I need help with my Vintage onkyo amp!

Factual Questions
1

I have an ONKYO TX-4500 (1977).
Its clear as a bell with my Cerwin vega AT-10s
When the stereo is on FM is great.
When i use the CD player-the sound sucks!!
HELP!!

2

Sure you don’t have it plugged into the PHONO jacks? I know on my Marantz vintage receiver anything other than a turntable plugged into those RCA jacks will sound like shit.

3

Yes, inputs designed for turntables apply amplification/equalization to the signal, so that could be the issue (there weren’t CD players in 1977!).

4

Tape recorders were the most common line-level components back in the 70s. If there are inputs for a tape machine (usually paired with outputs for recording) they should be suitable for CD.

5

Although the phono input is not RIAA it is still much too sensitive for a typical CD player, its rated at 2.5mV

the line input is 150mV, however some CD players have a much higher line output and you might need to use some means to drop the signal.You did not state what make and model your CDplayer is so its not easy to know how to advise you

6

A 1977 unit is due for new power supply capacitors, even if it sounds OK, btw. They are well past their “best by” date. This a preventive maintenance procedure and will help save the now unobtanium other components from being roasted. If you are reasonably handy with a soldering iron and promise to be careful you can do it yourself for probably $20 in parts.

7

[germane only in the slightest]
I could not shake Yoko Ono out my head when I read, and re-read, OP.
[/germane only in the slightest]

8
9

Here’s a pic of the back.

Here’s a pic of the front

Assuming you using one of the 3 tape inputs make sure it is not in monitor mode.

It’s old enough some components may have started to degrade.

10

You’ve tried playing it through each of the three tape inputs? Before you start shopping around for replacement parts or a tech to work on it for you, I suggest 2 more things.

  1. Have you got a friend who’ll let you plug your CD player into their receiver? Try that.
    B. Either/or, borrow someone’s CD player and try it through your receiver.

You’ve got 2 items that together, don’t work. Let’s narrow it down to 1 thing that doesn’t work.