How to reduce hum with phono preamp

[mahiruha]

Hi Guys,
I am trying to setup a TT based system in my bedroom and encountered this strange problem with hum. I am trying to connect my Project Debut III TT to my Creek OBH-15 phono preamp which is connected to a sony receiver which I am using as an amplifier. The problem is there is considerable hum from the speakers when the volume is raised a bit.
I tried the following experiments.
1) I just raised the volume of amplifier when nothing is connected to it and there is no hum
2) I connected the phono pre with amplifier but didn't connect TT to the phono Pre and raised the volume of the amplifier there is no hum

3) I connected the TT to the phono pre but TT was switched off and I could hear the hum as the volume is raised.
4) Same as 3 but this time the TT is switched on and Hum remains the same as 3.

Interesting was I tried moving the wire that comes out of the turntable and goes into the phono preamp and the magnitude of the Hum varies. It seems the TT wire acting like an antenna and whatever it captures that noise is getting amplified insdie the phono pre. This hum is bit annoying in quiet passages.

Can anybody please suggest any solution for this?
Thanks.

 

[gobble]

Do both devices use 3 pin plugs? Are they plugged into the same socket?

Is the wire that varies the hum shielded? Is the shield chassis grounded (ask the manufacturer or google) Take a wire from the RCA signal ground and ground it to metal chassis of phono and check.

I spent a week last month troubleshooting hum on my preamp and cracked it, but I had access to the insides and ensured good star grounding of RCA ground signal along with AC earth and properly using all grounding facilities provided in PCB to establish the star ground.

Regards

 

[Hiten]

Have you connected ground wire from Turntable to Phono preamp ?

 

[mahiruha]

Gobble- The phono preamp uses 2 pin plug and the TT uses a three pin plug.
They are connected to different sockets. I think the wire that varies the hum is shielded and it is hard wired to the turntable. How to take a wire from RCA signal gound? I am not fully understandig your point here.

Hiten- Yes I have connected the ground wire to the phono pre.
Thanks.

 

[Hiten]

..... and from phono pre to receiver ???

 

[mahiruha]

..... and from phono pre to receiver ???

No. From phono pre the connection to the receiver is made using simple RCA connectors. Receiver doesn't have any option for ground connection.

 

[odyssey]

As gobble mentioned - pls check that the cable from the TT to the phono stage is a shielded cable - use the audio art ICs if you have a doubt as to whether your present ICs are shielded. The power ground/star ground should have nothing to do with it as this problem occurs with the TT switched off. Shielding has nothing to do with whether there is a cover over the bare wire - its about using something like Teflon or another form of shielding

cheers

 

[gobble]

Gobble- The phono preamp uses 2 pin plug and the TT uses a three pin plug.
They are connected to different sockets. I think the wire that varies the hum is shielded and it is hard wired to the turntable. How to take a wire from RCA signal gound? I am not fully understandig your point here.

Hiten- Yes I have connected the ground wire to the phono pre.
Thanks.

I was hoping or assuming some access to the internals.

I may be wrong but if the 3 pronged plug is on the TT only then you should try any grounding on the TT side rather than the phono side.


Hiten is a TT owner, he will have better advice for you

Cheers

 

[mahiruha]

As gobble mentioned - pls check that the cable from the TT to the phono stage is a shielded cable - use the audio art ICs if you have a doubt as to whether your present ICs are shielded. The power ground/star ground should have nothing to do with it as this problem occurs with the TT switched off. Shielding has nothing to do with whether there is a cover over the bare wire - its about using something like Teflon or another form of shielding

cheers

I was thinking in this line the problem is the interconnect and ground wire is hardwired in the TT body for Project Debut III. Is there anyway I can offer more shielding to the existing cable. Some sort of Teflon pipe. Not sure if such a thing exists.

Thanks.

 

[odyssey]

Yes, you should be able to buy a Teflon pipe or even Teflon tape that you can wrap over the wire completely. Concentrate on doing this for the signal IC ignore the ground wire for now
cheers

 

[mahiruha]

Yes, you should be able to buy a Teflon pipe or even Teflon tape that you can wrap over the wire completely. Concentrate on doing this for the signal IC ignore the ground wire for now
cheers

Hi,
Can you please tell me who sells this teflon pipe or teflon tapes.
Thanks.

 

[myriad]

Mahi,
Don't know about teflon pipes but you will get teflon tapes in plumbing stores. They also might be stocking teflon pipes. If not, they will be able to tell you where to find.
Regards

 

[odyssey]

Vasu is right, Teflon tape is also called plumbers tape. The material is very distinct and should be easy to make out. Teflon tubling should be available in any electronics parts/cables store

Cheers

 

[shaizada]

I know this is going to sound weird, but can you also try out Aluminum foil? Wrap it all around the cable that is acting like an antenna and see if it lessens or eliminates the hum.

If it does lessen the hum, please find yourself some quality shielded interconnects between the turntable and the phonostage. Keep the interconnect as short as possible with the excellent shielding.

You can try and look into some Belden cable or Canare star quad. They have excellent noise rejection and are relatively inexpensive while being very neutral in sound.

