Replacement of NE5532 op amps in Meridian speakers

[azl]

I have a pair each of the older Meridian M2 and M3 active speakers (from the early 80s) which use NE5532 dual op-amps in their electronic crossovers and time delay circuits. Each unit uses four of these op ams. They sound surprisingly good as is, but can probably benefit from an op amp upgrade. Any suggestions/advice on more recent offerings from Analogue Devices, Linear Technology, Texas Instruments (Burr Brown), etc that would provide a noticeable sonic improvement over the old 5532s? Thanks in advance for your input.

[gianxdiy]

I would think to LM4562!!! Hard to beat...

[UV101]

get the HA version in tin hats! they are much better than the 8DIL package!

[gfiandy]

Hi,

I would recomend being catious in changing these parts. The NE5532 is very stable and you can get away with very little power supply decoupling on it. Newer designs are often more demanding and may become unstable without the right decoupling on them. If the opamps are decoupled with electrolitic capacitors and no ceramics. It is possible that by now these parts have a very high ESR and are not decoupling very well.

You may find if you put new opamps in the become unstable and feed a high frequency signal into the power amplifer. This would likely overheat it and may cause damage.

So if you are changing the opamps, look at the decoupling. If there are no ceramic caps decoupling the opamps then you should at the very least change the electrolitic decoupling. You may also consider adding 100nF decoupling to your new opamps as this would also help.

This is by no means a definate problem, you may just get away with it. But with a very old product like this I would check first rather than damage it and end up with a very difficult to repair fault.

Regards,
Andrew

[azl]

Andrew, thanks for the warning about the power supply decoupling for the NE5532s.

Here is a brief desc of the original Meridian M2/M3 supply. After each power supply electrolytic (for both V+ and V-) there is an inline 270R followed by an 18V zener to ground. The zeners are each bypassed by 0.47u mylars and followed by 79X15 (for +15V) and 78X15 (for -15V) regulators. Each regulator is bypassed to ground on the regulated side also by 0.47u mylars. Do you think this would be sufficient decoupling for the modern opamps such as OP275 or the recommended LM4562?. Thanks for your input, Arthur

[gfiandy]

Hi, The Mylar cap is almost certainly to keep the regulator stable. Is there no decoupling near the opamps, I just had a look at the circuits for the M60s that I have and they show 1uF decoupling caps near the opamps. If you have the same configuration I would recomend replacing these.

The LM4562 has anicdotal evidence to suggest its stability is good, however this arcitcle still recomended 100nF ceramic decoupling to ensure stability. I have not used the OP275, but in the back of my mind I seem to remember somone saying that these were a bit of a bugger with stability, but I could be completely wrong.

Regards,
Andrew

[Conrad Hoffman]

The National parts (I use the LME singles) are wide bandwidth and need good decoupling right at the opamps. Use small film or ceramics between .1 and .47 uF within a quarter inch of the part on both supplies. Hopefully there will be a suitable ground close by, as lead length is a killer. IMHO, the National parts are superb, but the NE/SE553x family is remarkably free from audible flaws. You may hear a difference or you may not.

[UV101]

Got to honest and say, I've never had a problem with psu or decoupling.

That said, I've normally changed the decoupling caps at the same time. Normally Black gates or ZA's.

The LM4562HA is possibly the best chip opamp I've ever heard. If you solder it to a DIL socket, it plugs straight in!

IMHO

[kaos]

Install sockets, try a variety of different op-amps. The perfect op-amp hasn't been invented, they all have their warts.

[azl]

Thanks for all the input.

The Meridian M2/M3 crossover boards are small ( less than 2x6 inch) and the four NE5532s are scattered throughout the board. The two decoupling 0.47u mylars are near the regulators, so they can be 3 to 4 inches away from some of the opamps. Distance could become a stability issue for some of them and space for extra decoupling at individual opamps is tough to find.

As an aside, Andrew, would you be willing to share your M60 schematics with me? I have a single M60C that I use as center channel in my video setup and it would be nice to know what is inside. If you are interested, i would be happy to share with you my M2/M3 schematics. You can reach me at: azl@atmos.albany.edu