Tube Amps / Music Electronics
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|11/23/1998 10:06 PM|
||Low noise opamp|
Wondering if anyone knows the low noise, low power equivalent to the 4558 op amp. I've got a few older effects units that I'd like to quieten down!!
|11/24/1998 7:03 AM|
Try TL071 for a quick, cheap replacement. There are others, but the '071 is very much more available.
|11/24/1998 8:23 AM|
||Oh how the mighty have fallen!|
RG meant well, but a TL071 installed into the former receptacle of a 4558 will not behave terribly well, simply because the TL071 is a single op amp. What you want is obviously a DUAL op-amp. You have several to choose from, as a pin for pin replacement, among them:
- various other commercially available chips that are numbered as 4558 but have a suffix to indicate lower noise
- the TL072 dual bi-fet op-amp
- the LM412 dual BiFet op-amp
- the dual 5532 low noise op-amp
- the CA3240 dual MosFet op-amp
Where you need a high input impedance, the BiFets will outperform the others with respect to noise (mind you use a 72 and not a 62; both are Bifet, but the 6x series trades lower current consumption for higher noise). Where you are working with generally lower input resistor values, and lower input impedances, the 5532 will tend to outperform the BiFets. I used the 3240 in a mixer I made over 20 years ago, and it behaved rather nicely, and was somewhat less battery draining than other types. Bear in mind it is to be treated like a CMOS chip and is static sensitive. They also tend to be more expensive these days.
There are occasions where the lamented 4739 outshines any of these with respect to noise, but they are getting fairly rare, and will not simply fit into the spot formerly held by a 4558 (since they are 14pin chips).
No doubt there are other pricier options (like the various OP-xx chips) but the ones mentioned above tend to satisfy. A number of mod articles from early 80's magazines report improvement to sonic quality (chiefly noise reduction) using these as replacements, and nost current kit construction articles simply use them as the default parts instead of 4558's.
|11/24/1998 11:26 AM|
OK, sign me up for that remedial counting course *<8-O)
|1/18/1999 4:51 AM|
FWIW I put a NE5532 in my tubescreamer and
the tone pot got reversed and a bit lower range on it too, besides that it sounded nice, but at the moment I'm using a MC4558.
|11/24/1998 4:44 PM|
||Re: Low noise opamp|
I stuck a LM833 in a Boss CE-2 chorus and it worked very well. Much clearer, quieter sound. Much like a T.C. Electronics.
You can get them from Mouser Electronics for about .60 each.
|11/25/1998 6:44 PM|
One thing you have to watch with the LM833 and the 5532 is the low input Z (especially on the latter)
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