FALKEN
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mshilarious said:
thanks!!! u just saved me a bunch of cash, time, and aggravation!!!! I couldn't be more appreciative.
thanks!!! u just saved me a bunch of cash, time, and aggravation!!!! I couldn't be more appreciative.
mshilarious
Banned
FALKEN said:
Hey if you still need a box, check out this auction:
http://cgi.ebay.com/ws/eBayISAPI.dl.../search.dll?from=R40&satitle=5860447910&fvi=1
FALKEN
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nice!
Acutally, I decided to change the design slightly, to allow for more upgrades later. I ordered up 3 2-space racks and 2 1-space racks. each of the 2-space racks will hold 8 channels. so I will first build 8, and then 16, and eventually 24. each 8-channel box will have bus outputs and inputs (thru) so that they will daisy-chain. eventually the busses will terminate at one of the 1-space racks. The other 1-space rack is going to be a double-M/S matrix (encode/decode with spread). Its going to be a lot of work but I figure if I do it this way I can constantly grow and expand. I could even build in active circuitry if I want.
I already ordered all of the parts. It wasn't cheap but I think I'm going to be happy. at least if I'm not this time I can only blame myself. NOT foreign companies or sleazy ebay sellers.
I have been experimenting more with the small circuit I built and I think I am getting hiss from going into the preamp unbalanced. It would be nice if I could figure out how to add output transformers to it. I guess its another week of no sleeping for me until I figure this out. I have already searched a bunch and I think I could go 1:1 but if I go 4:1 I think I could eliminate the shunt resistor. but I have no idea.
Acutally, I decided to change the design slightly, to allow for more upgrades later. I ordered up 3 2-space racks and 2 1-space racks. each of the 2-space racks will hold 8 channels. so I will first build 8, and then 16, and eventually 24. each 8-channel box will have bus outputs and inputs (thru) so that they will daisy-chain. eventually the busses will terminate at one of the 1-space racks. The other 1-space rack is going to be a double-M/S matrix (encode/decode with spread). Its going to be a lot of work but I figure if I do it this way I can constantly grow and expand. I could even build in active circuitry if I want.
I already ordered all of the parts. It wasn't cheap but I think I'm going to be happy. at least if I'm not this time I can only blame myself. NOT foreign companies or sleazy ebay sellers.
I have been experimenting more with the small circuit I built and I think I am getting hiss from going into the preamp unbalanced. It would be nice if I could figure out how to add output transformers to it. I guess its another week of no sleeping for me until I figure this out. I have already searched a bunch and I think I could go 1:1 but if I go 4:1 I think I could eliminate the shunt resistor. but I have no idea.
FALKEN
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I feel that I should qualify my last post. I know that a 24 input passive mixer with busses is too much. but....I have a work-around.
That is, to use 6 channels of gain makeup.
the input channel will look like this:
in--->vol--->mute--->pan switch(3 pos rotary)--->bus switch(3 pos rotary)
the 3 bus positions are 1-2,3-4,LR
so, by using that in combination with the pan switch I can have 4 busses plus stereo mix. the busses will output to standard mic preamps, which will feed into 4 more channels of the mix bus, each with pan as well.
So, by using the busses, I am actually taking channels off of the main bus. This should help maintain the integrity of the signal.
For the bus resistors I am using 20k so for the center pan resistor I chose 8.6k. Not sure if that was exactly right but it shoudl'nt be that far off I hope. I got several sets of resistors to use on the shunt so I could try some things out.
I really appreciate all of the help.
That is, to use 6 channels of gain makeup.
the input channel will look like this:
in--->vol--->mute--->pan switch(3 pos rotary)--->bus switch(3 pos rotary)
the 3 bus positions are 1-2,3-4,LR
so, by using that in combination with the pan switch I can have 4 busses plus stereo mix. the busses will output to standard mic preamps, which will feed into 4 more channels of the mix bus, each with pan as well.
So, by using the busses, I am actually taking channels off of the main bus. This should help maintain the integrity of the signal.
For the bus resistors I am using 20k so for the center pan resistor I chose 8.6k. Not sure if that was exactly right but it shoudl'nt be that far off I hope. I got several sets of resistors to use on the shunt so I could try some things out.
