Hi everybody,
i want to design a sla battery driven active mono crossover.
i attached a circuit diagram below, i guess you can see from that what i'm going to do.
i want to use sallen-key topology with butterworth characteristic because of the obvious advantages.
single supply is kind of a problem especially with the low-pass.
maybe i should use mfb-design instead?
what i did:
input buffers
- does it work like that with single supply?
- from what i understand i create a virtual gnd in that stage. i needed that when i only did the low-pass. does it make sense like that?
adder
- i already used exactly that adder, but never with single supply
high-pass
- that high-pass usually works with single supply, but i have no idea if it makes sense together with the input buffer (vcc/2 and so on)
low-pass
- ?
other
- is an output-buffer necessary?
here is the diagram.
i tuned the r for 150hz crossover-frequency.
this my first ever attempt with this prog.
the ic are not named correctly and may have done a bunch of other mistake.
but i'm here to learn.
i want to design a sla battery driven active mono crossover.
i attached a circuit diagram below, i guess you can see from that what i'm going to do.
i want to use sallen-key topology with butterworth characteristic because of the obvious advantages.
single supply is kind of a problem especially with the low-pass.
maybe i should use mfb-design instead?
what i did:
input buffers
- does it work like that with single supply?
- from what i understand i create a virtual gnd in that stage. i needed that when i only did the low-pass. does it make sense like that?
adder
- i already used exactly that adder, but never with single supply
high-pass
- that high-pass usually works with single supply, but i have no idea if it makes sense together with the input buffer (vcc/2 and so on)
low-pass
- ?
other
- is an output-buffer necessary?
here is the diagram.
i tuned the r for 150hz crossover-frequency.
this my first ever attempt with this prog.
the ic are not named correctly and may have done a bunch of other mistake.
but i'm here to learn.
You have a few errors.
1) The input buffers are OK.
2) IC1A has the opamp inputs reversed.
3) R11 and R13 need to go to the opamp + inputs.
Instead of a resistive divider for biasing, why not have one stable reference. It doesn't have to be exactly VCC/2 either. Take your supply voltage and divide it by 2, then pick a zener closest to that value. Use the zener plus a resistor and decoupling cap to create a clean and stable reference. Then use a single resistor to each opamp that needs biasing.
1) The input buffers are OK.
2) IC1A has the opamp inputs reversed.
3) R11 and R13 need to go to the opamp + inputs.
Instead of a resistive divider for biasing, why not have one stable reference. It doesn't have to be exactly VCC/2 either. Take your supply voltage and divide it by 2, then pick a zener closest to that value. Use the zener plus a resistor and decoupling cap to create a clean and stable reference. Then use a single resistor to each opamp that needs biasing.
thank you very much.
i was a little hasty to upload this, so i even did the s-k-topology wrong.
and i also messed up the values of a few resistors.
your advice with the zener and not directly using vcc/2 is good news to me.
the perfect fit for the rest of the setup would be using three of the 6v sla batteries.
when the are fully charged, their are something around 6.8v and use them until they reach 5.8v or 5.7v volt.
the 100uF cap should be an elko?
i was a little hasty to upload this, so i even did the s-k-topology wrong.
and i also messed up the values of a few resistors.
your advice with the zener and not directly using vcc/2 is good news to me.
the perfect fit for the rest of the setup would be using three of the 6v sla batteries.
when the are fully charged, their are something around 6.8v and use them until they reach 5.8v or 5.7v volt.
the 100uF cap should be an elko?
Yes electrolytics in the power supply are traditional. You can buy 10000 hour service life rated ones at farnell.com or mouser.com, farnell has the hours service life in the selector table. I hate changing e-caps over and over, I've done the ones in my ST70 tube amp 4 times.
I use two 1n5344 8.2 zeners and two resistors (typically 33 ohm) to make a split supply with about even characteristics. The signal ground is the middle of the two zeners. The plus and minus supplies of the op amps are the top and bottom of the two zeners, not the actual supply from the battery/transformer. You don't need three 6v batteries if you can get something like an 18 VDC wall transformer for a battery hedge clipper or race car. I paid $1 for mine at the charity resale shop. I'm using an 18v wall transformer with the two 8.2 v 1n5344's for my disco mixer. I use two capacitors, one across each zener diode. then if my op amps are faster than 5322 I use a ceramic 10 nf cap near each one. Lots of op amp kits like tubelab don't have holes for the electrolytic or ceramic caps.
Please Mooly, I've had a protection circuit up on PA amps thread for a couple of days, you mind taking a look? PV-1.3k vs PV2000? Sorry Buehgemeiste, this has nothing to do with your circuit.
