NJM 4580 opamp replacement?

[tubejay]

I'm looking at one of these cheap 8 channel mic preamps out there right now, and it's got the NJM 4580 opamp in it. Is there a replacement opamp that will be significantly better? Is that opamp any good? Is that the biggest factor in sound quality? I'm looking at one of those SM Pro Audio 8 channel preamps, because I just need some extra preamps to pick up the loose ends. Any info would be appreciated. I figure it might be a fun and easy DIY project for myself.

Thanks,

Jay

[gyraf]

Depends very much on how the opamps are used. Do you have a schematic we could see?

Jakob E.

[tubejay]

No, unfortunately I don't have the schematic. I did some searching and couldn't come up with anything. Anybody have one??

[ciminosound]

If that is in a DIP package you can try any "standard" dual opamp like the 5532, or OPA2604. Just be aware of the current draw of the chips.

[cuelist]

[QUOTE]Originally posted by Jay Lison:
I'm looking at one of these cheap 8 channel mic preamps out there right now, and it's got the NJM 4580 opamp in it. Is there a replacement opamp that will be significantly better? Is that opamp any good? [/QUOTE

It's not a bad opamp at all, better than average actually. If you can get a significant improvement by swapping it for something else depends on the circuitry. In a budget amp like this I suspect that more 'upmarket' opamps will be wasted.

You can find the datasheet here:

http://www.profusionplc.com/static/i...s/NJM4580D.pdf

[doulos21]

hey jay have you heard that pre? I have it and i love it lol i bought it for one reason using it for drums grant you i wouldnt run my main vocal through it ,but the rest of it sounds extremly sweet for the money. I had it along with a presonous pre the digimax and choose it over the digimax for recording drums also compared it with my art mp and each channel sounded as sweet as that pre and i paid 100 bucks for that so for the list of 200 the thing rocks

[tubejay]

Hey hey hey!

Someone over on the TapeOp forum was kind enough to send me a schematic of this preamp. Any suggestions of upgrades would be awesome...from capacitor brands/types, to values to whatever you can think of.

Schematic for PR8 Preamps

[ssltech]

That 4.7K resistor in series with the 470µF and the 100Ω should be a variable pot, shouldn't it? -(Between the collectors of the input transistors) -Looks like it needs to be variable to give you a gain control... also, the output drover (which looks like a poorly-implemented cross-coupled design) is missing a junction point on it's lower op-amp output, -should be linked to the 10k/47p feedback combo to mirror the upper half...

Even allowing for the drawing errors I don't like that output design feeding an unbalanced load with either leg tied to ground... It might benefit from being reworked a little to take the cross-feedback sensing from after the output limit resistors. That would lower the effective drive impedance and at the same time more effectively allow each half to raise it's gain if the other side sees a dead short, while killing the drive to the ground-shorted side. -As long as it sees a truly balanced load you should be fairly okay though...

Just a couple of things that struck me... (there's also a line of people waiting to strike me too, it should be noted! ;) )

Keith

[gus]

I would check the caps first. Are the electros SMDs are there SMD cer chip caps? I do not like Electro SMD caps the ESR is higher and the life seems to be shorter. I use a sencore LC102 to check. IMO a cap upgrade might be a better way to go. IMO the opamp used is not bad.