It is very likely that the two outputs are just two sets of connectors from the same amp, so combining them gets you nothing.
OTOH, all you really need is a decent RCA-to-XLR cable. This does not do anything except enable the connection. Not ideal. http://www.adorama.com/HOGXR134.html
One can make/buy an adapter that actually converts the signal to/from SE to/from BAL such as http://www.mcmelectronics.com/product/555-8485 |
Kal - This is just the sort of thing I've been looking for to connect an unbalanced preamp to a balanced amp. I've tried DIY cables, but wound up with a hum problem. Do you think this converter is of sufficient quality to use with Rowland & Placette gear without degrading the signal? Thanks. |
Kenl
Have you tried asking Kimber or Nordost if they will fabricate adapters using the same wire you are using? Audioquest made a pair for me once and they worked great, after I had tried the Hosa and didn't care for what they did to the sound!!!! |
You could give these a try. CardasRegards, Todd |
A great option here is Burly cables, made by Pass.
http://renohifi.com/burley.html |
If your "balanced amp" is "fully balanced," meaning that its internal signal path is entirely balanced, and both its red and black speaker terminals are actively driven (as opposed to the black terminal being grounded internally), an rca-to-xlr adapter or adapter cable is not a suitable solution. It would probably result in 75% of the amplifier's power capability becoming unavailable, because only one side of the balanced signal path would be driven with a signal. I have used this transformer-based converter in voice recording applications, and for that purpose at least it has proven to be completely transparent sonically. It's spec sheet is at http://www.artproaudio.com/downloads/specsheet/dti.pdf. It can be purchased here. They appear to be having a special sale on it, and when you add it to the "shopping cart" you will see a much lower price than the $60 that is initially indicated. I don't know how its sonic quality would compare to the results you would get from the active (powered) unit Kal suggested. If you really want to do it right, although at several times the cost, call Jensen Transformers and have them help you select one of their "Iso-Max" units. Also, see their technical white paper on interfacing of unbalanced and balanced equipment: http://www.jensen-transformers.com/an/an003.pdfBTW, NEVER connect two outputs of any component together, via a y-adapter or otherwise. In this case it would most likely have no effect, as Kal explained, but in other situations it could result in damage. On the other hand, connecting two inputs together, to a common signal source, will not cause damage and will usually (although not always) give good sonic results. Regards, -- Al |
Almarg has completed my thoughts. The transformer-based ARTS and, especially, the Jensen units are superior on paper. I have no hand's-on experience with any of them as I have used only Cardas or Kubala-Sosna cable adapters when necessary.
Kal |
As Al indicates, not all balanced amps are equally balanced. My ARC VT-130SE will lose app. 1/2 of its output capability (per ARC's service dep't) if you merely use an adaptor. As I understand it, the lack of cancellation provided by the balanced signal will cause the protection circuit to step in early and shut the party down.
Bottom line: Talk to the manufacturer of the amp before you try this.
Marty |
Thanks guys. I didn't mean to highjack the discussion, as I'm not the originator of the thread, but I do have an interest in the topic.
For those who might be interested, here's my actual situation. . .
I'm waiting on delivery of a pair of Maggie 1.7's. I thought I would use my very good sounding Rowland Concerto Class "D" integrated with internal phono. However a friend let me try a DIY SS Class "A" 45w amp that is based on a Nelson Pass design. As good as the Rowland sounded, I fell in love with vocals thru the DIY amp. Hard to beat Class "A" for midrange purity.
With this in mind, I thought I might purchase either a Pass XA30.5 or XA 60.5 mono's to go with the Maggies. My room is small (12'x 14'x 10') so I shouldn't require a huge amount of power for them to play at satisfying levels for my usual jazz, blues, female vocal listening. A stereo XA30.5 might be all I need. The heat wouldn't be as big a factor vs the mono's either.
I'm currently using a custom Placette RVC (unbalanced) that has 2 inputs. My Squeezebox is connected to one input via a PS Audio PerfectWave dac, and I'd like to use the phono of the Rowland thru the 2nd input. Unfortunately the Rowland only has balanced connectors for it's output, thus the need for conversion.
Not knowing whether I'll keep the Rowland or not, I'd rather not spend a lot of $$ on cabling at this point. Almarg & Kal have provided several alternatives for me to explore. I thank them and everyone else who has provided suggestions. Hopefully I will discover something that works and is relatively inexpensive. |
If you use an adapter, sometimes you can wind up with a hum because the adapter is not grounding the unused input.
