Trying to finish up a rebuild project from years ago. It's a Rosenblit Grounded Grid preamp built on a turret board and installed in a Lite Audio enclosure with V-03 relay attenuator.
This was my stab at the grounding but it must not be correct.
It seems to be something with the V-03 board. I did try bypassing with an Alps RK27 and the buzzing went away.
A previous incarnation kept the signal grounds off the V-03 but the V-03 itself still had to be grounded to avoid a deafening hum.
This was my stab at the grounding but it must not be correct.
It seems to be something with the V-03 board. I did try bypassing with an Alps RK27 and the buzzing went away.
A previous incarnation kept the signal grounds off the V-03 but the V-03 itself still had to be grounded to avoid a deafening hum.
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Different boxes connected to your system may have different AC cord grounds. Have you checked to see if that is why you are getting hum/buzz?
Also, looks like V-03 doesn't switch grounds from connected input devices: https://www.audiophonics.fr/images2/3774/LITEv03_2.pdf ...In that case ground loops can potentially exist whenever a device is plugged in whether or not such device is the selected input.
Also, looks like V-03 doesn't switch grounds from connected input devices: https://www.audiophonics.fr/images2/3774/LITEv03_2.pdf ...In that case ground loops can potentially exist whenever a device is plugged in whether or not such device is the selected input.
"Different boxes" = different sources?
While I've wired up all inputs, I only have plans to use one. My current source is a pair of shorting plugs but otherwise it would be a USB DAC (e.g. Modi 3). I hear the buzz with either.
Between channels, I measure a resistance of about 6M ohms when the signal grounds of each are not joined.
What else can I try?
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As a test only, you could try a ground lifter AC adapter. Such devices should not be used to fix ground loop problems since AC power grounds are for safety. For example: https://www.amazon.com/prong-Polari...&keywords=ground+lifter&qid=1631644426&sr=8-7
You might try one on the power cable for your dac. Or you could just try unplugging the dac power cord and see if the buzzing stops. If so, there may be a ground loop through the AC power grounds. In that case you could plug all your audio devices into one of these: Monster Power HTPS 7000 Signature Series | eBay ...I would just note that not all power conditioners are equally effective. IMHO Monster HTPS 7000 Mk II is an especially good one (The one I linked to looks like it might be a Mk I, probably better to look for a MK II). I have two of them, one for the stereo and one for the bench. Both were picked up used from ebay.
You might try one on the power cable for your dac. Or you could just try unplugging the dac power cord and see if the buzzing stops. If so, there may be a ground loop through the AC power grounds. In that case you could plug all your audio devices into one of these: Monster Power HTPS 7000 Signature Series | eBay ...I would just note that not all power conditioners are equally effective. IMHO Monster HTPS 7000 Mk II is an especially good one (The one I linked to looks like it might be a Mk I, probably better to look for a MK II). I have two of them, one for the stereo and one for the bench. Both were picked up used from ebay.
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I've tested with and without chassis ground connection with no change in behavior.
I've also tested with a double insulated Adcom amp and a grounded LM3875 amp.
I've also tested with a double insulated Adcom amp and a grounded LM3875 amp.