My appreciation to everyone for their serious advices.
Answer to Lloydedee21:
"Is it possible the tubes are slightly microphonic, and your speakers are picking it up? Have you tried tube dampers? Borrow some if you can before going out and buying. Sometimes when a tube is microphonic it will pick up certain noises either internal to the tube due to vibration or due to vibration in the room outside the tube...and translate it as distortion thru the systems signal."
I do have dampers from Herbie's Audio Lab on all tubes so I assume no issue with microphonic effect. |
Answer to Mrderrick:
"You tried a second tube amp and still had the same issue.
I would try all of the output taps on the Ref150 and see if there is a difference. ( without the auto formers first )
I would then try the auto formers with the best performing tap if you still need them.
My experience is that Maggies need to be driven at moderate levels at the very least to sound best."
In my case I do agree the Maggies need to be driven at moderate levels to sound best as the distortion were less obvious or even disappeared with lower volume. Perhaps I need a more powerful amp but this would be my last resources to solve this. In the mean time I will try all output taps to hear the difference. No harm trying! |
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. |
Answer to Brownsfan: "There are plenty of people that drive Maggies with tube amps. I agree that tube microphonics would explain what you are hearing, and it is pretty easy to address. Also, the fact that you tried two other speakers, one of which gave you the same result, probably means it is not the Maggies per se. However, because they are dipoles, they may direct more energy back to the tubes. Just wondering, the other speakers you tried--- were they both rear ported? If the one that didn't give you distortion is front or bottom ported, or sealed, that could also be a clue."
Please refer to my answer to mrderrick about tubes's microphonic. Both pair of speakers I used for testing were box speakers. One pair was KEF Ref 201/2 which has the same distortion while the other Focus Audio FC9 pairs sounded okay. The KEF is upright ported while the FC is back ported at medium height. Any clue?
I did swapped ICs and speaker cables but nothing change. |
Czarivey, My XV-1S is zero hour brand new cartridge. It has just been about 50 hours now. Yes, I have the same problem with my previous XX2 cartridge.
Regards |
Answer to 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."
I do have a CD player but don't have CD version of distorted recordings on LP as my CD collection was very limited. It's definitely not the SUT. I bypassed the SUT and the CAT preamp by connected phono cable of tonearm directly to a phono preamp with volume control and feed the signal directly to Ref 150 with the same distortion. |
Answer to Lack:
"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?"
Tried that. Nothing change. |
Answer to Mofimadness:
"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."
Please refer to my answer to Jfrech. |
Answer to Bifwynne:
"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. "
I do speculate perhaps Ref 150 not powerful enough to drive the Maggie properly. Remember I said Maggie dealer used a transistor amp to test and it sounded okay without distortion? That Class D Esoteric can output 400 watts into 4 ohms. So probably power is the issue.
Btw, before adding the Zeros, I run Maggie with 4 ohms tap with the same distortion. |
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. |
Thanks for valuable input from all!
Yes, trouble shooting procedures which I've been carried out also includes bypassing the SUT and CAT SL1 in the system, by using a EAR 834P phono preamp that comes with volume control and MM/MC function connected directly between the tonearm and Ref 150. Same thing happens! So I assumed there is no issue with overloading from the SUT and preamp.
Last night I did a final test by listening again to digital sources from a Wadia 381i CD player connected to line stage of the CAT SL1. To my surprise, the same distortion also happens on the digital source which I thought didn't exist! I'm not a big fan of digital hence very seldom listen to it. The last time I listened to it were kind of background listening with lower volume. This time I crank up the volume control to about the same level while listening to LPs and the same distortion shows off immediately!
In the mean time, I also tried listening closely to the speakers and found that the distortion appears almost on all frequency including bass while cranking up the volume.
With these latest discovery I began to suspect that the true problem might be coming form either the Ref 150 or the Maggies.
Any thought?
Thanks again! |
BTW, I do agree that my system sounds more linear and faithful to the source by connecting the 4 ohms tap directly to the Maggie.
Thinking about the beginning when I first bought the Ref 150, it was used to drive my previous KEF 201/2 speakers and from that time on I started to experienced distortion on certain recording. Only not as severe as with the Maggie. Perhaps the Maggie's higher resolution and the recently purchased XV-1S which replaced the XX2 has made the issue worst.
