I agree that Baxandals ALONE are not the sort of EQ you would expect on what the OP now calls a 'pro' mixer. As I said before they are quite limited but they do have their uses.
What I seem unable to get across to you is that EQ is not just about correcting deficiencies in other parts of the signal chain. It is an artistic tool used to help paint a sound picture so it is quite appropriate to use it on ANY instrument for that purpose.
Cheers
Ian
I totally agree with you that a paint brush is a good tool! But I can't imagine Leonardo wearing professional belt with many pockets, with flat painter's brush of the same form and size from Home Depot in each pocket...
Right; that's why pockets are needed, to put a needed brush in each, when needed! It is called Inserts for Outboard Gear, speaking Professional Language of Audio Engineers.
For a sine wave, 10V * 1.414 = 14.14V peak.
Ohm's Law: 14/2 = 7
But actual signals on outputs of mixers are not sine waves.
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Unfortunately, analogies only work to an extent. Whatever your personal feeling about what a professional mixer should or should not include, the fact is that the majority of professional mixers today have comprehensive EQ per channel (in fact this has been the case for over 30 years). And they all include a Baxandal type HF/LF boost. They may be a more sophisticated version with switched frequencies but they are essentially the same.
They all have inserts too which may occasionally be used for EQ that is not provided by the channel strip but more often they will be used to insert special effects into a single channel.
Cheers
Ian
Do you want schematics of professional mixers? I have some...
First of all, channel strip EQs are more than just Baxandals.
Second, they are zero insert loss, and third they are bypassable.
However, if you mean some cheap mixers for rock groups, they sometimes had Baxandals always on, non-bypassable, but is it your professional feeling on what professional mixer have to look like them?
Good luck!
Hi Antonio,
Your general schematic explains a lot about what I meant when I asked the intended use.
From this, it looks like your mixer is for a special purpose:
10 input channels (duh) with mic amps and line inputs, selectable per channel, aikido mic amps.
Each channel has an aikido makeup gain amp ahead of a passive Baxandall filter.
Each channel has an insert that bypasses the makeup amp and filter.
The monitor is set up as four mono sends pre-EQ and pre-fader (despite what's shown on the other diagram...)
There are 3 main buses, 2 mono called "voice" and "bass" and a stereo LR with a pan control.
How the summing on the main buses actually works is not clear but feedback is your friend here.
So far this seems pretty straightforward for a live PA mixer for a small ensemble.
OK, the monitors. What you seem to have in mind is a 4x10 send matrix ala Allen&Heath small PA boards. You'll want to add a master volume for each monitor channel.
You only need one buffer for all 4 send pots on each channel and with the source as shown do not need RC coupling.
Can you calculate the low cutoff frequency of the RC network? Set the values to something that makes sense for your use, like 20 Hz or so.
R4 is not necessary.
For the choice of IC, I'd suggest looking at THAT Corp. for the balanced line driver. They have a nice single chip solution that has good common mode and one-side-shorted characteristics, which will be improvements on your circuit.
For the other opamps, anything with decent gain bandwidth. TL082, NE5532 if you want to get fancy. This is a really uncritical appication.
If you think you might one day want to use your monitor outs as effects sends or aux recording outputs, get a little more picky.
As far as the rest of the signal path, I'd say do go and study some more mixer schematics to look at summing techniques, etc. and start thinking about your gain and level structure interms of nominal level e.g. +4 dBu and headroom to clipping throughout your signal chain inside the mixer. Also think about the noise floor vs. signal levels as you have the gain structure at some extremes.
One example, why would you want more than unity gain from your line input to yout insert return?
How will you control the gain of the aikido stages, and how does that influence the channel noise with the fader all the way up?
Also I'd recommend thinking about your gain/level in dB and dBu, which make it a lot clearer and easier to understand (at least for others in the business).
No phantom power? Direct Instrument inputs?
For the input switching there are some clever ways to arrange relays for phase/mute/P48 bypass.
Anyway, it looks like you have a workable direction for your specific purposes.
cheers,
Michael
Your general schematic explains a lot about what I meant when I asked the intended use.
From this, it looks like your mixer is for a special purpose:
10 input channels (duh) with mic amps and line inputs, selectable per channel, aikido mic amps.
Each channel has an aikido makeup gain amp ahead of a passive Baxandall filter.
Each channel has an insert that bypasses the makeup amp and filter.
The monitor is set up as four mono sends pre-EQ and pre-fader (despite what's shown on the other diagram...)
There are 3 main buses, 2 mono called "voice" and "bass" and a stereo LR with a pan control.
How the summing on the main buses actually works is not clear but feedback is your friend here.
So far this seems pretty straightforward for a live PA mixer for a small ensemble.
