All passive ...
I guess you will have to read a bit about Sallen-Key filters first but it should be pretty easy to adapt the second order filter in the shown op amp schematic which is a Sallen-Key filter.
any chance of getting rip of the opamps? I prefer all passive.
peranders>
Would you kindly let me know the name of the book?
Thanks.
I guess you will have to read a bit about Sallen-Key filters first but it should be pretty easy to adapt the second order filter in the shown op amp schematic which is a Sallen-Key filter.
any chance of getting rip of the opamps? I prefer all passive.
peranders>
Would you kindly let me know the name of the book?
Thanks.
Sallen-Key revisted
It is not neccesary to use op amps to build the filter. Please read some of the web resources posted. You need a follower circuit for the filter; Tube, BJT transistors, or fets. I don't know what else I can tell you. The filters passive component values are in the schematic. It should be pretty straight forward to adapt this circuit to tube or what ever active stage you would like to use.
http://www.newwaveinstruments.com/r..._circuit_software.htm#Active Filter Tutorials
H.H.
It is not neccesary to use op amps to build the filter. Please read some of the web resources posted. You need a follower circuit for the filter; Tube, BJT transistors, or fets. I don't know what else I can tell you. The filters passive component values are in the schematic. It should be pretty straight forward to adapt this circuit to tube or what ever active stage you would like to use.
http://www.newwaveinstruments.com/r..._circuit_software.htm#Active Filter Tutorials
H.H.
I/V
I tried 100ohm just to get enough voltage for me to test it out.
But inputs from others, if there is enough gain, theyl suggested something like 50ohm, where 33 gives you more a relaxing sound, while 50 give you a more balanced sound, 75-100 will give you a more dynamic sound.
But in theory, the smaller the resistor is better. Actually, people's preception of a bit lack of "dynamic" when a small value is used may be the result of not enough gain in the following stages.
So for me, at the end of the day, I will try to go as low as possible without lossing any "dynamic" (with the correct gain).
I tried 100ohm just to get enough voltage for me to test it out.
But inputs from others, if there is enough gain, theyl suggested something like 50ohm, where 33 gives you more a relaxing sound, while 50 give you a more balanced sound, 75-100 will give you a more dynamic sound.
But in theory, the smaller the resistor is better. Actually, people's preception of a bit lack of "dynamic" when a small value is used may be the result of not enough gain in the following stages.
So for me, at the end of the day, I will try to go as low as possible without lossing any "dynamic" (with the correct gain).
Sallen-Key last remarks
You need a follower circuit for the filter; Tube, BJT transistors, or fets. I don't know what else I can tell you. Give it shot since it sounds like you know tube circuits. Most active filter circuits can not be turned into passive filters that's why they are active circuits and a Sallen-Key is about as simple as they come for active filters.
Thats all folks,
H.H.
You need a follower circuit for the filter; Tube, BJT transistors, or fets. I don't know what else I can tell you. Give it shot since it sounds like you know tube circuits. Most active filter circuits can not be turned into passive filters that's why they are active circuits and a Sallen-Key is about as simple as they come for active filters.
Thats all folks,
H.H.
Sorry, no active components (even tube) in the filter.
Sorry, may be I did not make my question clear. All I wanna to know is how to design:
"a simple ALL PASSIVE low pass filter with a gentle peak of 3dB around 20KHz, then roll off on 2nd order slope. The phase of the filter should be keep constant (Bessel filter?), and lagging in phase."
This site is good (online LC filter design):
http://www-users.cs.york.ac.uk/~fisher/lcfilter/
but it can't design a filter with peaks.
Sorry, may be I did not make my question clear. All I wanna to know is how to design:
"a simple ALL PASSIVE low pass filter with a gentle peak of 3dB around 20KHz, then roll off on 2nd order slope. The phase of the filter should be keep constant (Bessel filter?), and lagging in phase."
This site is good (online LC filter design):
http://www-users.cs.york.ac.uk/~fisher/lcfilter/
but it can't design a filter with peaks.
clarifications ...
Some sites/info/materials which can show me how to design something like this.
Thorsten designed this for TDA1543, he said this can't be used by TDA1541A, so I have decided to roll my own ...
Some sites/info/materials which can show me how to design something like this.
An externally hosted image should be here but it was not working when we last tested it.
