jimk04 is correct, I want to run 4 channels from the 2 low side crossover outputs-
My hunch is--whatever your preamp will let you get away with is going to be the determining factor.
I don't know what the metric is for a preamp to do this happily. Is it output impedance? Needing to be very low.?
I know my Salad DCG3 would be happy doing this, but don't know the technicalities why!
I know my Salad DCG3 would be happy doing this, but don't know the technicalities why!
@jimk04 Yeah, that looks like an absolute beast!
I'm back to thinking it's going to be as much to do with the XO on account of its buffers; a combo of the two, I suppose. Plus amp properties.
Current goal: Qudelix 5k ---> active xo ---> low pass filter split to four ACA-mini channels (and high pass to a third ACA-mini)
Edit: I've attached the datasheet to the Qudelix's output stage in case a determination can be made there-
I'm back to thinking it's going to be as much to do with the XO on account of its buffers; a combo of the two, I suppose. Plus amp properties.
Current goal: Qudelix 5k ---> active xo ---> low pass filter split to four ACA-mini channels (and high pass to a third ACA-mini)
Edit: I've attached the datasheet to the Qudelix's output stage in case a determination can be made there-
May I pick your brains for an issue I'm having with my build? Bear in mind this is my first substantial electronics project, so tailor advice accordingly. I've begun adding filter CR's to the low pass filter sections of two boards (tri-amp, one board per channel; L+R). Plugged in a 50hz sine wave and the left board seems to be doing the right thing, 50hz in, 50hz out, ~2.8Vpp. I read ~9.6V at the point between the 1M and 1K resistors on the input buffer.
So far so good. However the right channel low pass is outputting a lower voltage sine wave after filter stage 1 (T4), and almost flat 2hz wave after filter stage 2 (T4). I've noticed I have only ~4.5V between the 1M and 1K resistors on the input buffer. Where to start or what to check?
I'd appreciate any advice. It's quite daunting not knowing where to start with this!
So far so good. However the right channel low pass is outputting a lower voltage sine wave after filter stage 1 (T4), and almost flat 2hz wave after filter stage 2 (T4). I've noticed I have only ~4.5V between the 1M and 1K resistors on the input buffer. Where to start or what to check?
I'd appreciate any advice. It's quite daunting not knowing where to start with this!
Attachments
More info. With the power off, most of the resistance values across the 1M resistors is 500-800k. The low pass with the issue is measuring 120k across the 1M resistor, and the band pass 1M resistor is measuring 66k.
@Haze Head What is the input impedance of the amps you want to connect in parallel to the LP output? I assume you can just split the LP output and drive both amps.
Good post from @Mooly regarding this topic:
"Whether or not to parallel the outputs all really depends on the output impedance of your active XO. Just looking at the output stage of that should give a good idea of output impedance or alternatively you just measure it by loading it resistively and looking if the output is affected in amplitude. In any case its not really an issue beyond reducing the amplitude... so you just turn the ACA gains up to compensate.
Most solid state line outputs are normally very low impedance, sometimes artificially increased a little by series feed resistors. Just measure it, play a constant tone and load the output with say a 1k and see if there is any drop in amplitude as a first step."
"Whether or not to parallel the outputs all really depends on the output impedance of your active XO. Just looking at the output stage of that should give a good idea of output impedance or alternatively you just measure it by loading it resistively and looking if the output is affected in amplitude. In any case its not really an issue beyond reducing the amplitude... so you just turn the ACA gains up to compensate.
Most solid state line outputs are normally very low impedance, sometimes artificially increased a little by series feed resistors. Just measure it, play a constant tone and load the output with say a 1k and see if there is any drop in amplitude as a first step."
@Haze Head In this situation I would definitley not go through the trouble of doubling the output buffer of the crossover. 50k input impedance (two ACA mini in parallel) is still very reasonable. There are amps that have 10k or 20k alone. The output buffer has 100 Ohm in series with the output and the buffer itself should have less than that. So I expect no more than 200 Ohm total output impedance. Even better with 2SK170 as output device😉 Don't take the numbers absolute... its just from the top of my head.
Well, I seem to have located a Q1 LSK170 that was misbehaving, swapped it out and the low pass on right board looks to have a better signal. However I suppose they were all broken the whole time, I hadn't noticed while testing with the oscilloscope.
From all but one output, there are horrible crackling, popping, and hissing noises - some outputs louder than others. I do have a bandpass with a chained HP and LP for Mid. But the tweeter high pass is also crackling. Could this be wrong bias resistors? I had worked out to drive them around 80-90% of Idss.
Thoughts?
From all but one output, there are horrible crackling, popping, and hissing noises - some outputs louder than others. I do have a bandpass with a chained HP and LP for Mid. But the tweeter high pass is also crackling. Could this be wrong bias resistors? I had worked out to drive them around 80-90% of Idss.
Thoughts?
Does anyone else have experience with LSK170's? I'm finding they can be quite temperamental and unstable if run under 90% Idss. Can anyone else confirm this or should I be looking elsewhere for faults? Some are rock solid, others will shut down on and off, and when they start working again (if they do), it will be at around 86-89% of Idss. You would think if it's biased to that it wouldn't be so unstable. Unless Idss can drift after some run-in?
Could unmatched (between input, filter stage 1, filter stage 2) FETs running at different currents affect each other? It's my understanding that they are better matched left channel to right channel? Some filters seem to be working fine all the way up the filter using different current levels.
Could unmatched (between input, filter stage 1, filter stage 2) FETs running at different currents affect each other? It's my understanding that they are better matched left channel to right channel? Some filters seem to be working fine all the way up the filter using different current levels.
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And I'm back! I have been using this cross over almost daily since built. It has been excellent so far but....on some of my older records I am getting woofer pumping. How can I reconfigure my low pass to run 80hz-20hz and drop everything else? I see my options as buying a separate subsonic filter, adding another crossover board configured as a subsonic filter, or figure out what to change on my current low pass section. Any help is much appreciated.
I'm not sure if this is helpful or not, but in my active system, the bass dipoles woofer/subs (<120Hz) have substantial EQ gain at the lower end. I was quite shocked how much woofer flap I got when I tried vinyl again for the first time with the system. I was getting large cone excursions from slight warps in the vinyl.
I fixed it simply by summing the woofer/subs to mono in the channels below 120Hz. The warp signal is anti-phase between L & R, so when summed to mono just disappears - no more wild cone excursions. Sound is great too. I believe there is no stereo info below about 100Hz in vinyl anyway.
Might be worth a try to save you further filtering?
I fixed it simply by summing the woofer/subs to mono in the channels below 120Hz. The warp signal is anti-phase between L & R, so when summed to mono just disappears - no more wild cone excursions. Sound is great too. I believe there is no stereo info below about 100Hz in vinyl anyway.
Might be worth a try to save you further filtering?
He meant there is no STEREO separation of musical content below 100 Hz. This is well known.
David, how did you sum the two channels? I am interested in this for subwoofer signal only.
David, how did you sum the two channels? I am interested in this for subwoofer signal only.