OK, the monitors. What you seem to have in mind is a 4x10 send matrix ala Allen&Heath small PA boards. You'll want to add a master volume for each monitor channel.
You only need one buffer for all 4 send pots on each channel and with the source as shown do not need RC coupling.
Can you calculate the low cutoff frequency of the RC network? Set the values to something that makes sense for your use, like 20 Hz or so.
R4 is not necessary.
For the choice of IC, I'd suggest looking at THAT Corp. for the balanced line driver. They have a nice single chip solution that has good common mode and one-side-shorted characteristics, which will be improvements on your circuit.
For the other opamps, anything with decent gain bandwidth. TL082, NE5532 if you want to get fancy. This is a really uncritical appication.
If you think you might one day want to use your monitor outs as effects sends or aux recording outputs, get a little more picky.
As far as the rest of the signal path, I'd say do go and study some more mixer schematics to look at summing techniques, etc. and start thinking about your gain and level structure interms of nominal level e.g. +4 dBu and headroom to clipping throughout your signal chain inside the mixer. Also think about the noise floor vs. signal levels as you have the gain structure at some extremes.
One example, why would you want more than unity gain from your line input to yout insert return?
How will you control the gain of the aikido stages, and how does that influence the channel noise with the fader all the way up?
Also I'd recommend thinking about your gain/level in dB and dBu, which make it a lot clearer and easier to understand (at least for others in the business).
No phantom power? Direct Instrument inputs?
For the input switching there are some clever ways to arrange relays for phase/mute/P48 bypass.
Anyway, it looks like you have a workable direction for your specific purposes.
cheers,
Michael
Michael,
I thank very very much for your long, critical, and helpful reply.
The mixer was born as a project for my son (16 yrs) ... that has a musical group.
After reading your reply ... I got some doubt whether we'll be able to realize such a complex device. I've only a little experience in Electronics and tube amp (I'm a medical doctor), even though I have realized several tube amplifiers and numerous other electronic devices.
In addition, that project requires considerable costs and time (the last not scaring me).
Profiting of your experience (you are an engineer) and before embarking into a such complex project I'd like to ask if you think that the the game worth the candle (effort) ... in order to avoid an icarus flight.
Many thanks ...again
Antonio
I thank very very much for your long, critical, and helpful reply.
The mixer was born as a project for my son (16 yrs) ... that has a musical group.
After reading your reply ... I got some doubt whether we'll be able to realize such a complex device. I've only a little experience in Electronics and tube amp (I'm a medical doctor), even though I have realized several tube amplifiers and numerous other electronic devices.
In addition, that project requires considerable costs and time (the last not scaring me).
Profiting of your experience (you are an engineer) and before embarking into a such complex project I'd like to ask if you think that the the game worth the candle (effort) ... in order to avoid an icarus flight.
Many thanks ...again
Antonio
Hi Antonio,
Elaborating on what Michael Koster has observed, the intended use for the mixer appears to be for PA use on a small group.
I see it important to also know whether the mixer is being designed for a specific ensemble - a band you regularly work/perform with - or something you wish to be able to use on any group that doesn't exceed the input capabilities. Also, are you feeding moderate power amps and small to med FOH speakers or BIG amps with subs etc?
Point here being that there's quite a difference in groups playing mostly acoustic type instrumentation and your average headbanging rock band as far as your EQ needs, headroom, input padding and aux patching is concerned.
I think that either situation will call for a comprehensive EQ and the suggestion of an insert is a good idea. Live mixing will be seldom if ever be ideal and you should expect the extremes. Cutting rumble for small speakers on stands may not be as critical as it would be with big amps and sub boxes. sussing out gain before feedback often requires small bandwidth capabilities.
Mic placement technique helps but the realities of room/stage signatures, musicians preferenceseek, and shrinking time schedules in the face of watch tapping club owners and antsy fans often force the solution into the hands of an equalizer - and you do want to have a good one ready. Unfortunately for most live use situations, EQ for subtle sweetening is often swamped by the demands for survival. The struggle for gain before feedback can send most ideal tonal balance plans far off course.
Adding an insert with some type of buffering and removing the existing EQ would simplify the design a bit and improve the impedance/loading issues that Ian alluded to. Passive loss should be returnable to unity since most outboard EQs have an onboard gain section.
If this were a studio only design I think the Baxandall could be designed and used to good results but I see it being limited in scope by the realities of most live mixing situations. There may be some close to ideal situations where you could get by well with the Baxandall + outboard EQs on the monitor sends and main outs. It really depends on your needs and situation.
Best of luck with the build!
Elaborating on what Michael Koster has observed, the intended use for the mixer appears to be for PA use on a small group.
