Hi. Is anybody familiar with this preamp? I have had it since new and its a nice preamp but I have a minor problem with its digital inputs. Once playing it is fine but when you press PLAY on an attached device a momentary loud crack is heard from the speakers. It didn't do this when new and it is getting worse.
I have the schematic and it speaks of an output from an ic that goes low when a signal is detected. It claims that this turns off an external mute circuit but when I follow the circuit on the schematic and on the device its output goes nowhere. It definitely has a mute circuit but it doesn't go into mute when the digital input is selected. This ic does indeed produce an output that goes low when a signal is applied.
Has anybody had a similar problem? Arcam don't exist anymore in reality so won't help. I have just completed a recap of all electrolytics that had deteriorated and though overall sound quality was improved by this it hasn't removed the crackle.
Any thoughts?
I have the schematic and it speaks of an output from an ic that goes low when a signal is detected. It claims that this turns off an external mute circuit but when I follow the circuit on the schematic and on the device its output goes nowhere. It definitely has a mute circuit but it doesn't go into mute when the digital input is selected. This ic does indeed produce an output that goes low when a signal is applied.
Has anybody had a similar problem? Arcam don't exist anymore in reality so won't help. I have just completed a recap of all electrolytics that had deteriorated and though overall sound quality was improved by this it hasn't removed the crackle.
Any thoughts?
Thoughts... might not be much help...
Playing what? Do you mean listening to any analogue input and you hear the noise when you happen to press play on a connected digital source?
Are ALL sources the same now as when it worked OK?
I would suggest a scope to see where the noise is entering the chain. Work forward from the output sockets forward toward the inputs.
Which digital inputs? TOSLINK or coax?
I've no answers 🙂 but that is how I would approach it.
Playing what? Do you mean listening to any analogue input and you hear the noise when you happen to press play on a connected digital source?
Are ALL sources the same now as when it worked OK?
I would suggest a scope to see where the noise is entering the chain. Work forward from the output sockets forward toward the inputs.
Which digital inputs? TOSLINK or coax?
I've no answers 🙂 but that is how I would approach it.
Thanks for your reply.
The crack sound only appears when either (labelled 'digital' and 'optical') digital input is selected so it appears to be coming through the audio stages of the DAC. It happens on both Toslink and coax inputs.
Your advice is good and I will look again at the signal path. It's 1 bit dac so it has fairly complex filtering.
The service manual is vague but does seem to suggest that the preamp should go into MUTE mode when digital is selected and that the presence of a digital pulse will disable that MUTE state, presumably after the crackle is past. The fact that the signal to do that goes nowhere on the mainboard is perplexing...
The crack sound only appears when either (labelled 'digital' and 'optical') digital input is selected so it appears to be coming through the audio stages of the DAC. It happens on both Toslink and coax inputs.
Your advice is good and I will look again at the signal path. It's 1 bit dac so it has fairly complex filtering.
The service manual is vague but does seem to suggest that the preamp should go into MUTE mode when digital is selected and that the presence of a digital pulse will disable that MUTE state, presumably after the crackle is past. The fact that the signal to do that goes nowhere on the mainboard is perplexing...