Leak Delta 30 - Hum on phono input - UK Vintage Radio Repair and Restoration Discussion Forum

PJay1966 · 19th Mar 2023, 1:40 pm

Hi Everyone

I thought my restoration of a Leak Delta 30 was progressing well so I decided to set it up in my system and test it out. I have connected a Rega Planar turntable to the DISC1 input and my Sony TC-377 to the tape inputs. I also have an bluetooth receiver connected to Tuner1. The bluetooth device sounds fantastic but the others are not good at all. There is hum on the phono input and the volume needs to be cranked nearly fully up to get a reasonable volume. The tape player works but again needs the volume up high to get enough volume both of the gain switched have been cleaned and set to high.

Any ideas, could be that the sources are too low in output for this amp and what might cause the hum only on the phono stage? All of the sources work 100% and are now connected to my Arcam Alpha with no issues.

Would be grateful for any advice or guidance!

PaulR · 19th Mar 2023, 7:40 pm

The hum on the phono stage could be due to an earthing issue. My Lenco GL75 has a separate earth lead which needs to be connected to the amp to stop it humming. Ironically an earth lead can also cause a hum loop if the turntable is otherwise earthed and needs to be disconnected. Have a play around with earthing the turntable and you should hopefully be able to stop the hum. Of course any hum caused by the connections will be exacerbated by having to turn the volume right up. What cartridge are you using? If it is a moving coil the output may be too low for the phono stage. If it is a moving magnet or high output m/c then it should have sufficient output. I am using Disk 1 with a m/m cart and the volume is fine. I know that Disc 1 is the correct one to use but it might be a good idea to try Disk 2 just to see whether it makes any difference.

I am using the tape input as an aux input and again the volume is fine.

The high/low gain switches are only effective on Disc 2 and Tuner 2 so they aren't relevant to your problem. However, all the switches on these amps including the push button ones can cause problems so a first step would be to spray switch cleaner onto them and work them whilst listening to the output.

The tape input feeds into the selector switch so if the tuner input is working I would expect it to work as well. Try connecting your bluetooth receiver to the tape input to see how it sounds.

vidjoman · 19th Mar 2023, 9:37 pm

Back in the early 1970’s I had a Leak stereo 30. After a house move, I had a nasty hum on the phono input. All the equipment was exactly the same as in my previous house. Baffled, I tried various screening techniques, connecting/disconnecting earth leads. The problem wouldn’t go away. Eventually traced to the tuner aerial. Disconnecting from the tuner and the phono hum disappeared. The builders of the new house had connected the screen of the aerial in the wall outlet to the metal box and connected that to the mains earth in the nearby 13 amp outlet. This caused an earth loop and the hum on the phono input.
Try disconnecting the various earth leads that go to the mains from different parts of the system but make sure the earth lead from the turntable is connected to the connection on the back of the amplifier.

19th Mar 2023, 1:40 pm	#1
PJay1966 Pentode Join Date: May 2021 Location: Buckinghamshire, UK. Posts: 133	Leak Delta 30 - Hum on phono input Hi Everyone I thought my restoration of a Leak Delta 30 was progressing well so I decided to set it up in my system and test it out. I have connected a Rega Planar turntable to the DISC1 input and my Sony TC-377 to the tape inputs. I also have an bluetooth receiver connected to Tuner1. The bluetooth device sounds fantastic but the others are not good at all. There is hum on the phono input and the volume needs to be cranked nearly fully up to get a reasonable volume. The tape player works but again needs the volume up high to get enough volume both of the gain switched have been cleaned and set to high. Any ideas, could be that the sources are too low in output for this amp and what might cause the hum only on the phono stage? All of the sources work 100% and are now connected to my Arcam Alpha with no issues. Would be grateful for any advice or guidance!

19th Mar 2023, 7:40 pm	#2
PaulR Dekatron Join Date: Oct 2003 Location: Southport Lancashire, UK. Posts: 3,237	Re: Leak Delta 30 - Hum on phono input The hum on the phono stage could be due to an earthing issue. My Lenco GL75 has a separate earth lead which needs to be connected to the amp to stop it humming. Ironically an earth lead can also cause a hum loop if the turntable is otherwise earthed and needs to be disconnected. Have a play around with earthing the turntable and you should hopefully be able to stop the hum. Of course any hum caused by the connections will be exacerbated by having to turn the volume right up. What cartridge are you using? If it is a moving coil the output may be too low for the phono stage. If it is a moving magnet or high output m/c then it should have sufficient output. I am using Disk 1 with a m/m cart and the volume is fine. I know that Disc 1 is the correct one to use but it might be a good idea to try Disk 2 just to see whether it makes any difference. I am using the tape input as an aux input and again the volume is fine. The high/low gain switches are only effective on Disc 2 and Tuner 2 so they aren't relevant to your problem. However, all the switches on these amps including the push button ones can cause problems so a first step would be to spray switch cleaner onto them and work them whilst listening to the output. The tape input feeds into the selector switch so if the tuner input is working I would expect it to work as well. Try connecting your bluetooth receiver to the tape input to see how it sounds. __________________ Paul

19th Mar 2023, 9:37 pm	#3
vidjoman Dekatron Join Date: Jun 2013 Location: East Sussex, UK. Posts: 3,326	Re: Leak Delta 30 - Hum on phono input Back in the early 1970’s I had a Leak stereo 30. After a house move, I had a nasty hum on the phono input. All the equipment was exactly the same as in my previous house. Baffled, I tried various screening techniques, connecting/disconnecting earth leads. The problem wouldn’t go away. Eventually traced to the tuner aerial. Disconnecting from the tuner and the phono hum disappeared. The builders of the new house had connected the screen of the aerial in the wall outlet to the metal box and connected that to the mains earth in the nearby 13 amp outlet. This caused an earth loop and the hum on the phono input. Try disconnecting the various earth leads that go to the mains from different parts of the system but make sure the earth lead from the turntable is connected to the connection on the back of the amplifier.