Distortion with ARC Ref 150 and Maggie 3.7

I didn't realize you didn't have the Wadia in your house. I was just going by this:

"Last night I did a final test by listening again to digital sources from a Wadia 381i CD player connected to line stage of the CAT SL1. To my surprise, the same distortion also happens on the digital source which I thought didn't exist! I'm not a big fan of digital hence very seldom listen to it. The last time I listened to it were kind of background listening with lower volume. This time I crank up the volume control to about the same level while listening to LPs and the same distortion shows off immediately!"

That's why I thought you had one. Also, I didn't think you sold your 150, it just looked like you may do so. I was just saying to give it a chance before you did sell it. Its a very nice amp. I also didn't realize you had an LS25. I'm sure there's no distortion when use that with you 150. Either way, its good that you were able to figure out what the problem was.

ZD, the comment you were responding to was from the OP, Pakwong, not from Martykl (who is not the OP).

Best regards,
-- Al

My bad, I should have seen that ZD had confused me for the OP. To the best of my knowledge Pakwong's ARC adventure is still unfolding and we'll all have to wait to see how it plays out.

ZD, your suggestion has save me from selling an excellent amp. Today I loan a XLR cable form the Maggie dealer to try a direct connection from the Wadia which have balanced output and volume control to drive the Ref 150. Guess what? Not only the distortion has disappeared even at maximum volume, the sound it produced was something I never heard in my system!

First thing which I immediately aware of was the dead silence background and powerful bass with very good authority and definition. I never realized low frequency from Maggies can be that great!

Such experiment has confirmed that the ARC do need balanced only signal and that you guys has proved your points to be very true.

Right now, what was left is to find a way to change the CAT output signal to balanced. Al, please forgive my ignorant. Can you explain to a guy like me with almost zero electronic knowledge about how the transformer from Jensen or SMc can actually convert unbalanced signal to true balanced signal?
My Maggie dealer also talked about something like pin 1 or pin 2 "hot" in the RCA to XLR cable and he suspected that the termination of my RCA to XLR cable was not done correctly hence the distortion. How true is it?

Thanks in advance.

Best regards

Outstanding! And a great suggestion by ZD.

Can you explain to a guy like me with almost zero electronic knowledge about how the transformer from Jensen or SMc can actually convert unbalanced signal to true balanced signal? My Maggie dealer also talked about something like pin 1 or pin 2 "hot" in the RCA to XLR cable and he suspected that the termination of my RCA to XLR cable was not done correctly hence the distortion. How true is it?

Taking your second question first, the problem you have been dealing with cannot be avoided with an adapter cable, no matter how it is wired.

To work properly, your amplifier (and other ARC and other amplifiers that are similarly designed in the relevant respects), must be provided with a balanced pair of signals at its inputs. That means two signals that are essentially identical except that one is inverted relative to the other (i.e., when the voltage of one signal moves in a positive direction, the voltage of the other signal moves in a negative direction, and vice versa). An adapter cable cannot produce those two signals, when it is only being provided with one of them.

A transformer can do that, however. A voltage will appear between the terminals that are connected to the two ends of the secondary (output) winding of a transformer, that in the absence of any external connections to that secondary winding would be electrically isolated (i.e., unconnected, or "floating" in EE terminology) relative to the ground of the signal source, and relative to all other voltages or grounds or other reference points that may exist in the system.

If the input circuit of the amplifier is designed as a balanced receiver, it will process the voltage that exists between those two ends of the transformer secondary in a manner that is symmetrical relative to the amplifier's circuit ground, which means that it will "see" that voltage no differently than if a balanced source (providing two equal voltages of opposite polarity) were being used.

This Jensen white paper, although somewhat technical, goes into further detail that may be of interest.

BTW, regarding the transformers I suggested, be sure to note that (as indicated in the manual I linked to for the particular Jensen model I suggested) that particular Jensen model would have to be placed close to the amplifier, and connected to the amplifier with a very short (less than 2 foot) length of XLR cable. The RCA cable from the preamp could be any reasonable length. I believe that no such constraint would exist with the SMc transformer (or with some other Jensen models, although those other Jensen models may not perform quite as well as the one I suggested).

Best regards,
-- Al