Hi guys, I'm new here, I hope this is the right place to post this.
I'm wanting to get into making some mixers (a matrix mixer and a more standard 4-channel mixer with EQ).
I have already put together a few guitar pedal kits and have been simulating circuits on LTSpice for a while now to learn the basic concepts.
I feel like I'm now ready to move on to experimenting with real components.
I have two topics I'd like to clear some things up on though before I start ordering stuff.
First, What do you guys use to power your active and opamp circuits? I was considering purchasing this: STONTRONICS - S2263ST - AC-DC LINEAR PSU, 24V 400MA UNIVERSL | eBay and going single supply but am not sure if this has enough current to power opamps/lots of LEDS and potentiometers(64 for the matrix mixer) etc.
I also have an ATX supply if that would be better (though I'm not sure if it's safe with the amount of current those things pump out).
Secondly, from reading Small Signal Audio Design by Douglas Self I understand that NE5532 is a good choice of opamp throughout the mixer. Is this correct?
As mentioned I plan on making active summing, gain and EQ circuits though when making preamps I want them to be able to accept any signal from a guitar pickup to a piezo and even a dynamic microphone, I've heard JFET based opamps might be better for this stage because of their input impedance? Is TL072 good for this or is it too old and noisy? Also is it plausible to have a 'one size fits most' preamp?
I'm sure there will be many more questions along my journey but could really do with some advice so I can start making informed purchases of components and avoid obvious beginner mistakes.
Thanks.
I'm wanting to get into making some mixers (a matrix mixer and a more standard 4-channel mixer with EQ).
I have already put together a few guitar pedal kits and have been simulating circuits on LTSpice for a while now to learn the basic concepts.
I feel like I'm now ready to move on to experimenting with real components.
I have two topics I'd like to clear some things up on though before I start ordering stuff.
First, What do you guys use to power your active and opamp circuits? I was considering purchasing this: STONTRONICS - S2263ST - AC-DC LINEAR PSU, 24V 400MA UNIVERSL | eBay and going single supply but am not sure if this has enough current to power opamps/lots of LEDS and potentiometers(64 for the matrix mixer) etc.
I also have an ATX supply if that would be better (though I'm not sure if it's safe with the amount of current those things pump out).
Secondly, from reading Small Signal Audio Design by Douglas Self I understand that NE5532 is a good choice of opamp throughout the mixer. Is this correct?
As mentioned I plan on making active summing, gain and EQ circuits though when making preamps I want them to be able to accept any signal from a guitar pickup to a piezo and even a dynamic microphone, I've heard JFET based opamps might be better for this stage because of their input impedance? Is TL072 good for this or is it too old and noisy? Also is it plausible to have a 'one size fits most' preamp?
I'm sure there will be many more questions along my journey but could really do with some advice so I can start making informed purchases of components and avoid obvious beginner mistakes.
Thanks.
In later editions Douglas Self raves about how much better the LM4562 is over the NE5532...
If you want to power the op amps, you should go for a dual, regulated, low noise psu.
Dual is easy, regulated is also fairly easy, low noise...aahaa... and this is what matters the most.
I am not into showing the difficulties, but if you are not an expert, stay with the NE5532(made by Philips) and stay away from LM4562.
There is an improvement to be achieved in every circuit but you have to decide the limit.
Gajanan Phadte
Dual is easy, regulated is also fairly easy, low noise...aahaa... and this is what matters the most.
I am not into showing the difficulties, but if you are not an expert, stay with the NE5532(made by Philips) and stay away from LM4562.
There is an improvement to be achieved in every circuit but you have to decide the limit.
Gajanan Phadte
The TL072 is a Great opamp to work with I have been using it since its introduction in the 80's and I still use it today.
TL072 | General Purpose Amplifier | Operational Amplifier (Op Amp) | Description & parametrics
There is a newer upgraded version that is available from TI as well, it is the TL07x-EP series.
TL072-EP | General Purpose Amplifier | Operational Amplifier (Op Amp) | Description & parametrics
For even better performance you can also take a look at the OPA and LME series available from TI as well.
Audio Operational Amplifier | Products for Audio Operational Amplifier
Just to mention a few number I have used the LME49860, LME49720 (it has been said that LM4562 is the same), OPA1664 and I just got some LME49990's.
Then there is everybody's favorite the OPA2134's and its variants.
The NE5532's are excellent to work with as well and they were the ones to beat for many years.
They are a very cost effective device even by today's standards as they now can be found for about 1/8 to 1/10 the price of what they used to cost.
LT has a few very good opamps for audio use as well in the form of their LT105x series as well as many others.
I have been using these in a few recent circuits.
http://cds.linear.com/docs/en/datasheet/10578fd.pdf
I just love all of LT's opamps!!
I have been working with them a lot lately.
