Hi
I am thinking about building a B1 buffer.
The point is that i want to use active crossover to without having any op-amps.
Sow my thought is to use a passive volume control, then split the signal to one HP and one LP crossover. And after each crossover put a B1 buffer.
I want to do this to get everything in one box and to avoid op-amps and to avoid any passive crossover in my speakers.
Also i want to try the B1 buffer as a preamp
I planed to make the crossover from passive components.
Will this work?
Is it possible to put the crossover were i planed?
I am grateful for an help from people that know more about electronics then myself.
I am thinking about building a B1 buffer.
The point is that i want to use active crossover to without having any op-amps.
Sow my thought is to use a passive volume control, then split the signal to one HP and one LP crossover. And after each crossover put a B1 buffer.
I want to do this to get everything in one box and to avoid op-amps and to avoid any passive crossover in my speakers.
Also i want to try the B1 buffer as a preamp
I planed to make the crossover from passive components.
Will this work?
Is it possible to put the crossover were i planed?
I am grateful for an help from people that know more about electronics then myself.
Attachments
Active crossover, with what? Do you mean an active filter because you have drawn a passive filter (surely) with a B1 afterwards?
Yes of course, you are right. It is not correct with active crossover.
A passive line lever corssover might be a better description.
A passive line lever corssover might be a better description.
A buffered PLLXO. I still call these active as i define an active speaker system as any one with amplifiers for each speaker.
This same thing is in our queue, and as i understand, similar to the B2 (Nelson?)
dave
Hi,
I have a thing like that up and running for almost one year now. Topology:
Input - Volume control <
The high and lowpass are ordinary 2nd order PLLXO. The high- and low-volume are stepped attentuators with 1dB steps (up to -5dB). As B1 I used the schematic with dual supply ZenMod posted, just to save some capacitors. In the version now, I was lazy and used lm317/lm337 series regs.
Everything was built on stripe-board and it fits on two 16cm*7cm boards.
Sound great, I recommend it.
Did not use the Sallen-Key filters then because the simulation lead to a little less distortion with the passive filters (less important) and I was not sure if I could run unbuffered Sallen-Key filters with a B1. A buffered Sallen-Key would have caused even more B1s in the box (12 right now).
After some experience, I would try
volume - B1 - lp(Sallen-Key) - low-volume - B1
For every path. But i am not sure if it sounded even better.
Best regards
Flo
I have a thing like that up and running for almost one year now. Topology:
- b1 - hp - b1 - high volume - b1
- b1 - lp - b1 - low volume - b1
The high and lowpass are ordinary 2nd order PLLXO. The high- and low-volume are stepped attentuators with 1dB steps (up to -5dB). As B1 I used the schematic with dual supply ZenMod posted, just to save some capacitors. In the version now, I was lazy and used lm317/lm337 series regs.
Everything was built on stripe-board and it fits on two 16cm*7cm boards.
Sound great, I recommend it.
Did not use the Sallen-Key filters then because the simulation lead to a little less distortion with the passive filters (less important) and I was not sure if I could run unbuffered Sallen-Key filters with a B1. A buffered Sallen-Key would have caused even more B1s in the box (12 right now).
After some experience, I would try
volume - B1 - lp(Sallen-Key) - low-volume - B1
For every path. But i am not sure if it sounded even better.
Best regards
Flo
Thanks for all replays and ideas.
If i build a Sallen key filter do i need 3 B1 for each channel?
One before the filter one in the filter and one after the filter, or is it enough to have one before and one inside the filter?
it seam that i need one B1 between the volume control and the filters, would it work to only use one B1 and then split the signal to the filters. I guess the signal strength will be 3dB lower. But is there any other problems?
If i build a Sallen key filter do i need 3 B1 for each channel?
One before the filter one in the filter and one after the filter, or is it enough to have one before and one inside the filter?
it seam that i need one B1 between the volume control and the filters, would it work to only use one B1 and then split the signal to the filters. I guess the signal strength will be 3dB lower. But is there any other problems?
I would use three one after the volume, one for the filter, a kind of attentuation after the filter (>10kR) to keep some fexibility, and another b1 after that for the output. You would need that one if you need an attentuation. If you would omit it, th impedance of the attentuation should be very low (<4k). In my experience, the b1 does not like it that low, leads to a lack of bass.
