2 OT's in a VH4S

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Ventura

Ventura

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In the Tech Corner section off the official site, there's a tutorial about biasing tubes - no sweat. My VH4S has TWO OT's, so when biasing, does it still run true to use 100mA per wire pair? Or does this puppy run 1 x OT per pair which means bias accordingly (so in the case of 6550's - 50mA per wire pair, EL34's - 30 to 35mA per wire pair, etc).

THANKS!
V.
 
The bias recommendations are of course the same. Reading the current off the OTs gives you single tubes though, which means each side of each OT should result the following readings:

6550: up to 50mA
EL34: up to 35mA



ok?
 
One small question about the biasing procedure in the Tech corner, just for my understanding:

When measuring current with a DMM for one pair (or one tube in the VH4s case), you are effectively shorting one half of the primary of the OT with the DMM, right? (so you measure the current through the tube that's connected to the half that's not shorted)

The way I did my previous bias was by measuring the voltage across the OT, and by dividing through the resistance of the OT half I got the current.

Any pro's / cons to either way?
 
hansdevries":1ebp57dl said:
One small question about the biasing procedure in the Tech corner, just for my understanding:

When measuring current with a DMM for one pair (or one tube in the VH4s case), you are effectively shorting one half of the primary of the OT with the DMM, right? (so you measure the current through the tube that's connected to the half that's not shorted)

The way I did my previous bias was by measuring the voltage across the OT, and by dividing through the resistance of the OT half I got the current.

Any pro's / cons to either way?
Click to expand...

Very good question... Peter? :confused:
 
You are not shortening one side, but measutring in parallel, which is only (reliable) possible with a good DMM - which has a super low internal resistance.
 
duesentrieb":jehtzrc3 said:
You are not shortening one side, but measutring in parallel, which is only (reliable) possible with a good DMM - which has a super low internal resistance.
Click to expand...

Good point. I guess that as long as there's no input signal to the amp, that would be no problem.

A lot easier than having to calculate the current from the voltages :doh:
 
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