In the 90's I re-opamped my Fostex 454 mixer with TL072's and NE5532's and it gave my Mackie 32-8 mixer a run for the money and it sounded just as good as the Mackie as it is loaded with the NJM4560's and it was the opamp to beat back in the day(mid 90's).
The difference was more than just Night and Day compared to the 455x's that were in it.
Very transparent in comparison!!
I am planning to gather up all of the samples of different types that I do have so far and do a sound check for myself as well (mostly the LME types).
With a properly design test jig so that I can switch any one type in and out of the circuit at will.
So far I am quite impressed with what I have seen using squarewave test signals and such with my scope using just the LME49860's and the LT1057's so far.
The stuff I have done was by just using my protoboard and I haven't done any real listening tests yet.
Here is a loop through tests that I did with a LT1210 buffer I made with also a LT1057 in line for the buffered input to my Gina24 sound card.
http://www.diyaudio.com/forums/soft...re-capacitor-impedance-graph.html#post3848338
I am just now getting setup for this study as I am in the process of designing a matrix patch bay switching section for my recording system using the AD75016 16x16 switch matrix from Analog Devices.
http://www.analog.com/static/imported-files/data_sheets/AD75019.pdf
I have many other unfinished audio projects too, only lately I have been just been focusing on MCU programming so that I can control the digital switches and pots.
In fact I just ordered today some samples of Microchips new HV series of digital pots, some 5k and 100k verisons.
http://www.microchip.com/wwwproducts/Devices.aspx?product=MCP45HV51
I doubt that I will hear very much of a difference considering their specs.
FWIW
jer 🙂
TL072 | General Purpose Amplifier | Operational Amplifier (Op Amp) | Description & parametrics
There is a newer upgraded version that is available from TI as well, it is the TL07x-EP series.
TL072-EP | General Purpose Amplifier | Operational Amplifier (Op Amp) | Description & parametrics
For even better performance you can also take a look at the OPA and LME series available from TI as well.
Audio Operational Amplifier | Products for Audio Operational Amplifier
Just to mention a few number I have used the LME49860, LME49720 (it has been said that LM4562 is the same), OPA1664 and I just got some LME49990's.
Then there is everybody's favorite the OPA2134's and its variants.
The NE5532's are excellent to work with as well and they were the ones to beat for many years.
They are a very cost effective device even by today's standards as they now can be found for about 1/8 to 1/10 the price of what they used to cost.
LT has a few very good opamps for audio use as well in the form of their LT105x series as well as many others.
I have been using these in a few recent circuits.
http://cds.linear.com/docs/en/datasheet/10578fd.pdf
I just love all of LT's opamps!!
I have been working with them a lot lately.
In the 90's I re-opamped my Fostex 454 mixer with TL072's and NE5532's and it gave my Mackie 32-8 mixer a run for the money and it sounded just as good as the Mackie as it is loaded with the NJM4560's and it was the opamp to beat back in the day(mid 90's).
The difference was more than just Night and Day compared to the 455x's that were in it.
Very transparent in comparison!!
I am planning to gather up all of the samples of different types that I do have so far and do a sound check for myself as well (mostly the LME types).
With a properly design test jig so that I can switch any one type in and out of the circuit at will.
So far I am quite impressed with what I have seen using squarewave test signals and such with my scope using just the LME49860's and the LT1057's so far.
The stuff I have done was by just using my protoboard and I haven't done any real listening tests yet.
Here is a loop through tests that I did with a LT1210 buffer I made with also a LT1057 in line for the buffered input to my Gina24 sound card.
http://www.diyaudio.com/forums/soft...re-capacitor-impedance-graph.html#post3848338
I am just now getting setup for this study as I am in the process of designing a matrix patch bay switching section for my recording system using the AD75016 16x16 switch matrix from Analog Devices.
http://www.analog.com/static/imported-files/data_sheets/AD75019.pdf
I have many other unfinished audio projects too, only lately I have been just been focusing on MCU programming so that I can control the digital switches and pots.
In fact I just ordered today some samples of Microchips new HV series of digital pots, some 5k and 100k verisons.
http://www.microchip.com/wwwproducts/Devices.aspx?product=MCP45HV51
I doubt that I will hear very much of a difference considering their specs.
FWIW
jer 🙂
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By the way, I use a Bipolar supply (+V,GND,-V) to power my opamp circuits.
Even though you can use them with a single ended supply it is more of a chore to do so especially if you are using many opamp stages.
This is because you will have to create a virtual ground system anyhow, so it is an easier and straight forward method to just use a Bipolar supply design.
If you are going to use a single voltage wallwart then you should use an AC type, then you could get away with using a voltage doubler circuit to create a bipolar supply.
Be sure that you watch how much voltage is coming out of the wallwart as -/+ 15V is the typical value for most opamp circuits.
