Valve Itch phono

[merlin el mago]

What's happen when the arm cable capacitance is higher than the recommended load capacitance?

Linn K9 capacitance loading 200pF including arm cable
Linn Ekos capacitance arm cable 220pF

 

[Salas]

More treble peak

 

[merlin el mago]

Thanks.

 

[Salas]

Input valve on the Itch has unusually low Cgp. In this gain stage it adds better Miller than others but you should expect another added 60pF roughly. Remember your post #2020

 

[merlin el mago]

I listened with 68K as load resistance, treble is better than lowering VTF but still not happy, can be time to play with RIAA treble cap?

 

[Salas]

If its necessary, why not. That's why its DIY. You can fix for a certain cartridge and restore for another. HiMC like DL-110 with 10K-47K Load would be nice for new "cheap" workhorse cartridge, no cables capacitance considerations.

 

[stajo]

Does your power amplification use global feedback? I had a time when I raised and lowered the treble and I never got satisfied. Global feedback thru capacitors compensates harmonics with a time delay. My ears hate that so I never use GF in high regions anymore.

 

[Salas]

Since he has got more than enough cable+Miller capacitance for an AT cartridge (K9 is kind of AT95 with better diamond) it could be just peakiness. Another 68k in parallel or a straight 33k for input load before tweaking the treble cap maybe.

 

[stajo]

Who knows but I see a pattern in this. Peakyness is not a problem you write home about. Very easy to get rid off. Unasked harmonics is a more common problem seldom talked about. I just measured a HQ coupling cap and it stayed in phase up to some 5-10k then it drifted off around 5-10% above that. Some people are allergic to certain video formats. I am allergic to phase drifts in global feedback

 

[merlin el mago]

At the moment I left fixed 47K resistor.

 

[hego]

Felipe , I try and try....at the end I add a 18k resistor with the usually 47 kohms. about total 12kohms load.

But the situation is diferent: is for a MC + jensen SUT. This low value can do control the overshot/ringing of the trafo.( verify with gen and oscillo) The treble is good and the rest fine.The reflected load is ( 1:10) 120 ohm.Minimal ten times the resistence of the cartridge ( cart 10 ohm > refl 100 ohm)

The cable capacitance is minimal and the 6n2p-ev is also very low. Sound very well.

I like it.

Cheers

 

[Salas]

Jensen can take an RC or just damp secondary in lower than 47K. Must check that the frequency response remains wide enough when damped heavy. Generator & oscilloscope are best advisers indeed.

 

[hego]

Jensen can take an RC or just damp secondary in lower than 47K. Must check that the frequency response remains wide enough when damped heavy. Generator & oscilloscope are best advisers indeed.

I agree, Salas.

The frecuency range is very flat.

I use really a zobel network ( RC - a resistor with a little styro cap in serie), but the important is the resistance value.It works at the ringing region only: the trebles.

Regards

 

[Salas]

What cartridge you use it for?

 

[hego]

A vulgar AT33ptg/II.

 

[merlin el mago]

Does your power amplification use global feedback? I had a time when I raised and lowered the treble and I never got satisfied. Global feedback thru capacitors compensates harmonics with a time delay. My ears hate that so I never use GF in high regions anymore.

My power amps yes but I'm listening with headphones without GF.

 

[merlin el mago]

Felipe , I try and try....at the end I add a 18k resistor with the usually 47 kohms. about total 12kohms load.

But the situation is diferent: is for a MC + jensen SUT. This low value can do control the overshot/ringing of the trafo.( verify with gen and oscillo) The treble is good and the rest fine.The reflected load is ( 1:10) 120 ohm.Minimal ten times the resistence of the cartridge ( cart 10 ohm > refl 100 ohm)

The cable capacitance is minimal and the 6n2p-ev is also very low. Sound very well.

I like it.

Cheers

Thanks hego I'm trying now different kind of 47k resistors, 1st was a plastic trimmer to know what's the value I like more, 2nd was a metal film PRP & actually is a carbon wire wound ARMSTRAN.

A vulgar AT33ptg/II.

I have in mind to buy the same AT, could you describe the kind of sound?

 

[hego]

Felipe, I use ever no expensive, vulgar an noisy carbon film resistors, like Piher, Bradley Allen, Kimawe or similars.I think . they haven the best sound. (At my taste, of course)

The AT33PTG/II sounds very well, may be a few analytic and detailed, but is also dynamic and natural.I fell in love with this cart and is affordable.

Xto

Regards

 

[merlin el mago]

I changed the 6SN7 for 1578, to be sure I measured again B+ was ok but heaters not, one measured 6.5v and the other 6.2

Now the treble sounds ok, the Itch never sounded so good.

 

[Salas]

MELZ?