Originally Posted by Asr
Sorry for a delayed response to this, I forgot my ATH-ES5 at work again yesterday.
Anyway I do hear some background hiss with the ES5, regardless of which lower-impedance setting I use (6-32, 32-64). It was noticeable right away too, didn't even need to listen closely for it.
How much did your replacement tubes cost? I might go for those too.
Like a guitar amp, the first tube (12AX7) affects noise level the most.
I would recommend oder 12AX7 and 12AU7 from Tube depot, and choose the low noise and microphonics option for only $4 more. They will hand select the quietest tube for you. Among all the 12AX7 tubes I have tried (Ei, Grove Tube Mullard reissue, Chinese C8, Chinese C9, JJ, Sovtek LPS, used Raytheon, EH), I like Sovtek LPS the most. But I found used JAN GE 5751, an 12AX7 alternative (70% gain, softer tone), to be better with Cayin HA-1A (but not in my other amp).
Tube depot still sells quite a few 12AU7 NOS tubes with alternative names. They are inexpensive and worth trying. I have Sylvania 5963, Philips 6189, JJ 12AU7, Ei Gold Elite 12AU7 and Japanese 12AU7 branded Channel Master. I like the Japanese tube because of its low noise, and it was only $11 used from Coherent Audio.
EL84 cost more and I have only tried EH, JJ, Sovtek and NOS Japanese labeled Marconi Radiotron. I like Janpanese the most.
Japan made a lot of OEM tubes in the 70's for US and Europe. Some people think Japanese tubes can't compete with American and Western tubes of 50's and 60's. Some say Japanese tubes have low noise but sound sterile. In my limited experience I find Japanese tubes really good and reasonably priced. After all, Japan has been making tubes since 1930's, and by 40's has the technological capability to attack Pearl Harbor.
Anyway, once you install some selected low-noise preamp tubes noise should go down a lot. No company I know sell low-noise EL84, but Ei Gold Elite should be pre-selected for low noise already.