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Post by svart on Jan 5, 2016 8:40:30 GMT -6
So I've been thinking about a medium term personal project.. There are a few things I want to design and build, and there are a few projects that I've started but will take money to finish, another 2254/33609 and 4x more 1272s, but over the holidays I ran into a few issues with some mixing that would have been much easier had I had certain features on my mixer.
Namely, I need variable filters and better control over highs and lows.
I have HPF on the console but it's fixed frequency. I was able to change the caps around the circuit and tune it to a more usable range, but it would have been nice to just sweep it. I would have also liked to have a LPF on some tracks. I ended up using an EQ plugin for this, but I hate plugins and would rather have it all on the console if I could.
The HF and LF shelves are fixed frequency. I installed switches to swap parts in and out of the circuit to change the frequencies but I also find that the rolloff isn't steep enough, I need more poles in the sections and make them sweepable.
The answer would be to get an old SSL console, but I can't swing that.
What I can do is use my particular set of skills to create what I want.
Preamp: Don't need much here, I mostly use mojo pres like 1272's and 312's but I do have a design I want to try out..
I/O: ELCO I/O, XLR/TRS all provided by the console frame. I'll reuse those but change the receiver/transmitter circuits.
Filters: HPF and LPF, sweepable or switchable, relatively steep rolloff like 3rd or 4th order.
EQ HF/LF: Higher order shelf/bell setup, sweepable or switchable.
EQ mids: 2 band fully parametric CAPS style. I'll just copy the one from my console since it's pretty awesome as-is.
Compressor: VCA style compressor, ALA a stripped down SSL channel strip version. Switchable pre/post EQ and pre/post fitlers.
Gate/Expander: I'll investigate if I can dual purpose the VCA circuits to make a gate/Expander as well, but if not, no biggie.
Sends: I'll reuse the 8 channels of sends the console frame already has, but break out the 7/8 send as it's currently shared.
Monitor path: I never use it, but I'll turn it from a short fader to a knob for space saving.
Muting: Already has FET mutes, so I'll retain the ability to use them, but change their design.
Panning: Possibly revise the panning design.
Fader: Investigate better fader/bus driving design
My console already has an SSL9K group/summing amp network installed so I won't need to change much in that regard. Eventually I'll need to change the master and busses to better designs.
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Post by rocinante on Jan 5, 2016 11:06:55 GMT -6
Curious, what is your console svart?
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Post by jimwilliams on Jan 5, 2016 11:14:58 GMT -6
Buy a used Aphex 612 expander/gate for $75. Those have a stereo pair of sweeping 2 pole butterworth LPF and HPF's accessable via key listen mode. It also has a very nice expander circuit but I realize increased dynamic range is no longer needed in today's productions.
I mostly use mine for reverb sends/returns here.
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Post by svart on Jan 5, 2016 12:21:12 GMT -6
Curious, what is your console svart? Alesis X2. Back in the mid 90's they tried to enter the mid-level market, between low end stuff like Mackies and high end things like SSL. Unfortunately a changing market (going towards digital and away from consoles and ADAT), higher price and manufacturing issues effectively killed it before it had a chance. It's a surprisingly good console as-is, with 100khz+ bandwidth and some features that are only on higher end consoles, but it's also becoming very rare so a lot of parts are hard to find. |
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Post by rocinante on Jan 5, 2016 19:10:43 GMT -6
Neat. Iv'e read numerous nice things about the x2. Definitely a few Grammy's have been done iirc.
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Post by svart on Jan 6, 2016 10:05:28 GMT -6
So the first hurdles of the design:
Potentiometer values, sizes, tapers and availability. If I were to cobble together the design with values from similar circuits, I would have an extreme amount of unique values and tapers. Compounding this, is the sheer number of pots I'll need in circuit, around 25 pots. Some of these are hard to get, like reverse logs for the EQs, so I'd need to resort to doing things like taper bending linear pots to make them log and reverse log, so they are easier to obtain. Secondly, I'll need to adjust and scale circuits to try to reuse common values across multiple portions of the design.
Pots like dual 10K Log are generally used in pan circuits and sometimes in EQ circuits for variable filters, so I'll try to leverage those for other things like the Aux sends and possibly other portions of the EQ.
I've also thought of ways to consolidate some rotary switches into pots, like for the attack/release controls for the compressor.