I see it important to also know whether the mixer is being designed for a specific ensemble - a band you regularly work/perform with - or something you wish to be able to use on any group that doesn't exceed the input capabilities. Also, are you feeding moderate power amps and small to med FOH speakers or BIG amps with subs etc?
Point here being that there's quite a difference in groups playing mostly acoustic type instrumentation and your average headbanging rock band as far as your EQ needs, headroom, input padding and aux patching is concerned.
I think that either situation will call for a comprehensive EQ and the suggestion of an insert is a good idea. Live mixing will be seldom if ever be ideal and you should expect the extremes. Cutting rumble for small speakers on stands may not be as critical as it would be with big amps and sub boxes. sussing out gain before feedback often requires small bandwidth capabilities.
Mic placement technique helps but the realities of room/stage signatures, musicians preferences
eek, and shrinking time schedules in the face of watch tapping club owners and antsy fans often force the solution into the hands of an equalizer - and you do want to have a good one ready. Unfortunately for most live use situations, EQ for subtle sweetening is often swamped by the demands for survival. The struggle for gain before feedback can send most ideal tonal balance plans far off course.Adding an insert with some type of buffering and removing the existing EQ would simplify the design a bit and improve the impedance/loading issues that Ian alluded to. Passive loss should be returnable to unity since most outboard EQs have an onboard gain section.
If this were a studio only design I think the Baxandall could be designed and used to good results but I see it being limited in scope by the realities of most live mixing situations. There may be some close to ideal situations where you could get by well with the Baxandall + outboard EQs on the monitor sends and main outs. It really depends on your needs and situation.
Best of luck with the build!
No thanks, I have plenty from when I designed mixers at Neve in the 70s.
That's what 'comprehensive EQ' means.
Indeed.
I think you are missing my point. I was not commenting on the OPs implementation, merely stating that all pro mixers include Baxandal like EQ per channel. Whether they are bypassable or zero insertion loss was not at issue.
The OP's design as it stands is not what I would call 'pro'.
Cheers
Ian
You probably designed Baxandal EQs for channel strips. I see now...
...it is off-topic then.
I was just trying to help Antonio to save time, money, dynamic range, and get more optimal design: he probably does not have a marketing department who's requirements he must satisfy, so is free in choices in topology & architecture...
That's a good goal. I think we first need to hear from Antonio exactly what he is going to use this mixer for - then we'll be in a much better position to advise him.
However, he did say it is for his son's musical group (which could be anything from an acoustic ensemble to a rock band), so my first reaction (knowing how impatient 16 year olds can be) would be to advise him to go out and buy one. There must be a Soundcraft, Behringer, Mackie etc that would be more than sufficient for his son's needs.
Cheers
Ian
Right. I recently bought for my brother in law Behringer 16 channel mixer; it has all controls and even reverberator inside; more than needed for a rock group, including phantom power; in a 4U box. And it costs a fraction of what I paid for my input transformers only for my 8 channel powered tube mixer which consumes the same 300+W for mic pres as for the power amp.
I disagree...
I think if Antonio wants to build a desk you should help him with your experience, and not offer alternatives. Especially Behringer desks, right, it may be for a teenagers band but from my experience Behringer mixers have never sounded good, and this clearly isnt the aim of the thread.
I often ask similar questions with my designs, and am always grateful for the help, as I am a novice designer. Im sure the experience there is on this forum you guys could help Antonio come up with the design he wants.
Charlie
I think if Antonio wants to build a desk you should help him with your experience, and not offer alternatives. Especially Behringer desks, right, it may be for a teenagers band but from my experience Behringer mixers have never sounded good, and this clearly isnt the aim of the thread.
I often ask similar questions with my designs, and am always grateful for the help, as I am a novice designer. Im sure the experience there is on this forum you guys could help Antonio come up with the design he wants.
Charlie
Hi Charlie old friend,
I agree we should give Antonio the benefit of our advice and skills and if he really wants to build this console then I for one am happy to help him. It's just that as the father of three grown up children I know that his son is likely to run out of patience before Antonio finishes building it. So maybe he should buy his son a cheap mixer AND build this one too.
Cheers
ian
Hi Charlie,
Despite my protracted discussion with wavebourn on whether a mixer needs EQ or not, the answer really does depend on the application. For example, right now I am building a 6 into two all tube mixer for a guy in the USA. This is intended for on location classical music recording. The only EQ it has is a switched high pass filter per channel.
See attached picture of the prototype PCB.
Cheers
Ian
Despite my protracted discussion with wavebourn on whether a mixer needs EQ or not, the answer really does depend on the application. For example, right now I am building a 6 into two all tube mixer for a guy in the USA. This is intended for on location classical music recording. The only EQ it has is a switched high pass filter per channel.
See attached picture of the prototype PCB.
An externally hosted image should be here but it was not working when we last tested it.
Cheers
Ian
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