Valve Itch phono

[Salas]

Indeed. Since you separate upper tube to lower un the mu follower. Have you experimented with another top tube?

In this one no because the noise was good. But there are always possible combinations.

 

[vgeorge]

Thanks stajo & Salas, about cart repair wich one do you repair first Denon or Linn?

Felipe, check the repair cost and the alternatives regarding new cartridge.
When i had my Shelter 901 suspension going bad, I checked the repair cost and it was not much difference from a new one. So i bought an Audio Technica ART-9 with a lit bit more cost and also got much much better sound.
If it was me, instead of repairing two cartridges I would get a new better one.

 

[merlin el mago]

Felipe, check the repair cost and the alternatives regarding new cartridge.
When i had my Shelter 901 suspension going bad, I checked the repair cost and it was not much difference from a new one. So i bought an Audio Technica ART-9 with a lit bit more cost and also got much much better sound.
If it was me, instead of repairing two cartridges I would get a new better one.

Thanks for the advice George.

 

[stajo]

Some interesting diode cathode bias experiments from member mogliaa http://www.bartola.co.uk/valves/2015/05/04/diode-cathode-bias/

 

[Salas]

Having traced such in detail in the past I would rather say 1.5mA is the base. Depends on the tracer and the samples also. Injecting extra current to the diode etc. has to be judged as an extra current noise vs signal swing vs delta Ohm result. Obviously needed in a line stage, more of a trade off in a phono input stage.

 

[stajo]

Having traced such in detail in the past I would rather say 1.5mA is the base. Depends on the tracer and the samples also. Injecting extra current to the diode etc. has to be judged as an extra current noise vs signal swing vs delta Ohm result. Obviously needed in a line stage, more of a trade off in a phono input stage.

The results for the rectifying diodes was a bit of a surprice to me tho, they look far worse regarding linearity in their datasheets at low currents

 

[Salas]

1N4007 is good. Does not include those few better low mA curve looking IR ones we recently singled out.

 

[Salas]

As a matter of fact, wait, I have both 1N4148 and 1N4007 near me. I will freshly trace now.

 

[stajo]

Can a DCA75Pro trace diodes?

 

[Salas]

Red is 1N4007 brown is 1N4148. Resolution is 50 plot points per Volt.

 

[Salas]

Can a DCA75Pro trace diodes?

That's what produced the traces

 

[merlin el mago]

Better two 1N4148 than an IR LED?

 

[stajo]

Red: IR 333/S2
Green: HIR7373B/L289

 

[stajo]

Red: THLR 4400
Brown: HLMP-K150

 

[stajo]

Red: IR 333/S2
Green: dual DO-35
Blue: HIR7373B/L289

No Merlin, an IR is better

 

[Salas]

The curves show no problem with 1mA bias and proper IR for the Valve Itch. Do you agree?

 

[stajo]

I agree, given grid current doesnt show up.

 

[Joshua_G]

Which one of the above IR LEDs is preferred for Valve Itch?

 

[stajo]

The HLMP K150 is a beauty to for applikations working at 1,6-1,7 at 1 mAish also

 

[Salas]

Better two 1N4148 than an IR LED?

One is not really really bad but worse than IR as Stajo's traces showed. Two is naturally worse than one because in series doubling the resistance and easily worse than an IR that gives you about the Vf you need anyway.