good compressor for vocals?

[jfrabat]

Hey, anyone got any suggestions for a good compressor for vocals?  Although I do not currently need it, I would like to future proof with 48V phantom power if possible, but that is not a requirement. 

I am going to have to get the XLR socket shipped, so any components I may need that I don't have I can get with the same shipment...  I currently use a FMR Audio RNC1773, and I am extremely happy with it, but my daughter wants to have recording gear in her room to record her playing, so I figured I could build her a compressor.  I am making her an EQ (4-band semi parametric) as well, after all (almost done on that one)...

Thanks in advanced!

[StephenGiles]

There was an excellent compressor build in ETI (UK) which included noise gate circuitry in late 1980s - LM13700 based, not sure about phantom power though, you could probably get away with less than 48v. Also look at Rolls circuits. I'll check on my PC later as I'm on my iphone now taking advantage of 6am cool breeze before the 33c humid nightmare ahead today!!!

Found it:
https://worldradiohistory.com/UK/Electronics-Today-UK/80s/Electronics-Today-1985-12.pdf

[jfrabat]

There was an excellent compressor build in ETI (UK) which included noise gate circuitry in late 1980s - LM13700 based, not sure about phantom power though, you could probably get away with less than 48v. Also look at Rolls circuits. I'll check on my PC later as I'm on my iphone now taking advantage of 6am cool breeze before the 33c humid nightmare ahead today!!!

Found it:
https://worldradiohistory.com/UK/Electronics-Today-UK/80s/Electronics-Today-1985-12.pdf

That is A LOT like what I am looking for!  Thanks!  I may just give it a go!

[jfrabat]

You know, I checked, and I have most components for this... I may even have a box it could fit in!  I just need to get the push/pull pots, but I think I got everything else (need to check the IC's, but I think I got those as well!).

[jfrabat]

You know, I checked, and I have most components for this... I may even have a box it could fit in!  I just need to get the push/pull pots, but I think I got everything else (need to check the IC's, but I think I got those as well!).

Hmmm...  Looks like I spoke too soon... Those pots are FREAKING HARD TO FIND!  100K log push/pull SPST and 10K log with DPDT switch are not so popular!  Searched in Tayda and Mouser; nothing!

Also, there are a couple of things I do not understand in the schematics.  Here is the schematic:



Here are the bits I do not understand:

• I know magenta is the switch from the 100K log push/pull SPST pot, but where are the 2 switches of the 10K log with DPDT switch?  Is it the red?  If not, what the heck is the red???
• Orange I have NO IDEA what it is!
• Yellow is a 3 pole power supply.  My question here is if anyone know a good place to buy these.  Worst case, I intend to just use a 15VAC and split that into +15V and -15DC, but I have read that it is noisier to do it that way.
• Is green just 2 diodes going to the OpAmp, or is there something more going on here?  I have never seen it drawn like that before!
• Purple is a center negative 3-terminal led.  That I got.  But, just to check, it is center negative (single grounding cathode), right?  I know I have one of those somewhere, but I cant remember if it was single anode or single cathode...

Anyway, I would still like to build this thing.  It will be challenging (certainly a long term project!), but I like what I read; it can be used with mics and instruments (and line in), it has a side chain (for both compressor and gate), balanced XLR output, and 2 line-level outputs.

I would probably use a regular pot for Attack of the compressor (it uses a trimpot); I could do also something similar with the depth of the noise gate, which also uses a trimpot in the original, but may be useful to have that adjustment handy.  And to be honest, I think I prefer switches (which, by the way, I have!) to push/pull pots anyway, so I just need to figure out the second switch to be able to change that.

The only thing this is missing from my wish list is the phantom power!  And I know that is fixable, but I do not have the knowledge to do that!

[mth5044]

I can't help with everything, but the Ic symbols with the diodes that you have circled in green are part of the internal circuitry of the 13700. Those are the typical symbols used to represent the internal circuitry on the schematic.

I thiiiink your red, blue and orange circles are some sort of voltage/wave form readings for that part of the circuit. Red circles look like a square wave oscillating between power supply rails, blue circle looks like a rectified sine wave and orange looks like some sort of saw tooth.

