DH-101 with a noisy phono stage

grtyvr · 4th January 2012, 04:12 AM

I have a Hafler DH-101 with a noisy phono stage. The noise is a hiss that is very apparent at high volume and is not related to the cartridge itself. It is noisy with no phono input connected. All the other inputs do not exhibit this noise. Any suggestions regarding what to check?

Thanks!

Guy

kevinkr · 4th January 2012, 04:18 AM

This is probably normal, the high gain required for phono inputs comes with a price, provided that you cannot hear any pre-amplifier noise during normal playback there is no issue. The noise levels of the phono stage should be well below the surface noise level of the record..

grtyvr · 4th January 2012, 01:40 PM

That is comforting. I was in the process of hunting down the cause of a hum from my Thorens TD-160 MkII + Grado MF-1 and wanted to figure out what I was hearing on the bare input first.

sreten · 11:58 AM

Hi, phono inputs always have hiss compared to line level inputs, rgds, sreten.

Grado's seem to be more susceptible to hum than other cartridges,
though I've never had the problem with the ones I've used.

pixpop · 10th January 2012, 09:14 PM

I have a DH-110, and the phono inputs are noisy. I quit using them, and built a Pearl, with which I'm more than happy. I feed the Pearl into the Tuner input of the DH-110.

grtyvr · 10th January 2012, 10:36 PM

i will keep the pearl phono stage as a future enhancement. Thanks!

jackinnj · 11th January 2012, 12:55 AM

The phono stage shouldn't be "that" noisy, and I wouldn't replace it -- why not try replacing the MC7818/MC7918 voltage regulators with LM317/337 -- and place 100uF cap between the adjust pin and ground. I think you can get almost an order of magnitude reduction in noise with this simple change. I would also replace the RCA female jacks with new ones. Clean switch contacts with isopropyl acohol, the high test version if you can get it.

grtyvr · 11th January 2012, 01:09 PM

Thanks for the tips jackinnj. I have replaced the rca sockets with gold plated and I have cleaned them recently. I just cleaned the switches and pots with Deoxit. I am trying to decide what mods to make first out of the following:

Power supply and line stage capacitor upgrade.
Full capacitor upgrade.
Active components upgrade.

Odd. My power supply has Motorola devices. 185 M2159 QQ7948 is on the right hand side.

--
Guy

grtyvr · 11th January 2012, 01:21 PM

Also, I am not sure what you mean by the "adjust pin".

DF96 · 11th January 2012, 02:10 PM

Have we established whether we are talking about a fault to be repaired or a design shortcoming to be upgraded from? A failing resistor can create noise, or a poor solder joint. Solder flux residue which has got damp can create a lot of noise in a high impedance circuit. I would look for simple repairs like that before doing the usual audiophile thing of 'upgrading' all the components.

4th January 2012, 04:12 AM	#1
grtyvr diyAudio Member Join Date: Sep 2010	DH-101 with a noisy phono stage I have a Hafler DH-101 with a noisy phono stage. The noise is a hiss that is very apparent at high volume and is not related to the cartridge itself. It is noisy with no phono input connected. All the other inputs do not exhibit this noise. Any suggestions regarding what to check? Thanks! Guy

4th January 2012, 04:18 AM	#2
kevinkr diyAudio Moderator Join Date: Sep 2004 Location: Boston, Massachusetts Blog Entries: 6	This is probably normal, the high gain required for phono inputs comes with a price, provided that you cannot hear any pre-amplifier noise during normal playback there is no issue. The noise levels of the phono stage should be well below the surface noise level of the record.. __________________ www.kta-hifi.net

6th January 2012, 11:40 AM	#4
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, phono inputs always have hiss compared to line level inputs, rgds, sreten. Grado's seem to be more susceptible to hum than other cartridges, though I've never had the problem with the ones I've used. __________________ There is nothing so practical as a really good theory - Ludwig Boltzmann When your only tool is a hammer, every problem looks like a nail - Abraham Maslow Last edited by sreten; 6th January 2012 at 11:58 AM.

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4th January 2012, 01:40 PM	#3
grtyvr diyAudio Member Join Date: Sep 2010	That is comforting. I was in the process of hunting down the cause of a hum from my Thorens TD-160 MkII + Grado MF-1 and wanted to figure out what I was hearing on the bare input first.

10th January 2012, 09:14 PM	#5
pixpop diyAudio Member Join Date: Jan 2005 Location: Los Angeles	I have a DH-110, and the phono inputs are noisy. I quit using them, and built a Pearl, with which I'm more than happy. I feed the Pearl into the Tuner input of the DH-110.

10th January 2012, 10:36 PM	#6
grtyvr diyAudio Member Join Date: Sep 2010	i will keep the pearl phono stage as a future enhancement. Thanks!

11th January 2012, 12:55 AM	#7
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	The phono stage shouldn't be "that" noisy, and I wouldn't replace it -- why not try replacing the MC7818/MC7918 voltage regulators with LM317/337 -- and place 100uF cap between the adjust pin and ground. I think you can get almost an order of magnitude reduction in noise with this simple change. I would also replace the RCA female jacks with new ones. Clean switch contacts with isopropyl acohol, the high test version if you can get it.

11th January 2012, 01:09 PM	#8
grtyvr diyAudio Member Join Date: Sep 2010	Thanks for the tips jackinnj. I have replaced the rca sockets with gold plated and I have cleaned them recently. I just cleaned the switches and pots with Deoxit. I am trying to decide what mods to make first out of the following: Power supply and line stage capacitor upgrade. Full capacitor upgrade. Active components upgrade. Odd. My power supply has Motorola devices. 185 M2159 QQ7948 is on the right hand side. -- Guy

11th January 2012, 01:21 PM	#9
grtyvr diyAudio Member Join Date: Sep 2010	Also, I am not sure what you mean by the "adjust pin".

11th January 2012, 02:10 PM	#10
DF96 diyAudio Member Join Date: May 2007	Have we established whether we are talking about a fault to be repaired or a design shortcoming to be upgraded from? A failing resistor can create noise, or a poor solder joint. Solder flux residue which has got damp can create a lot of noise in a high impedance circuit. I would look for simple repairs like that before doing the usual audiophile thing of 'upgrading' all the components.

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