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
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almarg
9,670 posts
 
Thanks for the update, Pakwong. Sounds like a good plan, which will greatly reduce the risk I had been envisioning if the CAT doesn't work out.

BTW, although I could be wrong, I had been interpreting Knghifi's comment about doing homework before purchasing to be in reference to the CAT purchase, not to the ARC purchase. As you said, it's very unusual for a balanced amp to not be able to work in a reasonable manner when provided with an unbalanced input, so that "oversight" is certainly understandable. And since you have a fallback strategy which minimizes the risk I and perhaps he were envisioning regarding the CAT purchase, it seems like all the bases are covered (to use a baseball analogy).

Continued good luck as you proceed. Regards,
-- Al
knghifi
1,668 posts
 
Almarg, until Minorl post, I felt tone of the thread was blaming and questioning ARC design which was unfair IMO.

So I want to make a GENERAL SUGGESTION best do pre-purchase homework to avoid compatibility issues post purchase so I guess it applies to both Pakwong ARC and CAT experiences.
bifwynne
2,206 posts
 
Knghifi ... your comment applies not just to amp/preamp combos but to other system components as well, such as speaker and tube amp matches.

Believe me, just read some of my posts where Al (Almarg) and Ralph (Atmasphere) had to walk me through electrical compatibility issues involving my Ref 150 tube amp and my Paradigm Sig 8s (v3). The issue being electrical consequences of matching my tube amp's somewhat high'ish output impedance and the rock and roll impedance and phase angle plots of my S8s.

I'm ok now ... but only after lots of on line conversations with Al and Ralph, off-line learning, and ultimately putting together a combo that makes a lot of sense in terms of integrating my Ref 150 amp, my speakers, my self-powered sub woofer via a new gizmo I just bought ... the DEQX PreMate.
knghifi
1,668 posts
 
10-10-14: Bifwynne
Knghifi ... your comment applies not just to amp/preamp combos but to other system components as well, such as speaker and tube amp matches.
Not just to other system components as well but to everything in life.

If your house has no access to natural gas, would you buy a natural gas furnace? Post purchase, install propane and all the hassles in getting it to work.

Just common sense.

This is no knock on Pakwong and he has learned his lesson. Sometimes we all have to learn the hard and expensive way. Like the time I was the general contractor building my house with no prior experience. Bought the land ... cost me BIG $$ but very valuable lessons.
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atmasphere
11,807 posts
 
**Most of the time** you can expect an amplifier with a balanced input to work just fine with a single-ended source.

However, balanced line and single-ended operation are not normally considered to be compatible (by the pro audio industry). As a result, you usually have to jump through some hoops to make the two work together. In our equipment, that means joining pin 3 to pin 1 on the XLR and its all good. With the ARC amplifiers, the *only* way to do it is to use a transformer; Jensen makes some of the best transformers world-wide for this application.
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