Receiver recently repaired - Now producing fuzzy distortion in higher frequencies??

I have recently had my Yamaha R-300 repaired after the relay was no longer clicking and not allowing sound through to speakers. Before this problem came up, I had a beautiful sound hooked up to a pair of JBL 4301B speakers and with a Luxman PD-284 record player. 
Since getting the amp repaired however, all high frequencies like high piano notes, guitar, vocals, strings etc. are very fuzzy and distorted on all inputs including FM, Tape, CD, Aux, and Phono.
I brought it back to the repair shop and described my issue and they plugged in into their speakers and played a CD and allowed me to play songs that the distortion was really obvious on and it sounded fine?? I then took it back home and am getting the same results as before so i'm really not sure if I am doing something wrong here or what?
Any help would be greatly appreciated!
Probably blew your tweeters. If you like to listen real loud then almost certainly that's what it is. Way to test, find any other speakers you can and see if they make that same sound.
If you have headphones you should try them and see if you have any distortion. If you don’t, MC is correct on the tweeters being blown or the x over might be damaged!
Thank you both for your responses! I have tried other speakers and am getting the same results, I tried a different amp and the speakers are fine.
I plugged in headphones and the sound is great but if I turn the speaker channel on, (A or B) I get that same distortion in the headphones too !
You verified that the problem is the Yamaha. That receiver is about 40 years old . I would let it go and buy another receiver instead of spending money to have it repaired. That’s up to you!!
This new Yamaha has all the features you need!
I suspect that the bias diodes used to give thermal feedback from the heatsinks are shorted. This will cause the amp to sound exactly as described. It causes the amp to have extreme crossover distortion. I would take it back to the service shop and have them finish the job. They should have tested the amp prior to sending it out- they should have caught this.