Distortion with ARC Ref 150 and Maggie 3.7

I didna read the entire thread but any chance the cable could be wired wrong? RalphK once warned me certain XLR/RCA adaptors are wired incorrectly, eg Cardas leave pin 3 floating.

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

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

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

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

Pakwong,

I switched out a Joule Electra preamp for an ARC LS 25 line stage. The sound was a little less romantic or "tubey", but the distortion disappeared. I'm not suggesting that you go this route (like all gear, the ARC stuff isn't for everyone), but a true balanced signal is a MUST for your amp.

Thanks for the response Al. Your explanation was very good.

Martykl,

Did you happen to connect the Wadia directly to your amp? Doing so will allow you to get a feel for how well your ARC can drive the speakers. I suspect that once you get is set up properly with a balanced signal, it won't have any problems driving your speakers. Not only that, its just a very good sounding amp. If it were mine, I wouldn't be so fast to get rid of it.

Zd,

Some confusion here, no Wadia components in my house. I never sold the ARC amp either. In fact, I still use the ARC LS 25/VT 130 SE with Verity Parsifal Encore speakers and a Qsonix front end (which, come to think of it, does utilize a Wadia digital section).

I also kept the Joule preamp paired with Cary 300b mono sig amps and Merlin VSM SE speakers. Analog only from an Oracle/Graham/Graham front end. I still really like all of this gear and have been using every piece mentioned here IIRC for over a decade.

Most of my listening time is now spent in front of an Ohm (sometimes Magnepan) and Rythmik based system with an Onkyo pre-pro and rotating power amplification. Digital sources continue to vary but the analog front end is Acoustic Solid/Rega/Lyra.

Variety being the spice of life and all....

I didn't realize you didn't have the Wadia in your house. I was just going by this:

"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!"

That's why I thought you had one. Also, I didn't think you sold your 150, it just looked like you may do so. I was just saying to give it a chance before you did sell it. Its a very nice amp. I also didn't realize you had an LS25. I'm sure there's no distortion when use that with you 150. Either way, its good that you were able to figure out what the problem was.

ZD, the comment you were responding to was from the OP, Pakwong, not from Martykl (who is not the OP).

Best regards,
-- Al

My bad, I should have seen that ZD had confused me for the OP. To the best of my knowledge Pakwong's ARC adventure is still unfolding and we'll all have to wait to see how it plays out.

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

Outstanding! And a great suggestion by ZD.

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?

Taking your second question first, the problem you have been dealing with cannot be avoided with an adapter cable, no matter how it is wired.

To work properly, your amplifier (and other ARC and other amplifiers that are similarly designed in the relevant respects), must be provided with a balanced pair of signals at its inputs. That means two signals that are essentially identical except that one is inverted relative to the other (i.e., when the voltage of one signal moves in a positive direction, the voltage of the other signal moves in a negative direction, and vice versa). An adapter cable cannot produce those two signals, when it is only being provided with one of them.

A transformer can do that, however. A voltage will appear between the terminals that are connected to the two ends of the secondary (output) winding of a transformer, that in the absence of any external connections to that secondary winding would be electrically isolated (i.e., unconnected, or "floating" in EE terminology) relative to the ground of the signal source, and relative to all other voltages or grounds or other reference points that may exist in the system.

If the input circuit of the amplifier is designed as a balanced receiver, it will process the voltage that exists between those two ends of the transformer secondary in a manner that is symmetrical relative to the amplifier's circuit ground, which means that it will "see" that voltage no differently than if a balanced source (providing two equal voltages of opposite polarity) were being used.

This Jensen white paper, although somewhat technical, goes into further detail that may be of interest.

BTW, regarding the transformers I suggested, be sure to note that (as indicated in the manual I linked to for the particular Jensen model I suggested) that particular Jensen model would have to be placed close to the amplifier, and connected to the amplifier with a very short (less than 2 foot) length of XLR cable. The RCA cable from the preamp could be any reasonable length. I believe that no such constraint would exist with the SMc transformer (or with some other Jensen models, although those other Jensen models may not perform quite as well as the one I suggested).

Best regards,
-- Al

Thanks. It looks like I finally did something right. It feels strange. I don't know what to make of it.

Nice going ZD! I learned something today. Nice one.

It's pretty rare when a real problem like that faced by the OP is posted and a straight up creative solution is offered by an Audiogon respondent. Congrats, ZD, you found a high quality, zero cost solution to a thorny problem.