I 12Vac wallwart would produce about +/- 8.5 to 9.5 volts using the method mentioned above and a 24Vac type would produce double that at about +/-16.9V or so.
Many opamps are good for as much as +/- 18v to 22v and some only good to 5.5Vdc to 16Vdc maximum as well.
So, Regulation is very desirable depending on your design goals and type of opamp that you are working with.
Especially if your line voltage fluctuates a lot, so you must account for this as well.
For pro audio use you should use at least +/- 18Vdc to 22Vdc for your supply.
But for most applications +/- 9V to 15V is just fine depending on your application.
Typically I use the LM78xx and LM79xx series regulators in such supplies or anything that is equivalent.
I also use ones from LT as well.
I just ordered some super super low noise (20uv of noise) regulators from Linear Technologies for my opamp test jig.
The LT3030 and the LT 3090.
These are good for about 500 ma or so as one of them is a dual type (250ma/750MA).
http://cds.linear.com/docs/en/datasheet/3030fa.pdf
http://cds.linear.com/docs/en/datasheet/3090fa.pdf
There are many others that are suitable as well, I just spec'ed these for their super low noise for use in my testing jig and for use with some precision types that I have, as it is basically over kill for common audio circuit design.
But then again there is nothing wrong with overkill......Sometimes!!! 😉
Keep on DIYin'!!! 😉
jer 🙂
P.S. Oh, and, Welcome nGedd to DIYAudio, you have made a very wise choice!!! 🙂
Even though you can use them with a single ended supply it is more of a chore to do so especially if you are using many opamp stages.
This is because you will have to create a virtual ground system anyhow, so it is an easier and straight forward method to just use a Bipolar supply design.
If you are going to use a single voltage wallwart then you should use an AC type, then you could get away with using a voltage doubler circuit to create a bipolar supply.
Be sure that you watch how much voltage is coming out of the wallwart as -/+ 15V is the typical value for most opamp circuits.
I 12Vac wallwart would produce about +/- 8.5 to 9.5 volts using the method mentioned above and a 24Vac type would produce double that at about +/-16.9V or so.
Many opamps are good for as much as +/- 18v to 22v and some only good to 5.5Vdc to 16Vdc maximum as well.
So, Regulation is very desirable depending on your design goals and type of opamp that you are working with.
Especially if your line voltage fluctuates a lot, so you must account for this as well.
For pro audio use you should use at least +/- 18Vdc to 22Vdc for your supply.
But for most applications +/- 9V to 15V is just fine depending on your application.
Typically I use the LM78xx and LM79xx series regulators in such supplies or anything that is equivalent.
I also use ones from LT as well.
I just ordered some super super low noise (20uv of noise) regulators from Linear Technologies for my opamp test jig.
The LT3030 and the LT 3090.
These are good for about 500 ma or so as one of them is a dual type (250ma/750MA).
http://cds.linear.com/docs/en/datasheet/3030fa.pdf
http://cds.linear.com/docs/en/datasheet/3090fa.pdf
There are many others that are suitable as well, I just spec'ed these for their super low noise for use in my testing jig and for use with some precision types that I have, as it is basically over kill for common audio circuit design.
But then again there is nothing wrong with overkill......Sometimes!!! 😉
Keep on DIYin'!!! 😉
jer 🙂
P.S. Oh, and, Welcome nGedd to DIYAudio, you have made a very wise choice!!! 🙂
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Thanks so much for the warm welcome and all the advice guys! I chose the right forum clearly.
I've decided I'm going to use this as my power supply to get ±12v from a 12vAC 1000mA wall wart without having to deal with the dangers involved with handling transformers plugged into the mains. http://www.musicfromouterspace.com/analogsynth_new/WALLWARTSUPPLY/WALLWARTSUPPLY.php
Although because I'm in the UK I'm going to buy the parts and put it together on veroboard.
I then thought to use XLR connections to connect the supply up to the modules I make.
I'll be sure to post up pictures when I finish making it!
After I've put that together then it's on to the mixers! The NE5532 sounds like the one to go with, it's much cheaper than the LM4562 and sounds like it might be easier to deal with from what you guys have said.
I guess the last thing I want to clear up is whether my idea for a 'one size fits most' input buffer/preamp sounds wise? As I said I want to be able to plug in piezo disks, magnetic pickups and microphones. My understanding is that I need a high impedance to cover all of these types of input, which is why I thought of the TL072.... a lot of piezo buffers seem to have large resistors on the input (I understand this is to set the maximum impedance). I'm worried about johnson noise though from the high value resistor.
Maybe I should have a switch to select various ranges to suit the input.
Sorry if the last bit is a tad rambley, thanks again for all of your comments, it's a long way up hill for someone who has zero background in electronics but maths aside, I'm enjoying it.
