brucega
Member
Before Gary Richrath joined REO, he was in a band in Peoria and one of my house mates worked at the tv station where I worked and was their roady. They would practice at our house all the time. Those were some interesting times.
Compact desktop line mixer?
- Thread starter OneRoomStudio
- Start date
Help Support GroupDIY Audio Forum:
MidnightArrakis
Well-known member
[Did you manage to record any live Grateful Dead to cassette?] -- I, myself personally, didn't record the YES concert. That show was actually recorded by the -- YES -- FOH mix engineer using their own equipment and he -- GAVE ME!!! -- the two complete cassette tapes of that show!!! He patched in a rack-mount TECHNICS RS-M85 MKII into the "Stereo Send" signal that was feeding the stereo-audio signal down to the PA amp-racks!!! So, this signal was the "Stereo Out" signal from his mixing console and AFTER all of the signal-processing equipment and then going out to the entire PA-system!!! MAN!!! You talk about one POWERFUL sound on tape!!! THIS IS IT!!!.....
A couple of weeks or so later, I took those YES cassettes and my own TECHNICS RS-M85 MKII cassette deck over to a 24-track studio I occasionally worked at and carefully transferred the 2 cassettes over to 3 - 10-1/2" reels of SCOTCH 207 tape. Instead of running the signal through a stereo compressor, I manually "rode the faders" in order to smooth out the audio from the PA mix. It became somewhat apparent (to me, at least) that after a few repeated listening's of this concert, that I could hear what were small changes in level in the PA were rather noticeable changes in the cassette.
So, I had made a whole list of careful notes marking the time-stamp and the amount of level change at each point. Then, as I played the cassette and was recording onto an AMPEX 440 deck, I was "riding the faders" and acting as a "human compressor". All-in-all.....the end result is absolutely stunning!!! Easily at least 5-times better audio quality than any of the recorded YES "LIVE" releases!!! And.....it was so cool for me to be sitting at the console in a 24-track studio while listening to YES in a recording studio environment. I'll never forget that memory!!! Here's the tape-deck:
I had absolutely no idea at that point-in-time that just a few years later, I would find myself working at "one of the largest concert sound-reinforcement companies in the world" (at that time) and would end up mechanically designing the actual "10,000-Watt Transportable Amplifier Racks" that YES would be using during their 1984 South American Tour!!! So.....that was also thrilling!!!
>> EDIT: And.....here are the "10,000-Watt Transportable Audio-Amplifier Racks" I had mechanically-designed, as well as designing the internal-rack wiring-harness. In addition, I had also designed a "1U Rack-Mount 9-Fan Chassis" that was placed in-between each of the audio-amplifiers for cooling purposes:
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---------------- "1U Rack-Mount 9-Fan Chassis" -----------------------------------------
/
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studio1117
New member
I don't think anybody has mentioned this: https://www.ams-neve.com/outboard/88-series-range/8816-summing-mixer/. or it's deluxe sibling: https://www.ams-neve.com/consoles/small-format-consoles/neve-8424/
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Great story! Sounds like the profesion you chose combines quite a few interest of yours, always a good thing
I've been eyeing that for quite some time but the 8816 plus 8804 approaches 4 or 5 grand. It's what I would consider best of all worlds form factor and feature set wise that price for me is where I start looking for diy solutions tho
Back to the original topic, I was looking at Ian's document, and saw his comparison of single- vs dual-pot panning.
For the single-pot design, he says:
"In the centre position, equal signals from the input (IN) are sent to the L and R buses. At the extremes, one bus has its bus resistor shorted to ground so it receives no signal. The other bus receives a signal level slightly higher than at the centre position. With the values shown (different from my values), the levels fed to each bus in the centre position are 10.8dB below the level at IN. With the pan pot at one extreme, the bus receiving a signal gets a level which is 7.8dB below the level at IN. The level at the centre is thus 3dB below the hard panned level. The advantage of this circuit is that it only uses a single gang potentiometer. Its disadvantage is that even when hard panned there is a loss of level. This will require additional gain later in the signal chain to restore the level and this will inevitably increase noise.The worst case crosstalk between buses with this circuit occurs with the control centred. Another advantage of this circuit is that the crosstalk reaching IN from a bus is attenuated twice; once by the bus feed resistor and the pan pot and then by the 22K resistor and theamplifier source resistance. The overall effect is to reduce the worst case crosstalk by 10dB."