Id send the amp back to Audio Research for a look-see. I think thats where your problem is..

Stringreen, if you read through ALL of the above posts beginning with mine on 8-12-14, I think you'll conclude that there is nothing wrong with the amp.

Regards,
-- Al

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.

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

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.

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

Al, if I were ARC, I would have given the same statement! Thanks again!

Pakwong,

You're a hobbyist and - if you're willing and able to bite the bullet financially - you might want to consider building two systems. I was in your position and kept both my Juole preamp and my ARC power amp even tho they weren't well suited for use together. I added the ARC line stage and Cary power amps to form two very different systems.

You ask which alternative A'gon posters here might recommend and I'd say that it's really such a matter of personal taste that recommendations wouldn't be very useful, so.... you could build two systems to compare them. If you see the value in each and can afford it, enjoy both. If you prefer one over the other, sell the electronics that come up short.

If you don't want to (or can't) pay for this option, you might try to borrow suitable partnering electronics for each component from a local B&M dealer (if one is available to you) for audition and keep the system that you prefer.

Owning two electronics chains may be expensive, and it may not be a rational decision, but who ever said audiophiles are rational?

"If you were me, which do you prefer?"

Good question! Both are really fine options.

I really like the idea of trying the Jensen transformer as a stop-gap. Jensen makes really good transformers and this option might work sonically. Might.

If forced to choose one option over the other, I'd go the CAT route because the JL5 would, I feel, do a better job of driving your Maggies. It's not about watts. CAT amps are designed to drive pretty much anything.

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,

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

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

I listened multiple times to JL5 and I think it is a great amp. Are you ready to buy them unheard? Try to ask a dealer for loan, they won't do it for free but even when you pay the shipping both ways and an extra for the dealer .... this can be cheap when it will support your decision...but I would still do a comparison with a high powered transistor amp to check what is going on with the higher frequencies...

Pakwong ... I still think the Ref 150 is a marginally powered amp for your Maggies. But the most recent posts which speak to the Ref 150 using balanced inputs is extremely important. I cannot overstate how critical it is that you use a linestage/pre with balanced outputs.

Don't know what your budget is. But let me suggest that from time to time, I have seen ARC Ref 3s going for the low $5000s. Even an LS 27 linestage/pre would be a great match.

Last comment. I own a Ref 5 SE/Ref 150 combo. I love my ARC gear. The sound is great. It's built like a tank. ARC provides great customer support. I hope you can figure out a way to keep your Ref 150. IMO, it's a classic piece of kit that will keep its value for a long tim.

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,

My recommendation may have been overlooked as to its relevance, ARC made several active balanced line converters specifically to address the same issue you are having. The BL-1 and BL-2 balanced line converters. While these are out of production, I do see them come up for sale both here and on Ebay several times a year. You could post a "Wanted to buy" ad. You could then keep your current pre.

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?

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

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!

That was a very helpful thread and lots of very good information.

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!

Sorry to hear of this development, Pakwong.

However, I feel quite certain that a problem involving the AC power relay not closing within a few seconds after turn-on has nothing to do with the use of the Jensen signal transformer.

Also, the instructions you quoted from the CAT manual, while being applicable to most balanced amps, are not applicable to yours. As you had found when using the adapter cable, and as has been explained earlier in the thread, using the adapter cable (without the Jensen transformer) sacrifices approximately 75% of the amp's power capability, as well as having various sonic disadvantages.

In fact, although it is probably unlikely, and I'm not specifically familiar with the design, I wouldn't completely rule out the possibility that the amp became susceptible to this problem as a result of having frequently been driven into clipping (i.e., being required to exceed its greatly reduced power capability) when the adapter cable was being used for a prolonged period of time.

In any event, it sounds like either the relay or something in its associated circuit needs to be replaced.

Good luck. Regards,
-- Al

P.S: To clarify my previous comment about what is stated in the CAT manual, the adapter cable you had been using resulted in the amp being operated in exactly the same manner as what would occur if you were to do what is described in the paragraph you quoted from that manual.

Regards,
-- Al

It may have been covered earlier but was the rating and description of the amp on agon when you bought it consistent with your findings since? If not, it would seem to memaybe you have a case with the seller to either return or seek financial compensation for repairs.

Just a thought.

As you may have surmised by this time, the ARC amplifier cannot be used with a single-ended source! If you do so, the amp **will not make anywhere near full power** and it will be distorted.

