Denon 103R needs help.

Sunsun22 · 28th January 2005, 06:56 AM

I was using a Shure V15VxMR before. My new toy 103R arrivved today but after I installed it in my turntable, audiable hum started. I cannot hear hum from my Shure V15 before unless I turn the gain of my preamp to over 80 (92 max) but now I can hear it at 60. I did try the following ways: -

1. Reduce the gain of the phono stage from 35db to 30db
2. Change the impedence from 100 ohmes to 82 ohmes
3. Unplugged the TT's ground cable
4. Un-ground the phono stage
5. Tried to maintain 47K impedence and at the gain stage of MM cartridge but I can still hear hum at 60.

My phono stage is ASR Mini-Basis. It is quite obvious that hum is genereated after connecting the tonearm wires and cartridge pins.

Help is needed. Thanks

analog_sa · 28th January 2005, 10:04 AM

Strange problem. Before investigating how the arm and TT motor are grounded i would first try to exclude the preamp. If you connect just a 10ohm resistor across the input do you get any hum?

vuki · 28th January 2005, 10:42 AM

Denon is MC and Shure is MM. If you corrected the gain setting of your phono preamp (it should be higher for MC) the problem could be related to the grounding & shielding. ASR preamps have plexy enclosures so perhaps the shielding is not perfect. Also, because of higher gain setting all the hum&noise collected through the wires are amplified in the phonopre.
Unconnect turntable from the phono preamp and check the hum. If it's gone than you're picking hum via cartridge or tonarm to phonopre cables.
If there is hum although the turntable is unconnected try to move phonopre and find if there is place where it doesn't hum.

phn · 28th January 2005, 11:42 AM

Maybe a useless post. But when I had problem with hum on my Thorens, I believe it was due to poor connection. Whenever I got hum (which happened a few times) I wiggled the cartridge leads and it went away.

Sunsun22 · 30th January 2005, 12:45 AM

Thank you for all the advices. I went through each and every advice and finally discovered that the hum is from the ASR. I'll try to shield the entire unit and see what will happen. But it is sad to see such a good preamp is picking up so much hum.

vuki · 30th January 2005, 08:41 AM

Instead of shielding the whole preamp you could ground a piece of copper-clad board (blank pcb) and try to put it at various positions (over/under etc.) around preamp. Sometimes it helps.

28th January 2005, 06:56 AM	#1
Sunsun22 diyAudio Member Join Date: Jul 2004 Location: Hong Kong	Denon 103R needs help. I was using a Shure V15VxMR before. My new toy 103R arrivved today but after I installed it in my turntable, audiable hum started. I cannot hear hum from my Shure V15 before unless I turn the gain of my preamp to over 80 (92 max) but now I can hear it at 60. I did try the following ways: - 1. Reduce the gain of the phono stage from 35db to 30db 2. Change the impedence from 100 ohmes to 82 ohmes 3. Unplugged the TT's ground cable 4. Un-ground the phono stage 5. Tried to maintain 47K impedence and at the gain stage of MM cartridge but I can still hear hum at 60. My phono stage is ASR Mini-Basis. It is quite obvious that hum is genereated after connecting the tonearm wires and cartridge pins. Help is needed. Thanks

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28th January 2005, 10:04 AM	#2
analog_sa diyAudio Member Join Date: Aug 2002 Location: Sofia	Strange problem. Before investigating how the arm and TT motor are grounded i would first try to exclude the preamp. If you connect just a 10ohm resistor across the input do you get any hum?

28th January 2005, 10:42 AM	#3
vuki diyAudio Member Join Date: Jun 2002 Location: zagreb, croatia	Denon is MC and Shure is MM. If you corrected the gain setting of your phono preamp (it should be higher for MC) the problem could be related to the grounding & shielding. ASR preamps have plexy enclosures so perhaps the shielding is not perfect. Also, because of higher gain setting all the hum&noise collected through the wires are amplified in the phonopre. Unconnect turntable from the phono preamp and check the hum. If it's gone than you're picking hum via cartridge or tonarm to phonopre cables. If there is hum although the turntable is unconnected try to move phonopre and find if there is place where it doesn't hum.

28th January 2005, 11:42 AM	#4
phn diyAudio Member Join Date: Oct 2004	Maybe a useless post. But when I had problem with hum on my Thorens, I believe it was due to poor connection. Whenever I got hum (which happened a few times) I wiggled the cartridge leads and it went away.

30th January 2005, 12:45 AM	#5
Sunsun22 diyAudio Member Join Date: Jul 2004 Location: Hong Kong	Thank you for all the advices. I went through each and every advice and finally discovered that the hum is from the ASR. I'll try to shield the entire unit and see what will happen. But it is sad to see such a good preamp is picking up so much hum.

30th January 2005, 08:41 AM	#6
vuki diyAudio Member Join Date: Jun 2002 Location: zagreb, croatia	Instead of shielding the whole preamp you could ground a piece of copper-clad board (blank pcb) and try to put it at various positions (over/under etc.) around preamp. Sometimes it helps.

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