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HUM - I need some context please (Read 6888 times)
dingebre
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HUM - I need some context please
02/25/15 at 22:54:37
 
I hear hum. Very faintly at a comfortable level for music listening. I've done my homework, reading the articles on this site and others, searching my old and newly purchased text books regarding hum particularly in tube circuits, and did the required experimentation.

I've also had an excellent discussion with Steve Deckert, thank you again Steve. In the end, Steve thought the hum was probably normal after hearing some samples I sent him. I am happy to accept that conclusion.

I'm not sure exactly what the source is and after all I've done and Steve's great help, I don't think I much care anymore. It really doesn't affect the music.

What I want to discuss is the general concept of hum in a tube system.

I'd love to hear from others, however, to help me establish a context for what hum is normal, acceptable, reasonable, etc. I haven't owned a tube amplifier since I was a pre-teen in the late 60s and my memory was that there was hum in a tube amplifier, low level, but still there. So, why would a new design using the same tubes and basic construction techniques be any different?

So, on a subjective level (or objective, measurement level) what level of hum should I be willing to accept and how far do you go to minimize what's there?

Thanks
David


For the curious, not really looking for help on this...

Some background: I just bought a new/old turntable (Thorens TD-165 like the one I owned in the 70s) and a brand new turntable (Thorens TD-309), a ZP3, a CSP3. and a Thorens solid state phono stage.

I hear low level hum through the ZP3 with both turntables. I tried new interconnects, moving equipment and cables, EBTECH Hum Eliminators, MU-Metal sheets, swapped all the tubes in the ZP3, everything I could imagine. When nothing is connected to the ZP3, dead quiet.

The SS phono stage, no hum with either new or old turntable.

CSP3 connected to the Thorens phono stage and either turntable, almost scary quiet (excellent job Steve).

So, difficult to blame the ZP3 or the turntables. I think it's just the way it goes.

Thanks.
David
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Ace-Tone
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Re: HUM - I need some context please
Reply #1 - 02/25/15 at 23:23:52
 
I have a bit of transformer hum from SuperZen amp and ZP3...guess it's the nature of the beast...very low level, does not affect listening pleasure.
When I went from Grado Gold cart to Ortofon 2m black the hum thru speakers was easily reduced by 30% why? Wish I knew. But, volume level is now set lower with the 2M and I do not hear the hum unless I get within a  few feet of speakers or within a foot or so of amp and ZP3.
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dingebre
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Re: HUM - I need some context please
Reply #2 - 02/25/15 at 23:35:56
 
Thanks, your response helps. I tried three different cartridges, two the same kind in both turntables and didn't perceive a reduction in hum. I can only think it has to do with some EMI getting to the low level, high impedance inputs.

David
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Archie
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Re: HUM - I need some context please
Reply #3 - 02/26/15 at 00:45:22
 
David, Your experience sounds like mine.  I get the same hum from my TT through my ZP3 regardless of using a different TT, interconnects, headshell, etc.  I listen at relatively loud levels and I can hear the hum several feet away.  Across the room if it's really quiet in the room.  However, when I drop the needle, the hum sort of goes away and is lost in the "sound" of the needle in the groove.  I don't notice it even with really good quality, quiet vinyl.  Steve told me it was some kind of synergism (or lack) between the cart, wiring, etc.  I have a highly modified Technics with Cardas wiring and an Ortofon cart.  I'm not about to start buying different carts until I lose the hum though.