I've decided I'm going to use this as my power supply to get ±12v from a 12vAC 1000mA wall wart without having to deal with the dangers involved with handling transformers plugged into the mains. http://www.musicfromouterspace.com/analogsynth_new/WALLWARTSUPPLY/WALLWARTSUPPLY.php
Although because I'm in the UK I'm going to buy the parts and put it together on veroboard.
I then thought to use XLR connections to connect the supply up to the modules I make.
I'll be sure to post up pictures when I finish making it!
After I've put that together then it's on to the mixers! The NE5532 sounds like the one to go with, it's much cheaper than the LM4562 and sounds like it might be easier to deal with from what you guys have said.
I guess the last thing I want to clear up is whether my idea for a 'one size fits most' input buffer/preamp sounds wise? As I said I want to be able to plug in piezo disks, magnetic pickups and microphones. My understanding is that I need a high impedance to cover all of these types of input, which is why I thought of the TL072.... a lot of piezo buffers seem to have large resistors on the input (I understand this is to set the maximum impedance). I'm worried about johnson noise though from the high value resistor.
Maybe I should have a switch to select various ranges to suit the input.
Sorry if the last bit is a tad rambley, thanks again for all of your comments, it's a long way up hill for someone who has zero background in electronics but maths aside, I'm enjoying it.
Hi,
Hardly, it is better, and more expensive, and finally after
many years there is a better front end op-amp than
the venerable NE5534, but Self still uses the NE5532.
There is no one size fits all high quality input.
Its simply not that simple and is complicated.
rgds, sreten.
Good Deal!!!
Yes, The JFET input opamp's have a much higher input impedance than the bipolar ones do like the NE5532's.
But it all depends on the application.
Also remember that the current draw of the NE5532 is much higher than that of a TL07x's, keep that in mind as you start adding more stages.
Typically the choice of lower resistance ranges around the opamp is more desirable when it comes to noise and in some cases necessary when it comes to Bipolar input opamp's.
I had in the case of the Fostex 454 where I couldn't use the NE5532's in the filter sections, they would oscillate and change frequency as the frequency knob was swept (VFO).
I am suspecting that the range of the resistors in the circuit was to high for the NE5532 to operate properly.
I never was able to investigate as to why this happened over time as I don't have that board anymore, and, I just recently had found the schematic for it(The Fostex 450 version).
So I just used the TL072's in the filter sections and all was well and I used the NE5532's for the rest of the signal paths.
It sounded fantastic after I had replace all of the 100 something or so opamp's throughout the thing without any mods to the original circuit's.
I can say do be aware of the newer high bandwidth types as they may/will require some kind of compensation to keep them from becoming unstable.
I had made a current buffered amp using a TL072 and everything was fine and then I swapped to out for the LME49860 and it was trying to oscillate.
I had similar issues using the LT1057 as well, but this was an easy fix on the breadboard.
This may not be the case for others whom are just swapping out a bunch of them in an existing circuit, There are many discussions about this already.
Sometimes (as in the pro equipment) it is desirable to use a JFET or some sort of transistor front end such as you find in Mic preamp's.
Again it depends on your application and the type of noise floor that you are trying to achieve.
Cheers!!
jer 🙂
Yes, The JFET input opamp's have a much higher input impedance than the bipolar ones do like the NE5532's.
But it all depends on the application.
Also remember that the current draw of the NE5532 is much higher than that of a TL07x's, keep that in mind as you start adding more stages.
Typically the choice of lower resistance ranges around the opamp is more desirable when it comes to noise and in some cases necessary when it comes to Bipolar input opamp's.
I had in the case of the Fostex 454 where I couldn't use the NE5532's in the filter sections, they would oscillate and change frequency as the frequency knob was swept (VFO).
I am suspecting that the range of the resistors in the circuit was to high for the NE5532 to operate properly.
I never was able to investigate as to why this happened over time as I don't have that board anymore, and, I just recently had found the schematic for it(The Fostex 450 version).
So I just used the TL072's in the filter sections and all was well and I used the NE5532's for the rest of the signal paths.
It sounded fantastic after I had replace all of the 100 something or so opamp's throughout the thing without any mods to the original circuit's.
I can say do be aware of the newer high bandwidth types as they may/will require some kind of compensation to keep them from becoming unstable.
I had made a current buffered amp using a TL072 and everything was fine and then I swapped to out for the LME49860 and it was trying to oscillate.
I had similar issues using the LT1057 as well, but this was an easy fix on the breadboard.
This may not be the case for others whom are just swapping out a bunch of them in an existing circuit, There are many discussions about this already.
Sometimes (as in the pro equipment) it is desirable to use a JFET or some sort of transistor front end such as you find in Mic preamp's.
Again it depends on your application and the type of noise floor that you are trying to achieve.
Cheers!!
jer 🙂
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