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Stax pro SRD-7 hum
Stax pro SRD-7 hum
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Old 13th October 2015, 02:33 PM   #1
sfltrack is offline sfltrack  United States
diyAudio Member
Join Date: Dec 2009
Default Stax pro SRD-7 hum

I am getting a very low frequency hum in my Stax SRD-7 headphones. The frequency sounds much lower than 60hz. This is a recent development and I think my house's 110V power is dirty. There is no ground in the adapter's power supply cord. The HV supply in the adapter is a cap/diode ladder type so before I go to an isolation transformer, I was wondering if building a power supply DC filter would help?
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Old 21st October 2015, 12:48 PM   #2
sfltrack is offline sfltrack  United States
diyAudio Member
Join Date: Dec 2009
I bought a Tripplite isolation transformer on Ebay. Problem solved.
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Old 4th November 2015, 12:45 AM   #3
Struth is offline Struth  Canada
Join Date: Aug 2012
Location: books at londonpower.com
Hi Guys

The voltage multiplier effectively cuts the hum frequency by the number of stages of multiplication. It would seem that either a diode or a cap has failed in the supply - or more likely just a cold solder joint.

Resoldering every connection fixes most problems in most types of electronics device, so that would be the thing to do first. The caps in the Stax supplies are low-value and easy to replace if you have to.

The bias supplies I build use full-wave rectification and no doubling - just RC filters using Solen caps and metal-film resistors. Because the current is essentially zero and mpedances are very high, a few 1uF caps produces a dead quiet supply. The caps discharge almost immediately upon power-down.

Have fun
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