I am a HiFi-fan since I was 14 years old. I had a lot of different gear, and the possibility to take some stuff home over the weekend from a local HiFi-dealer where I jobbed.
some previous components:
Acapella Ion TW 1S plasma tweeter [in German: Ionenhochtöner], Corona plasma tweeter
The most devices in the mid range to entry level high end use ICīs
somewhere in their circuitry. There are standard types in use for the
analog audio sections in the input stages of amplifiers or analog output
stages of digital devices. In some cases you will find a NE 5534
(single channel) or NE 5532 (dual channel). There are older ones,
like TL-071 or LF-356, and so on. The NE 5534 are standard
types even in studio/professional equipment. The quality of this IC
limits the overall quality, no matter how good the rest of the circuits
might be. There are some types of very superior quality, made by
manufacturers like Burr-Brown,
Analog Devices, Ultra Analog, Precision Monolithics, ... I started with
some OPA-37 AZ a few years ago, and they were very much better in sound.
Today, Burr-Brown manufactures the OPA 604 (single channel) and
OPA 2604 (dual channel) especially for audio equipment, and the
newer types OPA 134 / 2134. They cost only a few Dollars each.
They are pin to pin compatible with the older ones you want to replace.
You just can solder the old ones out, and the new ones in. More
expensive and superior is the OPA 627 and OPA 637 (which is not unity
gain stable and needs an amplification of at least 5). Recently I
switched to Analog Devices LME 49710. The AD 847 is not bad, but it had
DC offset in several applications.
The most preferable type is the LME 49710 and the much more expensive Burr Brown OPA 627. It is available also in a metal can package, but then costs much more. It has FET input stages compared to the 27 / 37, which have not. Also here the 37 requires a closed loop gain > 5, the 27 is unity gain stable, as is the 627. The prize of a OPA 627 in metal can is (in Germany) about 30-40 times the prize of a simple NE 5534. In the ordinary platic DIP version still 10-15 times as much. But if this is a single limiting stage in your audio gear, worth thinking about. The circumstances, which have to be taken into account are aditional circuitery like offset-nulling or drift-nulling, which are not required in most cases, and they might not be compatible. If you have "naked" ICīs, you most probably can switch over. Take care of the gain. Some applications might be critical, like HF-signals in the digital parts of your CD / DAT devices. But in the analog input / output stages of amps or pre-amps it is less critical. In some cases the limited bandwidth of slow ICīs prevents the amps from deadly HF swinging. With these new high-speed ICīs without limiting in another area of the amp it can result in lethal breakdown - also for the rest of the chain after this device! In any case, these are tips regarding the sound quality, but no recipies for general cases. Itīs better to ask a technician or service station. It is not advisable to modify here with the first time a soldering iron in hand, or with no idea in which part of the circuitery you are - and whatīs happening there.
Also, you might want to refer to the manufacturer,
Burr Brown, which belongs now to Texas Instruments.