SB4000 Support Thread

[ruckus328]

Hi, I was wondering if any one could give me advice or tell if there is any audible sonic differences between using the 2181's and the 2180's for the audio vca's. I oviously want it so sound as good as possible but if the 2180's sound just as good and simply remove another calibration step, I'd rather go with those.

Depends on who you ask.  In my opinion no.

 

[etheory]

Got a little bit further on the weekend: http://www.evolutionarytheory.com/2011/07/sb4000-bus-compressor-%e2%80%93-build-%e2%80%93-day-4/

 

[Ptownkid]

Yeah duder, good job!!!

 

[Neil]

-15.41 vdc ok for the -15v rail?

All my other rails are +/- about .1 or .2, so this seemed a little high. I'm using Ptown's fixed resistors instead of pots on the p.s. board, and have it unloaded, ie, not connected to the main board.

 

[minor_glitch]

I'm definitely not the best person to be answering, but I think that should be ok. 
One of my rails was around 15.3 and mine seems to work fine: http://www.facebook.com/video/video.php?v=636393572294&oid=39721473245
(I think you need to be logged in to FB to see the vid)

 

[Ptownkid]

I'm sure small voltage discrepancies like that are fine.

 

[bieckmusic]

Quick question, my+15 v powersupply rail measures 17.08 volts.  Every other measurement was great.  Is this ok?  A couple resistors on the powersupply were off by .1 ro .25 k when I measured.

Just want to be safe!  Thanks, Greg

 

[Wembley]

Thanks for the helpful replies.  I lifted some pads desoldering headers and it's an experience I hope never to repeat!

 

[bieckmusic]

Do you think it's dangerous that the +15 rail measures +17?  The power supply is not driving anything right now it's disconnected.

Thanks Greg

 

[ruckus328]

Do you think it's dangerous that the +15 rail measures +17?  The power supply is not driving anything right now it's disconnected.

Thanks Greg

Your 15V rail should not put out 17V, either the 120R or 1K33 resistors at the LM317 are the wrong value (these 2 resistors set the regulator output voltage).

 

[bieckmusic]

Hi Everyone, Thanks for the help.  So I put in a pot in the power supply insted of the 1k3 resistor and tweaked it a turn or so and now I have +15volts exactly.    My compressor is working and sounds great, I love it   One glitch though the threshold knob is extremely sensitive and it overloads very easily especially in 10:1 mode.  If I have an intro to a song when the kick triggers just occasionally the compressor makes a whoosh sound and gets silent for a second or two when the threshold knob is half way up.  When I have a steady beat the compressor acts more normally. 
I've jumped the 47k resistor spot on the control board, should I install the 47k resistor?

Also, on the test points in SSL mode (the stereo sidechain button is not lit) I'm only getting 1.5millivolts is that normal voltage.
Also, with the threshold all the way up (clockwise so no compression) the input level and output level on are quite off.  The input level is about 5dB lower than the output. 

thank you so much!!!  I was so excited when I powered it up and it sounded so great, this is an amazing project!!  I've worked for years on an SSL and this is as close as I've ever heard in a clone.

best, Greg

 

[minor_glitch]

bieckmusic - did you follow all the calibration steps outlined in the build manual?

 

[bieckmusic]

Hi minor_glitch  thanks, I did and the calibrations worked fine mostly.  Except I ran out of travel on the pots to get the t1 and t2 exactly but it's really close.  There is something wrong with the threshold, it acts really strange after about 11 dB compression.  Not sure what I did wrong, and where I should start troubleshooting.  I checked solder joints and they looked good??

Any ideas would be greatly appreciated!!
I'm so amazed at the design of this compressor, it's really really cool! 
Thanks!!  Greg

 

[minor_glitch]

Not too sure about the threshold, I jumped the 47k and it seems to be working fine.
I had a similar problem calibrating T1. The best I could get was a .2V difference between TP11 and 12.  T2 was fine though.

