Yes, I said there is no stereo info below about 100Hz on vinyl - didn't say there is no info below 100Hz!
The LP output of my 120Hz crossover board goes into a stereo 50K level pot for the sub/bass channel only, then into a non-inverting gain stage of x11, then onto the rest of the dipole EQ (Linkwitz transform and Shelving low pass) for each stereo channel. This level pot is normally set around half way for listening. To sum to mono, I simply connect the output wipers of the pot's L & R channels together, before they go into the input of the next gain stages - this is how I sum to mono for the sub/bass channel only - and the warp problem is gone without any need for 'subsonic' filtering - ie you still have the full extended bass response but without the offending warp signals, which are summed to zero.
The LP output of my 120Hz crossover board goes into a stereo 50K level pot for the sub/bass channel only, then into a non-inverting gain stage of x11, then onto the rest of the dipole EQ (Linkwitz transform and Shelving low pass) for each stereo channel. This level pot is normally set around half way for listening. To sum to mono, I simply connect the output wipers of the pot's L & R channels together, before they go into the input of the next gain stages - this is how I sum to mono for the sub/bass channel only - and the warp problem is gone without any need for 'subsonic' filtering - ie you still have the full extended bass response but without the offending warp signals, which are summed to zero.
Hi Dirk, words can be tricky things 🙂. Here is the KAB filter which explains out of phase warp cancellation better than I did;
https://www.kabusa.com/frameset.htm?/rf1.htm
David
https://www.kabusa.com/frameset.htm?/rf1.htm
David
The kit is no longer available in the DIY audio store... any hope for that returning?
Hi, I would like to test Linkwitz Transform after the low pass part of the crossover, similar to post #1,242. Is it possible to use the Linkwitz circuit without a buffer stage? I assume the output impedance of the crossover is low enough. Is that correct, or should I follow Rod Elliott’s design?
You might take a look in the Marketplace section. I feel like I saw one for sale fairly recently.
Now even this link doesn't work. Nelson, do you have any influence over getting this simulation program back up and running? It seems a shame that all the trouble was taken to create it, and it worked passably well, and now it's gone into the ether.
I think that was probably Mike Rothacher's. I'll drop him a note. I recall that being considerably smarter than me, he wrote his own graphically controlled filter simulator.
Me, I just use MicroCap, easy for beginners and still a free download.
😎
Me, I just use MicroCap, easy for beginners and still a free download.
😎
If you need it now, until the cavalry arrives, the one you linked still works (in Firefox anyway). It's very slow , you have to proceed one change at a time and wait until the curve changes before moving ahead. A bit tedious for most maybe but it works.
Got it to work today. I had access yesterday, but the curves were displayed completely separate from the graphs! Don't know what I could have done to accomplish that, but all is good now.
I just have a quick question. I thought I had checked all my soldering very carefully and landed up leaving one side of both bias resistors unsoldered on a low channel right next to output. I didn´t realize this until after listening fow a couple of hours. Now I´m getting a lot of hum from that channel. Am I right in thinking that I´ve probably damaged one or both jfet´s in the middle of these resistors, and if so, how hard is it going tobe to replace them. thanks in advance for any help or suggestions
Hello violagran,
do you have 50 / 60 Hz - hum?
In an active sytem you can easily get into trouble with groundloops.
You could measure the voltage over your bias resistors in the different stages of the filter. Especially those ones which were not soldered correctly. This would confirm, that current is flowing through your Jfets. The currents should be a similar value (U/R = I). The JFets in the 6-24-AXO-kits are matched sets.
I don't think the JFets are damaged - but they could be.
You could also desolder the JFets in question and test them with a transistortester?
Cheers
Dirk
do you have 50 / 60 Hz - hum?
In an active sytem you can easily get into trouble with groundloops.
You could measure the voltage over your bias resistors in the different stages of the filter. Especially those ones which were not soldered correctly. This would confirm, that current is flowing through your Jfets. The currents should be a similar value (U/R = I). The JFets in the 6-24-AXO-kits are matched sets.
I don't think the JFets are damaged - but they could be.
You could also desolder the JFets in question and test them with a transistortester?
Cheers
Dirk
If a ground loop is suspected, the first question goes to the connection of the power supply - does the power supply have an AC mains ground in common with the secondary system ground?
Just about any SMPS has the minus output connected to the Mains Safety Ground for EMI reasons.
Thank you for the replies. The AC ground is not in common with the secondary ground. I checked the voltage across both bias resistors of the bad channel and get 872mV on both. Maybe what I didn´t clarify enough was that I´m only getting noise from the low output on one channel which is where I didn´t have the one side of both bias resistors soldered. My hearing isn´t what it used to be and it took me a couple of hours to notice a lack of bass on the one channel when I first connected it. After finding the culprits and soldering them is when the hum started. I have also eliminated the possibility that it is coming from my preamp or power amps.
Hi, I have finished my crossover project, and also added the Linkwitz Transform circuit (on top of the coupling capacitors).
Measurement of the crossover
It's an Open Baffle speaker (baffle width 450mm), with 12" Audio Nirvana Classic driver and Fostex FT96H tweeter. Measurement has been taken at listening position, without gating, 1/6 smoothing has been applied
Red colored graph is the measurement without sub, the light brown with sub.
Thank you Nelson to share this project
Measurement of the crossover
It's an Open Baffle speaker (baffle width 450mm), with 12" Audio Nirvana Classic driver and Fostex FT96H tweeter. Measurement has been taken at listening position, without gating, 1/6 smoothing has been applied
Red colored graph is the measurement without sub, the light brown with sub.
Thank you Nelson to share this project