With a balanced amp you have a non-inverted input and an inverted input that is part of the XLR connection. If the RCA to XLR adapter is only using the non-inverted input, often there will be no connection on the inverted input. This can leave you with some hum, and often less gain.
To correct this, open up the XLR side of the adapter and have someone (if you can't solder) connect pin 1 of the XLR (ground) to the unused connection (often pin 3, which is the inverted input).
This will get rid of the hum and the amp will have normal gain.
It would be better to have a cable that does the conversion rather than an adapter, as there are less connections.
If you go the transformer route as mentioned above, place the transformer as close as you can to the preamp can keep the cable to it short. Then run the balanced cable from the transformer to the amplifier- this cable can be a lot longer than you are used to with single-ended, and you will not have to sink as much cash into it for it to sound right.
The transformer will have some artifact; although the Jensens are very good I find they reduce bass impact and liveliness, so if your cable can be short from the preamp to amp I would go with the adapter rather than the transformer. |
If this is an entry level NAD preamp, and depending on the quality of the amp, it might be better to just sell the C162 and replace it with a balanced preamp. |
KenL, I'm not sure whether or not the Pass XA series amps would be good matches for a passive volume control, because of the XA's relatively low input impedance (20K unbalanced, 30K balanced). Although I note that Stereophile's measurements indicate that those impedances are "constant across the audio band," which will help matters. You should probably raise that question in a separate thread if you decide to pursue that possibility. As you may be aware, the XA30.5 is considerably more powerful than its rating suggests, and JA's measurement in the Stereophile review was 195 watts into 4 ohms (although the amp leaves Class A operation at considerably less than that). The Maggie 1.7's sensitivity of 86db/1m/2.83V corresponds to 83db at 1 meter for 1 watt input into its 4 ohm nominal impedance. 195W will result in about 106db at 1 meter. Given that for planar speakers volume levels fall off relatively slowly with distance, that strikes me as reasonable in relation to your small room dimensions and music preferences, assuming that the spec is accurate. As far as interfacing the balanced output of the Rowland to the unbalanced input of the RVC is concerned, my suggestion would be to have a custom cable made up which connects xlr pin 2 to the rca center pin (assuming the Rowland conforms to the USA convention of pin 2 non-inverted and pin 3 inverted); xlr pin 1 to the rca ground sleeve; and leaves xlr pin 3 open. If you were to use a standard adapter, that would most likely ground pin 3, which would mean that the Rowland's output signal on that pin would be shorted to ground. Most equipment can tolerate that, but some cannot. Check with Rowland on that point if you would prefer to use an adapter. If you want to consider a transformer instead of an adapter cable, my instinct with gear of that caliber would be to go with a Jensen. Although for the price at which B&H is currently offering the ART DTI, there is essentially no downside to experimenting with it. Regards, -- Al |
Ralph - Thanks so much for your detailed response. I have a good friend who can make a cable as you describe. He tried once before, but apparently had it grounded differently, thus the hum.
Almarg - The Placette is a temporary thing. I will eventually go with an active preamp. Thanks again for your advice. |
Hi i have a set of cables like KR4 MENTIONED.I will send them to you ,just pay for shipping. |
Energizer - Thanks for the offer. I need RCA at one end and female EBU at the other. Is this the config of your cables? |
Ken, re Energizer's nice offer, keep in mind as I indicated earlier that commercially made xlr-to-rca cables (and adapters) in most cases have pin 3 shorted to pin 1 (ground). I would not use that cable on an xlr OUTPUT without first checking with Rowland. See this thread for an example of a problem that was caused by doing exactly that, albeit with relatively inexpensive equipment. Also, I don't know how similar your Rowland is to the Continuum model that is currently listed on their website, but for that model, at least, it describes the xlr output as being "high current." That most likely means it has low output impedance, which will mean that the device driving pin 3 will be forced to supply LOTS of current if it is shorted to ground. Regards, -- Al |
With regard to Al's comment immediately above, you could set up the cable so that only pin 2 of the XLR at the preamp end is used. That way the inverting out would not be grounded and possibly damaged.
FWIW in the case of our preamps they are completely tolerant of pin 3 being grounded to pin 1. |
hi ken yes they are what you need balanced on one end rca on the other . |
ken, i am not expert on balanced cables but i used these cables with an A B INTERNATIONAL AMP.325 RMS.AND A BELLES LINE STAGE PRE AMP.HAD NO PROBLEMS. |
Thanks everyone. I think Almarg may have the best advice, and that's to contact Rowland. I just noticed that the owner's manual specifically suggests using a Jensen Model PC-2XR adapter box, but if I could accomplish the same result with a cable, that would reduce the number of connectors, and cost. Should I decide to go the cable route, I will be sure that my friend closely follows the advice of both Almarg & Atmasphere. Thanks guys.
