Quote:
Originally Posted by vampyretim
She sounds amazing the D.C coupling is producing lovely rich bass but she's humming quite a bit.
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This is a common misconception. The capacitor providing an AC ground for the second LTP grid has almost exactly the same effect on frequency response as a coupling cap would have.
Quote:
Originally Posted by vampyretim
lowest A.C range is 200v
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Do you mean 200mV?
There are two ways to build a 5-10:
1. do it exactly as Mullard said
2. learn enough about stability, hum, grounding etc. to design and debug your own layout
Your 'scope trace suggests to me that PSU charging pulses are going somewhere they should not go. This could be magnetic or ohmic coupling. Magnetic coupling is reduced by distance and by reducing loop area. Ohmic coupling is reduced by careful grounding design, so the charging pulses stay within the charging pulse loop.