Signal Degradation Balanced Output

Hmmm, well it certainly isn't cost prohibitive.  Worth a try, I guess.  I suspect it will have a negative impact though.  But, I've run out of ideas short of sellung the sub and monitors for full range speakers.

Thanks again.

cathy062 OP14 posts09-06-2021 10:45amIt sounds like there is no workaround to the problem, however.

You could use a SS low gain low output impedance SS buffer after the SF3 to drive everything via Y connectors from it’s output.

EG:
See if this guy still has this
https://www.usaudiomart.com/details/649322907-burson-audio-buffer/

Or this dual input one
https://www.ukaudiomart.com/details/649605507-burson-ab160-solid-state-buffer/

or
https://www.stereonet.com/forums/topic/253123-sold-fs-trade-in-burson-audio-ab160-audio-buffer-rca/

Cheers George

It sounds like there is no workaround to the problem, however.  

Thanks George.

 Would the same thing be the cause here as well?

Yes, your at best halving the load impedance seen by the dac they would come back to the same dac buffer/s only depending how it's configured one could have the load of the rca and 1/2 of the xlr on it, the other the other half of the xlr, so it's load sharing could be bit lopsided also.

Best to use all from the RCA output or all from the XLR output and hope that either will have enough low impedance drive to handle the parallel load impedance of what your driving into.

Cheers George    

I should add that a dear friend used a SF3 via balanced interconnects into 4 factory matched B&K M200's into Dunlavy SCIV's and the sound was glorious. The advantage of 4 mono amps over just 2 was not subtle.

While I am typically rather entrenched in the solid state camp, I can't deny that the Sonic Frontiers Line 3 is amongst best line stages I've ever heard. The SF3 is not your typical tube pre, and ironically the biggest complaint against it seems to be that if doesn't have enough tube "magic", that it's too solid state sounding. Before condemning it as having the typical tube technical issues, take a look at this :

Sonic Frontiers Line 2 line preamplifier Line 3 Preamplifier, July 2000 | Stereophile.com
 

Thanks George, for confirming the likely cause of the problem. Let me ask, I have the same issue occuring when my Audio GD NFB-1 hp amp is connected to my Denafrips Terminator Plus DAC via RCA, while the DAC outputs balanced XLR to the Athena preamp. The same diminished sound quality occurs. Would the same thing be the cause here as well?

cathy062 OP
Has anyone developed a workaround that solves signal degradation when splitting. The problem that I have occurs even when the preamplifier has two balanced outputs.
Years ago I became aware of this problem when using my Sonic Frontiers Line 3

Trouble is when you drive into two amps from the SF3 output, those two amps present a much more difficult load to the SF3, and being tube it’s not as good as driving into low input (2 amps) as a solid state pre can.

EG:
Two amps both with 50kohm input each, the SF3 will then see 25kohm load.
Two amps one with 50kohm input the other with 25kohm input, the SF3 then sees 16.5kohm load
Tube preamps don’t like this kind of low impedance loading.

Cheers George

@cleeds , Ok, I get it.  Hmmm, I guess it is what it is until I get some floorstanders.  I feel like I've tried just about everything and don't want to add more components in a feckless attempt to better the sound, when less sounds right.

Thanks everyone for all your help!

cathy062

ARC tube amp specs 200K ohms balanced,
Jeff Rowland amp specs 20K ohms balanced
Sub6 specs 10K ohms input balanced
Athena preamp specs 400 ohms output balanced

Do you see a problem? What should I be looking for?

Typically @cathy062  -  the rule of thumb is the amplifier(s) input impedance should be 10x the preamp's output impedance.  (There's debate on that with some arguing it should be more and others arguing that it can be less.)

If I'm correctly recalling the formula for calculating combined impedance (Z) is (1/R1 + 1/R2 + 1/R3 ...), then you're around 6.4K for a combined input impedance. While that would seem to be ok, input impedance varies by frequency, so it's difficult to say for sure. Your results suggest it's an issue, especially because your sub has such a low input Z.

I'm totally confused at this point. When that happens, I break down my system to the bare essentials. Source, amplification, and speakers. Everything else sits in the corner for now. If you can't get your system sounding right with the bare minimum components, you'll be able to isolate the culprit. 
If the subs are the issue....are they forward firing and between your mains?  If not that is where I would start. My next step would be stereo woofer towers and a good crossover. That would be a big step up. 

Has anyone developed a workaround that solves signal degradation when splitting. The problem that I have occurs even when the preamplifier has two balanced outputs.

Years ago I became aware of this problem when using my Sonic Frontiers Line 3, which has 2 pairs of balanced outputs, to drive a Theta Dreadnaught amp and a pair of Entec LF-20 subs. I thought the sound was excellent until oneday, I disconnected the cable to the sub and that’s when I heard what I had been missing from the Wilson Cub I, transparency and reverb that allows you to hear deep into the music.

I think @cleeds got this right. The impedance of the two inputs is a bit much for your preamp. especially when the ISOMAX is involved. One solution would be to have a preamp that supports the balanced line standard (many 'high end balanced' preamps don't). Some of the ISOMAX transformers present the preamp with a rather low impedance. Unless the preamp is really designed (which, if its balanced, it should be, but regrettably most high end audio manufacturers were simply jumping on a bandwagon with their balanced entries...) for the low impedances which are common with balanced operation, its likely to fall flat on its face when presented with such things, as you've described.

A different ISOMAX **might** solve the problem if its able to present the preamp with a higher input impedance. But that would still be in parallel with whatever the input impedance of your amplifier is.


