restorer-john
Grand Contributor
Is the mains plug a parallel US two pin that you can rotate through 180 degrees?
Please disconnect all the input cables and check if the noise on the speakers is still there; test first with volume to the min., then you can increase the volume slowly and recheck for noise (no input cables connected!).It makes no difference whether I choose an analog (record) or digital source (optical from TV, USB from RPI4, Bluetooth). The noise is permanently present.
The tonearm ground should always be connected to the GND on the phono preamp chassis.I have a Rotel RA-1572 that I also noticed has a slight buzz that is noticeable close to speakers but inaudible (for me at least) at my listening position. I spent some time tracking it down and could not find an input to blame, but my phono stage when grounded to the amp chassis was particularly noisy. At some point I was able to reduce phono stage noise by tying the tonearm via the phono cable to earth ground, so assumed that at least that problem was related to EMI or a poor ground connection. I haven't had much luck reducing amplifier noise but am interested in what you find.
I should clarify what I said - the tonearm is always connected to the phono preamp GND, however the preamp is integrated into the RA-1572. What I noticed was that when the chassis is tied directly to earth GND the noise is reduced.The tonearm ground should always be connected to the GND on the phono preamp chassis.
More likely that you have a ground loop. What is your connection chain (eg source to dac to amp to speakers), what is the interconnect type, and which of the devices in the chain is earthed.hello. While looking for a solution for my own problem I saw this. I have the exact same problem with the same symptoms. I have identified that RF is picked up by quality RCA cables with good shielding (acting as the perfect antenna) and my buildings ground line is inadequate to drain the noise. If I use cheap non shielded RCA the hum gets less. Give it a try and good luck.
Hi, Streamer to Pre/Dac to Amp. The Amp is grounded but the ground wire is disconnected in the electrical box of my flat. I tried connecting the amp to phone directly, same humm. The amp humms even when RCA cables are connected free on the other end. The Humm changes pitch when I move the RCA’s around. Hence me guessing that it’s RF interference.More likely that you have a ground loop. What is your connection chain (eg source to dac to amp to speakers), what is the interconnect type, and which of the devices in the chain is earthed.
When I use good quality, shielded RCA’s the amp switches off into safety mode. When I use cheap RCAs at certain random routings, the hum diminishes. Irrelevant to their proximity to power chords. Only the mid drivers and tweeters reproduce humm (Even some faint radio music buried in the hum) I tried with different speakers, the same. The amp in question is a Audio Analogue Donizetti. My previous Rega had no such issue, but than again it wasn’t as clear and open as the A.A.An unconnected RCA will just act as an aerial to pick up any old crap in your environment. It is not representative of the noise you are experiencing when properly connected.
Do you get hum with nothing connected to the amp? When you connect the phone - have you disconnected everything else? Do you still get hum?
When you say the earth is disconnected in the electrical box what do you mean? Which electrical box, where (this might be related to your problem) - and why is it disconnected? How is electrical safety ensured?
Fair enough - i have seen some interesting wiring in Istanbul. Do you have any RCD or similar fault current detection breakers in your system for safety?When I use good quality, shielded RCA’s the amp switches off into safety mode. When I use cheap RCAs at certain random routings, the hum diminishes. Irrelevant to their proximity to power chords. Only the mid drivers and tweeters reproduce humm (Even some faint radio music buried in the hum) I tried with different speakers, the same. The amp in question is a Audio Analogue Donizetti. My previous Rega had no such issue, but than again it wasn’t as clear and open as the A.A.
I don’t get any hum when the amp is only connected to speakers. Yes, the amp is a dual mono without a preamp stage. The Phone was the sole connected device.
I live in a building made in the beginning of 1900’s and in Istanbul. We take our time
Thank you for your time and effort. Cenk