I really appreciate all of the help.
frederic
New member
mshilarious said:
I'm now watching that auction. I think I just found a new case for my new bench power supply I started soldering together.
FALKEN
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argh!
ok. I wanted my next post in this thread to contain pictures, but we are not quite there yet.
My futurlec order came today (from bangkok!).
so, eh, I dont know quite how to explain this, but, although my rotary switches and my 10k pots *looked* the same size on the website, they are not even close. The shaft (?) of the rotary switch sticks out like an inch further than it needs to be. it is not the kind that you cut down either like from radio shack. argh!!! and the volume pots are like, miniature!! it might not matter but I'm not sure yet. both of them have a metal piece on the side that I'm not quite sure how to deal with. the piece sticks out in the same direction as the shaft (again, not sure if you call it that) and I guess it is there to keep the pot from rotating in its position. when I was building my altoids mixer I just cut that part off and sanded it (which was grueling, but I didn't know what else to do) and I'd rather not do that 53 times if I could avoid it. arrgh!!! I think using an extra nut might get me where I want to be. though I'm still not sure about what to do about the rotary switches and the volume pots. they are so weird. the switches are almost like they are intended to be installed a half inch *behind* the face of the unit. and the volume pots I just expected to be bigger but these might be useful to squeeze an aux in or something later. the dpdt switches are the "extra heavy duty kind and each one takes up about a single rack space, not to mention that they are not very easy to maniupulate; they probably are not going to work very well for mute switches which have to be activated very precisely......its like I screwed up every single aspect of this....I'm off to a great start.
what should I do?
ok. I wanted my next post in this thread to contain pictures, but we are not quite there yet.
My futurlec order came today (from bangkok!).
so, eh, I dont know quite how to explain this, but, although my rotary switches and my 10k pots *looked* the same size on the website, they are not even close. The shaft (?) of the rotary switch sticks out like an inch further than it needs to be. it is not the kind that you cut down either like from radio shack. argh!!! and the volume pots are like, miniature!! it might not matter but I'm not sure yet. both of them have a metal piece on the side that I'm not quite sure how to deal with. the piece sticks out in the same direction as the shaft (again, not sure if you call it that) and I guess it is there to keep the pot from rotating in its position. when I was building my altoids mixer I just cut that part off and sanded it (which was grueling, but I didn't know what else to do) and I'd rather not do that 53 times if I could avoid it. arrgh!!! I think using an extra nut might get me where I want to be. though I'm still not sure about what to do about the rotary switches and the volume pots. they are so weird. the switches are almost like they are intended to be installed a half inch *behind* the face of the unit. and the volume pots I just expected to be bigger but these might be useful to squeeze an aux in or something later. the dpdt switches are the "extra heavy duty kind and each one takes up about a single rack space, not to mention that they are not very easy to maniupulate; they probably are not going to work very well for mute switches which have to be activated very precisely......its like I screwed up every single aspect of this....I'm off to a great start.
what should I do?
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mshilarious
Banned
FALKEN said:
You drill a little hole next to the shaft hole for the tab.
The switches, I dunno. Post a pic, lemme see. Or maybe a link to the spec sheet.
Moral: always read the dimensions in the spec sheet
FALKEN
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eh; um; hmmm;
a little hole next to the shaft?
um......
all the way through the face?
won't that be ugly as hell?
unless I'm incredibly stupid (total possibility) I don't think I've ever seen that on any of my gear before......
The switches I can use for something else later on I am sure...
here was the description:
DPDT11EX DPDT on-on Extra Heavy Duty Toggle Switch
my other option was this:
DPDT11 DPDT on-on Miniature Toggle Switch
not what I think I wanted (maybe it is)
unfortunately there were no spec sheets that I can see on futurlec for the switches.
here is the rotary switch i got:
http://www.futurlec.com/Switches/ROTP4P3.shtml
and here is the 10k pot:
http://www.futurlec.com/Potentiometers/POT10K.shtml
which is actually only about the size of one "link" of one finger, but the shaft is a normal diameter. despite this it could actually "work", unlike the rotary switch, which is just tooo long.
