Dear Mr Pass,
I would be very grateful if you can help me answer some questions about jfet buffer (B1) on active crossover.
Firstly, if I had an analog active crossover schematic with opamp as buffer, could I change the opamp for the jfet buffer and keep the original characteristic of crossover? I think the output impedance of jfet buffer is higher than opamp buffer, but don't know if it can make the difference or not.
Secondly, if I used the bipolar power supply (+9V/-9V, for example) and matched JFET, could I omit the blocking capacitor 10uF?
I want to use JFET buffer from 2sk209BL with Yfs = 15mS and Idss = 7 mA
Thanks,
Trung
I would be very grateful if you can help me answer some questions about jfet buffer (B1) on active crossover.
Firstly, if I had an analog active crossover schematic with opamp as buffer, could I change the opamp for the jfet buffer and keep the original characteristic of crossover? I think the output impedance of jfet buffer is higher than opamp buffer, but don't know if it can make the difference or not.
Secondly, if I used the bipolar power supply (+9V/-9V, for example) and matched JFET, could I omit the blocking capacitor 10uF?
I want to use JFET buffer from 2sk209BL with Yfs = 15mS and Idss = 7 mA
Thanks,
Trung
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Cube Audio Magus
Hello Mr. Pass,
I saw in 1 article you use the Cube Audio Magus on open baffle with a LX Mini Crossover. I bought a set of crossover pcb + FET's , the Magus is already in my music room fired by a F2J clone. I like to add a Sub and intend to use the crossover. The Magus is still a bit hot in the sibilants. Did you adress this issue with the crossover (EQ in the upper mids)? If so, I am real interested how to do this, I didn't do any measurements, so I didn't know, where the peak occures (I suppose, somewhere between 5 and 10 k). The second possibility may be to add an R/C combination to smooth down the speakers, but I have no idea witch values to choose.
Greetings from Germany and thanks in advance
Helmut
Hello Mr. Pass,
I saw in 1 article you use the Cube Audio Magus on open baffle with a LX Mini Crossover. I bought a set of crossover pcb + FET's , the Magus is already in my music room fired by a F2J clone. I like to add a Sub and intend to use the crossover. The Magus is still a bit hot in the sibilants. Did you adress this issue with the crossover (EQ in the upper mids)? If so, I am real interested how to do this, I didn't do any measurements, so I didn't know, where the peak occures (I suppose, somewhere between 5 and 10 k). The second possibility may be to add an R/C combination to smooth down the speakers, but I have no idea witch values to choose.
Greetings from Germany and thanks in advance
Helmut
Generally speaking you can just replace the op amp with a discrete buffer. The output impedance of the 15mS fet will be about 60 ohms or so, and in my book it is low enough for your purposes. You can parallel Fets for lower if you want. If you want low DC offset, then you will need matching and maybe evena little trimming, depending on what offset you are willing to tolerate.
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Mr. Pass,
I modified my crossover again since my previous mods did not give me the correct summation of phase response alignment. Here's the final plot for my version of XO at 135 hz. Closed enough to what i needed.
I think the best part of this version is the perfect in-phase response summation with one driver inverted matches closely the phase of LP and roughly flat freq response summation.
Let me know your thoughts on this one.
Thanks Mr. Pass
Regards,
Tom
I modified my crossover again since my previous mods did not give me the correct summation of phase response alignment. Here's the final plot for my version of XO at 135 hz. Closed enough to what i needed.
I think the best part of this version is the perfect in-phase response summation with one driver inverted matches closely the phase of LP and roughly flat freq response summation.
Let me know your thoughts on this one.
Thanks Mr. Pass
Regards,
Tom
Thank you for the response, Mr. Pass. I'm putting this ckt together and will report back the sonic result.
Regards,
TD
I was tempted to follow the first advice anyone can give "use search". I did, with no success. But i remember when I went trough this thread that the dimensions were specified somewhere as 15cm x 15cm
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Lucky i saw your posts. Measured from the actual board. Dimension is 5inch x 5inch or 12.5 cm x 12.5 cm ... you're welcome 
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Lucky i saw your posts. Measured from the actual board. Dimension is 5inch x 5inch or 12.5 cm x 12.5 cm ... you're welcome
Many many thanks
I'm playing with early stage layout/chassis options and its pretty damn frustrating wout the correct measurements.
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Yep.. as I did say.. I've looked everywhere (including a search on this thread) and couldn't find? It's often the simple things that get overlooked. Many thanks anyway
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I put together the kit with R,C values of my simulation. Play around with the simulation some more. Did many audition sessions and REW measurement to finally decide that 125 hz XO frequency was the best optimal sonic for my OB speaker.
Man, the sound really comes to life with alot of details and 3D. It trumps over the miniDSP with the same setting at the same XO frequency.
Thank you Mr. Pass for a wonderful gift to the DIY community from a happy DIYer and music listener
With this much of sound quality from this kit, I'm really intrigued and anxiously waiting to get my hands on the new XO ckt with multiple slope settings coming up ahead in the store
Thank you sir. I have more goodies hiding under the closet
I really love the sweet and open tones of Russian PIO and Teflon caps. I've been collecting over the years from my past DIY builds and have a full box of them. I'm planning to do another LX mini XO build with all PIO/teflon caps populated and see if there're any differences in sonic result. My guess is It might take a while before I notice any differences since those caps take forever to really break in and sound sweet but it's worth a try anyway.Those Red/green/blue resistors are special 1% precision resistors that I inherited from one of my family member's friend who used to be a WWII electronics engineer. The values of those resistors are very precise to 0.01th. It's amazing how people care about build quality and control many decades ago!
Best,
Tom
