[Larsf333]

I have recently bought a set of amg/pra/sta, and i am pretty satisfied with the performance after initial break-in.
But I have discovered a strange problem with my riaa amplifier, when connecting it to the preamplifier.
When the riaa is connected to an input not selected as active, the riaa will not power up. When the riaa is connected to the input actually selected as active, it will power up.
I contacted the manufacturer of the riaa, and he thinks, that the not active inputs on the preamplifier are blocked in some way to avoid noise. The problem does not occir with my old preamp.
I wonder if anybody else have encountered similar problems, and if nuprime can clarify, if inactive inputs actually are blocked in some way, that could explain this strange behavior?

[rustydoglim]

Perhaps this is due to the 1Mohm input impedance. Why does it matter if your RIAA is not powered up if it is not selected as the input? That means you are not using your RIAA anyway.

[Larsf333]

It does matter, as I have to remove cables to power up the riaa.
Also, it could be a concern if the input impedance on the unused inputs is very low, then the load on the riaa amplifier could be a problem, as it is normally powered up, even if other sources are playing.
So I am very interested to know what happens with the unused inputs, what is the input impedance in that situation.
Of course I know the input impedance on the active input i 1 Mohm, and the riaa does work fine when selected.
Having the information, I can contact the manufacturer of the riaa and find out if it is a problem.

[rustydoglim]

I will ask our chief engineer to take a look at this topic. I think this is beyond anyone of us can figure out

[Genez]

I have recently bought a set of amg/pra/sta, and i am pretty satisfied with the performance after initial break-in.
But I have discovered a strange problem with my riaa amplifier, when connecting it to the preamplifier.
When the riaa is connected to an input not selected as active, the riaa will not power up. When the riaa is connected to the input actually selected as active, it will power up.
I contacted the manufacturer of the riaa, and he thinks, that the not active inputs on the preamplifier are blocked in some way to avoid noise. The problem does not occir with my old preamp.
I wonder if anybody else have encountered similar problems, and if nuprime can clarify, if inactive inputs actually are blocked in some way, that could explain this strange behavior?

I am  wondering why that should be a problem?   There are manufacturers that make audiophile shorting caps to go over unused inputs. They are to lower the potential noise seeping in. 

I would think its a positive feature.  But, to each his own?    Just Google this  -   Noise Stopper Caps RCA

[rustydoglim]

I think this is specific to his phono preamp. Our engineer offers two suggestions:
1. connect the chassis grounds of AMG PRA and RIAA.
2. When AMG PRA is power off, all the input impedances are low. This may affect his RIAA. Also try to change the order of turning on the components. Turn on AMG PRA, select input for RIAA, then turn on RIAA amp. Turn on the power amp last.

[Larsf333]

Thank you for the reply.
Yes, turning on amg pra, selecting the input for the RIAA, then turning on the RIAA, solves the problem, and the RIAA plays nicely as it should.
In conclusion, when amg pra is turned off, the input impedance is low, and when on, the not active inputs also have low impedance.