Dark purple circle led's may just be two LED's, but if they are in the same package, youd be looking for common cathode

[11-90-an]

^^^ what he said...

Using a +/-15 psu is ideal, but if you can't, You can still use +15v and use a charge pump, but power supply noise blah blah...

What you can do is use a capacitance multiplier to filter some noise out like in the PMC and sprinkle lots of decoupling caps everywhere. 

https://sound-au.com/project15.htm

[merlinb]

I suggest you build a mic preamp / DI box. Then you can plug it into any compressor you like, or anything else for that matter!

[Ben N]

Lotsa interesting options here: http://www.thatcorp.com/Design_Notes.shtml

[andy-h-h]

Are you recording to tape or some kind of older hard disk recorder?   Most folks just use plugins on their DAW. 

[moosapotamus]

For the pots with the integrated switches, I would think that you could just use regular pots and separate switches. But, I only see one switch (circled in magenta) in the whole schematic, and there is nothing to indicate that it is integrated with a pot. So, not sure where/how those switches would be connected, or what they are intended to do. Maybe it explains those switches in the article?

[jfrabat]

I can't help with everything, but the Ic symbols with the diodes that you have circled in green are part of the internal circuitry of the 13700. Those are the typical symbols used to represent the internal circuitry on the schematic.

Ahhh... that one is new to me.  Just looked it up, you are 100% correct. OK, one more thing learned...

Dark purple circle led's may just be two LED's, but if they are in the same package, youd be looking for common cathode

The parts list has it a tricolor round LED.  So it must be a common cathode.  Just need to find my tricolor LEDs and see if they are in fact common cathode.

Using a +/-15 psu is ideal, but if you can't, You can still use +15v and use a charge pump, but power supply noise blah blah...

My first priority is to get a +/- 15V power supply, if I can find one.  If not, I intend to go with the same circuit (except for 15V) that I used in my EQ (top part of the below schematic minus the switch):

You can read about that one here.

I suggest you build a mic preamp / DI box. Then you can plug it into any compressor you like, or anything else for that matter!

I was thinking the same thing.  No need to add phantom power to this.  I have a tube mic preamp, so I could go for something with a little different color, and it would be a nice addition.

Are you recording to tape or some kind of older hard disk recorder?   Most folks just use plugins on their DAW.

I am trying to step away from DAW Plug Ins and go with hardware.  Personal choice, but part of it has to do with lag.  Plus it is so much cooler...  (yeah, you can probably guess I am close to 50 by now!  I just think physical analogue stuff is the bees knees, and software is for video games!  LOL!)

For the pots with the integrated switches, I would think that you could just use regular pots and separate switches.

As I mentioned above, that is my intention.  In fact, I prefer to have separate switches to push/pull pots (plus, I actually have the switches in my inventory!).

But, I only see one switch (circled in magenta) in the whole schematic, and there is nothing to indicate that it is integrated with a pot. So, not sure where/how those switches would be connected, or what they are intended to do. Maybe it explains those switches in the article?

Switch 1 (the one I found) is tied to RV5, which is the RELEASE (compressor).  RV5 is on the top right quadrant in the schematic above.  "A switch is provided to reduce the overall sensitivity of the unit by 10 dB. With the compressor RELEASE knob pushed in the compression gate is matched to -10 dBm line and mic level signals. With it pulled out the unit is matched to 0 dBm line and mic levels."  If my schematics understanding is improving, this is done by changing resistance from 30K to 10K (R11 and R12; when in parallel, 30K and 15K give 10K resistance, correct?).

Switch 2 is tied to RV6, which is TRIG LEVEL for the compressor (RV6 is in the lower left quadrant).  Switch 2 seems to turn ON and OFF the noise gate, which is why I think the red circles indicate that SW2 is cutting power to IC5 and IC6 (hence the DPDT).  IC5 I get (this OpAmp is used only for the gate), but it looses me because IC6 is also used on the compressor side (at least it seems that way to me with my limited knowledge!).