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Post by tasteliketape on Jan 8, 2016 21:29:40 GMT -6
Are thes mixer worth 900 dollars plus ?kinda interested in these but have know ideal what they should go for
There's one on reverb supposed to be in great shape
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ericn
Temp
Balance Engineer
Posts: 16,107 
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Post by ericn on Jan 9, 2016 21:31:31 GMT -6
If you have the skills like Chris or have a good tech yes Buy it!
Everybody I know who bought one either bought a second for parts or junked it because while the design was good the cost cutting made for $8000 audio version of a 70s Jaguar! The guys at Alexis new they had screwed the pooch and were way out of their league when it came to building a reliable board!
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Post by svart on Jan 11, 2016 8:47:00 GMT -6
Are thes mixer worth 900 dollars plus ?kinda interested in these but have know ideal what they should go for There's one on reverb supposed to be in great shape If you can get it without shipping costs, then yes. If you have to ship it, then maybe less. If you can, try to get a Rev B board, you'll know them because they are about 2" deeper in the chassis, and the boards are a light brown color rather than a dark green color. Rev B boards have a lot of small fixes for issues found in the Rev A units. |
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Post by svart on Jan 11, 2016 8:48:18 GMT -6
If you have the skills like Chris or have a good tech yes Buy it! Everybody I know who bought one either bought a second for parts or junked it because while the design was good the cost cutting made for $8000 audio version of a 70s Jaguar! The guys at Alexis new they had screwed the pooch and were way out of their league when it came to building a reliable board! Their Rev A version had a lot of small issues. The Rev B boards were a lot more reliable overall, but now the boards have aged so much that a well used board might start needing faders and caps, etc. |
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Post by svart on Jan 11, 2016 8:53:48 GMT -6
So I've been doing a block diagram of the channel to gauge number of pots, switches, etc.
I think I'll add things like:
Insert switching: Pre-filter, post-filter/pre-EQ and post EQ.
Compressor switching: Pre-filter, post-filter/pre-EQ and post EQ.
Doing one large PCB to span the channel length won't work as the PCB becomes prohibitively expensive the larger it gets. What I think I'll do is 3x 1/3 panel PCBs that connect together with edge connectors. That way the PCB can be snapped into 3 sections and then hooked up end to end to form the PCB that spans the entire length of the channel.
I also purchased a bunch of pots and knobs from Ebay, so I'll start layout soon, but I have some work projects and work on the converters to do first.
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Post by tasteliketape on Jan 11, 2016 9:00:39 GMT -6
Thanks guys don't really need a board but would like to have one if not to much money
When I get if ever get my Radar I'll spend on one
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Post by svart on Jan 11, 2016 12:41:14 GMT -6
So I might revise my plans to only include inserts and compressor pre or post EQ and not switch around the filter. I'm not sure it's needed or justified having such complex switching.
If I wanted to switch around the filters as well as the EQ it would need 7 switches, whereas just switching around the EQ reduces the number down to 4, including the bypass switches.
Now, I need to determine if the compressor should be switched before or after the inserts..
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Post by svart on Jan 11, 2016 13:09:27 GMT -6
One of the other possibilities is to have the filters (HPF/LPF) in circuit all the time, but make them variable such that I can turn the HPF down to like 20hz and the LPF up to like 20Khz so that they are essentially out of the way. I almost always use them no matter what, so it wouldn't be a big deal to me if they were always in circuit.
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Post by svart on Jan 11, 2016 16:31:16 GMT -6
And here I thought you guys liked diy..
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Post by EmRR on Jan 11, 2016 18:32:23 GMT -6
This is BIG diy....