 

[mahiruha]

I know this is going to sound weird, but can you also try out Aluminum foil? Wrap it all around the cable that is acting like an antenna and see if it lessens or eliminates the hum.

If it does lessen the hum, please find yourself some quality shielded interconnects between the turntable and the phonostage. Keep the interconnect as short as possible with the excellent shielding.

You can try and look into some Belden cable or Canare star quad. They have excellent noise rejection and are relatively inexpensive while being very neutral in sound.

Thanks for the advise shaizada. Well I tried it as per your suggestion.I reduced the hum a bit say before it was aduidable at volume level 18 but with the wrap it can be heard at volume level 20. I guess if I can connect a quality shielded interconnect it might solve the problem. I need to find out if somebody in Calcutta can mod the project TT so I can attach a shielded interconnect. Btw since you have experienced lot of phono stages is it general case with phonostages that all of them produces hum at higher volume levels. I was having the idea that only tube phono stages produces hum but now I see solid state phono stages also produces hum.

@Vasu: Thanks for your suggestion will try the Teflon tape solution before trying to mod my TT
Thanks.

 

[Hiten]

you can try one more thing. Try connecting Phono Pre amp ground wire to body of sony receiver (If it is of metal)

 

[shaizada]

Thanks for the advise shaizada. Well I tried it as per your suggestion.I reduced the hum a bit say before it was aduidable at volume level 18 but with the wrap it can be heard at volume level 20. I guess if I can connect a quality shielded interconnect it might solve the problem. I need to find out if somebody in Calcutta can mod the project TT so I can attach a shielded interconnect. Btw since you have experienced lot of phono stages is it general case with phonostages that all of them produces hum at higher volume levels. I was having the idea that only tube phono stages produces hum but now I see solid state phono stages also produces hum.

@Vasu: Thanks for your suggestion will try the Teflon tape solution before trying to mod my TT
Thanks.

Not at all my friend. A quality phono stage will be dead silent even at it's full gain. My Einstein and Nighthawk are DEAD DEAD DEAD silent even if I put the gain all the way up on my preamp.

The Nighthawk is battery powered and I highly suggest you guys to look into it. Viren heard it himself, so it would be good to ask him about it as well

I push that phono strongly on this board. Only because the quality of sound that one gets at this price point is unheard of!

Oh by the way, start with a quality shielded cable. Make sure it is AS SHORT as possible. Preferably 0.75m or less.

 

[mahiruha]

Not at all my friend. A quality phono stage will be dead silent even at it's full gain. My Einstein and Nighthawk are DEAD DEAD DEAD silent even if I put the gain all the way up on my preamp.

The Nighthawk is battery powered and I highly suggest you guys to look into it. Viren heard it himself, so it would be good to ask him about it as well

I push that phono strongly on this board. Only because the quality of sound that one gets at this price point is unheard of!

Oh by the way, start with a quality shielded cable. Make sure it is AS SHORT as possible. Preferably 0.75m or less.

Hi Shaizada,
after hearing from you that phono stages can be dead silent I just tried the Creek phono stage in my main vinyl set up. I find it is abosolutely silent. There is no hum atall. So in my other setup I guess the Project Debut III is the problem with not so good interconnect. Now I know why I hear hum even in my onkyo receiver. It is funny while searching for some other problems solution to some previous problem could be located.My main priority over the weekend is to mod this project debut III to connect a better shielded IC.
Regarding Nighthawk I will try and get it. It is good to have few phonostages at disposal. Kind of adds variety to the musical presentation. Actually I got this Creek which was recommended by various hifi dealers in UK that matches my Dynavector cartridge. It has a different way of presenting music but Lyrita phono pre presents music in such a manner which is more involving with excellent midrange.Have you heard microgroove from Tom Evans? Some UK dealers were highly recommending it.
Thanks.

 

[shaizada]

A phono stage is MEANT to be dead silent if it is well designed.

I have heard the Tom Evans Microgroove and Microgroove X. They sound very very good. However, they are very good for the price. They sound different from other phono stages in the same price range, and have a very natural presentation that I liked. However, they don't sound like something comparable to a $3k or above phono stage. The Nighthawk does. It defies it price bracket and competes with products in the $5k to $10k realm. That is an anomaly and VERY admirable about a product.

We are always looking for a bang for the buck product. This product is the "big bang" then At least in my experience. You should have this conversation with Viren as well when he comes back to Delhi. Since he heard BOTH the phono stages, he can give you his perspective as well. It's always good to have a second set of ears to have another opinion. It's good to have a common reference point as well, something Viren can provide more easily.

 

[mahiruha]

Hi Guys,
so finally there is some solution to the original problem. Actually the problem I was facing was hiss not hum. As somebody mentioned to me hum is something which is always there but hiss is something that increases with volume. I changed the Project Debut III stock interconnect with very well shilelded audio art interconnects by directly shouldering them in the truntable which has elimineted the hiss problem to a great extent. I would suggest anybody having a project debut III TT is bound to have this hissing problem so it is better to change the stock interconnect with a better shielded interconnect and it will give very good results by decreasing the noise floor to a very large extent. Thanks everybody for their inputs.
Thanks.