Tube Power Supply Mechanical Hum - Tube Recommendations?

LL21

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Hi All,

My Zanden DAC has a separate power supply which uses: (2) 6CA4 and (1) 6X4

i got great recommendations from Brent Jessee: Mullard 1950s 6CA4 and Sylvania 6x4

The problem is after 1200 hours or so, the mechanical hum from the power supply is big and comes thru the speakers. i just switched to a backup set of the identical tubes...and the noise is slightly greater! At the volume set at 35 (of 99) and 55 being very, very loud...i can hear the hum throughout my room and within 10 feet...irritating.

Is it these NOS 1950s tubes? Do tube dampers help? Or is it DC coming thru the line? If tubes, can you all recommend quieter tubes? thanks for any guidance.
 

RogerD

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Tubes or have you moved any cables? Also it could be a power supply cap also. I doubt it's the tube(s),but it could be.
 

LL21

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Hi Steve,

Thanks for the quick response as usual! Symptoms: when i put my ear to the tube power supply, i hear a distinct mechanical hum with the other half of the DAC powered down. That exact same frequency/hum is what i hear through my speakers...plus "soft tv static-like noise"...it is constant and rises/lowers with volume. And again, the noise thru the speakers sounds identical to the noise i hear when i put my ear to the power supply.
 

LL21

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Tubes or have you moved any cables? Also it could be a power supply cap also. I doubt it's the tube(s),but it could be.
Hi Roger,
I have not moved any cables recently. I have emailed Eric Pheils at Zanden as well. Last time, the noise was due to tubes, but this time in switching it is the same if not more....unless i got 2 batches of noisy tubes? Does mechanical hum get improved by tube dampers?
 

RogerD

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Hi Roger,
I have not moved any cables recently. I have emailed Eric Pheils at Zanden as well. Last time, the noise was due to tubes, but this time in switching it is the same if not more....unless i got 2 batches of noisy tubes? Does mechanical hum get improved by tube dampers?

If the noise is that loud and is volume dependent it could be the tubes. Last time you had the problem was it just as loud? But it could be a problem in the signal path ie capacitor ect.
 

Steve Williams

Site Founder, Site Owner, Administrator
If the noise is that loud and is volume dependent it could be the tubes. Last time you had the problem was it just as loud? But it could be a problem in the signal path ie capacitor ect.

It would also rule out a ground loop hum
 

LL21

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If the noise is that loud and is volume dependent it could be the tubes. Last time you had the problem was it just as loud? But it could be a problem in the signal path ie capacitor ect.

Hi Roger. Honestly, I cannot remember...it was louder but perhaps not quite this loud. Note i also got a new pre with a much lower noise floor. Might be a combination of both...
 

LL21

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Given the fact that when i put my ear to the power supply, i can hear a steady hum from the back of the unit, i have to imagine it is power supply/transformer/tube??? And the hum thru the speakers is the identical noise plus the soft static noise...
 

LL21

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Definitely I agree about the effect of the new pre
thanks steve. thought so. i love how my system sounds...but as with all new components...the balance does get reset. I have not found any digital to satisfy me like the Zanden...fingers crossed i can get Brent Jessee or Upscale Audio to recommend quieter tubes?
 

microstrip

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Given the fact that when i put my ear to the power supply, i can hear a steady hum from the back of the unit, i have to imagine it is power supply/transformer/tube??? And the hum thru the speakers is the identical noise plus the soft static noise...

You have to separate mechanical hum from the power supply from hum sound coming from the speakers.

Your sentence "the mechanical hum from the power supply is big and comes thru the speakers" only means you have two sources of hum in your system, that most probably are not correlated.

Both tubes you refer are rectification tubes - if any of them would age it could lower the HV supply to a point that it is so low that ripple can not be rejected and you have electrical hum in the output of the Zandem.

The frequency of this electrical signal is the same of the harmonics of the vibration of the power transformer so you think they are related, but they are independent. Only if the mechanical noise in the power transformer was due to a faulty transformer (very improbable, but can happen) they could be related.
 

LL21

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Hi Microstrip,

thanks...as a non-technie, does this mean i need to try new rectifier tubes?
 

microstrip

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It would also rule out a ground loop hum

Steve,
I have seen situations where the hum due to ground loops is volume dependent - I would not rule out a ground loop so fast.
 

microstrip

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Hi Microstrip,

thanks...as a non-technie, does this mean i need to try new rectifier tubes?

Yes! And while waiting for them look for ground loops.
 

microstrip

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thanks steve. thought so. i love how my system sounds...but as with all new components...the balance does get reset. I have not found any digital to satisfy me like the Zanden...fingers crossed i can get Brent Jessee or Upscale Audio to recommend quieter tubes?

Usually rectifiers tubes are not selected for low noise, but for matching of sections and low dynamic resistance. But I think any good quality ones will do the job perfectly.
 

LL21

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interesting...where would i look? cabling?
 

LL21

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i discovered when i flip the preamp to a different source (my oppo audio out for example on movies)...the hum is gone. i only get it when i use the Zanden dAC. can a ground loop hum only run on one source component?
 

mep

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i discovered when i flip the preamp to a different source (my oppo audio out for example on movies)...the hum is gone. i only get it when i use the Zanden dAC. can a ground loop hum only run on one source component?

Yep, it sure can. How old are your rectifier tubes? Usually tubes themselves don't hum. Tubes can make noise though. Usually if you hear hum coming from a tube piece of gear, there is a grounding issue going on or you actually have some bad power supply filter caps. Unless you have a couple of years on those tubes of yours, I highly doubt they are the source of the problem.
 

LL21

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ok...thanks. i turned off CD player, sub and tv. so only DAC, pre and amp. still had hum.

meanwhile, the static remains there even with DAC off (pre and amp on only)...as Microstrip said, 2 different problems!!! The static disappears with the pre on mute...but that was not the case when i had a different amp in place with the same pre (whcih is brand new). maybe a bad interaction between pre and this loaner amp i have while the main amp is in for repair?
 

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