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RE: How to implement these for my Ultrapath?

76.90.100.230

Tre'

In Reply to: RE: How to implement these for my Ultrapath? posted by SuperB on August 07, 2023 at 15:42:57

If you have a cathode bypass capacitor in place then it is not UltraPath.
There is no need for a cathode bypass capacitor when there is an UltraPath capacitor in place.
It is true that any hum from the power supply is now being amplified by the circuit. The simple answer? Build the power supply to not have any hum. It is easy because the last cap in the power supply filter is no longer in the signal path so it can be large without harming the audio signal.
You can just use the proper size cathode resistor instead of the diodes. You will not want to put a capacitor across it (bypass cap) because it is already bypassed by the UltraPath cap. The AC flows through the UltraPath cap (for the most part), only DC flows through the cathode resistor (for the most part).
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
http://www.nutshellhifi.com/library/ETF.html (Open in New Window)

Edits: 08/07/23

Follow Ups:

RE: How to implement these for my Ultrapath? - SuperB 17:04:13 08/07/23 (3)
My friend suggests I use 500 ohm 1w resistor for the cathode and lower the UP cap to 200uf.

The power supply must be rebuiltt with Vandervern mec electronic choke and Salads HV Shunt reg

He says, once the power supply is regulated, the UP Cap should be way smaller than 200uf. And the ps provided a very low impedance at the same time.
- If you want to regulate, you are better off - Ralph 08:14:29 08/08/23 (2)
  regulating the filament voltage. The 6SN7 has a mu of 20 or so; its not going to be particularly sensitive to the B+ voltage and if you did your power supply homework, the B+ will be entirely free of ripple while also unregulated.
  
  It is more sensitive to the filament voltage. So you are better off regulating that (which is pretty easy, use an LT1084 or the like). The new ones in the TO-220 case have a 1V dropout so you should have some overhead if the AC line voltage drops a little.
  
  I should also point out that a lot of modern 6SN7s have troubles with cathode/filament leakage. The Russian made 6SN7s seem particularly prone to this problem. That can interject buzz into the output. If you regulate the filament, this problem is vastly reduced!
  - RE: IRegulated Power Supply - SuperB 12:29:05 08/08/23 (1)
    Therefore, those solutions for UltraPath is not effective once both HV and LV are regulated, right?
    - The Ultrapath is a great setup. - Ralph 12:40:48 08/08/23 (0)
      Jack knew what he was doing when he designed this circuit (he also holds a patent on class A3 operation for SETs).
      
      To improve on it, the way you do it is to use better quality components, do a clean layout that is properly grounded, and regulate the supplies. If you want the output transformer, changing the circuit itself will only degrade it, in what can be heard and measured.

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