Valve Itch phono

[merlin el mago]

Max. is 2.5W?

 

[Salas]

Per section, yes

 

[merlin el mago]

Still safe.

 

[merlin el mago]

Salas worth the work to use Sylvania 7N7 at 9mA, the SQ is very high together the Siemens E283CC.

 

[merlin el mago]

Salas it's a good idea TO convert the passive RIAA in active RIAA?

 

[Salas]

As tubes age the curves would change too. Passive I prefer.

 

[merlin el mago]

 

[merlin el mago]

Salas do you know the input inductance of Valve Itch?

 

[merlin el mago]

Can be 4.4H?

 

[Salas]

Not that high, that's hv psu choke values territory. It does not have much more than each build's internal wiring would present.

 

[merlin el mago]

I measured this value at the phono RCA input with the PSU disconnected.

 

[Salas]

Was it Henry or microhenry (μH)? Because if audio signal tried pass through 4.4 Henry it would be strongly filtered.

 

[stajo]

If you dont have a SUT in front of the Itch, the only thing you measure at the input with the PSU disconnected is the cart load resistor and the wiring. Would be scary if that was 4,4 H

 

[merlin el mago]

Attached pic with measurement.

 

[merlin el mago]

LCR set to 200H scale

 

[merlin el mago]

I measured some inductors that I have for loudspeakers crossover and I can confirm the LCR is measuring OK, maximum inductor value 1.2mH.

 

[kevinkr]

I assume you are mistakenly measuring across the input, as Salas says you should see uH or less (nH) in series with your input resistance. If you are measuring from ground to signal you are mis-using the inductance measurement mode since there is no shunt inductor across the input is there?

You can measure the actual wiring inductance from input jack to end of the signal input wire (not grid pin if grid stopper resistor is present).

 

[merlin el mago]

Thanks Kevin. I have to measure the inductance of wire like I did with the crossover inductors

 

[kevinkr]

Yes, exactly.. I'd expect it to be in the nH range.

 

[merlin el mago]

From RCA input to grid 4uH