Valve Itch phono

[merlin el mago]

Yes, the Claret was active if I remember and Thorsten had cloned it.

Doctorjohn Cheaptubeaudio: Audio Reviews and More: Review: SHINDO Claret preamplifier

http://community.fortunecity.ws/rivendell/xentar/1179/projects/claret/Claret.html

 

[merlin el mago]

Salas can't match equal gain changing E283CC. I have more 7N7 I will try & let you know.

 

[merlin el mago]

Can't match equal gain changing 7N7.

 

[merlin el mago]

Attached voltage measurements, Left pic is left channel & Right pic is right channel.

 

[merlin el mago]

Across R10 left channel 6.8mA & right channel 6.5mA

 

[merlin el mago]

Across R2 left channel 0mA & right channel 0.88mA

 

[vgeorge]

Did you try to switch tubes?

 

[Salas]

Salas channel right have more gain than channel left, attached scope shot 1kHz 10V/cm 1ms

That's 2dBV difference. Exchange tubes between sockets in their respective stages as George said. Both for input and output ones to average out their gains, not only trying various samples, it helps.

 

[merlin el mago]

Across R2 left channel 0mA & right channel 0.88mA

Isn't the issue?

 

[Salas]

Can't be 0mA unless its an error or a tube's section is dead. Measure across R2 (18k) that shows more drop easier.

 

[merlin el mago]

Swaped the two tubes so now the two tubes were channel left on the channel right and the two tubes were channel right on the channel left. Still right channel more gain.

 

[merlin el mago]

Measurement is across R2 18K, measurement 0mA left channel still swapping the E283CC, could be a cold joint?

 

[Salas]

That's a build level thing, you can only find, but check if the infrared is broken or a resistor, whatever is in that same "tree". You should see voltage drop across the series resistors when the respective tube section is conducting. Then translate to mA from Ohm's law regarding their values.

 

[merlin el mago]

Infrareds are OK, I will desolder R2 18K left channel and measure it.

 

[merlin el mago]

Measures 18K

 

[merlin el mago]

Infrared left channel 1.063
Infrared right channel 1.042

 

[merlin el mago]

R2, R3 and R4 the value is OK, also C1 have rigth value.

 

[merlin el mago]

Left channel

Wired incorrectly see attached schematic

 

[merlin el mago]

Why all bad things happen to me

 

[hego]

This mod or mistake is similar as srpp not a mu-follower.The mu has ever more gain.

Good luck, Felipe.