Line Level splitter/mixer and multichannel master volume control
I originally posted in the Multiway speaker forum and it was moved to this forum.
I figure that most people that have active crossovers and multiple subs need some type of solution to source and feed all the different amps. Hopefully some of you already have built something similar and will be able to assist.
I have been playing with both MINIDSP active crossovers and multisub setup to equalize room LF. The problem I always have is the gain structure of the MINIDSP. The minidsp likes a full line level signal. Using the minidsp for volume control is not good IMO.
Has anyone build something like this diagram below or know if something similar is commercially available for home use (small, nice looking unit).
I originally posted in the Multiway speaker forum and it was moved to this forum.
I figure that most people that have active crossovers and multiple subs need some type of solution to source and feed all the different amps. Hopefully some of you already have built something similar and will be able to assist.
I have been playing with both MINIDSP active crossovers and multisub setup to equalize room LF. The problem I always have is the gain structure of the MINIDSP. The minidsp likes a full line level signal. Using the minidsp for volume control is not good IMO.
Has anyone build something like this diagram below or know if something similar is commercially available for home use (small, nice looking unit).
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I use an active xo and needed a multi way vol control.
currently, I'm trying out (and liking) the cs3318 chip. it gives 8ch and 3 master faders that you can assign the 8 chans to.
see my post on 'arduino and cs3318'. its not a pcb yet but its on its way to being one. I do plan a group buy once the proto stage is complete.
the attenuation is all in the analog domain even though control is digital.
that's my take on the 'how to match XO outputs to amps'
your box would need some extra mixing or summing but that's all I see as being different.
currently, I'm trying out (and liking) the cs3318 chip. it gives 8ch and 3 master faders that you can assign the 8 chans to.
see my post on 'arduino and cs3318'. its not a pcb yet but its on its way to being one. I do plan a group buy once the proto stage is complete.
the attenuation is all in the analog domain even though control is digital.
that's my take on the 'how to match XO outputs to amps'
your box would need some extra mixing or summing but that's all I see as being different.
Looks really good! Like you say, I would still need the splitting/mixing portion.
I think the box could be quite flexible. The drawings below are applicable for multiple sub woofers, but similarly it can be applied to 2/3/4 way active crossovers.
I have been researching and I am initially leaning towards using DIY B1 Pass buffers and a LDR master volume control.
If I add input selection I might be able to eliminate my existing preamp from the chain. I have started to purchase some of the components already.
I think the box could be quite flexible. The drawings below are applicable for multiple sub woofers, but similarly it can be applied to 2/3/4 way active crossovers.
I have been researching and I am initially leaning towards using DIY B1 Pass buffers and a LDR master volume control.
If I add input selection I might be able to eliminate my existing preamp from the chain. I have started to purchase some of the components already.
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I'm not sure ldr's are best if you have to gang them (multi channel). but that's a religious discussion and some people like ldr's.
my needs are at least 4ch (for a 2way active xo spkr system), and ideally 5way to include a discrete sub. doing 5 is the same as doing 6. the cirrus chip supports 8, so there's room left over
the neat thing about multichannel chips is that you have accurate atten on all channels and its atomic (you set one value and they all 'run' at the same time, at least in theory). you set offsets between them and they stick.
its like relays: they work well when there are only a few channels. but as you want more channels and you want them to 'click' at the same exact time, as you vary the vol knob, relays just don't scale (numbers of boards of them, that is).
the solid state way seems to be best, but you are free to choose the method you think best. at least consider the solid state solution.
my needs are at least 4ch (for a 2way active xo spkr system), and ideally 5way to include a discrete sub. doing 5 is the same as doing 6. the cirrus chip supports 8, so there's room left over
the neat thing about multichannel chips is that you have accurate atten on all channels and its atomic (you set one value and they all 'run' at the same time, at least in theory). you set offsets between them and they stick.
its like relays: they work well when there are only a few channels. but as you want more channels and you want them to 'click' at the same exact time, as you vary the vol knob, relays just don't scale (numbers of boards of them, that is).
the solid state way seems to be best, but you are free to choose the method you think best. at least consider the solid state solution.
Master Volume Proposed Circuit
Here is the master volume proposed circuit, I simply took the respective designs and spliced them together.
Pass Labs B1 Buffer
DIY LDR Attenuator
There is a circuit from Nelson Pass with both the LDR attenuator and a Buffer. That one requires a complimentary to the 2sK170 that is hard to get and would not be cost effective for me. The B1 uses two 2sk170 per channel. I got the 2sk170 for $0.38 each at MCM electronics (hope they are not fakes). Bought plenty so I can match pairs.
My plan is to use a large DELL 19V laptop power supply to power it. I will definitely have to test if in the end I will have enough gain for my system. I think I will, I have >95db speakers.
I am now drawing up the Splitter and Mixer circuit, will post it once done.
Here is the master volume proposed circuit, I simply took the respective designs and spliced them together.
Pass Labs B1 Buffer
DIY LDR Attenuator
There is a circuit from Nelson Pass with both the LDR attenuator and a Buffer. That one requires a complimentary to the 2sK170 that is hard to get and would not be cost effective for me. The B1 uses two 2sk170 per channel. I got the 2sk170 for $0.38 each at MCM electronics (hope they are not fakes). Bought plenty so I can match pairs.
My plan is to use a large DELL 19V laptop power supply to power it. I will definitely have to test if in the end I will have enough gain for my system. I think I will, I have >95db speakers.
I am now drawing up the Splitter and Mixer circuit, will post it once done.
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First Pass at Splitter and Mixer Circuit
For the Splitter buffers and mixers I also used the B1 buffer. I just put modules back to back. I think I may be able to remove either the 10uf Cap on the input L & R buffers or all the 1uf on all the output buffers. Can someone confirm if my thinking is correct.
Does the mixing seem correct? Will I need to attenuate the L+R outputs?
For the Splitter buffers and mixers I also used the B1 buffer. I just put modules back to back. I think I may be able to remove either the 10uf Cap on the input L & R buffers or all the 1uf on all the output buffers. Can someone confirm if my thinking is correct.
Does the mixing seem correct? Will I need to attenuate the L+R outputs?
Attachments
A bit more progress on the sourcing front. A trip to the surplus store yielded all the resistors needed, all 1% and appear to be of very good quality. Also as a surprise, i found a nice regulated power supply made by Genex Audio. I believe these were made for their 8 channel ADC and DAC. It puts out 5v and +- 15v. It is probably too high but changing the regulators r1,r2 ratio will change the output. Already tested with a Decade box and a 1k resistor brings it to +- 9 volt.
Lastly, found some proto boards that appear to be silver plated.
Lastly, found some proto boards that appear to be silver plated.
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i'm not 100% sure the other outputs are configurable but if memory serves you can turn any output into bandpass that may or may not serve your application
i'm wondering what the criteria for multiple sub outputs is? there are several multiple mix matrix's units that are used for zone paging applications that might also fit the bill but if x-over and level control are required on each output you could be more in the realm of a Protea
i've personally had success in using LM 1972 N ic as digitally controlled attenuators and combined with minidsp you may well being on the way to rolling your own!
i'm wondering what the criteria for multiple sub outputs is? there are several multiple mix matrix's units that are used for zone paging applications that might also fit the bill but if x-over and level control are required on each output you could be more in the realm of a Protea
i've personally had success in using LM 1972 N ic as digitally controlled attenuators and combined with minidsp you may well being on the way to rolling your own!
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