For the dual-pot design, he says:
"The advantage of this circuit is that it it has no loss when panned hard left or right and only 3dB in the centre. This means less gain make up is required compared to the previous circuit which reduces noise. The disadvantage of this circuit is that it loads the driving amplifier with about 7K. As this pan control has no insertion loss there is no improvement in crosstalk. Worst case crosstalk occurs with the control centred."
So...they both have the worst crosstalk in the center (as I would expect). The single-pot results in 7.8dB less level than the dual-pot, but has lower overall crosstalk. Since we're keeping these circuits simple, using low-noise opamps, and have a low channel count, is the gain increase really worth the expense of a dual-pot and worse crosstalk performance?
For the single-pot design, he says:
"In the centre position, equal signals from the input (IN) are sent to the L and R buses. At the extremes, one bus has its bus resistor shorted to ground so it receives no signal. The other bus receives a signal level slightly higher than at the centre position. With the values shown (different from my values), the levels fed to each bus in the centre position are 10.8dB below the level at IN. With the pan pot at one extreme, the bus receiving a signal gets a level which is 7.8dB below the level at IN. The level at the centre is thus 3dB below the hard panned level. The advantage of this circuit is that it only uses a single gang potentiometer. Its disadvantage is that even when hard panned there is a loss of level. This will require additional gain later in the signal chain to restore the level and this will inevitably increase noise.The worst case crosstalk between buses with this circuit occurs with the control centred. Another advantage of this circuit is that the crosstalk reaching IN from a bus is attenuated twice; once by the bus feed resistor and the pan pot and then by the 22K resistor and theamplifier source resistance. The overall effect is to reduce the worst case crosstalk by 10dB."
For the dual-pot design, he says:
"The advantage of this circuit is that it it has no loss when panned hard left or right and only 3dB in the centre. This means less gain make up is required compared to the previous circuit which reduces noise. The disadvantage of this circuit is that it loads the driving amplifier with about 7K. As this pan control has no insertion loss there is no improvement in crosstalk. Worst case crosstalk occurs with the control centred."
So...they both have the worst crosstalk in the center (as I would expect). The single-pot results in 7.8dB less level than the dual-pot, but has lower overall crosstalk. Since we're keeping these circuits simple, using low-noise opamps, and have a low channel count, is the gain increase really worth the expense of a dual-pot and worse crosstalk performance?
Ok, I found a panning circuit that @NewYorkDave designed that is simple and elegant, so I incorporated that, as well as a pre-fader peak-detector and a post-fader bar-graph meter. I also tweaked the solo to be AFL and to light an LED and have the ability to trigger a relay going to the monitor, like a true solo. Now the features are:
-THAT 1200 balanced line receiver
-Peak Detector
-Mute, Solo, Fader, Pan
-Aux sends 1 & 2 are mono sends with pre/post fader and level
-Aux send 3 is stereo with pre/post, level, and pan
-Post-fader 20-segment bar-graph LED VU meter
-Fairly inexpensive, flexible, and only 3 electrolytics in the signal path!
-THAT 1200 balanced line receiver
-Peak Detector
-Mute, Solo, Fader, Pan
-Aux sends 1 & 2 are mono sends with pre/post fader and level
-Aux send 3 is stereo with pre/post, level, and pan
-Post-fader 20-segment bar-graph LED VU meter
-Fairly inexpensive, flexible, and only 3 electrolytics in the signal path!
ruffrecords
Well-known member
I am not sure which NY Dave pan circuit you are referring to but as drawn the right bus will never get any signal.