This is because the amplifier has a very poor Common Mode Rejection Ratio figure, on account of its input circuit (which apparently is differential) is not in fact very differential. IOW, IMO/IME, ARC missed a bet here.

At any rate, the only way to use this amplifier with a single-ended source such as the CAT is to use a transformer like you are doing (The Wadia worked of course because it has a balanced output).

There are several problems with this. The Jensen, while excellent, does not load the CAT ideally nor does it have the bandwidth of the CAT, so you are not hearing everything it does. However, unless you sell the CAT and get a balanced preamp, this is the only game in town.

I have to admit I am puzzled why the amplifier is designed in this fashion, but in conversations with the good people at ARC (a good number of whom I have known for decades) this is very much the case (As a manufacturer of balanced line products, we had to sort out compatibility with single-ended equipment many years ago). If I were you I would be seeking a balanced line tube preamp, but that's me: I don't like transformers. Plan B: Sell the amp and get something that works with your CAT. Both units are capable of excellent performance; its really a matter of which you like more. Good Luck- keep us informed.

If it were me, I would only run an amp like that designed for balanced input with a well matched balanced output device feeding it, like Atmasphere suggests.

If you can establish that a proper balanced output device works as it should, I would agree with Atmasphere that that is the way to go, assuming the ARC is working as it should mated to the right input. If it does not, then there is some defect at play that would have to be addressed, but hopefully that is not the case.

I think the real problem here is as stated by several other posters...that is the incompatibility between the CAT and the ARC. I think ARC is simply trying to cater to fashion in regards to their seeming insistence on only using balanced inputs on their current gear. This fact has made me stay away from their gear and will continue to do so until they get the picture. I can see no reason why the extra electronics needed with the balanced option is at all necessary, except to add cost and to cater to as I stated earlier....'fashion'. Personally, I feel that single ended gear sounds better than balanced gear; IMO,unless one is using their gear in a VERY highly corrupted noise environment or with VERY long runs of cable, balanced is nothing but a joke in high-end.
My advice, dump the ARC Ref 150 and get a more suitable amp for the CAT...like maybe a CAT amp!

Gentlemen, keep in mind that the problem at hand is simply that the amp has broken down.

Also keep in mind that Pakwong was quite happy with the sound he was getting using the Jensen transformer, prior to the recent breakdown of the amp. And some other highly experienced A'goners having very high quality systems have reported in the past being similarly pleased, using the same Jensen transformer.

I have no doubt that Ralph's/Atmasphere's statements about the compromises the transformer introduces are correct, but it seems based on these anecdotal reports that the degree of those compromises is small enough that for many users it would not warrant replacement of either the amp or the preamp.

Best regards,
-- Al

Atmasphere mentioned using only a balanced source. This I assume is only referring to the preamp. It is very possible to use single-ended sources into a balanced ARC preamp, going into a Ref150. They work great, it is only the preamp which needs to be balanced. ARC even makes a few of the single ended sources...

Davef, this quote is incorrect:

single ended gear sounds better than balanced gear; IMO,unless one is using their gear in a VERY highly corrupted noise environment or with VERY long runs of cable, balanced is nothing but a joke in high-end.

If you have ever heard a difference in audio interconnect cables, then you now know why balanced lines are not a joke- because they solve that problem if used properly! Further, it does not matter the length, 6 inches is easily enough to hear a difference, especially if there is a noisy environment. Further, the proper use of balanced lines and balanced operation offers lower distortion.

Tubes are often docked for having that ever-lovin 2nd harmonic, which is nice and rich sounding, but not neutral as it is distortion. That can be eliminated by employing balanced operation, resulting in more transparency and no loss of smoothness.

By running balanced lines, I can put my amps much closer to my speakers, allowing me to run shorter (thus better sounding) speaker cables, plus I can put my front end where I want it, rather than in between the speakers. The first thing I noticed in doing this was greater ability to make out vocals. It was not subtle.

Al, what I was describing in my post above is not a malfunction. The OP did have a malfunction, but it was coincidental and unrelated to the basic problem: distortion when driven by the CAT directly.

Ralph, IMO the loss potential generated by the additional electronics needed to go balanced in home electronics; is more of a problem than what one typically sees as noise infiltration into the system by outside sources. Unlike in the pro audio world, in home hi-fi, we're talking of cable runs of what...a few meters at most. In pro audio it may be 50-60'++ , then i can see the potential benefit. A cable that is effected by noise that is 6" in length must be a ****poor cable IMHO.