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Basic question regarding noise and grid leak resistor
Hello
I have a "second" preamp that I've been using for a few years made up of Audio Note kit parts (from years ago) just in a different chassis. I also have an Audio Note kit preamp and DAC with AG recommended txs and different output stages that I've been running happily for years in another system with similar changes described below. So I've done this output stage change with a very similarly configured preamp using 1 x e80cc and 1 x 6350 tubes . . . (just not the grid leak resistor change - see below) Sooooo, I decided to implement a similar output stage that changes to 1 x 12au7 and 1 x 6463 instead of the 5687/7119 configuration. Easier to find single tubes than matched pairs of 7119s etc. . . So I have successfully done this (change opt stage) twice (preamp above and DAC) but this time I'm having issues. . . My voltages check out. The preamp plays music. But, their is an loud noise that doesn't sound to me like typical 60 or 120hz hum but more like a 120hz static of sorts . . . after changes the preamp was put back in the system it was used in successfully for years (including a nice recently recapped pair of WAD 300B PSE monoblocks). Questions: 1-could significantly reducing the grid leak (with the desire to create a voltage divider to reduce gain) lead to the noise issue? 1M to 2K2 with a 1K grid stopper 2-what other issues are likely at fault? music plays, voltages are good, noise not affected by volume change . . . just loads of static type noise (I've replaced the tubes; disconnected the source)?? Thanks in advance for any assistance! Mike Anchorage, Alaska |