Distortion with ARC Ref 150 and Maggie 3.7

Answer to Zd542:
"Try that first. Use any CD/DVD player you can find. It doesn't have to be expensive. If that doesn't work, I would try a different pair of IC's between your amp and preamp. I don't think you can switch your amp to run in SE or Balanced operation. I think it just runs in Balanced. I've seen several times where you can get a noise because of it. The solution, in the cases I've seen at least, was to use a good quality shielded IC. Any Audioquest with the DBS system always worked (providing that was the problem). Most ARC dealers have AQ. See if they will lend you a balanced and a SE IC to try in your system. You'll also need 2 adapters. If your dealer doesn't have them, you can get them at any music store. You need male xlr/male rca adapters for the balanced cable and male xlr/female rca adapters for the SE cable.

You've probably already did this, but you may want to try some different taps on you amp, both with and without the autoformer. "

It so happens that I have some AQ Columbia ICs with DBS but it just didn't work after I tried them this afternoon. I also tried with different taps with and without the autoformer and it didn't work either.

Answer to Wlutke:
You have described the distortion problem I have been working on for some time now, although yours sounds more severe. Mine was with high pitched, high amplitude vocal "air", mostly female, but piano was ok. I have the DV XX2 MK2 and also use the Mint tractor. The problem turned out to be the distance from the spindle to the tonearm pivot was off a little. A very tiny little. Because of that the Mint Tractor made me align, very precisely, to the wrong arc and overhang. I used the VPI jig that came with the arm to reset the distance. After realigning the cart with the Mint the distortion was eliminated and replaced by incredible detail. Double wow! I had tried everything I could think of for months on end. The DV carts have a well deserved reputation of being sensitive to setup error. Good luck!

This is something I never think of. Well worth a try.

Answer to Skinzy:
"I once had a similar problem and it was cart alignment issue as several others have suggested."

Although I have done this many time but I will surely do it all over again as suggested by Wlutke.

Answer to Alan:
"Try increasing the tracking force to the maximum recommended for your cartridge."

Another good suggestion. Will try out.

I agree with many of the others that the likeliest cause of the problem is related to cartridge installation and adjustment, including VTF. One thing that hasn't been mentioned is anti-skating. Take a look at the cartridge from the front, while a record is playing, and see if the cantilever is pointed approximately straight ahead, or more precisely, that it is at the same angle as when it is lifted off of the record. If there is a significant deflection of the cantilever to the right or the left while the stylus is in the groove of a rotating record, relative to its rest position, it means (IMO, at least) that anti-skating is significantly misadjusted.

However if further work with the cartridge-related adjustments does not resolve the problem, overloading, as mentioned by others, is also a strong possibility IMO. I say that despite the fact that the SL1 appears to have unusually good overload margin.

08-11-14: Pakwong
Answer to Jfrech:
"Do you have the Bob's devices SUT into the MC or the MM input on your CAT pre?"

CAT SL1 Ultimate MK2's phono stage are thought to be MM only. Is doesn't comes with MM/MC switch.

According to the specs shown here for your particular version of the SL1, its phono stage gain is 47 db. The lowest gain setting of your SUT (which I assume is the setting you are using) is 26 db. The line section of the preamp will add up to another 26 db depending on the setting of the volume control. That all seems very high even for a cartridge rated at 0.3 mv.

So an experiment that would seem to be very much in order would be to see if the distortion still occurs with the SUT removed from the system, even if that results in unacceptable noise levels.

Susceptibility to overload will be further increased (especially when high frequency energy is present at high amplitudes, consistent with your description of the problem) if the cable between your SUT and the preamp is long and/or has high capacitance per unit length. The capacitance of that cable, as seen by the cartridge, will be multiplied (not divided) by the square of the voltage step-up ratio of the SUT. In other words, by 400 times (for the 26 db gain setting). That will raise the amplitude and lower the frequency of the ultrasonic resonant peak in frequency response formed by the interaction of the inductance of the cartridge and the capacitance it is loaded with.

In addition to keeping the cable length between SUT and preamp short, you might try putting a load resistor across either the input or the output of the SUT. I see that the recommended load resistance for your cartridge is specified as ">30 ohms," while the 26 db gain setting of your SUT together with the 47K input impedance of the preamp will result in a load of 118 ohms. You might try something like 50 to 100 ohms across the primary (input) side of the SUT, or 20K to 40K across the secondary (output) side.

One final point: You mentioned that the problem remained when you tried a single-ended tube amp. If that amp provided an XLR input even though its internal signal path is unbalanced, and if you connected the preamp to that amp with the same RCA-to-XLR cable used with your ARC amp, the cable is not ruled out as a suspect. If the unused signal pin on the cable's XLR connector (generally pin 3, although possibly pin 2 in some countries) is not grounded (i.e., connected to pin 1), it could account for the problem. Proper connections within the cable can be easily verified with a multimeter.

Hope that helps. Regards,
-- Al