Good replacment for BB OPA 2604/604

[safetyman]

Can the chip master Carlos or someone please suggest a chip that can be a direct replacement for the OPA2604 in a car amplifier situation? I have a car amplifier that uses this chip but find the mid band unsatisfactory. I believe that the OPA2604 is in the pre section. Thanks.

[lineup]

Try change the mid woofer.
OPA2604 has very good data,
maybe even better than your mid woofer

[safetyman]

Originally posted by lineup
Try change the mid woofer.
OPA2604 has very good data,
maybe even better than your mid woofer

I think I'll stick to my mids. I'd rather try chaning the opamp. Thanks.

[float]

Try the opa2134 or 2132. Nicer mids than the 2604, but maybe a bit tubbier in the bass. Worth a go and its cheap.

[carlosfm]

Originally posted by safetyman
I have a car amplifier that uses this chip but find the mid band unsatisfactory. I believe that the OPA2604 is in the pre section. Thanks.

You are right, it does sound crude in the midband, distortion is much higher than other op-amps.
As Float said, you can try the OPA2132 or 2134, but good results are only achievable with very good PSU bypass.

[safetyman]

Originally posted by carlosfm


You are right, it does sound crude in the midband, distortion is much higher than other op-amps.
As Float said, you can try the OPA2132 or 2134, but good results are only achievable with very good PSU bypass.

Carlos, does this mean I have to do more than just changing the chip? What else is needed? The amp manufacturer claims that their PSU is very good, but then, most vendors make such claims.

Thanks Float and Chipmaster.

[IanAS]

With those car amps don't they use an oscilator to break up the +12DC into AC that can then be transformed to the required higher voltage?

If so some decent capacitors in the right places might help. Black Gates maybe. In the switch mode supply for DVD players there's usually one electrolytic in a critical place that needs upgrading and also put X7R dipped ceramic 0.1 or 0.47 mic caps across all the electrolytics and from the pins of the chips to earth.

It's probably only a UK thing this next comment but Maplin are selling the +12V (or so) 1 Farad 'power' capacitor for £39 at the moment. Was £100 or so last year I think.

[float]

You should have the power rails bypassed as close to the opamp as possible. I'd suggest 100nf + 100uf on each rail and also a 100nf between + and - rails (directly over the chip for this one).

Carlos and others have much more experience here than me though. There's a lot of info on bypassing here in this and other threads; you might need to dig a bit.

[IanAS]

Having said X7R multilayer ceramic, i think it's felt they can be microphonic, and polyprop 0.1 mic might be better, but a lot larger.

The ceramics are good for geting rid of the high frequency noise as their indcutance is very low. Three is parallel is a lot better than one, on my scope anyway. So should be good in the switched mode supply and just after it.

A few posts up i think Carlos mantioned a 390n across the chip.

[safetyman]

Sorry guys, all this sounds like Greek to me. I am a noob and wouldn't have an idea where to begin. You guys think that I shouldn't just swap the OPA 2604 with the OPA 2132 or 2134? Originally, t came with an OPA 7??. I have forgotten the number, and the manufacturer suggested to switch to the OPA 2604. I did, it's nice but found the mid section rather glaring. Wanted to see if there were other chips that would make it sound better.

Thanks.