VF14 Rejuvenation in U.K.?

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Look at the smokescreen: SPIRIT (phantom powered tube) - I don't see anything but BS.. :)
Yeah that’s a little sneaky marketing. On their defense though I have used their ac701 fet replacement in my p2p m49 “clone” and it brought the mic a lot closer frequency-wise to the original I compared it to than the 5840 and 6s6b. The mids were a tiny bit harder ( around 2k) and lacked some 3 dimensionality but pretty close nonetheless. Of course there are other variables but I wasn’t going to mess with the original haha. Capsule in both mics is an original Neumann k49 but I am sure even those don’t sound exactly the same.
By the way that’s subjective using my ears and my listening environment…others might find the difference vast. Also I am far from the level of knowledge and expertise in technical matters that some members have here like gyraf and kingkorg
 
Last edited:
@bezenuk once posted this:


There is my best recipe of how to reanimate contaminated tube (it worked 100% with two VF14 tubes, as well as many others).

Connect the tube in triode configuration (G2,G3 to plate).
Connect G1 to cathode via 1kOhm resistor.
Connect current meter between plate and plate and plate voltage source (or use 1 Ohm cathode resistor as current sensor).
Apply full heater voltage conform tube's datasheet (55V for VF14).

Cathode and G1 heating:
Find in tube's datasheet maximum allowable plate current (<18mA for EF14 and so for VF14).
Apply 0V plate voltage and rise it until plate current reaches maximum (<18mA for VF14).
Check if plate current is stable and doesn't drift to higher value.
Keep this process for 4-8 hours.

Plate and G2,G3 heating:
Apply datasheet's voltage values for heater, G1 and plate(+G2and G3) (for VF14: 55v, -4.5V and 250V respectively).
Check if plate current is in datasheet's range (12mA for VF14).
Keep this process for 4-8 hours.

G1 and cathode heating is needed because these parts tend to poisoning.
Plate heating is needed to run the whole tube at high temperature.

Sometimes you need more time to detoxicate the tube.”
 
@bezenuk once posted this:


There is my best recipe of how to reanimate contaminated tube (it worked 100% with two VF14 tubes, as well as many others).

Connect the tube in triode configuration (G2,G3 to plate).
Connect G1 to cathode via 1kOhm resistor.
Connect current meter between plate and plate and plate voltage source (or use 1 Ohm cathode resistor as current sensor).
Apply full heater voltage conform tube's datasheet (55V for VF14).

Cathode and G1 heating:
Find in tube's datasheet maximum allowable plate current (<18mA for EF14 and so for VF14).
Apply 0V plate voltage and rise it until plate current reaches maximum (<18mA for VF14).
Check if plate current is stable and doesn't drift to higher value.
Keep this process for 4-8 hours.

Plate and G2,G3 heating:
Apply datasheet's voltage values for heater, G1 and plate(+G2and G3) (for VF14: 55v, -4.5V and 250V respectively).
Check if plate current is in datasheet's range (12mA for VF14).
Keep this process for 4-8 hours.

G1 and cathode heating is needed because these parts tend to poisoning.
Plate heating is needed to run the whole tube at high temperature.

Sometimes you need more time to detoxicate the tube.”
This is easy process with good old tube testers(Neuberger, AVO, Metrix etc) find somebody in the UK.
 
Back
Top