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Electronics Forum / Electronics / July 2008LM741 opamp substitute?
Greetings, I am hoping to replace the somewhat dated LM741 opamps in an old 1970s PKE phono preamp. There are 3 in each channel (6 total). I can post a close-up pic of the circuit board to anyone who may be happy to comment specifically. I am hoping to apply a drop-in solution if possible, but understand that this may not be preferable. Many thanks, Stephen "langleycello" > I am hoping to replace the somewhat dated LM741 opamps in an old 1970s > PKE phono preamp. There are 3 in each channel (6 total). I can post a > close-up pic of the circuit board to anyone who may be happy to comment > specifically. I am hoping to apply a drop-in solution if possible, but > understand that this may not be preferable. ** The nearest * readily available * op-amp to replace the venerable LM741 in most audio applications is the TL071. It is indeed pin for pin and a drop in replacement - much more bandwidth & slew rate but very similar noise level to the 741. Need to see a schematic to exclude any ( not very likely ) issues with the substitution. ....... Phil > Greetings, > [quoted text clipped - 7 lines] > > Stephen PKE are still active, why not ask them ? Rheilly P > > Greetings, > > [quoted text clipped - 10 lines] > PKE are still active, why not ask them ? > Rheilly P Yes, I have, but they no longer have the available info. Thanks Phil for your suggestion. For the sake of it, I include some photobucket URLs of one phono card (back and front) which may cast some extra light on things, in the absence of a schematic. http://i16.photobucket.com/albums/b17/langleycello/IMG_2144-1.jpg http://i16.photobucket.com/albums/b17/langleycello/IMG_2145-1.jpg Cheers, Stephen "langleycello" > Thanks Phil for your suggestion. ** " Lament of the 741 " Why substitute me for another type ? Have you all fallen for a load of hype ? I look pretty small but my pins are high The simple specs you see are all complicated I may be pretty old but I'm not outdated - yeah ... Note: The uA741 first appeared in May of 1968 - it was very expensive. The TL071 first appeared in July of 1977 - it was dirt cheap. ....... Phil <snip> > For the sake of it, I include some photobucket URLs of one phono card > (back and front) which may cast some extra light on things, in the [quoted text clipped - 3 lines] > > http://i16.photobucket.com/albums/b17/langleycello/IMG_2145-1.jpg The circuit is easily traced in order to create a schematic. From there you should be able to update the circuit. > Greetings, > [quoted text clipped - 3 lines] > specifically. I am hoping to apply a drop-in solution if possible, but > understand that this may not be preferable. **Assuming no oddball circuit highlights, the OPA604 will do nicely. If you want to take it further, the AD825 (a carrier PBC will be required) will be (slightly) better again.  SignatureTrevor Wilson www.rageaudio.com.au -- Posted via a free Usenet account from http://www.teranews.com Thanks everyone for your thoughts, I'll get some 8-pin sockets and opt for a flexible arrangement. Maybe I'll first experiment with some TL071s, which hopefully should be OK as an immediate drop in, and then perhaps the OPA604 down the track. Cheers, Stephen "langleycello" > Thanks everyone for your thoughts, > > I'll get some 8-pin sockets and opt for a flexible arrangement. Maybe > I'll first experiment with some TL071s, which hopefully should be OK as > an immediate drop in, and then perhaps the OPA604 down the track. ** Another low cost & readily available op-amp type that ought not be ignored is the very famous NE5534P - available from DSE and many others. It will likely require a 33pF capacitor between pins 5 and 8 to be " unity gain stable " - as the 741 is inherently. According to my ( not inconsiderable) experience and also that of renound pommy audio expert Doug Self, the NE5534 is the lowest noise, best performing MM phono stage op-amp available. ( MM = moving magnet = high impedance = 47 kohms) ........ Phil > Thanks everyone for your thoughts, > > I'll get some 8-pin sockets and opt for a flexible arrangement. Maybe > I'll first experiment with some TL071s, which hopefully should be OK as > an immediate drop in, and then perhaps the OPA604 down the track. **Just a point: With the OPA604 and most other replacement chips (the 5534 is notorious in this regard), you need to ensure that the supply rails are up to the task. Most other chips consume considerably more current than the 741, although, in absolute terms, we're not talking about a great deal of current. SignatureTrevor Wilson www.rageaudio.com.au -- Posted via a free Usenet account from http://www.teranews.com > I am hoping to replace the somewhat dated LM741 opamps in an old 1970s > PKE phono preamp. There are 3 in each channel (6 total). I can post a > close-up pic of the circuit board to anyone who may be happy to comment > specifically. I am hoping to apply a drop-in solution if possible, but > understand that this may not be preferable. Whats wrong with the 741? If it aint broke, dont fix it! >> I am hoping to replace the somewhat dated LM741 opamps in an old 1970s >> PKE phono preamp. There are 3 in each channel (6 total). I can post a [quoted text clipped - 3 lines] > > Whats wrong with the 741? **Let's see: * It's noisy * It has a crappy slew rate. * There are other, audibly superior devices available. 741s should be removed from almost ANY product which uses them. They work fine at or near DC, however. > If it aint broke, dont fix it! **The 741 is already broke. SignatureTrevor Wilson www.rageaudio.com.au -- Posted via a free Usenet account from http://www.teranews.com "Trevor Wilson" > "Two Bob" >> >> Whats wrong with the 741? ** Big mistake asking Australia's most notorious audiophool plus hi-fi dealer vampire. > * It's noisy ** EIN = 3 uV ( in 20 kHz bandwidth ) Signal to noise = 110 dB ( unweighted) relative to 1 volt at unity gain. > * It has a crappy slew rate. ** An ignorant audiophool opinion TW gets to keep. > * There are other, audibly superior devices available. ** Another ignorant audiophool opinion TW gets to keep. > 741s should be removed from almost ANY product which uses them. ** An ignorant audiophool opinion TW gets to keep. > They work fine at or near DC, however. ** Yawn - all totally irrelevant. >> If it aint broke, dont fix it! > > **The 741 is already broke. ** An ignorant audiophool opinion TW gets to keep. > Trevor Wilson > www.rageaudio.com.au ** Do look at the vampire's lair. ....... Phil >>> I am hoping to replace the somewhat dated LM741 opamps in an old 1970s >>> PKE phono preamp. There are 3 in each channel (6 total). I can post a [quoted text clipped - 14 lines] > > **The 741 is already broke. Geez - now I understand why the ACS demodulator kit (EA 1993) doesn't sound so crash hot. I shouldn't have used a 741 to do the de-emphasis! ;-) Bob Sorry about resurrecting such an old thread, but I am looking for a couple of LM741CN op amps made in the 1970's. Used is OK as long as they function. Anyone know a source or the model number of the PKE device mentioned in this thread? Thanks >Greetings, > [quoted text clipped - 7 lines] > >Stephen |
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