I use two 1n5344 8.2 zeners and two resistors (typically 33 ohm) to make a split supply with about even characteristics. The signal ground is the middle of the two zeners. The plus and minus supplies of the op amps are the top and bottom of the two zeners, not the actual supply from the battery/transformer. You don't need three 6v batteries if you can get something like an 18 VDC wall transformer for a battery hedge clipper or race car. I paid $1 for mine at the charity resale shop. I'm using an 18v wall transformer with the two 8.2 v 1n5344's for my disco mixer. I use two capacitors, one across each zener diode. then if my op amps are faster than 5322 I use a ceramic 10 nf cap near each one. Lots of op amp kits like tubelab don't have holes for the electrolytic or ceramic caps.
Please Mooly, I've had a protection circuit up on PA amps thread for a couple of days, you mind taking a look? PV-1.3k vs PV2000? Sorry Buehgemeiste, this has nothing to do with your circuit.
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i hope my question isnt a lot out of topic. in order to drive two different amplifiers with the same signal i designed the schematic below..should i add an input filter at the first opamp? and regarding the two buffers,will they be ok like this or it would be better to add some resistors and compensation caps even if they are stated to be unity gain stable?
Attachments
Basic error on the first opamp. No DC bias reference on the non inverting input needs and input resistor to ground the value of which will define Rin)
Input filters are generally regarded as a good thing although actual real world use has to be taken into account. In other words is it in a "noisy" environment and/or is it being fed from a source that could have noise/hash present.
Unity gain buffers are fine as they are... big question is whether or not they do "sound" better running away from unity gain. I don't as yet have a definitive answer to that but its worth a try.
Input filters are generally regarded as a good thing although actual real world use has to be taken into account. In other words is it in a "noisy" environment and/or is it being fed from a source that could have noise/hash present.
Unity gain buffers are fine as they are... big question is whether or not they do "sound" better running away from unity gain. I don't as yet have a definitive answer to that but its worth a try.
the problem is that the circuit is for a friend of mine and has a lot of unused ne5532 and we think of using 6 of them for a stereo version. i remember most of your advice you gave me in my other threads. So... A better improve over the last one. is attached below.. what do you say?....other wise we can use a tl074 and a tl072 to make a stereo version...
Attachments
wow, this thread got hijacked.
we noobs need more constructive comments on our noobish projects.
some jumped at the opportunity.
i think i will have to add some kind of output-buffer to my circuit.
but at first i want to get the power supply working as it should.
i have a 9.1V-zener rated for 1W and a 100uF elko rated for 50V.
i guess i must somehow approximate the maximum current to calculate the resistor.
considering that it is likely that i will add another opamp and the fact that i also got a set of tl071 opamps, what is a good approximation for the current?
is the difference in the power consumption between ne5532 and tl071 marginal?
on the cheapo-breadboard i hear no difference so maybe i would like to switch between those two when everything is soldered.
(i also have some tl062 in my slowly growing stock, but i guess they will not fit circuit.)
is it right to calculate the resistor like this:
R=(U-Uz)/I
?
we noobs need more constructive comments on our noobish projects.
some jumped at the opportunity.
i think i will have to add some kind of output-buffer to my circuit.
but at first i want to get the power supply working as it should.
i have a 9.1V-zener rated for 1W and a 100uF elko rated for 50V.
i guess i must somehow approximate the maximum current to calculate the resistor.
considering that it is likely that i will add another opamp and the fact that i also got a set of tl071 opamps, what is a good approximation for the current?
is the difference in the power consumption between ne5532 and tl071 marginal?
on the cheapo-breadboard i hear no difference so maybe i would like to switch between those two when everything is soldered.
(i also have some tl062 in my slowly growing stock, but i guess they will not fit circuit.)
is it right to calculate the resistor like this:
R=(U-Uz)/I
?
Yes, the resistor is easily calculated in this case because the opamp inputs draw negligable current. So you have a 9 volt zener and I assume around an 18 to 20 volt supply. Something in the region of a 4k7 would be fine and allow a couple of ma zener current.
The 5532 is far more power hungry than a TL072 (the TL071 is a single). For a couple of opamps it may not matter but for a mixing console that say used 100 opamps, the difference between 3 or 4 millamps per opamp and perhaps 12 to 15 milliamps per opamp adds up.
The TL062 will certainly work but it is really for low power consumption applications and it also has a poorer spec, particularly at hf.
You don't really need separate buffers, the final opamps as they stand serve that purpose.
Edit... yes, your formula is correct because the opamps take essentially no current from the zener supply. If they did then you would have to allow for that in the calculation such that there was always a small zener curren flowing.
The 5532 is far more power hungry than a TL072 (the TL071 is a single). For a couple of opamps it may not matter but for a mixing console that say used 100 opamps, the difference between 3 or 4 millamps per opamp and perhaps 12 to 15 milliamps per opamp adds up.
The TL062 will certainly work but it is really for low power consumption applications and it also has a poorer spec, particularly at hf.
You don't really need separate buffers, the final opamps as they stand serve that purpose.
