Installed bulk foil resistors in phono amp


I installed four of these Vishay Z-Foil (TX2575) in my phono preamp - the loading and series input resistors on the first triode. Considerable improvement in clarity, image stability and perception of speed. Highly recommended upgrade. PartsConnexion. 4 for $65.

128x128noromance
It won’t attenuate the signal at all. Its not a matter of input resistance as it is input capacitance. This is also known as ’Miller effect’. The input stopping resistor does two things- it attenuates RFI by acting as a simple high frequency filter in conjunction with the input capacitance of the tube, and it prevents reflections from the signal coming in the grid and then ’bouncing back (’reflected’) to the input circuit. The latter can cause oscillation and instability, which can cause ticks and pops in a phono preamp. By increasing the stopping resistor value this latter issue is addressed.
But how high can you go? You can’t keep increasing the value hoping for more and more rejection! Maybe the designer deemed 1k enough.
The amp uses 2 diodes in series to bias the cathode. Can you suggest a better way to do this? I’ve seen NiCads and LEDs used.
@gs5556 Good to hear. 
The only manufacturer I know of that uses bulk foil resistors is VAC in their ref or sig series at $80k!
Oscillation is a nasty beast, as it can be inaudible and fry downstream components.
@noromance
VAC offers an "SE" upgrade for their standalone Renaissance phono stage that adds some 30+ of those Z-foil resistors and Jupiter copper/beeswax coupling caps. Still not a cheap stage by any means, but $14.4K is a hell of lot less than 60 - 80! Unfortunately a lot of those Z-foils are allocated for the MC loading, and I bypass it all to come into MM because I prefer other SUT's to the built-in Lundahls. 

I’ve had both the SE and non-SE versions of this Renaissance phono in my system, currently own the SE. Both sound amazing. The SE does have extra clarity and detail but honestly the extra warmth of the non-SE ($10K) can be appealing too. Can’t go wrong either way if you have a high-end upstream to take advantage of it; they both make magic.