I run a similar setup but my preamp doesn't care about the low impedance loads involved.

I suspect your ISOMAX is creating a different problem than the one created by  employing your pre amp's two outputs simultaneously. 

As you correctly concluded a few posts up, your ISOMAX is not a product one can associate with audiophile quality sound. Whether you apply it to a line level signal or an output level signal, nothing good is going to come out of it. Your idea is sound, but you need to step up to a product that is substantially better (and sadly, much more expensive).

Active crossovers present the same dilemma - the vast majority (all?) of them are complete junk and sound terrible. I believe Bryston made a hifi quality crossover but I could never track one down to try.

I think there is value in considering that the combined (i.e. lowered) input impedance of your ARC and Focal makes the Athena unhappy, but I'm at a loss as to how you would test that. 

In your shoes, I would probably roll with a set of full range floor standers and junk the sub. Not a cheap solution but the safest I would think. 

@cleeds I feel like you're on the right.  Let me look into that.  I know already that the problem still persist when only one balanced output from the preamp is connected to the Jeff Rowland amp input, while the amp's output is sent to the speakers and to the ISOMAX line level converter.  The sub doesn't even need to be connected to the ISOMAX... Just connecting the ISOMAX to the amp is enough to cause the problem.

Yes, I have.. no change.  The change comes from disconnecting the balanced cables from the sub or disconnecting the ISOMAX from the amp.  At first I thought it might have something to do with channel summing circuitry of the sub, but not so.

I was using it from the amp's output to be converted to a balanced line level that is then sent to the sub. Same problem.

Have you tried turn off the subwoofer instead of disconnect it from the amp output?

@Paul, haven't tried that... but, that seems like jumping into the fire.  

Forgot to mention, the ISOMAX, though they sell it as transparent sound, it definitely is not.  So, I would never use it immediately after the preamp on a line level.  I was using it from the amp's output to be converted to a balanced line level that is then sent to the sub.  Same problem.

You could look into using an active crossover between your Athena and ARC&Focal. 

No, I have never tried calculating impedances.  Not even sure how to do that.  I remember a cable tv installer told me that a coaxial splitter causes a 6db loss to the signal when inserted.  I was thinking that something like that is going on here, but I'm not using a splitter anywhere, unless the 2 pairs of balanced outputs are internally split.  A few minutes ago I disconnected my Audio GD headphone amp from my Denafrips DAC.  I had it connected using the unbalanced RCA interface.  The same type of problem was happening there.  The sound immediately got more resolving simply by disconnecting the RCA cable. Denafrips says not to use the unbalanced  RCA when using balanced XLR -- not sure why however.  I know that all my source components are fully differential, including both amps.

As for the ISOMAX, I tried it in hopes of getting a line signal from the amp's output.  The thinking here was that it would be separated from the amp's input signal.  It didn't work either.  So, I disconnected the balanced input from the Jeff Rowland amp feeding the ISOMAX and the same thing happened, the sound transparency and reverb immediately improved.  The analog cabling is all Acoustic Zen Silver Ref II with Matrix Ref II on the sub.  This is where I'm at.

https://www.google.com/search?q=jensen+transformers+sp-2sx&oq=jensen+&aqs=chrome.0.69i59j69i...

athy062

I’ve tried balanced, unbalanced, Y-splitters with cables and one piece metal RCA Y-splitters, even made ulp some splitters with Neotech 1002 cable and pure copper contacts... same problem.

Understood. Did you calculate the effective combined input impedance of the amplifiers? None of the other efforts you mention would affect that, and using unbalanced lines would actually make things worse if the amplifiers themselves are differentially balanced.

I eventually decided to try the ISOMAX, thinking the problem was in the impedance matching of the preamp and amplifier... dame problem.

What is Isomax??

Yes, I've tried balanced, unbalanced, Y-splitters with cables and one piece metal RCA Y-splitters, even made ulp some splitters with Neotech 1002 cable and pure copper contacts... same problem.  I eventually decided to try the ISOMAX, thinking the problem was in the impedance matching of the preamp and amplifier... dame problem.

This is not a new problem, but one that has persisted over many different system components, cabling and configurations over the years.  I've spent hours, days, even months dialing in my system.  The speaker imaging of Wilson Audio and Focal is superb when setup right.  Mine is.  The sound is detached from the speakers and the soundstage is well behind and center of the speakers and sound fabulous.  except that it lacks the lower fundamentals.  Connecting a sub diminishes the reverb and  transparency. I can hear minut differences.

Righy now, I think my only solution is to move to a full range floor stander, thereby eliminating the sub. I read some older threads that mentioned Linn was doing something with daisy chaining amps or something.  The problem is real.  I challenge some of you to seriously a/b test your dialed in systems, I'd bet you'd hear a difference or maybe I just have golden ears. lol

I’m not familiar with your exact components, but most preamp outputs are wired in parallel. That means the preamp now has to drive the lower combined impedance of the two amplifiers. That could be an issue, especially if your preamplifier’s output impedance is high. Although the exact number is debatable, manufacturers typically recommend that the preamp see an impedance from the amplifier(s) that is 10x greater (or more) than the preamp output impedance.

Did you try the RCA outputs? 

I’ve been splitting line outs for years no problem.
When I upgraded the pre I hooked it up customarily. It sounded slightly distorted compared to the old. Some upgrade!
Then I un Y’d. Problem gone.
For your situation I would try converting the sub feed to unbalanced and run it through an isolation transformer before any active stages.
Or try the IsoMax immediately after the Athena.

Tried it, same problem.

"Y" off a single pair of outputs.