Well, these might be candidates:Mooly said:
LTC6014 145uA / 9.5 nV/rt-Hz
OP2177 500uA / 8 nV/rt-Hz
OP727 290 uA / 15 nV/rt-Hz
Hi,
As I hinted earlier, I don't think the OpAmp is the problem really. If you just unsolder one leg of C2 and see if the hiss drops away it will prove whether it is the IC and tone circuit or if it is noise from the FET that is being amplified. You have to do this to see 🙂
Is the IC in a socket or not ?
Noise is very subjective and whats normal or not is hard to describe.
I must admit I was under the impression it was a commercial unit and ready built. Is it one you have copied ?
Unfortunately with OpAmps the "raw" noise figure doesn't tell the whole story. The surrounding impedances seen by the OpAmp inputs have much more effect. It's an extremely complex issue to analyse. If you are not convinced just drop a TL072 or a NE5532 in to prove to yourself.
As I hinted earlier, I don't think the OpAmp is the problem really. If you just unsolder one leg of C2 and see if the hiss drops away it will prove whether it is the IC and tone circuit or if it is noise from the FET that is being amplified. You have to do this to see 🙂
Is the IC in a socket or not ?
Noise is very subjective and whats normal or not is hard to describe.
I must admit I was under the impression it was a commercial unit and ready built. Is it one you have copied ?
Unfortunately with OpAmps the "raw" noise figure doesn't tell the whole story. The surrounding impedances seen by the OpAmp inputs have much more effect. It's an extremely complex issue to analyse. If you are not convinced just drop a TL072 or a NE5532 in to prove to yourself.
Hello Markus,
Sorry not ignoring you, some of your comments were a bit strange thats all such as whats VCC and VCC/2 etc 🙂
Sorry not ignoring you, some of your comments were a bit strange thats all such as whats VCC and VCC/2 etc 🙂
I was just refering to inconsistant net names labels. The +9V rail is marked on the schematic as Vcc and Vdd. And the gate of the input JFET is connected to Vcc/2 instead of ground. But of course this doesn't matter much to the noise.
Mark
Mark
It is a standard Ibanez preamp installed in a relatively cheap Ibanez bass guitar.
That's a great suggestion and trivial to try. I've got some 5532s around here someplace. If there is no improvement I may just bypass the active EQ altogether and go passive, or perhaps add a simple FET buffer.Mooly said:
I actually was a baseband designer once. I was several years younger and more than a few pounds lighter (mid eighties).
part of the problem with using a TL072 or NE5532 in this circuit is that they have to operate from +/- 4.5V rails. the TL062 can operate at +/- 2V rails (battery voltage 4V), the TL072 down to +/- 3.5V (battery voltage 7V), and the NE5532 works down to +/- 3V (battery voltage 6V). that's a rather large difference running from a 9V battery. you have a 5V battery margin with the TL062 (subtract minimum operating voltage from original battery voltage), a 3V margin with the NE5532, and only a 2V margin with the TL072. plus you have to contend with 8mA quiescent current for the NE5532, and 1mA for the TL072 against less than 500uA for the TL062. the battery life with the TL062 will be 5 times as long as the TL072, and at least 18 times as long as the NE5532.
you can use a "quick and dirty" method to calculate a battery life "fudge factor". take the margin voltage and divide it by the operating current. the higher the ratio, the longer the battery life.
you can use a "quick and dirty" method to calculate a battery life "fudge factor". take the margin voltage and divide it by the operating current. the higher the ratio, the longer the battery life.
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