And in response to your prior post re pan controls where you say:
"The single-pot results in 7.8dB less level than the dual-pot, but has lower overall crosstalk. Since we're keeping these circuits simple, using low-noise opamps, and have a low channel count, is the gain increase really worth the expense of a dual-pot and worse crosstalk performance?"
The answer is it depends. If you are happy with 7.8dB more best case noise then use the single pot version. My original crosstalk comments were in the context of passive mixing. If you use virtual earth mixing then crosstalk in pan pots is pretty much a non-issue. Dual pots are not that expensive. I tend to use vertical Alpha pots because you can mount them directly to a PCB which sits parallel to the front panel - and the Alpha dual gang pot is the same size as the single gang (and not a lot different in price) and they do a version with centre detent which is ideal for pan pots. e.g.
https://www.thonk.co.uk/shop/alpha-9mm-pots-dshaft/
Cheers
ian
You’re absolutely right, I made a (dumb) copying error - the bottom of the lower pot should connect to the top of the upper pot as seen here.
Brian Roth
Well-known member
A couple of observations:
1. Dave's design seems to be for passive summing. If an active summer is used, the 5k1 resistors could be omitted which will decrease the loss in the circuit.. I'll dig up some typical panner circuits used in "mainstream" consoles and post them as examples.
2. Since the Aux 3 level control isn't buffered, the pan pot circuit will load the wiper and throw off the taper.
3, Coupling cap C9 seems too low in value considering how many pots are in parallel. I need to print out the schemo and crunch numbers.
4. I would feel better if the AFL control line switch was connected to the control bus with a series resistor.
I see Feature Creep with the added meters <g>. IMHO they should be powered from a separate supply to keep all that "chatter" isolated from the audio circuits.
Since I'm still snow-bound at home (2 weeks now!) I'll spend some more time pondering this all. In my mind, the X-Desk is kind of the target design. Just for grins, here is the block diagram.
Bri
Brian Roth
Well-known member
I just tried uploading that file (after renaming) to the FP Express website's "webshop" page to get a price quote (I was curious) but it would not recognize it as a valid file.
Maybe tomorrow I'll download their app and try it that way....
Bri
MidnightArrakis
Well-known member
[it would not recognize it as a valid file] -- I imported Ian's FPD-file and then turned right around and did a "Save As" just to "freshen" it up a bit. However, I also changed the name just a tad in order to differentiate it from its original file. The newly "freshened" file is attached here with the added new extension of -- .pdf -- so it will upload on this forum. Should you wish to use this file, just remove the -- .pdf -- extension and you will be "Good-To-Go"!!!
Then, when I uploaded my file to "Front-Panel Express", it was accepted immediately, while also producing the price-quote that you see below. So, this tells me that at least my file "works". Your call as to what to do next. I, at least, can confirm that this file "works"!!!
/
All great feedback, and I appreciate the help. In my mind, I think the block diagram for this mixer can be a lot simpler than the X-Desk. Here's a rough idea of what I was thinking (I got a little lazy with some of the stereo buses and balanced connections - but hopefully you get the idea):
ruffrecords
Well-known member
I have a general question about the stereo AUX send. Are there actually any truly stereo FX units with analogue inputs? The only ones I have ever seen with stereo inputs simply mono the inputs before effecting them complete with pseudo stereo for the output.
Cheers
Ian
Cheers
Ian
Brian Roth
Well-known member
If I thought hard enough (a SCARY concept! lol) I could come up with something. OTOH a stereo aux is handy for creating a stereo cue mix.
Bri
They aren’t quite as common, but there are plenty of stereo-in spring & plate reverbs, as well as analog choruses (i.e., Dimension D), and even some newer analog delays are true-stereo. Plus - as @Brian Roth mentioned, it gives you the option to create a stereo cue mix or any other stereo sub-mix
Brian Roth
Well-known member
I just recalled one. Decades ago I built a semi-clone of the Aphex Exciter. It was stereo in/out and was fed from a stereo aux on the MCI desk.
Bri
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