Edit... yes, your formula is correct because the opamps take essentially no current from the zener supply. If they did then you would have to allow for that in the calculation such that there was always a small zener curren flowing.
i have found the following in the datasheets:
ne5532:
Icc= 8mA (typical) to 16mA (max)
tl071:
Icc= 1.4mA (typical) to 2.5mA (max)
considering the formula above is right, this gives the values:
Rv:
1. for typical consumption:
1.1 almost empty batteries
ne5532: 1kOhm
tl071: 5.6kOhm
1.2 fully charged sla
ne5532: 1.5kOhm
tl071: 8.2kOhm
2. max consumption
2.1 almost empty batteries
ne5532: 500Ohm
tl071: 3.3kOhm
2.2 fully charged sla
ne5532: 750Ohm
tl071: 4.7kOhm
looks like a bad idea to switch between those two.
i´m still not sure which resistor to pick.
ne5532:
Icc= 8mA (typical) to 16mA (max)
tl071:
Icc= 1.4mA (typical) to 2.5mA (max)
considering the formula above is right, this gives the values:
Rv:
1. for typical consumption:
1.1 almost empty batteries
ne5532: 1kOhm
tl071: 5.6kOhm
1.2 fully charged sla
ne5532: 1.5kOhm
tl071: 8.2kOhm
2. max consumption
2.1 almost empty batteries
ne5532: 500Ohm
tl071: 3.3kOhm
2.2 fully charged sla
ne5532: 750Ohm
tl071: 4.7kOhm
looks like a bad idea to switch between those two.
i´m still not sure which resistor to pick.
As a noob,you can always learn new things and enrich your knowledge from other peoples' questions that happen to be quite relevant with the subject of your thread.
I am using LTspice IV. It is free.You can not only draw a circuit but also simulate it. You can find it here : http://www.linear.com/designtools/software/#LTspice
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The current consumption of the opamp has no bearing on the zener current... I think you see that now All that matters is the current drawn from the 9.1 volt reference, and that is negligable.
The ground is an interesting point.
You can call the zener voltage (the 9.1 volts) ground and treat the circuit as DC coupled running with a virual ground as if it were a dual supply or, use the supply 0 volts as ground and treat it just as a normal AC coupled single ended circuit... and I think that would be my choice tbh. Both will work though.
All that matters is the current drawn from the 9.1 volt reference, and that is negligable. The ground is an interesting point.
You can call the zener voltage (the 9.1 volts) ground and treat the circuit as DC coupled running with a virual ground as if it were a dual supply or, use the supply 0 volts as ground and treat it just as a normal AC coupled single ended circuit... and I think that would be my choice tbh. Both will work though.
dammit i have no 4.7k resistor.
for now i will try two 2.2k.
i won't have too much time this week.
but i will try to get this forward, because when i have more time i'm going to build some speakers.
i'll give the LTspice software a try.
and i have a few questions about parts.
opamps:
tl07x and ne5532 seem both to be quite satisfying for audio.
tl07x has higher impendance.
would it make sense to use the tl071 for the input-buffers and the 5532 for the filters?
or is it bad to have different opamps in one circuit?
caps:
my local store had only wima mks4 1uF.
is that a very bad choice?
for the filters i have two different types of 0.1uF mkp.
is mkp the way to go (i know i can always pay more. i have also seen the 20€ capacitors from siemens.)?
i worry about the mks4, because they are rated with 20% tolerance.
for now i will try two 2.2k.
i won't have too much time this week.
but i will try to get this forward, because when i have more time i'm going to build some speakers.
i'll give the LTspice software a try.
and i have a few questions about parts.
opamps:
tl07x and ne5532 seem both to be quite satisfying for audio.
tl07x has higher impendance.
would it make sense to use the tl071 for the input-buffers and the 5532 for the filters?
or is it bad to have different opamps in one circuit?
caps:
my local store had only wima mks4 1uF.
is that a very bad choice?
for the filters i have two different types of 0.1uF mkp.
is mkp the way to go (i know i can always pay more. i have also seen the 20€ capacitors from siemens.)?
i worry about the mks4, because they are rated with 20% tolerance.
The resistor is very non critical. 1k, 10k, anything in between. All will work.
Both TL072 and NE5532 are good for audio. The NE5532 has better output capability so would be a better choice for the filter, the FET based TL072 has better imunity to rf and would be good for the input stages. Mixing opamp types is no problem, use them according to their strengths. 20% tolerance on caps for a fliter like this isn't an issue in practice. Its not as if you are making a high Q notch filter or anything like that.
Just one thought, and it depends how far you have gone into constructing all this, would be to make the first two stages inverting and to use a proper "virtual earth" mixer for summing the channels.
Both TL072 and NE5532 are good for audio. The NE5532 has better output capability so would be a better choice for the filter, the FET based TL072 has better imunity to rf and would be good for the input stages. Mixing opamp types is no problem, use them according to their strengths. 20% tolerance on caps for a fliter like this isn't an issue in practice. Its not as if you are making a high Q notch filter or anything like that.
Just one thought, and it depends how far you have gone into constructing all this, would be to make the first two stages inverting and to use a proper "virtual earth" mixer for summing the channels.
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