My stereo receiver is a little too bright. Can a cable help me out?

I just had my vintage Pioneer SX-1050 refurbished.  I had a severe case of sticker shock when presented with the bill - oops!!  Which unfortunately pretty much forces me to use it. 

I will say It is sounding very powerful which is no big surprise because there is a lot of horsepower under the hood.  But the audio impression is that it’s also a little too bright.  The only way I know to tame brightness is with the right interconnects.  But I’m not experienced in that area.  Recommendations would be most welcome.

It’s probably important to know how I am using  the Pioneer SX-1050.  It is responsible for all audio in my TV system.  My choice of music is almost exclusively opera and classical.  

 I send the HDMI signal from my four sources ( TV-DVR, OPPO DVD, ROKU streamer and Pioneer Elite Laser Disc Player ) to my AVR, an ARCAM SR-250, and I send the respective analog audio signals to the Pioneer.  I am into opera and classical music and I didn’t think my ARCAM AVR sounded as good as I wanted it to, even though it’s ideally  suited to my needs, a two-channel product touted for its exceptional audio.  The audio is good but definitely not great.  Prior to deciding to refurbish it I had paired the Pioneer with a Musical Fidelity A3cr Preamp, using the Pioneer just as an amplifier, and I was getting very good audio that way.  But one of the goals of the refurbishment project was to feature the Pioneer and eliminate the musical influence of the Musical Fidelity preamp.   And now, after spending so much,  I wanted to hear how my now very expensive Pioneer sounded, so I pulled the Musical Fidelity Pre and attached my sources directly to the Pioneer.  Currently all the interconnects are Blue Jeans Cable.  Obviously I can’t spend huge amounts replacing cables for all four sources, so the DVD is priority.
Lowrider57 12-23-2019
Once again, use the tone controls and put more hours on the Pioneer.... I wouldn't get caught up in buying cables and new components. Give it some more time.

Echolane 12-23-2019
I think the most sensible thing to do  is to have some patience and decide whether to move on or not after a couple hundred hours of break in.  Believe it or not, now, only 24 hours later, I think it sounds quite a bit better. The rawness is gone, or if not gone, considerably tamed.

Using the Pioneer’s tone controls is another easy fix.  

+1. There's no reason to do anything else at this point.

Good luck. Regards,
-- Al

As others have said, try your tone controls. Start with a little bit up on the base and listen for a few minutes, then add a little bit down on the treble. Listen for ten minutes and walk away. Come back and make an adjustment.  Make small adjustments in this fashion for a week, then either live with it or plan a replacement.  Have some confidence in your own judgement  -- you can do this.  Good luck.
Agree, let it run in. If that's not enough, try moving the speakers so they point more away from your ears to the outside. Toe them out, if you know what I mean. Tweeters can be very bright on axis but fall off more than other drivers as you move off axis. Much more can be done cheaply by moving your speakers than any other tweak. Trust your ears!

Perhaps in a drag-race or simple oval, with drag-race being watts into 8 ohms, and simple oval, being THD on a sine wave, then I would agree with you. Put them on a road course (real music), and that "old" Camaro or Corvette is hopelessly outclassed no matter the engine upgrade or what tires you put on it. Only way it competes is with effectively a new chassis under the old body (and even then it needs aerodynamics upgrades), so really it is not an "old" Camaro or Corvette any more is it?
Like a old Camaro or corvette, etc... being refitted to take on a modern carbon fiber bodied racing F1 Ferrari, on the track.... and be dead even some minds... even win. Imagine that.

The idea of the new circuit and so on being better, exists as companies have to sell you the new in order to be alive and exist, so expect them to convince you that all is new all the time --- when in fact it is not. Not at all.

While there is truth to this, these receivers are from a period where IM distortion was poorly understood, hence why later products like the NAD3020 or even the Sansui integrated mentioned above are better.

(link is for the image of a ’properly’ modded out NAD3120, which, when finalized [finally finished], might [and generally will] exceed the sonic qualities that most seek to experience from a modern $5k integrated.)

A single set out 3055/2955 output transistor places some inherent limitations w.r.t. what loading this will work best on. Those same parts are still available, likely better quality or at least more consistent due to modern process controls.

Those over-priced "audio" electrolytic power supply capacitors are certainly great marketing by the likes of Nichicon and others. Literally sell themselves, as some people are convinced they are "better", and it becomes a self sustaining market, no actual specifications needed, just some words on a marketing sheet. But better than what is the question?  Better than a 10,000 hour, 105C, modern capacitor with high ripple current and low ESR (and lower cost)? .... Weird that some of these high end audio capacitors have audio specs similar to a few generation back power supply caps (but with poorer rated life).
Regarding comparisons of vintage vs. recent equipment, a seemingly obvious point but one which often seems to not be taken into account in discussions of this subject is that comparisons should be based on similar present day prices. For example AustinStereo pointed out above that a restored SX-1050 is worth around $1000. So a fair comparison between that component and modern ones should be to a modern component (or a combination of components) providing preamp, power amp, and tuner functionality, with comparable maximum power capability, for a total of around $1000.

Regarding some of the other points that have been made, it is certainly true that "distortion wars" occurred during the 1970s, in which feedback was applied in a heavy-handed manner to produce the lowest possible Total Harmonic Distortion numbers. With the consequent adverse effects on Transient Intermodulation Distortion and increased emphasis of distortion components that are the most objectionable not yet being generally recognized. In fact as far as I am aware even today TIM is not normally measured or specified, and does not even have a standardized basis for measurement. That despite the fact that in the 1970s Dr. Matti Otala famously authored several papers on the subject, this being one example:

My own preference among vintage components is for well restored tube equipment from the 1950s and 1960s, a lot of which can provide very good sonics and great value relative to present day price points. But I know that there are many happy users of solid state products of the "distortion wars" era, and that’s fine too.

-- Al