The stuff I got from parts express all came much more quickly and was what I wanted. I am wondering if I should try to return this stuff or just start building even though i'll have to replace the parts anyway. or maybe I can modify the parts; I'm not even sure.
I am still really appreciative of all of your help; when my band finally goes on tour im goin to take you and frederick out for drinks or somethin. hopefully in may!!
a little hole next to the shaft?
um......
all the way through the face?
won't that be ugly as hell?
unless I'm incredibly stupid (total possibility) I don't think I've ever seen that on any of my gear before......
The switches I can use for something else later on I am sure...
here was the description:
DPDT11EX DPDT on-on Extra Heavy Duty Toggle Switch
my other option was this:
DPDT11 DPDT on-on Miniature Toggle Switch
not what I think I wanted (maybe it is)
unfortunately there were no spec sheets that I can see on futurlec for the switches.
here is the rotary switch i got:
http://www.futurlec.com/Switches/ROTP4P3.shtml
and here is the 10k pot:
http://www.futurlec.com/Potentiometers/POT10K.shtml
which is actually only about the size of one "link" of one finger, but the shaft is a normal diameter. despite this it could actually "work", unlike the rotary switch, which is just tooo long.
The stuff I got from parts express all came much more quickly and was what I wanted. I am wondering if I should try to return this stuff or just start building even though i'll have to replace the parts anyway. or maybe I can modify the parts; I'm not even sure.
I am still really appreciative of all of your help; when my band finally goes on tour im goin to take you and frederick out for drinks or somethin. hopefully in may!!
mshilarious
Banned
FALKEN said:
The knob should cover it up. Or you can bend back the tab with pliers.
Also note those pots are PC mount; you probably want solder lugs if you are doing point to point writing. Mouser sells those; they are $1 though rather than Futurlec, which for what they have is really low. Mouser part # is 313-1520F-10K. These are 16mm miniature pots rather than the standard 24mm you see on guitars, but the shaft is the same size so it shouldn't matter. However, if you want 24mm the Mouser part # is 313-2440F-10K.
The switches, try looking on p. 1221 of the Mouser catalog. I think 691-2BL62-73 is what you want, unfortunately it's $8.82
That's still cheaper than the guitar-style Switchcraft DPDT. If you want to go for the mini-toggle switch, those are about half that. Although for a mute I'd want a pushbutton switch anyway, those are much cheaper.
FALKEN
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so how have you been?
I am very close to completing this thing. I have one of the 8 channel racks drilled and a couple channels put together and working. Each channel includes a mute switch, volume, 3-position pan, and a bus selector. I am going to add an effect send, a high-pass filter and a low pass filter. I have already tested the high-pass and it works pretty good. I am confident that the low pass will work also. So far, everything is good.
I think I can control the amount of low pass by using a pot connected to a cap which is connected to ground. I think this is similar to a guitar's tone control circuit.
I am wondering if there is any way to control the cutoff frequency with a pot instead of the amount of cutoff.
Any Ideas?? Also, where in the circuit should the eq filters go?
So far the chain is:
input jack-->volume pot-->eq filter-->mute switch-->pan-->bus and it seems to be working just fine.
I am very close to completing this thing. I have one of the 8 channel racks drilled and a couple channels put together and working. Each channel includes a mute switch, volume, 3-position pan, and a bus selector. I am going to add an effect send, a high-pass filter and a low pass filter. I have already tested the high-pass and it works pretty good. I am confident that the low pass will work also. So far, everything is good.
I think I can control the amount of low pass by using a pot connected to a cap which is connected to ground. I think this is similar to a guitar's tone control circuit.
I am wondering if there is any way to control the cutoff frequency with a pot instead of the amount of cutoff.
Any Ideas?? Also, where in the circuit should the eq filters go?
So far the chain is:
input jack-->volume pot-->eq filter-->mute switch-->pan-->bus and it seems to be working just fine.
mshilarious
Banned
FALKEN said:
Sounds good to me. That does control the cutoff frequency.
