dual opamp BA4558

[lduarte1973]

I have Technics equalizer SH-GE70 with this dual opamp BA4558 , is there a better sounding drop in replacement ?

 

[bob91343]

That's a pretty good workhorse, used in many units. What's wrong with it?

 

[lduarte1973]

it´s working fine , just checking if there was a better one , i would like to improve my equalizer , maybe it´s time to replace the capacitors and not the opamp , this unit is 15 years now .

 

[bob91343]

You keep saying you want to improve the amplifier but you don't say what needs improving.

 

[Mooly]

Try the TL072 Dual FET oamp.
The 4558 has no place these days in high quality audio, the abysmal slew rate of 1volt/us is to low to allow anything like a full rail to rail swing at 20khz.

The TL072 will be a direct replacement, you don't have to alter anything else.

How many 4558's are there in it ?

 

[stratus46]

Try the TL072 Dual FET oamp.
The 4558 has no place these days in high quality audio, the abysmal slew rate of 1volt/us is to low to allow anything like a full rail to rail swing at 20khz.

The TL072 will be a direct replacement, you don't have to alter anything else.

How many 4558's are there in it ?

I'm partial to the OPA2134 probably because I got 50 for $85 some years back.

G²

 

[lduarte1973]

just one , i´m thinking of replacing the capacitors since the unit is 15 years old. I get a massive loss of power when i use the equalizer , still i need it to tame mid´s and high´s.

 

[Mooly]

just one , i´m thinking of replacing the capacitors since the unit is 15 years old. I get a massive loss of power when i use the equalizer , still i need it to tame mid´s and high´s.

Why not fit a socket, then you can try a different devices... the OPA2604 is very smooth sounding, which might be of some use.

Changing the opamp won't alter the gain at all... if you have a "massive loss of power" then that suggests either the equaliser has a gain less than one, or that you perhaps have a connection problem.

 

[Nrik]

The attenuation can be on purpose!
It could be to ensure that you can add say +20dB to any band at 750mV RMS input without clipping, if the powersupply is at +-12V or +-9V.

Replace opamps, and parallel all electrolytics at 10uF or higher, with 100-330nF polyester. I agree on the TL072 and OPA2605, but somewher in between the price and sound of those two could be OPA2134. This one sounds great and has a fair price.

 

[Sangram]

I've had good luck changing out to the cheap NE5532 from the 4558 in low-end equipment (Altec Lansing MX5021), and to better ones (LM4562) in soundcards and higher end equipment. I prefer to replace bipolar input opamps with similar types opamps, though the FET-input types suggested should work fine too 🙂

 

[indianajo]

4558 upgrade

My flea market find Herald RA-88A disco mixer was based on 4558's, it hissed fairly annoyingly. Not as bad as a $5 radio, but worse than my PAS2 preamp, which I recently discovered shorts out the CD player and FM radio inputs if phono is selected. (The PAS2 is a battery killer and might damage either source's transistors if I push a button in the wrong sequence). While I won't denigrate the premium products mentioned previously, 33078 op amps were about 3 for a dollar at newark.com(USA, Farnell UK) . They got rid of the hiss entirely, and got the noise low enough I am thinking about replacing all the electrolytic caps in the 1995? mixer to tackle the hum. One tip, put in sockets if the unit doesn't already have them, so you can move on if you don't like what you install.

 

[lduarte1973]

I found a TL072 from a velleman kit i had , tryed it after putting the socket , my first impressions are that bass is a bit better , and the overall sound is " cleaner ".Not a dramatic change but worth the trouble. Anyway i ordered 2 ad825 with adapter to single opamp .I also ordered some elna capacitors , i´ll let you know how it turned out.