2. amps-preamps
  3. 1407646817

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
pakwong OP
38 posts
 
Thanks Al for the detail explanation. Now I pretty much understand the fundamental of both signal type.

Can't wait to try the transformer with my CAT. Unfortunately I still did not received answer from either ARC, Jensen or SMc. Anyway my plan is try on a Jensen first.

Regards
kevinkwann
85 posts
 
If you plan on keeping the CAT SL1, buy the CAT JL5 amplifier. If you plan on keeping the ARC Ref 150, buy the ARC Ref5SE preamp.
pakwong OP
38 posts
 
Yes Kevin, nothing matched the CAT preamp better than their power amp. I also agree with the 5SE/150 matching. For me, the CAT combo looks like a better choice. If I choose the ARC, I will have to buy a phono preamp as the 5SE don't have phono stage option. If you were me, which do you prefer?
pakwong OP
38 posts
 
Answer from ARC:

"The REF150 is a balanced input power amplifier only and requires a true balanced differential input signal to operate correctly. You cannot use XLR to RCA adaptors as these do not generate the required negative phase input signal required for true balanced operation. You have 3 options: 1) Obtain a preamplifier that offers true balanced outputs (an Audio Research Reference model would obviously be the preferred match to your REF150); 2) Use an active SE to Balanced converter that generates a negative phase signal from the positive phase signal by means of a phase inverter circuit. 3) Use a transformer to generate both phases of the signal passively, as you referred to. Our experience is that options 2 and 3 do not preserve all the benefits of option A, with some loss of dynamics and /or transparency to be expected. We do not have any product recommendations for options 2 or 3, so you will need to do your own research to obtain a satisfactory product that performs up to your standards. The REF 150 has a 300K ohm balanced input impedance (150K each leg) and thus presents a very easy load to any device that must drive it."

This again confirmed that I have made a wrong choice. It's a shame I didn't do research before buying the Ref 150. Just pray that the sound will not be too bad with the transformer's option.

almarg's avatar
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almarg
9,670 posts
 
Good answer from ARC. As I indicated earlier, though, a number of other A'goners have reported using the particular Jensen transformer I suggested with extremely good results, in very high quality systems. Although that opinion, as might expected, has not been 100% unanimous. Personally, I suspect it will work out fine.

Best regards,
-- Al
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