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45157978
5
Mar 8, 2017
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Replaced the front tube with a NOS Sylvania 6sn7gtb. Let it burn in for four days still had a deep hum.  Did the FITZ Mod today DEAD SILENT. This mod works! Parts were 2 bucks at Micro Center. Took about 40 minutes from start to finish to install the two 220uf 25v capacitors. If you plan to tube roll this mod might be a must. This tube is a little warmer that the stock tube. A little wider sound stage too. I have the Grado RS1 and HD 600'S with a balanced 4 pin cable that I use mainly with my Jotunheim.  Made a 4 pin to 1/4 in adaptor to use the 600's with the 336. Really drives the 600's nice! Adds some fullness to the RS1's, because of their low impedance 2nd volume screw max. I use the iFi micro IDSD as my dac for both amps in pass through mode.  The IDSD is a really Good piece of gear. Will change the power tube in a little while after I hear half my music collection all over again.............       
Mar 8, 2017
iCeOL8TRAmnesia
130
Mar 10, 2017
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You just need to clean your power source mine has no hum. Its called heater hum its from dirty mains power either an appliance in your house backfeeding into your mains or some other interference source or dirty computer power or air conditioner likely its a faulty air conditioner component or major appliance like a refrig or your mains could be dirty from the power company. I posted a link for 4 dollar power cleaners on this thread. I wouldnt touch the amp unless your upgrading and know what you are doing otherwise you may lessen the precision of this amp which is what it is known for.
Mar 10, 2017
45157978
5
Mar 10, 2017
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Thanks for the reply. My situation is a little different. I have good clean power. My amp goes through a Richard Gray's unit not directly into the wall. The stock tubes are dead quiet. The NOS front tube is the problem. I ran it 48 hours straight to help burn it in, but no difference. The Fitz mod might not be for everyone, but it sure did work for me. Happy tube rolling iCe............................. 
Mar 10, 2017
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