NAD 3140 phono input mistake !!

[guizmo1967]

Hello,

I accidently connected my aux input (TV) to phono1 and now phono1 is louder (volume higher than phono2).

If I don't touch the volume knob and switch my turntable to phono2, the sound is very good on both but phono2 is just lower than phono1 ???

Do you have any idea why ??

I look at the service manual and there is two 330K resistors connected to ground and to each phono inputs. Do you think that could be one of those resistors ?

[petehall347]

yes check those resistors and clean the switch

[R_J]

The phono inputs are for different output cartridges, see manual
Phono 1 is for high output cartridges so its level will be lower compared to phono2 using the same level of source
This is normal and there is no fault with the amp.

[CapLeaker]

I put much higher levels of audio into a phono jack than there should be without any ill effects. Like R_J noted, there are amps that have different level phono jacks. This one seems to be one of them.

[guizmo1967]

I just read the phono input section of the Owner's manual and this paragraph explains everything:

For phono 1:

"This input may also be used with cartridges of other types which have lower-than-normal output voltage such as ..... The phono 1 input has a standard input impedance (47K ohms resistance, 100pF capacitance) but is 10 dB more sensitive than phono 2 input"

That's why with the same turntable and cartridge, phono 1 has a higher output level than phono 2 !!

Glad there is nothing wrong with my amp !

Thank you R_J !😉