FALKEN
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mshilarious said:
hmm... seems to me it would just control the amount of highs that are sent to ground. I'll have to think about that one for a while....
mshilarious
Banned
FALKEN said:
No, a simple RC filter is a 6dB/octave drop. The corner frequency is a function of the capacitor and resistor values.
FALKEN
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hmm...
I'll have to look at that formula again.
If I put it on a switch instead of a pot do I even have to use a resistor? I was just thinking of just shunting the highs above 16k to eliminate tape hiss on tracks that don't need the highs.
I'll have to look at that formula again.
If I put it on a switch instead of a pot do I even have to use a resistor? I was just thinking of just shunting the highs above 16k to eliminate tape hiss on tracks that don't need the highs.
mshilarious
Banned
FALKEN said:
No, you wouldn't need a resistor, you would just select a capacitor value based on the impedance of the circuit before the capacitor.
FALKEN
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mshilarious said:
right on; that's what I thought. I think I am really starting to get this stuff. Thanks again.
FALKEN
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Well,
I finally finished building this thing. It works pretty good. 8 channels, volume, pan, mute, and 1 aux send per channel. the aux can be used for a headphone mix or a reverb send or even a subgroup. I just have a couple channels to debug, which are most likely acting up because something came loose or I made a bad joint. There's probably over 300 joints so I'm not surprised by that.
Tonight, I will try and build the power supply, and see about adding some TL082's to this thing. If those work out, I will order up something nicer. Are there any safety precautions I need to take so that I don't kill myself? What should I get at radio shack to build the supply on? I'm assuming you can't run wall current through one of those pcb's, right? Also, do you use the same ground for the power as the signal ground? Finally, what kind of impedance does the op-amp need to see in order to function properly? should it be the same for the inverting input and the non-inverting input? Also, is it a good idea to build the PS in a separate box, so I can use it for other projects?
Thanks!
I finally finished building this thing. It works pretty good. 8 channels, volume, pan, mute, and 1 aux send per channel. the aux can be used for a headphone mix or a reverb send or even a subgroup. I just have a couple channels to debug, which are most likely acting up because something came loose or I made a bad joint. There's probably over 300 joints so I'm not surprised by that.
Tonight, I will try and build the power supply, and see about adding some TL082's to this thing. If those work out, I will order up something nicer. Are there any safety precautions I need to take so that I don't kill myself? What should I get at radio shack to build the supply on? I'm assuming you can't run wall current through one of those pcb's, right? Also, do you use the same ground for the power as the signal ground? Finally, what kind of impedance does the op-amp need to see in order to function properly? should it be the same for the inverting input and the non-inverting input? Also, is it a good idea to build the PS in a separate box, so I can use it for other projects?
Thanks!
C
chris-from-ky
New member
Pictures Please!!!!!!!!!!!!!!!!!!!!
mshilarious
Banned
FALKEN said:
The only thing really dangerous in a low-voltage power supply is the primary of the transformer when it's plugged in. Everything on the secondary side is low voltage. However, if you screw up a rating of a component, you could pop a cap, or get a resistor or regulator really really hot. Keep an ABC fire extinguisher handy
and also be careful about what parts you touch while you are messing around. Burning your fingers won't kill you, but it does hurt!You can, but you don't need to. The line from the wall should go into a fuse, a switch, then straight to the primary of the transformer, usually all done point-to-point, but it can be on a PCB.
The power ground wire is screwed to the chassis; signal ground often is attached to the same point, although unbalanced gear often has signal ground isolated from the chassis. I'm not an expert on grounding theory; it gets complicated sometimes
The input side of a FET opamp is very high impedance, so it's usually up to you where you set impedance with a resistor shunt to ground. 10K is typical for line input. Edit: Just had a look at the TL082 datasheet, it's limited to 20mA output, so: A FET opamp output can go down to around 1000 ohms, and often you will find resistors in series with the output to protect against shorts to ground.
Sure, you could even use an XLR connector to make switching easy, pin 1 ground, pin 2 +15V, pin 3 -15V.
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FALKEN
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thanks!! I got a box for it. in your ps schematic there is a 120v 1A fuse. all i could find is 250V 1A. is that ok or am I screwed? also, is it ok to omit the switch, or put it on the +/- 15V side ?