Valve Itch phono

[merlin el mago]

Vin 20mV

Vout
Left 2.732V
Right 2.703V

 

[Salas]

Peak to peak 1kHz figures or RMS?

 

[merlin el mago]

RMS DVM with scope timebase setting can't fix the 20mV sinewave

 

[merlin el mago]

I measured also the 20mV with the DVM true RMS

 

[Salas]

OK, so taken to read the same way in & out. Those translate to 42.7dB and 42.6dB gain for your implemented circuit that says 43dB on simulation as you posted it. Excellent agreement to theory and between channels for a tube phono you DIYed and its valves matching you achieved. Results show that the problem is NOT in your phono build.

 

[merlin el mago]

I will look with magnifying glass at the diamond cart, can be dirty.

 

[Salas]

Check everything mechanical about cart setup, condition, and all wiring. You now even got 0.000V input offset about grid current besides proven correct gain for MM, no suspicion on the phono build is left lingering.

 

[merlin el mago]

The cartridge looks OK

 

[merlin el mago]

Can be soft clips connecting the tonearm?

 

[Salas]

Something mechanical, something wiring, including clips. Tighten what seems loose. Or the cart magnet has lost potency? The suspension softened and glides low out of the flux focus? Try 1g, 1.5g, 2g VTF. What happens?

 

[stajo]

If you just play a record and disconnect the RIAA and put 47k over the outputs of your player. That would give an idea if the PUP is ok or not.

 

[Salas]

To check for anti-phase wiring between channels?

 

[stajo]

Well that too. But to see what kind of signal it is outputting. A scope or a true rms meter over the 47k

 

[Salas]

Better a test record with sinewaves

 

[stajo]

goes without saying

 

[stajo]

I ment over output and ground on both channels and read the results. Sorry if I didnt spell it out.

 

[merlin el mago]

Can be soft clips connecting the tonearm?

Yes was doing bad connection, now sounds with enough gain

 

[merlin el mago]

I'm in love with MM Linn K9, a lot f information lost but a lot of soul gained, remembered when I introduced in the HI-FI world: 40 years ago listening Linn Sondek LP12 + Ekos + K9, Copland integrated amp with MM, Dynaudio 3 way stand speaker.

 

[Salas]

Congrats. The Itch likes MM too.

 

[merlin el mago]

Me too.

Speaking of MM what's your favourite?