Thorsten designed this for TDA1543, he said this can't be used by TDA1541A, so I have decided to roll my own ...
Re: All passive ...
patwen you don't have to say "kindly" but some others have to (which aren't not around for a long while).
One of the books is simply the "Active Filter Cookbook" by ??? A practical book with a low price, good. The other one is thick and really heavy, not suitble for beginners, very little practical things, real heavy mathematics. McCraw-Hill book, "Active Filters" by ????
If you want good information for free search the big sites of the IC companies. LT, NS, ON and their application notes. Lots of good stuff. Sorry, no links.
patwen said:
patwen you don't have to say "kindly" but some others have to (which aren't not around for a long while).
One of the books is simply the "Active Filter Cookbook" by ??? A practical book with a low price, good. The other one is thick and really heavy, not suitble for beginners, very little practical things, real heavy mathematics. McCraw-Hill book, "Active Filters" by ????
If you want good information for free search the big sites of the IC companies. LT, NS, ON and their application notes. Lots of good stuff. Sorry, no links.
It is by Don Lancaster.
Not suitable for beginners?? Then where else are they going to learn this stuff? One can always skip the "math behind" section and just copy the rest.
Anyway.......we see what he REALLY wants is an L/C filter with a Cauer section. Would have been simpler to tell us that in the first place. But, since he doesn't have that level of expertise......
It is hard to give the right answer when the person asking the question doesn't know what question to ask.
Go back to sleep, Harry, you work is over here.
Jocko
Not suitable for beginners?? Then where else are they going to learn this stuff? One can always skip the "math behind" section and just copy the rest.
Anyway.......we see what he REALLY wants is an L/C filter with a Cauer section. Would have been simpler to tell us that in the first place. But, since he doesn't have that level of expertise......
It is hard to give the right answer when the person asking the question doesn't know what question to ask.
Go back to sleep, Harry, you work is over here.
Jocko
Jocko Homo said:
Yes, Jocko but I think a 16 year old (or anyone despite the age) can be hurt for life
starting with such a book. I have read much about active filters and almost none of the books can tell you anything about sonic properties because the asume ideal opamps. Where do I get those?I got a tube of them "ideal" op-amps for you right here peranders.
Problem I haven't figured out how to solve, is they are only ideal as long as they are kept in their original, unpowered state. As soon as they warm up, the ideal characteristics evaporate and they turn into TL071's.
Opps, better move this over to the trading post forum.
Phil
Problem I haven't figured out how to solve, is they are only ideal as long as they are kept in their original, unpowered state. As soon as they warm up, the ideal characteristics evaporate and they turn into TL071's.
Opps, better move this over to the trading post forum.
Phil
The supposed sonic properties is not the point of the book. The point of the book is how to build filters. Wish I had a book this good when I was 16. Could have slept through 4 years of boot camp, and not missed anything.
Wait.....I did sleep through 4 years of boot camp. Probably because they NEVER mentioned that filters even exist, let alone what they are, and how to make/use them.
If you don't like op-amps, then don't use them. Ever hear of a source follower????
Buy the book anyway. You'll learn lots.
Jocko
Wait.....I did sleep through 4 years of boot camp. Probably because they NEVER mentioned that filters even exist, let alone what they are, and how to make/use them.
If you don't like op-amps, then don't use them. Ever hear of a source follower????
Buy the book anyway. You'll learn lots.
Jocko
Jocko:
4 years of boot camp and no filters!?! Not to dump your school, but... well, ok, actually I guess I am going to dump on your school, it obviously <i>sucked</i>. They covered filters in my 2nd year of "boot camp". We made extensive use of them in 3rd year, building PID controllers and the like... Laplace analysis was old news by 4th year. Not that I still remember all that stuff too well, but it wouldn't take much to refresh my memory. I'm sure the next time I sit down to design a complex filter it will all come back to me.
So, if they didn't teach you filters, what did they teach you?
Patwen: Get the heavy book.
4 years of boot camp and no filters!?! Not to dump your school, but... well, ok, actually I guess I am going to dump on your school, it obviously <i>sucked</i>. They covered filters in my 2nd year of "boot camp". We made extensive use of them in 3rd year, building PID controllers and the like... Laplace analysis was old news by 4th year. Not that I still remember all that stuff too well, but it wouldn't take much to refresh my memory. I'm sure the next time I sit down to design a complex filter it will all come back to me.