Energizer - Thanks again for your offer, but I think I need to do more research to make sure I don't damage anything with good intentions. You're very generous though, and I sincerely appreciate your help. |
You guys are great. Really appreciate learning a thing or two every time I have a question. Thanks guys! |
Based on my use of transformers with my current gear, I will respond to a couple of Ralph's transformer comments, If you go the transformer route as mentioned above, place the transformer as close as you can to the preamp can keep the cable to it short. This applies if you are using output transformers. However, I had much better luck with input side transformers. Since my preamp to amp run is less than 3M, I use 2.5 to 3M single-ended IC's to two separate single channel Jensen input transformers then very short balanced IC's (less than 1M) from the transformers to my balanced Clayton M300 monoblock amps. The transformer will have some artifact; although the Jensens are very good I find they reduce bass impact and liveliness, The first part of this statement is true, but with the Jensens it is my experience this is inaudible, or at least unnoticable. So far, I prefer using my favorite single-ended preamp with the transformers to using the balanced preamp I have tried without transformers. In other words, I have found the sonic differences in preamps to be much greater than the sonic penalty resulting from losses that may occur when using the transformers. Some highly regarded manufacturers use transformers from companies like Jensen and Lundahl on the output side of preamps and and/or the input side of power amps. The literature provided by Jensen shows pretty much flat response throughout the audible frequency band. Source impedance (the output impedance of your preamp) must be below 2K ohms and the load impedance (input impedance of your power amp) must be above 10K ohms according to the literature, and they recommend keeping the transformer to amp cables as short as possible. I have found this to be an excellent solution to the problem of driving balanced amps using a single-ended preamp. I have not tried the transformers to drive balanced preamps from single-ended sources, although it seems that should also work if the output and input impedances are within the limits provided. One last thing, the Jensen transformers are relatively inexpensive, being just over $200 for the stereo model and around $125 for the single channel model (which comes in a slightly more robust case for pro applications). You have to ask them for the single-ended model, but it is perfect when using monoblocks that are more than a couple of feet away from each other. Check out the link to Jensen posted above by Al. |
Thank you Mitch.
What a useful information! I also have single ended preamp (Joule-Electra LA-300ME) and Spectron balanced monoblocks.
I did not understand your comment exactly:
"single-ended IC's to two separate single channel Jensen input transformers then very short balanced IC's (less than 1M) from the transformers to my balance "
Left and Right preamp RCA outputs can have only one IC each. If you need for each one of them two separate single channel input transformer then, as I understand it, you need to use "Y" connector at the end of each of your single ended SE interconnect to connect to two separete single channel transformer inputs
is this what you have in mind of each of your single channel transformer has one input for RCA and one output for XLR?
Thank you |
is this what you have in mind of each of your single channel transformer has one input for RCA and one output for XLR? Dob, yes there would only be one rca cable for each channel, connected between the preamp output and the input side of the transformer. And of course one xlr cable for each channel, connected between the output side of the transformer and the power amp input. As Mitch indicated, for an "input transformer" the xlr cable should be very short, less than 2 feet iirc. Jensen's site indicates that before ordering it is usually best to speak with them directly, for help with model selection and other guidance. Best regards, -- Al |
Dob, I could have been clearer. Al nailed it above.
Most of the pictures on the Jensen site show their ISOMAX transformers in a stereo box (both channels into and out of one box). After asking them, they set me up with mono transformers (only one channel input and output per box). Jensen most commonly sells these single channel transformers to their pro clients and the boxes are more heavy duty, but the transformers are identical to the stereo model. The single channel boxes were better for my monoblocks since the amps sit about 7 feet away from each other. If I had used the stereo box, the XLR cables from the box to the amps would have been longer than I wanted them to be. Al's comment on length is perfect, mine are about 2 feet long, and Jensen recommends as short as possible and no longer than about 1M. |
Most line transformers, including the ISOMAX are designed to load at 600 ohms or thereabouts.
