Tube pre amp

disneyjoe7

My pre at Troy's PF09 was modified to have has relays which will work for HT mode. These relays work a "Record 2 output" if the pre amp is off, the record 2 in an input for HT which switch's the outputs to the amp. The amp powers the front speakers which work for HT and 2 channel music. Since I use the front speakers for HT and 2 channel music I don't rewire the speakers so it's not phase inverting. I don't have any issues with this, if I did rewire the front speakers they will ok phase for 2 channel but out phase for HT mode since everything else is normal phase.


I used 2 relays so I could have a good crossover ratio, I felt if I used 1 relay I could get some crossover issue. A relay does Left and a relay does Right.

inspiredsports

george daniel wrote: »

I have connected phase inverting pre amps to my SDA's unknowlingly,and knowingly, suffered no damage,, I have tried it both ways(switching speaker wire connections.), and could not really tell a difference.If you feel uncomfortable, then by all means contact Mr. Thallman first.IIRC, there was a C-J connected to Troy's SDA's at Polkfest,and I think it was phase inverting,,in fact it might have been Steve's.You might wanna shoot him a pm.For the record,my current pre in my SDA rig,does NOT invert phase.Keep us posted as to what you find out,please.

THREAD RESURRECTED AT POST #91 with question about Conrad Johnson PHASE INVERSION in many of their PREAMPS

I'm only driving 2 channels so I don't have to worry about keeping up with surrounds.

I don't know for sure, but I think matching phase has more to do with how a recording was originally made and how it is reproduced sonically, rather than a bad electrical loading situation for the speakers if not reversed.

My current NAD 1700 preamp has a "phase invert" button that I use without hesitation, but it rarely if ever makes a sonic difference. There is no type of warning in the NAD literature to avoid using it with interconnected speaker, and I bought the preamp on the same bill of sale as my SDA-2B's back in the day.

With the PV-7, just to be sure, I am going to contact both CJ support and Bill Thallman before hooking it up

From what I could pick up in old posts around here, I think Troy did own a PV-7 at the time of that infamous PolkFest.

Ricardo

Phase inversion at the preamp changes the absolute phase (both channels), and probably no one can hear the difference. I think manufacturers suggest changing the wires at the speaker ends just to make it "right", not because there will be an audible difference or any damage.

With SDA's, the speaker expects a common ground amplifier. This is what the speakers "see" in the negative posts. If you swap the wires at the speaker, you will be placing the positive side of the amps in the negative posts. Not "common" anymore.
You can do it....at your own risk.

inspiredsports

Ricardo wrote: »

Phase inversion at the preamp changes the absolute phase (both channels), and probably no one can hear the difference. I think manufacturers suggest changing the wires at the speaker ends just to make it "right", not because there will be an audible difference or any damage.

With SDA's, the speaker expects a common ground amplifier. This is what the speakers "see" in the negative posts. If you swap the wires at the speaker, you will be placing the positive side of the amps in the negative posts. Not "common" anymore.
You can do it....at your own risk.

So just to be sure for us laymen as I am not an EE, we are saying:

--- "Phase" is an entirely different beast than "ground".

--- The "ground" side of a common ground amp is still "physically connected to earth ground" no matter what phase signal is passing through that wire.

--- Polk SDA circuitry depends upon being properly connected to that earth ground.

Based on the above, I'm never going to change the wiring at the speaker terminals.

If I ever happen to buy a DAC. etc. that has a phase inversion switch, I should use that switch when feeding signal to the phase inverting Conrad Johnson preamp.

I also put a call in to Conrad Johnson even though I am confident the above is correct, but they are closed for the holidays until January 4th.