Electric bass preamp.
TL062 is a dual, DIP-8 pkg.
Iq <= 500 uA/section approx
en <= 40 nV/rt-hz
I can make a SOIC-8 package fit if I have to.
TL062 is a dual, DIP-8 pkg.
Iq <= 500 uA/section approx
en <= 40 nV/rt-hz
I can make a SOIC-8 package fit if I have to.
Pretty well all drop-in substitutions will draw more current. If, as I suspect, this is an onboard preamp substitution will cost battery life.
For onboard preamp FET amplifier would be better choice than op-amp, but I guess it doesn't satisfy you at all. Low noise and low current, look at analog devices op-amps like OP297, but it has very low slew rate.
BTW: what was the question? Now I'm a bit confused... are you looking for substitusion?
Peace!
TH.J.B
BTW: what was the question? Now I'm a bit confused... are you looking for substitusion?
Peace!
TH.J.B
if this is a line powered unit, TL072,TL082, LF353, or any standard dual op amp will work. if it's battery powered, you will want to find a low power op amp as a replacement. TL062's are a very common item, and most suppliers should carry them (and they should be relatively cheap).
Re: Re: TL062 replacement recommendation
I usually thought of the TL072 as a reasonably low current device, I wouldn't think you'll lose that much battery life (or to a point that it becomes an excessive use of batteries).
Also an option...😎
I usually thought of the TL072 as a reasonably low current device, I wouldn't think you'll lose that much battery life (or to a point that it becomes an excessive use of batteries).
Brett said:
Also an option...😎
Sorry for not including the reason for wanting the replacement suggestion. This is a 9V battery powered, bass guitar on-board preamp and it is noisy. It is a typical three-band fixed tuned unit with two stages.
http://www.bellsouthpwp.net/n/4/n4ocb/misc_images/sr480_preamp.jpg
Looking at the offerings from Linear Tech and Analog Devices, it appears that low noise and low current consumption do not go together too well.
http://www.bellsouthpwp.net/n/4/n4ocb/misc_images/sr480_preamp.jpg
Looking at the offerings from Linear Tech and Analog Devices, it appears that low noise and low current consumption do not go together too well.
Choice is limited due to supply. Do you mean noise as in hiss ? If you remove C2 does the noise go ? A TLO62 shouldn't be that noisy -- true it's not the ultimate but noisy -no.
Should have said removing C2 will help prove whether the noise is "front end" ie the FET or not. The FET is just connected as a simple buffer or source follower. You can get noisy FET's .
Yes. Quite noticable as the treble control is rotated.Mooly said:
I hadn't thought of the FET. Rather than removing the FET I may consider lowering the gate bias enough to cut the FET off. Think that would do it?
sreten said:
not so.... the TL072 came first. the TL062 is a "redesign" of the TL072 for lower supply current and voltage. looking at the internal schematics, i can see that there are several things that are different between the two. the TL062 has added circuits, such as a totem pole current source for the input stage, a simplified current mirror, a better current source for the VAS, and adaptive bias for the output stage. the voltage reference for the input current source has extra circuits added to improve low voltage and current operation. look up the TI datasheets for both at www.datasheetarchive.com and you will see what i mean....
Hi,
Remove C2 just to see what happens. So easy and no room for error doing that.
I see on the circuit at the input to the FET is a "link"-- SW--EQ in. Is anything connected between here, or are you running it as shown with the link in place.
elseif said:
Remove C2 just to see what happens. So easy and no room for error doing that.
I see on the circuit at the input to the FET is a "link"-- SW--EQ in. Is anything connected between here, or are you running it as shown with the link in place.
Elseif,
I'm sorry to say that but there are many mistakes in the preamp design. And this is the main reason for the preamp being noisy. It's a pitty that you are looking for less noisy opamp instead of looking at the preamp's design.
Starting from the beginning:
1. You should think whether supply voltages are correct. What exactly are VCC, VCC/2 and VDD? Isn't VCC the same as VDD?
2. I'm not sure why R2 has so small value and it is conected to VCC/2? The value should be rather something like: 1M, 2.2M and the resistor should be connected to ground. R1 should be removed unless you just want to discharge C1 with it. You should also specify which JFET you are going to use. I think that J201 will work OK in this design.
