Ask an expert: Marantz 9 amplifiers, Rowland Coherence, hot pins on XLR connectors – and more.

Ask an expert

Can I use other tubes than the EL34s on the Marantz 9s? The amps themselves and the manuals are marked with those specific tubes. So I don’t know if tube rolling would create problems. If you feel it’s technically possible and advantageous, what would you recommend in connection with the Quads? 

Also, a phase issue with XLR pin determination, when pin 3 is hot instead of pin 2: my Rowland Coherence preamp has pins 3 hot. So when I had amps with pin 2 hot, I ordered my expensive Synergistic interconnects from pin 3 hot to pin 2 hot. 

Now that I have the Rowland amps which are also pin 3 hot, I still use the same interconnects and it seems that there is no problem. How is that? Further pressing the phase button on the preamp hardly makes any difference that I can hear. 

So what is going on? Why would the interconnect with phase 3 to 2, not be out of phase when connected to the amps with hot in pin 3? This is confusing. Should I resolder the termination of the cable at the amp side to pin 3 hot, which I am not too eager to since it would do an amateur job on an expensive cable. Will I see a difference? Thanks once more for any help.

I don’t know the internal conditions under which your Marantz 9 amplifiers drive EL34s (HT voltage, plate current, etc) and so cannot recommend alternative tube types, I’m sorry to say. Others may work, or may damage the amplifier (if excessive current is drawn and the amp cannot handle it). But you can try different brands of EL34 of course.

The ‘hot’ and ‘cold’ or +ve and -ve of balanced connections are relative. As long as you keep both channels connected the same way around they’ll be in-phase. You can check for in-phase condition simply by swapping the connection to one loudspeaker around: if the sound stage goes all phasey and weirdo then the channels were in phase and correctly connected. If you suddenly get focused centre stage images then the channels were out of phase.