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Signal Degradation Balanced Output

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.

Now, I’m running Focal Mini Utopia Be, Denafrips T+ DAC to Athena Pre, which has 2 pairs of balanced outputs driving a ARC VT-130 and a Focal Sub6. Same problem! I’ve tried inserting my Jeff Rowland Model 112, then tapping off the speaker terminals with a Jensen ISOMAX transformer which then goes to sub.. the problem persists.

The problem isn’t huge, it’s just that the higher the resolution of the components, the more noticable it is. My setup needs the lower fundamentals that a sub brings, but at a cost I’m not happy with.

Any ideas?




cathy062
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cleeds
5,959 posts
 
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.
cathy062 OP
15 posts
 
@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!
georgehifi's avatar
georgehifi
10,312 posts
 


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
cathy062 OP
15 posts
 
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?
unsound
7,329 posts
 
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
 
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