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Just bought another op amp

The LME49720 is also worth a try, you might want to bypass the supply pins with say 100nf on the back of the PCB, keep the leads as short as you can.
 
My friend Si has just bought a load from Farnell (he buys these these quite regularly) and unfortunately they are clearly fakes - so buying from Farnell is no guarantee the product is genuine I'm afraid.
 
YNWOAN said:
My friend Si has just bought a load from Farnell (he buys these these quite regularly) and unfortunately they are clearly fakes - so buying from Farnell is no guarantee the product is genuine I'm afraid.
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So who is the Bur brown one made by because from Mouser and farnell borh have it listec at about £26 each and made by Texas?
 
YNWOAN said:
My friend Si has just bought a load from Farnell (he buys these these quite regularly) and unfortunately they are clearly fakes - so buying from Farnell is no guarantee the product is genuine I'm afraid.
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Big distributors like Farnell go direct to the chip makers, so fakes are hard to get into their systems. There haven't been any BB devices made by BB since they were taken over by TI many years ago. The TI parts are genuine
 
Sorry guys but I only know what I was told, but Si did mention a number of differences that led him to believe they were fakes (poor print alignment etc).
 
Well, I'm now starting to wonder if I bought the right thing!

There is only 1 8 pin opamp in the MF A308 pre amp and it's very close to the phono stage. I can see no other opamp although all the MF Integrated amps have a 16 pin chip on the PCB??
 
Do you have the circuit diagram? It'd be very handy to know what role each part you're proposing to change does in the circuit before you dive in there. And don't change too much at once, or you won't know what did what. I find restraint hard....
 
Also need to know the supply rails. Some amplifiers use very high rails, that limit the choice of alternative parts
 
Replacing a 5532 with a dual OPA627 needs careful thought, the 5532 implemented properly is a formidable device, its widely used, along with its sibling the 5534, in mixing desks and musical products, so most of the music you listen to will have passed through one anyway. The OPA627 is a better specced device but its high band with make it sensitive to layout and decoupling, the 627 should really only be used if you have a top notch power supply and supporting circuitry but if you have that then the 5532 sounds good as well, LFD audio use the 5534 in their products and they seem highly thought of.
 
Putting opa627s in an DIP adaptor alone is a wasteful mess, owing to the high bandwidth and unneccessarily-increased loop area to the supply decoupling this fast amplifier part needs. Putting two such, on an 8pin DIP and suggesting such is a drop-in replacement is laughable for several wrong reasons. The result will be very, very unhappy, for reasons russel outlines.

A well-implemented NE5532 is hard to beat still in many existing circuits - not least because the 4nV/rt (hz) noise performance is still below most stray contributions in the ciruits it is usually used in, and the slew rate/distortion performance when fed from real-world source impedances remains way more than 'good enough'.

However one little wrinkle though that is missed for the NE553x has been identified by Doug Self in print: regardless of other psu/stability measures, 100nF (film) directly across the NE5532/34 power pins (4 and 8) with shortest-possible lead connections directly (and ocasionally, greatly) helps the NE5532's distortion performance. You rarely see this suggested on schematics.

That's a lot cheaper to try first than a badly-implemented pair of opa627s ..!
 
martin clark said:
Putting opa627s in an DIP adaptor alone is a wasteful mess, owing to the high bandwidth and unneccessarily-increased loop area to the supply decoupling this fast amplifier part needs. Putting two such, on an 8pin DIP and suggesting such is a drop-in replacement is laughable for several wrong reasons. The result will be very, very unhappy, for reasons russel outlines.

A well-implemented NE5532 is hard to beat still in many existing circuits - not least because the 4nV/rt (hz) noise performance is still below most stray contributions in the ciruits it is usually used in, and the slew rate/distortion performance when fed from real-world source impedances remains way more than 'good enough'.

However one little wrinkle though that is missed for the NE553x has been identified by Doug Self in print: regardless of other psu/stability measures, 100nF (film) directly across the NE5532/34 power pins (4 and 7) with shortest-possible lead connections directly (and ocasionally, greatly) helps the NE5532's distortion performance. You rarely see this suggested on schematics.

That's a lot cheaper to try first than a badly-implemented pair of opa627s ..!
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Not going to argue with any of that except it's pins 4 and 8 that should be bypassed, pin 7 is out not supply
 
+1 to Martin's post. When ibfirst started this DIY thing I spent time blindly opamp rolling and using adapter. Never a fig of positive outcome and occasionally an unstable device that sounded crappier. The circuit is designed around the intended part.
 
orangeart said:
+1 to Martin's post. When ibfirst started this DIY thing I spent time blindly opamp rolling and using adapter. Never a fig of positive outcome and occasionally an unstable device that sounded crappier. The circuit is designed around the intended part.
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Although it can work. Sometimes. My active crossover (DIY Ben Duncan design) started with TL071s, IIRC, changed to NE5534s were it stayed for many years, and then I rolled various opamps, including OPA627s, before settling on AD825s. I'm happy with those, but it took some time and effort.
 
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