Valve Itch phono

[Salas]

Don't worry I will left the red LED. Attached pic with other vinyl pearl.

I like this music too. I have it in different recording than yours. But also very nice

 

[stajo]

This one is a little rougher in character

 

[Salas]

Bet it sounds grinding in the treble

 

[stajo]

Merlin, move scope probe to after opt cap instead. Im a bad scetcher.

 

[merlin el mago]

Many thanks stajo.

 

[merlin el mago]

I had only roughly calculated it. This is a very low transfer capacitance tube we use here. Should be in the 60pF to 70pF range at our about 85x gain including strays.

Thanks Salas.

 

[merlin el mago]

I had only roughly calculated it. This is a very low transfer capacitance tube we use here. Should be in the 60pF to 70pF range at our about 85x gain including strays.

Mine MM cartridge recommends 200pF including phono cable to the Itch, have I to substract the 60pF to 70pF range at our about 85x gain including strays?

For example target 200pF
Phono cable 180pF
Itch 60-70pF
I don't need add any capacitance more, right?

 

[Salas]

Target 200pF means better have 130-150pF cable so the 6N2P Miller adds to about 200pF total. If 180+60=240pF is still tolerable you leave the cable as it is. If you will not hear treble resonance like too much highs and sibilance, is an indication its alright.

 

[merlin el mago]

OK thanks Salas.

 

[merlin el mago]

Salas using IR LED have I to change R3 47R for 820R & R2 82K for 18K?

 

[Salas]

Salas using IR LED have I to change R3 47R for 820R & R2 82K for 18K?

That is Rev 1.2 values yes. It works with previous values too though. But with less bias.

 

[merlin el mago]

Less Bias = less SQ = less gain????

 

[merlin el mago]

18K must be 1W, or can be 1/2W?

 

[Salas]

There is no problem with the 18K. R10 12K should be 2W only.
I had gone to rev1.2 straight up so I can't tell you if the little difference in bias is the main audible thing but its certainly the correct way to re-bias equally.

 

[dady]

18K must be 1W, or can be 1/2W?

With this law you can be sure.

See the current, the voltage, then you can calculate the power.

 

[fdegrove]

Hi,

Less Bias = less SQ = less gain????

No, nothing to do with it.
You really should take some time to learn the basic operating principles of electronic valves, Felipe.

No offense.

Best,

 

[merlin el mago]

@Salas
R10 12K is 2W

@Esteban
Gracias / thanks

 

[merlin el mago]

Hi,



No, nothing to do with it.
You really should take some time to learn the basic operating principles of electronic valves, Felipe.

No offense.

Best,

You are right, no offense taken.

Cheers
Felipe

 

[dady]

Get the Morgan Jones, but paper book, is an easy read and with a lot of basic and advanced information with easy math and the hand of a teacher that accomplish with good examples.

 

[merlin el mago]

OK guys I will include the MJ in my todo list.