I'm living with it and it doesn't bother me until someone starts another Forum Thread!   Wink
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Technics 1200G TT w/ Ortofon Jubilee MC cart
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ZR2 (25th A Mods)
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JD
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Re: HUM - I need some context please
Reply #4 - 02/26/15 at 01:25:08
 
For context I'm running my ZP3 to my CSP2+ to my Torii III.  When I turn everything on I let them warm up then turn my volume all the way up on my Torii III where there is hum while keeping the volume on the preamp all the way down. With my ear to the speaker I then turn it down till it is silent, I say on avg.  depending on my tube contingent is roughly 15-25%.  I then compensate by turning my CSP2+ up to roughly 9-12 on the dial depending on music and mood.  I am completely hum free even when music is not playing after doing this.  My inputs on my CSP2+ are at full tilt while my outputs are about 70% (estimate).  At various times I had hum that was associated with grounds, my cable box, location of multiple sources, tubes, interconnects.  
My two cents

JD
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Steve Deckert
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Re: HUM - I need some context please
Reply #5 - 02/26/15 at 01:28:52
 
Couple things that can effect hum with ZP3 that may get overlooked...

1) The RCA cables from the tonearm to the ZP3 or from the tonearm to the step up transformer must be shielded.  If there is a step up transformer, the cables between that and phono stage must be shielded.  Some cables have better shielding than others.

2) The RCA jack used on the cable must be fully metal in composition, ie., fully shielded.  You can not use Eichmann Bullets or other plastic connectors.

3) Seem obvious, but you would be surprised how many cartridges are wired with the grounds reversed between the left and right channel.  ZP3 will hum if this is done.

4) Also obvious is the ground wire on the tonearm cable has to be connected to the tonearm.  You'd be surprised how many are broken.  

3 and or 4 can be tolerated by some phono stage designs resulting in no hum.. Our original ZP1.0 was like that.  It didn't care.  The ZP3 has to have everything perfect.

ALso, the input tube especially, but all three signal tubes on the ZP3 can effect the noise and hum level by as much as a few dB, so it's worth having some around to roll into the ZP3 and see what effect they have.

Steve
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Archie
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Re: HUM - I need some context please
Reply #6 - 02/26/15 at 01:49:56
 
Now you tell me!  I've been using shielded ICs with Eichmann Bullets and I didn't notice any change from my Wireworld ICs but I can't swear that the WW were shielded.  That's why I changed them.  I guess I have something to try.
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ZLC
Technics 1200G TT w/ Ortofon Jubilee MC cart
ZMC1
ZP3 (25th A Mods)
ZR2 (25th A Mods)
CSP3 (25th A mods)
ZMA (25th A mods)
Homemade Big Betsy Speakers (F15s)
Silver Cabling
DIY Isolation platforms under amps & TT.
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dingebre
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Re: HUM - I need some context please
Reply #7 - 02/26/15 at 03:41:21
 
Thanks everyone, especially you Steve. I think this really has become more of an academic question at this point as the hum is barely there at normal listening volume and gets lost in the music.

That said, I don't suspect bad wiring because it happens on two different turntables and trying a couple of different sets of ICs. The 309 has a ground wire which connects directly to the headshell.

I don't suspect something in the ZP3 either because it's quiet when there is no input.

The reversed wiring on the cart is an interesting thought. not hard to test and swap one channel. I'm using a AT440MLa MM cartridge on both turntables, now. I've got an old Empire that I might try, too.

The new cables I made have a full metal connector, good point.

I'm getting some context now. Thanks everyone for the information and stories.

Steve, thank you again. Amazing customer service and amazing hardware. This is a great ride. Long live vinyl and electrons moving in a vacuum. I'm so glad I found your site. I was ready to pull the trigger on a different brand when I happened on your site. I'm very, very glad I clicked on that last Google result.

David
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Archie
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Re: HUM - I need some context please
Reply #8 - 02/26/15 at 17:29:20
 
That happened to me too.  I found the ZP3 and now I own it and the CSP3, ZMA, HR-1s and lots of cables!  Be careful, you could be next!
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ZLC
Technics 1200G TT w/ Ortofon Jubilee MC cart
ZMC1
ZP3 (25th A Mods)
ZR2 (25th A Mods)
CSP3 (25th A mods)
ZMA (25th A mods)
Homemade Big Betsy Speakers (F15s)
Silver Cabling
DIY Isolation platforms under amps & TT.
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