integrated amp - jumper between preamp and amp

If you do change them, before doing so tag them, L-R channel, jumper placement and direction of flow, generally perceiceived left to right should it be needed, that way, when you put them back they sound right.

A 125mm cable should be enough to know if an improvement is available, I found a pair on Aliexpress for $10, which would do the job

Interesting topic, I would have thought not.  However different cables between my individual preamp and power amp do make a difference in the sound quality. Out of 4 or 5 cables I have tried there is a clear winner among them that gives the best sound.  
Maybe worth a try for those with jumper included integrated amps.  

easythestrejamer said,  If you have a pair of RCA interconnects, plug them in to see if you notice anything. If you like what you hear, then you can consider buying a shorter "jumper" set.

Precisely! 

One of my first Audiophile Law articles I wrote for Dagogo.com, where I have been a reviewer for 20 years, was of the Dussun V8i Integrated amp, which had swappable jumpers. My initial experiment was to try interconnects. Then I had Jena Labs send a pair of their "Dussy" jumpers to test. Both passed my Law of Efficacy. I have written about that topic in my book The Audiophile Laws. 

I replaced the stock jumpers on my NAD C352 with customer Signal Cable jumpers and it made an audible difference. Experience is the best teacher. YMMV. 

I keep thinking about how adding a set of cables into the signal chain should not be better, different yes, but being better is questionable.

What if you could internally hard wire those connections, that would be the ultimate connection, and shortest/purest signal path. You would also eliminate four external connectors. This makes the short stock jumpers the next best thing from an EE design perspective.

After looking at an internal picture of the MA8950, this task would not be easy or safe for most of us.