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
 
Hi all, I finally got the Jensen transformer but they sent me the PI-2XX instead of PI-2RX which I order. When I requested for exchange, they said it's electrically identical to the PI-2RX but they were happy to exchange. Which means I could use a RCA to XLR conversions cable to achieved the same purpose. Since I'm not very sure of that and remember Almarg recommended the PI-2RX, I've placed another order for the PI-2RX just for comparison and send back one of them for refund later.

This afternoon I anxiously did a brief audition with the PI-2XX in my system with existing RCA to XLR conversion cable and a newly purchased two feet length XLR cable. Guess what? Those albums which were prone to distortion especially piano sound and vocal came out nice and clean! I also noticed significant improvement at the lower frequency.

Thanks Al and others for helping me overcome the distortion issue successfully. Now the question is, are the PI-2XX and PI-2RX actually electrically identical to each other, only differences were the XLR or RCA connector on the input side?

This Isomax device is very well build and there were some slots with screw on the other side of the device. Any idea what is that for?

The seller did mentioned that the PI-2XX were more versatile device whereas I could benefit form it if I eventually working in pure balanced environment. So, shall I keep the 2XX or 2RX?
almarg's avatar
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almarg
9,670 posts
 
Great!

I don't doubt their statements about the RX vs. XX. And actually when I suggested the RX I hadn't thought of the possibility of using the XX with your existing adapter cable.

I'd expect that either approach will work well, and will solve the initial problem, but there may be some sonic differences resulting mainly from differences between the cables themselves. Which would be preferable, if in fact there is any difference, is probably unpredictable.

Regarding the slots and screws you asked about, I believe those are to provide the option of connecting via bare wire, which is sometimes done in pro applications. So you can ignore them.

Best regards,
-- Al
pakwong OP
38 posts
 
Thanks Al, I'll wait for the PI-2RX for comparison. Will keep you posted.
pakwong OP
38 posts
 
Hi guys, got the RX few days back. They work the same as the XX, no difference in sound quality as I use the same IC which changed to RCA plug at output end.

Anyway this unit need a few days to sound their best just like every other audio product. I would say the Jensen transformer has done a great job on converting unbalanced to balanced signal. My system sound like never before with no perceivable anomalies. The balanced signal has makes the Ref 150 unleashed it's full potential by creating a fantastic deep and spaciousness sound stage through Maggie 3.7. I would recommend this product to anyone with the same issue. You'll get good price from eBay.

Thanks all!
syntax's avatar
syntax
2,193 posts
 
That was a very helpful thread and lots of very good information.
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