Yamaha CDX-550 mods: op-amp suggestions

I'm about to attempt some upgrades to my old Yamaha CDX-550 cd player. I know, it's not the best thing to start with (the tray mechanism is a flimsy piece of plastic, for example) but since it is available, I might as well see what I can do with it.

I don't have a service manual, but there are two 4570 dual op-amps labelled "LCH" and "RCH" which I'm guessing are I/V converters and / or output buffers. There is also one BA15218 op-amp in the output section.

Anyone have any suggestions on replacements for these? Would the OPA132 be a good replacement for the 4570's?

Here are some specs on the 4570:
4.5nV/rtHz noise
7V/uS slew rate
100dB CMRR

And for the BA15218:
1.0uV rms noise
3V/uS slew
single supply operation (not sure if it's being used with single or dual supplies - I will measure and find out).


diyAudio Moderator Emeritus
2002-09-20 7:20 am

I would use the OPA2604 because they really sound OK. I also have good memories on the OP249. Think they are out of production now. Special thing about the OP249 was that they have a symmetrical slew rate. Not very common with opamps.
Both types are FET input ones.
OP275 was not as good and forget about the NE5532.

Please check supply voltages first and check in the datasheets if the new ones can have the same supply voltages as the old ones were fed.
The 5218 is probably the headphone amp ?

Hope you can do something with this information.


Thanks for the suggestions. I've heard that the OPA2604 is a good sounding part; I looked at it once when I was building some mic preamps.

I've ordered some samples of OPA2132 and OPA627. I'm thinking about using four OPA627 to replace the two 4570.

I measured the supply voltages, and they are using +15 / -5, so compatibility shouldn't be an issue. Though I'm wondering if I should just add a separate +/-15V supply for the new op-amps?

I'm not sure about the BA15218 yet, since I don't have a schematic. I think you're right that it is a headphone amp. Though this player has a variable output level, and maybe this chip is not just for the headphones? I'm trying to locate a service manual to find out.

I'm also planning on adding a Kwak clock, if I can find the JFET anywhere (Newark has it, but it doesn't make sense to buy such a small part from them). Anyone know any substitues?


diyAudio Moderator Emeritus
2002-09-20 7:20 am
OPA627 is the best

Yes, the absolute winner is the OPA627BP. It has an almost valve-like sound. But it is a single opamp ! Not very easy when your cdplayer is equipped with dual opamps...
Forget about the 2132 and 2134. Tried them both and they're nothing special. Still have them in my drawer not knowing what use to give them. The OPA2604 is a lot better.
But if you don't mind the cost and the hassle, buy OPA627 and you will sure be satisfied. They are very expensive.
Maybe someone has a tip for you concerning that special 2 x single opamp to an 8 pin socket PCB's ?

A new separate power supply is better ( if you have room in your player ).
My samples just arrived from Texas Instruments - in only 1 day! :)

I have 3 x OPA627AP, and 3 x OPA672BP. I'm thinking of using one of each to replace a 4570 dual op-amp. I'll use the better part (OPA627BP) closest to the DAC (which is going to be difficult since I don't have the schematic yet). As you mentioned, it is going to be tricky to replace a dual op-amp with 2 singles, but I will figure something out. Maybe a small daughterboard?

I think I'll go with a separate supply, since I now have the ultimate in op-amps. :D

I'm still thinking about the Kwak clock... maybe I'll order the parts tomorrow.


diyAudio Moderator Emeritus
2002-09-20 7:20 am

Lucky you ! BP is tighter in specs but not spectacular better than AP. Please keep wires from the DAC output to the opamps short.

I have not tried the KWAK clock although I did receive the schematic from Elso Kwak. Haven't found the time to build the thing.
But I have experience with the Guido Tent XO clock. After having modified tens of cdplayers with the XO I can say this is a very good upgrade. Worth every penny.
The XO is small and easy to fit in your player. Price is reasonable too. :D

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