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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

Showing 3 responses by cleeds

cleeds
6,111 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.
cleeds
6,111 posts
 
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??
cleeds
6,111 posts
 
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.
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