listening done......
Of course Vunce, we are waiting for your result from detailed comparison with opamps
Unfortunately, I do not have good news to report
I’m getting background hiss from the speakers that can be heard from 4 feet away, no hum. Possible oscillation? DC offset is very high 100-120mV. With music playing there is audible distortion. When R4 was increased to 2K4, there was no increase in volume output.
I checked and double checked for errors with my implementation of the OPA860 circuit, it’s good, No shorts or solder bridges.
I will try a different location for R4 &C1 GND point. Currently they are tied into the vacant C37/C38 ground pads.
I’m getting background hiss from the speakers that can be heard from 4 feet away, no hum. Possible oscillation? DC offset is very high 100-120mV. With music playing there is audible distortion. When R4 was increased to 2K4, there was no increase in volume output.
I checked and double checked for errors with my implementation of the OPA860 circuit, it’s good, No shorts or solder bridges.
I will try a different location for R4 &C1 GND point. Currently they are tied into the vacant C37/C38 ground pads.
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Not sure what you mean, like the lower impedance load puts more strain on power supply?
The dac output is current limited so I dont think it makes a difference.
Unfortunately, I do not have good news to report
...
it's a pity, maybe there will be some hidden mistake
the connection is identical to that from Pedja ... at least you tried
I Reinstalled the first dac board that is unmodified and have the BursonV6 opamps installed. My spirits have been lifted again!! The combo sounds fantastic
I haven’t given up yet though, I will try to bypass the onboard OPA860 buffer, essentially making it an OPA861. (Those are also on the way)
I haven’t given up yet though, I will try to bypass the onboard OPA860 buffer, essentially making it an OPA861. (Those are also on the way
)
That is also what I thought.
I do not doubt that this circuit works very well, it comes from a very respected designer. I would build it as a standalone circuit, but the BF245A transistors are obsolete, is there a suitable replacement?
Yup ! Despite no decoupling at its feets, the magic of a good power supply design -the 100 uF caps are strategical there I mix both 47 uF & 100 uF, so a litlled isymetry, lol- Nore I use the 1500 uF Pan FM btw.
Sure, as I questionned : those chips lives bad to be on a socket, on adaptaor, should be directly soldererd and careffully decoupled right at their power leads.
750 ohms is ok after the opa861, it's what I use on the AYA before the buffer..., still the opa861 reversed in mine but a better buffer should exist... though the opa861 reversed is neutral fr my tastes. Ok off topic, perhaps can give some thoughts for Vunce.
Edit : are the pins of the opa861 copatible with most opa in a swap operation ??? Not sure it is iirc! Vunce, did you populate the miro's pcb or hacked the outputt with a wire on an extra board and managed a ground between the two boards ? Or I'm not understanding you are talking about the verroboard ?
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