So, if they didn't teach you filters, what did they teach you?
Patwen: Get the heavy book.
Passive only, passive only, passive only, passive
If you don't like op-amps, then don't use them. Ever hear of a source follower????
I am sorry if I haven't already make this clear (even if I have attached Thorsten's pure passive circuit above), I want to design a PASSIVE sin(x)/x filter, not a active one, so no opamp/source follower/tubes etc ...
Unless there is a source follower that is pure passive ...
I hope I have make myself clear this time.
If you don't like op-amps, then don't use them. Ever hear of a source follower????
I am sorry if I haven't already make this clear (even if I have attached Thorsten's pure passive circuit above), I want to design a PASSIVE sin(x)/x filter, not a active one, so no opamp/source follower/tubes etc ...
Unless there is a source follower that is pure passive ...
I hope I have make myself clear this time.
It did suck!!!!
I have spent the last 30 years telling people that, and you are the first one to believe me. And the same amounnt of time asking myself the same question.
The only answer I can come up with is:
Nothing.
Anyway.......back to filters.
So, if you don't like op-amps, source folowers, cathode followers, or anything that is NOT passive, then how they hell do you listen to anything?
We would all like to know..........
I know.....just like the guy in "Joe's Garage", you hear imaginary musical notes in your head. {joke} (Do I really have to tell everyone it is a "joke"? This one ought to be obvious. But on this thread.....maybe not.)
Jocko
I have spent the last 30 years telling people that, and you are the first one to believe me. And the same amounnt of time asking myself the same question.
The only answer I can come up with is:
Nothing.
Anyway.......back to filters.
So, if you don't like op-amps, source folowers, cathode followers, or anything that is NOT passive, then how they hell do you listen to anything?
We would all like to know..........
I know.....just like the guy in "Joe's Garage", you hear imaginary musical notes in your head. {joke} (Do I really have to tell everyone it is a "joke"? This one ought to be obvious. But on this thread.....maybe not.)
Jocko
Thanks!!!!!!!!!!!!!!!!
taterhead>
You have just provided one of the most useful answers in this thread, many thanks.
Guidence like this is what I been looking for, thanks again.
1.69K for 1543? So it is not a current output like the TDA1541A (2mA if I remember correctly?).
So if I use 50 ohm I/V resistor for the TDA1541A, do I just replace the 1.69K and scale all the compoments accordingly?
taterhead>
You have just provided one of the most useful answers in this thread, many thanks.
Guidence like this is what I been looking for, thanks again.
1.69K for 1543? So it is not a current output like the TDA1541A (2mA if I remember correctly?).
So if I use 50 ohm I/V resistor for the TDA1541A, do I just replace the 1.69K and scale all the compoments accordingly?
Guidence like this is what I been looking for
"So it is not a current output like the TDA1541A?'
Bit of both actually, it is whats called a hybrid transconductance device with voltage feedback (about 2k open loop output Z,so not a true current out device) if I am not mistaken. You really want to use resistors below 50 ohms or above 1K depending on rather you are designing a voltage mode or current mode filter. I prefer the current mode myself. It does need about 60dB of gain for the best signal to noise ratio though. Bit of a sticky wicket, but not too hard to acheive with about 3 stages of gain if you are using tubes.
"So if I use 50 ohm I/V resistor for the TDA1541A, do I just replace the 1.69K and scale all the compoments accordingly?"
Why yes, that should work spendidly for you. Jump right in! Try 10 ohms instead of 50, I'd say.
Cheerio
Guy
"So it is not a current output like the TDA1541A?'
Bit of both actually, it is whats called a hybrid transconductance device with voltage feedback (about 2k open loop output Z,so not a true current out device) if I am not mistaken. You really want to use resistors below 50 ohms or above 1K depending on rather you are designing a voltage mode or current mode filter. I prefer the current mode myself. It does need about 60dB of gain for the best signal to noise ratio though. Bit of a sticky wicket, but not too hard to acheive with about 3 stages of gain if you are using tubes.
"So if I use 50 ohm I/V resistor for the TDA1541A, do I just replace the 1.69K and scale all the compoments accordingly?"
Why yes, that should work spendidly for you. Jump right in! Try 10 ohms instead of 50, I'd say.
Cheerio
Guy
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