Hello,
I recently purchased a used Destiny Phono MM Preamp. When I play my records and switch inputs I can hear the phono input play through the other inputs at moderate volume, independent of the volume control. Is this much input bleed expected on this circuit? It is also noticeable but at much lower volumes when playing from my DAC. I'm concerned there might be something wrong with Phono preamp, or something else is amiss.
I've checked the ground turntable ground cable is connected to the chassis, and measured 10 ohms from the chassis to the RCA ground outer conductor). Any help is appreciated 🙂.
Input relays are Fujitsu RY-5W-K
https://www.mouser.com/ProductDetail/817-RY-5W-K/
I recently purchased a used Destiny Phono MM Preamp. When I play my records and switch inputs I can hear the phono input play through the other inputs at moderate volume, independent of the volume control. Is this much input bleed expected on this circuit? It is also noticeable but at much lower volumes when playing from my DAC. I'm concerned there might be something wrong with Phono preamp, or something else is amiss.
I've checked the ground turntable ground cable is connected to the chassis, and measured 10 ohms from the chassis to the RCA ground outer conductor). Any help is appreciated 🙂.
Input relays are Fujitsu RY-5W-K
https://www.mouser.com/ProductDetail/817-RY-5W-K/
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Can you provide us with other sections of the circuit: the phone/aux selection, phono preamp and volume. But maybe some undefined but of organic origin matter is sticking between the nc-no contacts at the bottom.
Sure, I've attached the amp and phono preamp sections. I recently replaced the phono input relay with another used relay thinking that was the cause. That didn't clear the issue, and both relays show 160 ohms across the coil. Thanks!
Ok, I did some more checking on the relay.
When the amp is on, the resistance from the Preamp Phono Rout to ground (RCA outer shell) is 50 Ohms, while another input is selected.
When the amp is off ... the resistance across Rout to ground is 100 ohms.
So It looks like the relay is not working properly which makes wonder if something else is causing the relay to malfunction. Could there be something wrong with U708?
When the amp is on, the resistance from the Preamp Phono Rout to ground (RCA outer shell) is 50 Ohms, while another input is selected.
When the amp is off ... the resistance across Rout to ground is 100 ohms.
So It looks like the relay is not working properly which makes wonder if something else is causing the relay to malfunction. Could there be something wrong with U708?
Lift the needle when not really listening to the record player.
This designer choose to dummy-load unselected inputs with 100r. If the source is playing, this dumps lots of signal current to general ground. It's gonna cross-talk. You can't afford enough copper to swamp that "to infinity". Surely unselected inputs should also be muted at the source (needle, digital stream, tuner, etc).
Where stray sources must be allowed to play, as in a radio network switching center, we don't put 100r to ground on unselected inputs.
This designer choose to dummy-load unselected inputs with 100r. If the source is playing, this dumps lots of signal current to general ground. It's gonna cross-talk. You can't afford enough copper to swamp that "to infinity". Surely unselected inputs should also be muted at the source (needle, digital stream, tuner, etc).
Where stray sources must be allowed to play, as in a radio network switching center, we don't put 100r to ground on unselected inputs.
Ok thanks. my dac is barely audible through the other inputs. While the phono preamp is at moderate volume, even when the volume is turned down. The dac and turntable seem to have comparable voltage outputs - at volume 20% they have the same loudness.
Is it worse with the phono preamp because it is connected to chassis ground? I’m thinking of replacing the relay with a new one. I’m fine with simply playing one source at a time but I’m concerned there’s something else that is contributing to the crossover. It is quite loud.
Is it worse with the phono preamp because it is connected to chassis ground? I’m thinking of replacing the relay with a new one. I’m fine with simply playing one source at a time but I’m concerned there’s something else that is contributing to the crossover. It is quite loud.
The resistance across Phono Rout to Ground (RCA outershell) is 100ohms while Phono is selected. Does this mean the relay is malfunctioning? Shouldn’t the signal go to RCOM?
Hi MarsBravo,
double checked no-nc contacts at the bottom and aren't shorted. It looks like there is an issue with the relay itself.