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Anyone running SE84UFO2 Balanced from DAC? (Read 2677 times)
doukhobar
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Anyone running SE84UFO2 Balanced from DAC?
03/07/16 at 01:10:39
 
Hello,

I was wondering if anyone here owns the SE84UFO2, or I believe also the SE84CKCS, with the optional balanced XLR inputs?

Some DACS, such as those from Electrocompaniet or other high end companies, are designed to run in balanced mode throughout the entire chain. I have such a DAC.

Has anyone tried their Zen Select running straight from such a DAC into the XLR? It is a major cost upgrade, but if you got a DAC designed to run in balanced, like maybe one from Sonic Fronteirs and you want to run a Decware amp, this could be the way to go.

Another options is the ZBIT with te RCA/XLR high bandwith transformers.

Thoughts on this topc?
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busterfree
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Re: Anyone running SE84UFO2 Balanced from DAC?
Reply #1 - 03/08/16 at 00:05:04
 
I have a SE84CKCS that I sent back for the UFO upgrade. I did not order the XLR input when I ordered the amp, and I thought hard about it when I sent the amp back for the UFO upgrade. I did not want to be locked into an XLR input, and cost was a factor. The amp only has two inputs, and the RCA is just far more common (at least on the equipment that I own).

I have debated about getting a ZBIT since it became available. I have one on order now, and I like that I can use it with any amp. Buy it once, and I do not have to worry about buying it again as an option on another amp.
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Decware ZTPRE, ZBIT, CSP3, SE84UFO, & SE84UFO2
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doukhobar
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Posts: 78
Re: Anyone running SE84UFO2 Balanced from DAC?
Reply #2 - 03/08/16 at 05:53:31
 
Hello Buster,

Thank you for your kind reply. I am a little taken aback this topic was not already addressed on the forum, and there is not more interest in the ZBIT and the balanced input transformers on the new UFO2 amplifier. As I'm sure that at least more than a small percentage of Decware users are recovering Solid State addicts, where the balanced inputs on amps are far more common - I would think that at least some Decheads have gear with XLR outputs they would want to use with their Dec amps. One company that I've noticed strongly does NOT believe in using XLR outputs on their DAC's is Audiomat, who generally run only SE RCA outputs. However, all Sonic Frontiers, Electrocompnaient and outer high end companies suggest running balanced out from their sources. I believe having a DAC with only RCA output is saying, we are focusing all our energy to SE as well as we can, and not diverting our resources into trying to double the circuitry output. Fully balanced DAC's tend to be much more expensive.

That said, you brought up an excellent point which I also considered. It is that the ZBIT can essentially assume one of the important functions of a pre-amp - which is to share the DAC's output source signal with multiple devices. In this case, I believe the ZBIT has two (2) single ended outputs. My DAC has just one RCA and one XLR output. Therefore, with one XLR output from the DAC/source, you could now bring the DAC /source signal to two different SE amps, or a pre-amp and an amp, depending on your configuration, and if you like to switch amps.

The main benefit you suggest, is that the ZBIT can be used to bring the balanced XLR signal to any one of your SE amps. This would provide the most flexibility. However, I question whether using the ZBIT has the same effect as running an actual balanced connection between a balanced source and a balanced amp. For example, one of the benefits of balanced configuration is common mode noise rejection, which from what I understand, benefits the most when run balanced all the way through, i.e. from DAC to pre-amp to amp (if pre-amp is in the chain). If that is not possible, I've also heard that at least it is most desirable to have balanced from preamp to amp (i.e. you want balanced going into the amp). So in this case, once you go for XLR -> SE in the chain before the amp, the question is if you are doing away with the benefit of the noise rejection? Or, if the noise was already rejected earlier in the chain using balaned out, does the common mode noise stay out of the signal path? Or, do you loose the common mode noise rejection as soon as you introduce SE configuration- then having any SE in the chain would negate the benefit. This is one of the weaknesses of the ZBIT, if true.