If you don't load the transformer it can ring. The best place to load it is at the end of the interconnect that it is driving, if that is an XLR you can run that cable 50 feet if you want to with no degradation. I've never in 40 years heard of a requirement to keep XLR interconnects short unless its for cosmetic purposes. |
Hi Ralph, See the following datasheet, and the note near the bottom of page 1 of the user manual for the PI2XX (the unit shown has balanced inputs and balanced outputs, but a similar model can be ordered with unbalanced inputs): Datasheet: http://www.jensen-transformers.com/datashts/pi2xx.pdf User Manual: http://www.jensen-transformers.com/datashts/pi2xx_usr_man.pdf Note that the recommended load impedance range is 10K to infinity. And that the output impedance of the transformer at 1kHz, with a 600 ohm source impedance connected, is very high at 4.65K, of which 1.9K is dc resistance. Given the very high output impedance, it would seem to make sense that cable capacitance should be kept very low, to avoid high frequency rolloff. That would apply whether the output is balanced or unbalanced. Your comments appear to be applicable to output transformers, such as this one, which as explained in this application note will not perform as well in terms of cmrr as will an input transformer. Best regards, -- Al |
Hi Al, I would not use that transformer for this application, because it does appear to leave you susceptible to the cable due to the high impedances involved.
Instead if you are running a single-ended preamp to a power amp, I would use something that steps down to 600 ohms, and then see if I had enough output at the amp end- if not I would step it back up again.
Of course, we could be talking at cross purposes, the main reason I use balanced lines is to get rid of the need for expensive and often short cables! |
Thanks Al, I had not noticed the impedance information in the literature. I would be interested in a more thorough reporting of the output impedance of the transformers at different frequencies resulting from a range of input impedances. The output impedance of my preamp at 1k ohms is low, at about 250 ohms, but rises at lower frequencies due to limited coupling cap size. Although my amps fortunately have a relatively high input impedance of 100k ohms, at lower frequencies approaching 20 hz, the output impedance of my preamp may exceed the 2k ohm "maximum" posted on Jensen's website. I suspect I may be getting some LF roll-off resulting from this. This condition could explain why my balanced preamp performs better in the bass than my single-ended preamp running through the transformers - although there are also other possible reasons for this such as the balanced preamp having higher gain and being SS, while the single-ended preamp is tubed (although it is noted for it's robust bass). I need to find a fully balanced (not pseudo-balanced) tubed preamp that I really like, but have not yet done so. |
Hi Mitch -- Assuming you are referring to the LAMM LL2 Deluxe, you've most probably seen JA's measurements, which indicate an output impedance rising to 3.3K at 20Hz. A phone call to Jensen sounds like it would be in order, to ask them what effects that would have. Best regards, -- Al |
Mitch2, my advice if you look for a preamp is look for one that is fully differential and balanced internally, not just at the inputs or outputs. If it is built right, the length or quality of the interconnect will be of no consequence. |
Hi guys, interesting thread, but since I don't understand most of the the tech stuff in the links posted above re jensen transformers, could any of you guys tell me what would be the best way to connect the BALANCED output of my CDP (Simaudio Moon Eclipse) to the UNBALANCED input of my preamp (Hovland HP100)? The CDP also have unbalanced outputs that I'm currently using, but the manual states that the balanced ones sound better, would this arrangement take advantage of these sonic benefits?
Thank you all,
Marco |
If your amplifier does not accept balanced inputs, it won't help to run a balanced cable that then uses an adapter to convert to single ended.
FWIW though your amplifier can easily be modified without changing any of the circuit design to accept a balanced input. We have been doing this mod for a while- its very simple and there are no transformers involved. |
Thank you Atmasphere, can you tell me more about this mod?
As I'm in Europe, I just need to know what to say to a local technician, I wouldn't understand the details anyway. |
Al, your suggestion to call Jensen resulted in some good information. I spoke to their designer, Bill Whitlock, who informed me the specifications shown on the website are referenced to a typically worst-case scenario where they considered a load (amp impedance) of only 10K ohms. The good news for me is that when the input impedance of the amp is higher, the load seen at the input of the transformer is also higher. Therefore, when using the transformers with amps having an input impedance higher than 10K ohms, the recommended 2K ohm preamp output impedance becomes less of an issue. Bill said, since the input impedance of my amps is 100K ohms, there would be no sonic penalty with regards to bass response resulting from my single-ended tubed preamp's higher output impedance into lower frequencies (3.3K ohms at 20Hz).
Ralph, I agree entirely that a fully differential and balanced preamp would be the best solution for my amps. However, by only looking for preamps that are fully differential and balanced, the field of available contenders has been significantly reduced. I do currently have a pretty good sounding differential balanced solid state preamp I am using, but the field for balanced tubed preamps is much smaller. Therefore, since I like the sound of my single-ended tubed preamp, and can apparently use it with the Jensen transformers without a sonic penalty, I believe (at least for now) that using the transformers is a good solution for me, and possibly also for the OP (depending on his preamp/amp impedances). |