If both KEF and Maggie suffer the same distortion from the Ref 150, and no sign of anomalies from other components, is it possible that I've purchased a defected Ref 150? Or simply because the Ref 150 did not match the Maggie perfectly? |
Martykl, if I have more than one listening room, I would have keep both! But I still think we audiophile should try to be rational as best as we can lol. The more I went deep into this hobby, the more I realized that we have to put a lot of effort to build a real good sounding system. Two or more system might be overburden to me!
Regards, |
Jtimothya, I didn't use adapter. It's a specially build RCA to XLR interconnect soldered according to many cable manufacturer's standard for RCA to XLR connection. I've two different set/brand of such cable but posses the same problem. |
Martykl, many thanks for your input. It sure help to further justified the issue with ARC amps. But you didn't mentioned how you finally addressed the issue. Did you changed to a balanced preamp or use a transformer?
Regards |
After many painful and time consuming experiments,I have to believe that single ended and balanced components does have mating problem. It seems like many balanced only component were designed to match with other similar or same manufacturer component only. Thus, I think I better trade in my preamp or power amp to set up a balanced or unbalanced only system.
The Maggie is something I cannot live without. So do the CAT SL1. And the Ref 150 seems doesn't up to the task to tamed the Maggie. So a more powerful single ended tubes or solid state amps would be a sensible replacement. Of course, before buying, I will have the dealer brings them to my house for audition to make sure there are no more distortion with the new set up.
Hopefully someone have good single ended amp in mind which could drive the Maggie efficiently and match well with the CAT can offer some suggestion.
BTW thanks Almarg, Syntax, MrDerrick, Zd542 and others for your kind assistant on this issue. |
Bifwynne，FYI after some serious listening, I do aware that the distortion were clearly less obvious bypassing the Zeros and used the 4 Ohm tap from the Ref 150 to drive the Maggie. Now the issue has narrowed down to the balanced and unbalanced interaction.
Regards |
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 |
Thanks Al for the insight of single ended and balanced design. I'm sure learn a lot from you. What you've mentioned about substituted amp I used was correct. It was a pair of VTL MB125 which rated 55-watts and 100-watts into 5Ω in triode and tetrode modes respectively. It do sounded louder with the Maggie at lower volume in comparison with the Ref 150 but have the same distortion perhaps due to clipping as you suggested.
For your information I've wrote to ARC, Jensen and SMc. We'll see what the answer's like.
Regards |
ZD, your suggestion has save me from selling an excellent amp. Today I loan a XLR cable form the Maggie dealer to try a direct connection from the Wadia which have balanced output and volume control to drive the Ref 150. Guess what? Not only the distortion has disappeared even at maximum volume, the sound it produced was something I never heard in my system!
First thing which I immediately aware of was the dead silence background and powerful bass with very good authority and definition. I never realized low frequency from Maggies can be that great!
Such experiment has confirmed that the ARC do need balanced only signal and that you guys has proved your points to be very true.
Right now, what was left is to find a way to change the CAT output signal to balanced. Al, please forgive my ignorant. Can you explain to a guy like me with almost zero electronic knowledge about how the transformer from Jensen or SMc can actually convert unbalanced signal to true balanced signal?
My Maggie dealer also talked about something like pin 1 or pin 2 "hot" in the RCA to XLR cable and he suspected that the termination of my RCA to XLR cable was not done correctly hence the distortion. How true is it?
Thanks in advance.
Best regards |
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? |
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.
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Al, if I were ARC, I would have given the same statement! Thanks again! |
Yes kevin, I try to keep rational thinking and focus on the Jensen transformer first.
A friend of mine also recommended JL 5. Although only rated 100 watts and have 8 KT120 power tubes just like the Ref 150, people who have been with CAT still think the JL 5 would be an all round winner. Only when think of the 100 watts JL 5 driving the Maggies which has been known to be extremely power hungry, it's normal for a audiophile to try to think "rational" lol |
Many thanks to Bifwynne and Syntax for your kind advice on amp selection.
I do have an offer for a Ref 5. Whether buying it or not I think I would still keep the Ref 150. For the JL 5 it kinda impossible to arrange for home audition down here but a single ended amp whether tubes or transistor would be a more "rational" option to me as my CAT already have build in phono stage. If I choose the ARC path I would have to digs for extra money to invest on a good phono preamp.
I do wish that the transformer option would eventually work out as I felt that the CAT-ARC-Maggie's combination sounded quite alright to my ear. It produced romantic and airiness sound stage with good ambient which suited my musical taste. I can't be more happy if it turns out that the Ref 150 does sounds much better when the amp finally able to unleashed their full potential with balanced input signal!
