Valve Itch phono

[stajo]

I would say it probably needs some counting, testing and tuning. White CF is hard to make sound good imho.

 

[merlin el mago]

Thanks for the info.

 

[merlin el mago]

I measured the capacitance of the phono cable between the Itch & the #26 and measures 500pF (3 meters long), have I to increase the C of the Zobel step-up Jensen to 200pF?

Attached pic just for fun of increased mass of Linn Ekos tonearm, now Itch + Denon DL103R plays in other league.

 

[merlin el mago]

Oooops my mistake have I to reduce to 100pF?

 

[Salas]

The SUT secondary termination (Zobel) is a different matter regarding the output of the full circuit. That Jensen could be fairly well compensated for square waves with 100-150pF in the Zobel too, at least on the oscilloscope tests I have shown before on my samples. You could try those values too for subjective impact.

The Itch output comes from a low impedance point (from the cathode follower part of the Mu circuit) and it can drive some cable capacitance. Its a 6mA 800 Ohm source with the 6SN7 in the V1.2.

 

[merlin el mago]

"The Itch output comes from a low impedance point (from the cathode follower part of the Mu circuit) and it can drive some cable capacitance. Its a 6mA 800 Ohm source with the 6SN7 in the V1.2."

Could you post a pic?

 

[Salas]

Nothing different. As the output stage values in the V1.2 http://www.diyaudio.com/forums/analogue-source/140635-valve-itch-phono-157.html#post3802065

 

[merlin el mago]

So I only have to change: R9-11 now 330R and R10 now 12K 2W?

 

[Salas]

Yes, only the resistor values. The circuit topology is the same from the start.

 

[merlin el mago]

I have Kiwame 330R but I don't have 12K 2W

 

[merlin el mago]

When you used the Denon DL103R wich tonearm used & how many effectiver arm mass?

Can I measure Ekos cable capacitance with the cartridge mounted?

 

[Salas]

I have Kiwame 330R but I don't have 12K 2W

Later then. Dale CMF60 250mW and CPF2 2W are good neutral parts to try sometime too.

 

[merlin el mago]

When you used the Denon DL103R wich tonearm used & how many effectiver arm mass?

Can I measure Ekos cable capacitance with the cartridge mounted?

?

TIA

 

[Salas]

When you used the Denon DL103R wich tonearm used & how many effectiver arm mass?

Can I measure Ekos cable capacitance with the cartridge mounted?

No, don't put any active test instrument on cables with the cart connected.

I had used it on SL1200MK2 arm and on silicon stuffed and counterweight reinforced mission arm both about 12g. Resonance was good since its a 13cu cart by US/European static compliance standards. But heavier effective mass arms control its lively cantilever and body resonances better. Sounds more 3D on those.

 

[merlin el mago]

Thanks for support.

103R shines with a total arm effective mass of 25g or more.

 

[Salas]

Fidelity Research FR-64s, ATP12T, Jelco SA-750D,E,LB, SAEC 407, Grace 714, SME3012, 3009 good for vintage carts. Or well distributed added mass on lighter arm as you did.

 

[merlin el mago]

I take note of all the arms, thanks.

Just received Linn Spain info about capacitance of Ekos cable is 220pF, now is sounding very good with C zobel for Jensen with only 100pF, do you increase or decrease the C value?

 

[Salas]

I would not use lower than 100pF or more than 200pF in that Zobel for Jensen SUT termination. If good on 100pF in your case, why make it slower with more compensation? Better at lowest acceptable without treble ringing IMHO. More open.

 

[merlin el mago]

Mids and lows are terrific good (never heard some so good and I listened a lot of TT), treble can be the roll off due to high cable capacitance between the Itch & the #26 so next adjust the Itch output resistors.

 

[Salas]

So listen first with 6mA on 6SN7 1.2 values and don't focus on the SUT. And play a little with more trebly VTA. Also verify VTF with electronic scale.