Valve Itch phono

[stajo]

Yes, but my point was how internal wiring/sockets etc can interfere.

 

[Salas]

A lot

 

[stajo]

I mean, if we care about if a toob or toob sample has 1,7 or 2,4 pF Cga and it differs 2 pF on how the wiring is made...

 

[stajo]

And there seems like theres no biggie difference between the OTK class samples then the other EV's. Maybe a little tighter intertriode-matching on transconductance but I have actually found tighter matches on the non-OTK already.

 

[Salas]

I mean, if we care about if a toob or toob sample has 1,7 or 2,4 pF Cga and it differs 2 pF on how the wiring is made...

The internal figure is going to multiply with gain, the external parasitic will just add

 

[stajo]

In miller feedback yes. But to Merlin it is important all the way.

 

[Salas]

Sure. Cin is additive.

 

[stajo]

What happens with grid current with a 47k load resistor and an MM PUP-coil. I guess the dc-resistance is far lower in the coils and the current will flow there and overflux it totally?

 

[Salas]

Its not that strong a current to mute it but it will certainly muffle it enough.

 

[merlin el mago]

Some voltage across the diode, yes. Since the current there is low it won't be full 0.7V that is why we may use IR LED or two diodes if the tube sample don't go very little mV across open input.

Right channel 0.582VDC
Left channel 0.577VDC

Have I to add other diode 1N4148 in series?

 

[stajo]

You could start with that and see how it behaves. Later on, if this is the problem, you should try some IR-leds and see at what bias grid current starts in yous circuit and with your tubes.

 

[merlin el mago]

Thanks stajo.

 

[merlin el mago]

Voltage across the 2 diodes
Right channel 1.145VDC
Left channel 1.130VDC

Voltage grid to gnd
Right channel -0.000VDC
Left channel -0.000VDC

 

[Salas]

For now good if not having an IR LED

 

[stajo]

Problem identified? How does it sound?

 

[merlin el mago]

Sounds better but still needs more gain, with step-up Jensen + Denon DL103R (R.I.P.) volume setting was half volume, now to start to listen music I have to set to half the volume attenuator & near full volume to have the same gain than Jensen+Denon DL103R (R.I.P.) of course full volume I have noise so not pleasant, with step-up listening setting was half volumen.

 

[Salas]

Can you confirm the gain is over 40dB with scoping 20mV peak to peak 1kHz sinewave from generator on the phono input, then scoping the phono output and calculate?

 

[Salas]

Also is the Linn K9 new or old? In good working order? Is the vertical tracking weight correct?

 

[merlin el mago]

Is old but in very good condition not very used, yes I used scale digital precision.

N.B. I think Linn not make anymore the K9

 

[Salas]

When working well and having 4.5mV output given the phono is alright as before and will measure 40dB gain or more without SUT there is no reason to have low volume other than some wiring mistake. Check the wire pins colors on the back of the cartridge also.