Another point I thought against using a ZBIT, as opposed to running balanced into the amp, is that I do not think that converting balanced to unbalanced and then plugging those RCA into your amp, is the same as having a truly balanced amplifier. I think the truly balanced amp has twice the circuitry (therefore twice the cost, ouch) in order to run balanced and get the true benefit, where the amp's output signal is output balanced from the amp, then to the speakers and recombines at the driver. I am not sure if this is the case, we should check with Steve. Alternatively, in a balanced amp, it would be the two signals in a single balanced channel are recombined in the amp itself. Either way, this certainly ads a level of complication to the amp, which is why most tube purists leave it out - because it can potentially detract from their simplicity and beauty of SE. However, I think that in the balanced case (i.e. balanced throughout the chain), the signal is output balanced throughout each of the amplifier's two output channels to the corresponding driver in each channel, where it recombines at that point (i.e. at the driver). That's why you get so much noise rejection. As such, I do not think the new balanced UFO2 with the XLR input is recombining the balanced signals internally, but actually passing on the balanced signal through the new transformers to your speakers.  And in this case, using a ZBIT (i.e. balanced to single ended converter) does not equate to having a balanced amp in the chain, because you lose the common mode noise rejection from the ZBIT to the drivers. I believe common mode noise is the part of the audio signal which is not out of phase 180* (wherein balanced mode, the audio signal is perfectly out of phase 180* between the positive and negative wires, contrary to the undesirable noise which is common to both phases), and therefore shows up on both the hot/cold signal paths in the XLR, and finally is canceled out when the two signals are subtracted.

The final quandary I have with the ZBIT, is that its major draw is that it seems merely to function as an adjustable gain stage (besides converting XLR/SE). In other words, the XLR outputs of most DAC's are about double the signal voltage then the RCA outputs. From my understanding, having the higher voltage output from the XLR is not the sole benefit of using this configuration. (and in some cases even worse, but that is rarely so). If  having the higher voltage from the DAC was the sole advantage, we could all just use simple connector converters from a truly balanced DAC to our non-balanced integrated amps, and use the higher voltage input, and adjust the volume accordingly (though our volume knobs may become too sensitive due to the higher voltage input). I believe the benefit of the balanced connection is primarily the lowered noise (aside from the higher voltage output of XLR DAc's, and therefore higher signal to noise ratio of the audio signal) due to the common noise rejection.

In these cases outlined above, it would seem the ZBIT actually does not give the true full benefit of running a completely balanced system, but one must use an actually balanced amplifier. I do realize, this takes away significantly from the flexibility you suggest of being able to use the DAC's XLR with any of your amps, and the ZBIT still does preserve the benefit of the higher voltage output from the DAC. However, I do believe you lose the benefit of the noise rejection.

I wonder what Steve thinks?







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« Last Edit: 03/08/16 at 06:17:32 by doukhobar »  
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busterfree
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Posts: 256
Re: Anyone running SE84UFO2 Balanced from DAC?
Reply #3 - 03/09/16 at 00:34:33
 
Great questions…In my situation, I think I need the higher voltage from balanced. My amp sounds great now, but I want to see how it sounds using the balanced outputs from my DAC. I want to see what riding the gain does in my system. The only way to know for sure is to order one and try it out.
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Decware ZTPRE, ZBIT, CSP3, SE84UFO, & SE84UFO2
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busterfree
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Posts: 256
Re: Anyone running SE84UFO2 Balanced from DAC?
Reply #4 - 03/09/16 at 00:45:22
 
I prefer to go direct from DAC to amp without the CSP3 at the moment. I could add an XLR input to the amp, but it is simpler for me to order a ZBIT. No risk of my amp getting damaged or lost by UPS.   Cry
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Decware ZTPRE, ZBIT, CSP3, SE84UFO, & SE84UFO2
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doukhobar
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Posts: 78
Re: Anyone running SE84UFO2 Balanced from DAC?
Reply #5 - 03/24/16 at 03:14:45
 
Hi there Buster,

I called Steve last week, and you are right about everything!

After this discussion, your idea of using the ZBIT over the UFO upgrade definitely makes more sense.

This is because, from what I remember from Steve, with the upgraded Zen amp, the balanced audio signal recombines in the UFO2's input transformer.  When using the ZBIT, the balanced signal recombines in the ZBIT Jensen wide bandwith transformer - the same transformer that is on the upgraded Zen. Therefore, the balanced signal does NOT in fact pass all the way from the amplifier's output and recombine at the speaker as suggested above in this system - the hot/cold voltages from the balanced signal recombine in the Zen amp/ZBIT itself. So with this system, there appears to be no engineering/sound quality difference between running the ZBIT, or having the upgraded amp.

The only minute difference would be, having a second pair of interconnects running in the stream to your amp, and also that the last bit of wire from the ZBIT to the amp would not be balanced. However, Steve suggested that you are in effect achieving the same amount of common noise rejection with both set ups, and that having the last bit of wire not balanced doesn't make an audible difference, since the Zen amp is so quiet anyway.

Do, if you decide to go for ZBIT, do not feel like you are missing out!
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busterfree
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Re: Anyone running SE84UFO2 Balanced from DAC?
Reply #6 - 03/25/16 at 03:32:27
 
Great!
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Decware ZTPRE, ZBIT, CSP3, SE84UFO, & SE84UFO2
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