Regards, |
Mrderrick, no wonder ARC didn't mentioned this in their reply mail to me. If they have produced such product before, I think they should continue the production as some user may have encounter same issue like what I've been dealing with. Anyway, a Jensen transformer already on it's way. I'll see how things work out. Thanks for the reminder. |
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? |
Thanks Al, I'll wait for the PI-2RX for comparison. Will keep you posted. |
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! |
Updates:
About one week after using the Jensen PI-2RX, the Ref 150 fuses blow twice. The second time one of the electronic part overheated. I wrote to ARC and here what they answer:
"The overheated part is the turn-on surge resistor, R67. This is a 21.5 ohm / 25W resistor that is designed to cushion the current in-rush at cold turn-on of the REF150. The reason the resistor has overheated is there is a fault that is preventing the RY1 AC power relay from closing after about 1.5 seconds and bypassing this resistor. If the AC relay does not close, R67 will very quickly overheat, as it is not meant to be in-circuit for more than a few seconds. A schematic is attached. Have your technician troubleshoot the soft-start circuit to determine the fault. Note that in 220-240VAC models, this resistor is 21.5 ohms, not the 5 ohms shown on the schematic."
I was asking is this cause by the transformer or due to tubes problem (power tubes about to change) but ARC didn't give any answer.
In the mean time, I got a copy of CAT SL1 Ultimate manual and noticed that there was some instruction on how to connect the preamp properly to a balanced amp as follow:
"When using amplifiers with balanced inputs, the negative leg of the balanced input should be shorted to ground. This prevents hum and noise problems caused by the floating inputs. While most amplifiers with balanced inputs provide a switch for this purpose, inserting a jumper in the XLR connector will accomplish the task. Alternately, an XLR connector can be prepared with this jumper soldered internally, and the connector then inserted into the XLR jack."
If the CAT's wired method for the RCA to XLR cable really works, I think perhaps it's better to stick to the conversion interconnect cable.
Any advice?
Thanks in advance!
|
Thanks all for good opinions and comments.
At the moment I'm still waiting for ARC to send me the resistor as my technician down here couldn't find resistor with such value. In the mean time, my ever faithful VTL MB125 monoblock continue to serve music with the CAT. They are both single ended so no distortion issue here. The sound with the Maggie is acceptable but there were some sort of distortion at higher volume/peak of music probably due to lack of driving power.
After having such bad experiences with the balance amp, I think it's better to stick to single ended. Moreover, my CAT has comes with decent phono stage so changing the power amp instead of the preamp might save me some money. While me and some of my audiophile friends has got very good offer from local CAT dealer, I've decided to grab a new Black Path JL 5 to end the misery!^^
Anyway, will keep you guys posted on the ARC issue.
Thanks again! |
Atmasphere, totally agree with your statement.
I would suggest all balanced amp should be more user friendly so people who has live with unbalanced equipment for a very long time could try their hand on balanced equipment which they are not familiar with and eventually discover the benefit balanced amps has to offer. |
Thanks Knghifi for the reminder.
Received the resistor from Audio Research and sent out the ARC 150 for trouble shooting this afternoon. Wish my technician would find out the problem with start circuit soon. In the mean time my listening room is under renovation so it's about right timing.
Regards, |
The fact is, though having trouble with the Ref 150, I'd still recognized it as a great amp after solving the matching problem with the CAT preamp. But as recommended by some of you here, I feels that the Ref 150 would be better matched with a true balanced preamp as the design concept suggested, in order to achieve the amp's full potential. If the new ARC preamp has build in phono stage like the good old days, I would have gone the ARC path!
Regards, |
I admit that I didn't do enough research before buying a balanced only amp for my single ended only preamp. So I'm the one that should be blame. However, it's a rare case when an adapter cable couldn't solve the connection problem. Anyway, I hope the negative comments on ARC shall end now.
Al, I didn't have the chance to audition the JL5 with my system. But I have friend whom I can trust to build confidence on the CAT amp. I only have moderate size room(10'x14x'17') and didn't go for high SPL while listening, so I think the 100 watts JL5 is good enough. I'll still keep the Ref 150 for comparison. If the Ref 150 is superior to the JL5, I don't worry about selling it as I bought with good price and there are plenty of CAT's fan down here. Perhaps I have same "problem" as Bifwynne, just don't feel comfortable with something else in the signal path!
Best regards,
Pakwong |