3. C2 is way too high. The preamp will work exactly in the same way if you decrease it to 10uF. And the capacitor cannot be removed because this would connect JFET directly to input pin of
opamp.
4. The tone stack is typical (or it isn't?) Baxandall tone stack. It's rather unusual because it's not linear when you put pots in the middle position. And what is the most painful: the gain for high frequencies is almost 20dB. Typical gain in this case should be between 12 and 15dB. The tone stack is definitely designed incorrectly.
5. The Mid filter is quite nice - it is setup to something like 480Hz and it has boost of about 8dB.
6. The R13 resistor (2k2) and C8 capacitor (15n) connected to the ground are completely wrong. You are just cutting high freqencies to ground. Is it intentionally?
So I suggest first to fix the design of the preamp and only later to look for a good opamp. In my opinion TL072 is OK.
Mark
I'm sorry to say that but there are many mistakes in the preamp design. And this is the main reason for the preamp being noisy. It's a pitty that you are looking for less noisy opamp instead of looking at the preamp's design.
Starting from the beginning:
1. You should think whether supply voltages are correct. What exactly are VCC, VCC/2 and VDD? Isn't VCC the same as VDD?
2. I'm not sure why R2 has so small value and it is conected to VCC/2? The value should be rather something like: 1M, 2.2M and the resistor should be connected to ground. R1 should be removed unless you just want to discharge C1 with it. You should also specify which JFET you are going to use. I think that J201 will work OK in this design.
3. C2 is way too high. The preamp will work exactly in the same way if you decrease it to 10uF. And the capacitor cannot be removed because this would connect JFET directly to input pin of
opamp.
4. The tone stack is typical (or it isn't?) Baxandall tone stack. It's rather unusual because it's not linear when you put pots in the middle position. And what is the most painful: the gain for high frequencies is almost 20dB. Typical gain in this case should be between 12 and 15dB. The tone stack is definitely designed incorrectly.
5. The Mid filter is quite nice - it is setup to something like 480Hz and it has boost of about 8dB.
6. The R13 resistor (2k2) and C8 capacitor (15n) connected to the ground are completely wrong. You are just cutting high freqencies to ground. Is it intentionally?
So I suggest first to fix the design of the preamp and only later to look for a good opamp. In my opinion TL072 is OK.
Mark
Another issue, which should be considered when tackling with the preamp is that it has gain < 1 
.
Mark
.Mark
I did not design the preamp. I transcribed it. It came with the bass and I don't care enough about the problem to redesign it. I was just asking about an op-amp. 😉Markus2006 said:
Elseif,
I'd say that it is possible that you made a mistake where reverse-engeneering the preamp. At least the output resistor and capacitor have incorrect values (double check whether the values are as on the schematic).
What I'm trying to say is that noise in this preamp is "by design". Changing the opamp may improve the results but only slightly. So the efforts (replacing the opamp) are not worth it. But you may correct the preamp easily (if this is not SMD version). Mainly the tone stack needs small adjustments. If the output resistor and capacitor are really 2k2 and 15n, I would just remove them.
If you are looking for a replacement for the opamp, you may consider OP282 (it's SMD version). It's often used in similar preamps. Or, as it was mentioned, NE5532.
Mark
I'd say that it is possible that you made a mistake where reverse-engeneering the preamp. At least the output resistor and capacitor have incorrect values (double check whether the values are as on the schematic).
What I'm trying to say is that noise in this preamp is "by design". Changing the opamp may improve the results but only slightly. So the efforts (replacing the opamp) are not worth it. But you may correct the preamp easily (if this is not SMD version). Mainly the tone stack needs small adjustments. If the output resistor and capacitor are really 2k2 and 15n, I would just remove them.
If you are looking for a replacement for the opamp, you may consider OP282 (it's SMD version). It's often used in similar preamps. Or, as it was mentioned, NE5532.
Mark
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