Splitting works, no loss of signal. Sometimes (layout etc.) it is of advantage to use a separate inut buffer for every signal-row. But you don't have to, the b1 is capable of driving two b1's (with sallen key).
Best regards
Flo
Tanks for your answer.
But if i decide to not use attenuation after the filter do i still need to have a B1 after the filter or will the B1 in the filter be enough to drive the output?
You could try, it depends on the next part in your setup. With a b1 at the output you are on the save side. Without the filtering b1 has to drive the network and the output. A b1 is not an opamp it delivers not as much current, that's what you pay for better sound and less (complex) distortion.
These points were one of the reasons why I chose a passive filtering between two buffers.
Regards
Flo
These points were one of the reasons why I chose a passive filtering between two buffers.
Regards
Flo
Ah ok makese sens.
I am thinking about what way to go, it looks lite passive filter might be the way to go as 3 B1 can be enough rater then 5 witch is a bit to many.
I am thinking about what way to go, it looks lite passive filter might be the way to go as 3 B1 can be enough rater then 5 witch is a bit to many.
At page 5 http://focus.ti.com/lit/an/sloa024b/sloa024b.pdf, it is stated that 2nd order PLLXO will have Q<1/2 and Sallen-key can be design to have very high Q.
May I know what is the significant of Q in filter design and what should be the optimum value?
May I know what is the significant of Q in filter design and what should be the optimum value?
That depends on your Chassis, your speakers and last not least your preferences. Not easy to explain all the aspects here, but with a Linkwitz alignment (Q=1/2 for 2nd order or two times 0.71 für fourth order) you have a kind of compromise and you won't that wrong. At least you get a starting point for further investigations.
See e.g. Active Filters and the other pages around there.
Regards
I have decided to move on with passive filter. But i have some question i hope someone with more knowledge can answer for me.
As i understand it i need to calculate with the input impedance of the B1 after the filter. And reading the documentation for the B1 it says that the input impedance of the B1 is the same as the alternator impedance.
Sow if i decide to not use a alternator on the input can i simply put a resistor (about 25kOhm) in its place instead?.
Or will it be enough with the 1kOhm resistor that is already there after the alternator in the schematics?
As the first B1 will drive the filter i guess it is not recommended to use to small values on the resistors in the filter to ease the load for the first B1.
What is the recommended input impedance to use after the B1?
Thankful for any help
As i understand it i need to calculate with the input impedance of the B1 after the filter. And reading the documentation for the B1 it says that the input impedance of the B1 is the same as the alternator impedance.
Sow if i decide to not use a alternator on the input can i simply put a resistor (about 25kOhm) in its place instead?.
Or will it be enough with the 1kOhm resistor that is already there after the alternator in the schematics?
As the first B1 will drive the filter i guess it is not recommended to use to small values on the resistors in the filter to ease the load for the first B1.
What is the recommended input impedance to use after the B1?
Thankful for any help
Have a look at this 12dB / Octave Linkwitz Riley Crossover
Rod recommends using resistor values between 2k2 and 20k for the filter section.
So I would probably use 20K resistors
Rod recommends using resistor values between 2k2 and 20k for the filter section.
So I would probably use 20K resistors
But this is an active Sallen-Key filter
Will look to find some time today to look for the schematics of my crossover, I think, I drew a schematic...
Hi,
I don't find the simulations (and the schematics) any more. But this is what I see from the construction:
I did a PLLXO like e.g. Martin King suggests Passive High-Level Crossover between two b1. As R1 I used 4,7k the rest was calculated according to Martin. I would not go lower than 4,7k, coud be too much work for the little sucker. If you wand to use one buffer for the input of hp and lp, I would recommend R1>10k.
You can omit Ramp in your calcs, the input impedance of the b1 at the output is high enough (some M)
best regards
Flo
I don't find the simulations (and the schematics) any more. But this is what I see from the construction:
I did a PLLXO like e.g. Martin King suggests Passive High-Level Crossover between two b1. As R1 I used 4,7k the rest was calculated according to Martin. I would not go lower than 4,7k, coud be too much work for the little sucker. If you wand to use one buffer for the input of hp and lp, I would recommend R1>10k.
You can omit Ramp in your calcs, the input impedance of the b1 at the output is high enough (some M)
best regards
Flo
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