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Distortion with ARC Ref 150 and Maggie 3.7

I have this problem that drive me nuts for quite a while. I purchased a like new fully balanced ARC Ref 150 tubes amp through Audiogon for my single ended only CAT SL1 Ultimate preamp and connected both with a RCA to XLR interconnect. It sounded okay with most recording but has awful distortion with certain recording specifically piano and vocal. Some of this recording happens almost on entire record but some only on certain musical passage. Most of the time with higher pitch or peak of music or higher volume.

For your information I listen to vinyl only most of the time and more on Jazz music. Other component listed as follow:

Turntable: Sota Nova, Tonearm: Origin Live Illustrious, Cartridge: Dynavector XV1-S, Step up transformer: Bob's Device CineMag 1131 (Blue) feeding directly to CAT's own phonostage, Speaker: Magneplanar Magnepan 3.7. Power cords, ICs, Speaker cable, Autoformer: Paul Speltz Anti-Cable.

Trouble shooting which has been done includes: checking preamp tubes condition and checking power amp bias. Since ARC claims their Ref 150 was design for balanced preamp only so I also tested by replacing it with single ended tubes amp but the distortion remain. As for the cartridge I believe I have done the alignment pretty accurate with the Mint's Best Tractor but not very sure with the azimuth.

While tested with my other 2 pair of speakers, one which has higher spec show the same problem while the lower spec one seems get rid of distortion. So I suspected the issue probably was with the new Maggie. Called the dealer and he performed a test with his transistor amp with no distortion at all. So he assumed my Maggie is okay. Is it true that the Maggie only good with transistor amps?

By now it leaves me with total confusion! Sincerely hope fellow audiophile here could give me some advice and save me from this endless misery !

Thanks very much in advance!
pakwong
lak's avatar
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lak
4,632 posts
 
I own a pair of Maggie 3.7's but I run them with a SS amp.
I have no idea what the problem is but was just wondering if you ever tried using the resistors with the Maggies and if that would correct any of your issues?
mofimadness's avatar
mofimadness
4,987 posts
 
From what you describe, I think that maybe you are overloading the phono input. Make sure you are using the MM input and not the MC. If you are using the MC along with the SUT, it could very well indeed be too much gain.
cerrot's avatar
cerrot
1,700 posts
 
I agree on the overloading. If its louder musical peaks, its a higher output voltage at those peaks and its just about exceeding somethings limit.
bifwynne
2,206 posts
 
As an fellow owner of an ARC Ref 150, I have a sense of what your Ref 150 can do. You cam confirm what I am advising with Kal at Audio Research.

Although I am not speaking to whether the rest of you rig has issues, I have serious doubts that the Ref 150 has enough power to properly drive the Maggie 3.7s. The consequence of over-driving the amp is ... distortion.

Btw, if the Maggie's have a nominal impedance of 4 ohms, especially in the bass/lower midrange frequency spectrum, I suggest trying the 4 ohms taps. While many tout the virtues of the Zeros, to me, they are just another artifact.

The Ref 150 is designed to produce clean power up to its rated spec (150 wpc) if the speaker's impedance (4 ohms) matches the amp's output impedance off the 4 ohm tap ... at least if tasked to produce in the power spectrum (bass/midrange). Impedance matching is less critical at higher frequencies because power demands are less.

Btw, btw, output voltage regulation is tighter off the 4 ohms taps. As a consequence, if the Maggie's impedance function rises in the mid/tweeter range, using the 4 ohm taps will result in the Maggies sounding less bright.

Let us know how you make out.

BIF
zd542
5,339 posts
 
"08-10-14: Smoffatt
Can you borrow a digital source (CD player) and play the same recording to see if you can identify the same distortion as with your analog source. If no apparent distortion, the problem may be with your tonearm/cartridge alignment.
Somewhat odd that only some recordings and/or passages of same are sound distorted. Could very well be your SUT or cartridge or alignment."

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. Now that I think about it, is it OK to use the autoformer with an amp that already has an output transformer? Hopefully, someone that knows will comment on that. I'm not sure.
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