 

[bieckmusic]

Thanks minor_glitch - That's the same for me.  T1 was off by around .2 and t2 was perfect.  When you run a signal into the compressor (on bypass) do your input and output levels match?  On my unit if I feed a -10 signal in, it comes back to my DAW (PT 192) around -15 or so...  Sound fishy to me?  So when I'm compressing I need to use a little more of the make up knob then I would normally use with a SSL comp...
Have a great day
greg

 

[etheory]

I can now join the "finished but not calibrated or tested/verified" club, however I did turn it on and it looked pretty and didn't explode, so that's encouraging:

http://www.evolutionarytheory.com/2011/07/sb4000-bus-compressor-%e2%80%93-build-%e2%80%93-finished/

 

[etheory]

Could someone please pass me to some documentation or explanation about how to wire the side-chain inputs?  They are marked as being like send/receive TRS's but are XLR's and on the BOM say "you can choose either Male or Female" yet on one set of images both Male and Female XLR is used and on another I found there was a 5 pin XLR connector on both.

I'm kind confused on a.) what that all means and b.) how to wire it.  I spend some time searching the net but I can't figure it out.  If you look at the website I linked too earlier it's wrong, but I want to verify what it SHOULD be wired as if I use 2x3-pin Female XLR connectors for the side-chain ( or if I should buy something else? ).

Thanks in advance,

Luke

 

[envelope]

Hookup wire.

Any minimum I should be looking at for the gauge of the hook up wire between the boards and say the power board or the switches? I have a bunch of #26 in different colors. Should I be using something bigger? Yes, I know about the 14 gauge for the star ground but I am looking at all the other wires.

So, I see the power supply as - Transformers 36.0V CT @ 0.69A 18V  - and looking on the web, see #26 up to 2.2 amps - http://www.powerstream.com/Wire_Size.htm - so I am guessing I am good, but I would rather not guess.

Use what I got, or go shopping?

26 gauge wire is way too small imho.  In some places you could probably get away with it, in others you'll likely see smoke.  You're looking at the wrong column, the one you should be looking at is the power transmission column.  The current carrying capability of wire is determined by both size and external thermal factors.  A bare copper wire all by itself in free air can carry more current than an insulated wire bundled with 10 other wires, as heat builds up from all of them.  If you put 2 amps on 26 gauge insulated wire you probably won't like the results.

22 gauge would be my recommendation for most places. 

For the connection from the main board to the Power Supply, I would use 18 gauge, and definately use 18 gauge for your mains/transformer wiring.  Using 14 gauge wire for your PS grounding is pointless if you cripple the ground connection between the main board and power supply (this needs a good ground connection to the power supply), unless you want hum.

BTW, you can get by with a slightly smaller size wire for you PS ground connection, 16 gauge would be ok too.  The point here is, thicker ground wire = better ground connection.

Hello Mike, what is the current being carried by the various conductors on the 28 AWG ribbon cable spec'd in the BOM? I haven't sourced that part yet, but curious to know...thank you

 

[ruckus328]

Hello Mike, what is the current being carried by the various conductors on the 28 AWG ribbon cable spec'd in the BOM? I haven't sourced that part yet, but curious to know...thank you

I have never measured actual current going through the ribbon cable as there has never really been a reason to.  It's only carrying CV signals, worst case no more than 5-10 milliamps.

 

[ruckus328]

Could someone please pass me to some documentation or explanation about how to wire the side-chain inputs?  They are marked as being like send/receive TRS's but are XLR's and on the BOM say "you can choose either Male or Female" yet on one set of images both Male and Female XLR is used and on another I found there was a 5 pin XLR connector on both.

I'm kind confused on a.) what that all means and b.) how to wire it.  I spend some time searching the net but I can't figure it out.  If you look at the website I linked too earlier it's wrong, but I want to verify what it SHOULD be wired as if I use 2x3-pin Female XLR connectors for the side-chain ( or if I should buy something else? ).

Thanks in advance,

Luke

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