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Post by rocinante on Jan 13, 2016 9:37:02 GMT -6
One of the other possibilities is to have the filters (HPF/LPF) in circuit all the time, but make them variable such that I can turn the HPF down to like 20hz and the LPF up to like 20Khz so that they are essentially out of the way. I almost always use them no matter what, so it wouldn't be a big deal to me if they were always in circuit. Why not a 3 p switch? On on off So 80 40 Off |
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Post by svart on Jan 13, 2016 9:48:30 GMT -6
One of the other possibilities is to have the filters (HPF/LPF) in circuit all the time, but make them variable such that I can turn the HPF down to like 20hz and the LPF up to like 20Khz so that they are essentially out of the way. I almost always use them no matter what, so it wouldn't be a big deal to me if they were always in circuit. Why not a 3 p switch? On on off So 80 40 Off I frequently HPF anywhere from 30hz up to 500+Hz. I'd like to have it variable to the point where I can just turn the knob until I need it! It's not that much different than having a switch. Currently on my console I have a switch that patches in different capacitors into the HPF that change the frequency. I could do the same, but with the resistors in the filter, with a triple gang pot, similar to how SSL did theirs in the 4k/9k EQ. Problem is though, that most situations like this call for a reverse (anti) log triple gang pot. A rare animal indeed. Because I'm limited in channel width (1.5"), I can't use larger pots like 24mm, so I'm stuck with 16mm or less for most pots, which limits the available parts. I have found some triple linear pots, so I'm going to try the "law bending" of the linear pots to anti-log. |
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Post by jcoutu1 on Jan 13, 2016 10:37:59 GMT -6
The variable hi-pass filter is 100% the way to go. I'm thinking hard about upgrading from my Midas Venice to a Verona for the variable hi-pass filters and 4 additional busses. I'd love to be able to crank a filter knob to do the job rather than set up a plug-in for filtering.
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Post by rocinante on Jan 13, 2016 10:38:37 GMT -6
Id like to know how this turns out with pots. As a matter of fact that alone would be incredibly valuable for many people. I have read of people making reverse log dual gangs from two pots but the info was vague. It would be great if you could confirm this.
Also yeah this is big diy.
Awesome though.
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Post by svart on Jan 13, 2016 12:15:52 GMT -6
Id like to know how this turns out with pots. As a matter of fact that alone would be incredibly valuable for many people. I have read of people making reverse log dual gangs from two pots but the info was vague. It would be great if you could confirm this. Also yeah this is big diy. Awesome though. There are tons of sites with varying amounts of info about law bending on pots. There are other approaches that do more or less the same thing too. |
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Post by wiz on Jan 26, 2016 15:54:50 GMT -6
And here I thought you guys liked diy.. I am following... just not commenting... keep a posting dude 8) what about harrison filters? I was looking at my Sound Craft Delta, and talking to Joe Malone at JLM audio, about incorporating a mac opto compressor into my channel strip, or at least some of them.. I will have to pinch the op amp from the HPF section, which is no big deal... I will start another thread when I am ready.. Just wanted to say, keep writing, cause you are giving me ideas.. cheers Wiz |
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Post by wiz on Jan 26, 2016 15:56:41 GMT -6
I meant to add... tonycamphd and I were discussing the delta/comp idea... I like my comp to come after my EQ, him before.... both are valid ways, depends on your work flow... So, for me, building a comp into the board, I would put it post EQ and not care about switching it.. cause I figure, if I wanted a comp, pre EQ I would patch it in... cheers Wiz |
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Post by svart on Jan 26, 2016 16:08:05 GMT -6
I meant to add... tonycamphd and I were discussing the delta/comp idea... I like my comp to come after my EQ, him before.... both are valid ways, depends on your work flow... So, for me, building a comp into the board, I would put it post EQ and not care about switching it.. cause I figure, if I wanted a comp, pre EQ I would patch it in... cheers Wiz With my current console, I have jumpers on the PCB to allow pre-eq or post-eq inserts. I find that I like one or the other depending on the situation. Sometimes I'll patch an insert post-eq, then on the insert return I'll patch it to another channel pre-eq, so that I can EQ the insert pre AND post eq.. I think I'll still retain the insert switching and comp switching around the EQ but do it post-filter. It greatly reduces the amount of switching needed when doing it this way. |
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Post by svart on Apr 7, 2016 13:14:57 GMT -6
So I'm going to resurrect this and see where it goes from here.
One of the decisions that need to be made is, what kind of dynamics do I want in this channel?
Honestly I don't care much about expanders or gates, as I do strip silence and all that in the DAW.
I'm a very SSL kinda guy, so I'm cool with doing a stripped down version of either the 4K channel which as a "sound" but would cost more since it utilizes a more rare RMS-to-DC converter (which is still available), which also gives me a gate and expander..
OR
Utilize the THAT audio engine and build a vanilla compressor..
OR
I'm thinking of doing a hybrid compressor that's more like the SSL bus compressor, but stripping it down and using slightly different components. This option would be simpler and cheaper by a lot.
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