SB4001 Support / Build Thread

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john12ax7

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So it's not meter. It turns out at 1.5 ratio there is always at least 4db compression regardless of level. So I must have wired something wrong, perhaps a bad component somewhere or a short.

I know I'm late to the party with building this, and there are no schematics. But could someone give me at least an idea of where to look on the board to find the problem? Ruckus?
 

ruckus328

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Check solder connections/values on R117, R118, R121, R122, R131, R132, R135, R136.

Check and make sure D101, D102, D103, D104 are soldered & orientated correctly (this is my biggest suspicion)

With ribbon cable plugged in, check continuity of all pins between the ribbon cable connectors (J1 & J2).

Check solder joints on ratio switch (maybe good idea to flux them and reflow all solder joints)

If still not fixed, lift D11L (which will disconnect output of left ratio network).  Feed unit a signal on the right channel, see if problem remains.  If problem remains, return D11L, now lift D11R, feed unit a signal on left channel.  This will help narrow down if problem is in left or right ratio network.
 

mulletchuck

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Finished building my 2nd box as part of my Rack #2 project.  i was gettin' crazy distortion on the right channel, so after swearing alot and disassembling the unit, i discovered one of the 1646 chips was in backwards, cuz I put the socket in backwards.  Flipped the chip, and she was good to go!  Fully calibrated and ready to rock! 
 

mitsos

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Just to say I got one built up about a week ago and it's rockin!

thanks mike!
 

saxmonster

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Hi guys,
The kit came with 3 fets which one should I use how do I measure it.  Do I want a lower or higher number?  Tia!!!!!
 

saxmonster

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So I got my sb4001 powered up and running tonight.

No smoke and sparks, woohooo.

I ran some mono prerecorded sax though it and turns out my left side is not compressing.  Right side seems to be fine.  It passes the audio but no compression.  Any ideas on where to start.  I haven't calibrated it yet either.  The only issue I had during the build was one of the legs of an TL074 fell off when trying to install so i just soldered it and checked for continuity between the bottom side of the pcb solder and the part of the leg left on the chip, all was good. This was on the left side of course.  Any ideas why left side is not compressing?

-TIA
Scott

 



 

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saxmonster

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I will start to take the measures that you requested Gandhalf to take and start from there I guess.

-Scott


 

saxmonster

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Ok, so i guess my eyes are getting old, I totally missed a row of leads on a relay on the left side.I fixed that and all seems cool now.  Compression on both sides. 

I had to flip the meter wires on the PCB though.  The yellow was hooked up to the positive side of the meter at the meter yet I had to hook it to the negative side on the pcb in order for it to work correctly and not in reverse. Does this mean I wired something wrong somewhere else?

Also I have not done the calibration yet as I am beat and need some zzzzzzzzzzzz's but when I was running a stereo mix through the sb4001 and hit the grind button and messed with the filter I could not hear any differences, I think it is was working cause the meter would flitch when choosing different filters.  Maybe I just dont know what I am listening for.

Man can this thing add some punch to a mix, loving it so much, thanks Mike for a great product.


-Scott



 

saxmonster

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Ok looking to doing the calibration tonight but was wondering if the grind button adds a lot to a mix.  I am pushing it in and out and don't hear a change.  Loud or soft input I still don't hear a change.  How can I double check to make sure the grind part of the compressor is working ok?  Everything else seems to be perfect and I can hear changes on every knob I mess with.  Its just the grind button that makes me worried cause I can't tell a difference when it is on or off. I guess when I do the calibration I can physically see it on the scope program.


TIA-Scott

 

saxmonster

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Hi Guys,
When I was calibrating my sb4001 I had a little issue but didn't think much of it and just remembered it today.  When I was adjusting the gain for each side I would have the levels set to even when at 0 gain.  Then when I crank up the gain to +18.  The levels would be off by just a bit.  Maybe a .25db.  I was zooom in pretty far inorder to see it.  So I adjusted the gain screws and so that they were level at the +18 gain setting but when I lowered the knob back to 0 the offset was now off at 0 gain.  So I readjusted the gain levels so that are equal at a zero setting and off that tiny bit when at the full +18 gain setting.

Any idea what would cause this to be off?  Is there something that I can match to maybe get them exact?  Just seems to be off in the gain knob.  I don't think the pot is bad but maybe the one side is restrictign the signal somehow that tiny little bit?

Thanks for you time
-Scott
 

mulletchuck

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the million components on either PCB aren't perfectly matched.  Also, Mike says in the calibration that the gain won't be perfect.  you won't get +18 if you set the -6 to be exactly -6, and likewise if you set +18 to be +18 then the -6 won't be -6.  just set 0 to be 0.  I have never needed to  use +18 with the makeup gain.  I'd wager that your signals going into the unit are too weak if you need to use +18 all the time. 
 

emrr

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If you use ALMOST ANY stereo analog gain element, you will see this level of error.  Including stereo master fader on 99% of consoles.  Tis normal. 
 

saxmonster

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Thanks guys,

I will leave zero at zero with a balanced level. 

I can't hear the difference when they are off anyways.

-Scott

 

saxmonster

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Ok Total noob here, don't shoot me I think I learned a hard lesson last nite.  ( always reread build threads)

So if my infinite wisedom I had replaced a tl074 because I broke a leg and had it soldered in there.  So I wanted to get rid of the solder and just have a new chip installed.  So after taking it apart last nite I decide to clean the flux off the back sides of the pcbs.  (should have just left it alone) I took all the IC's out and using alchold and water and some dish soap I got alot of the dirt and flux crap off.  Anyways I dried the pcbs out really well with a fan for like and hour or so and then put the back together. 

I put the unit in the rack and it came on for a sec and then the fuses blew out in the +16 and - 16.  After rereading this thread I think i put all the tl074 in backwards.  I thought the circle was pin one,  (idiot, idiot idiot idiot)  So after the fuses blew i just got pissed and went to bed.  So today when i realized what I did after rereading this at work I am wondering how much damage do you think i did.  I didn't hear any pops or scrapes or anything of the nature.  Do you think the rack fuses blew before anything got damaged?  I will flip all the tl074's and double check the other IC's.  Install new rack fuses and see what happens.  Is there anything I can test to make sure I don't blow anymore fuses or ruin the sb4001.  I just hope the fuses took the brunt of the force and all the IC chips will be ok.


Errrrrrrr.    I AM AN IDIOT, ERRRRRRRRRRRRRRRRRRRRRRRR!!!!!!!!!!!!!!!!!!!!!!!!!


 

saxmonster

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Well, I must be one very lucky dude!!!!!!!!!!!  I should go play the lottery or something.

I put the new fuses in the rack.  I took the sb4001 apart and flipped the tl074's around and put the thing back together and it works.  Don't know how but everything seems to be ok and working.  I will re-calibrate it again since i did replace the one tl074 before this mess started.  I did notice that on the filters when I switch from 120 to boost I do get an interruption in the sound and I don't remember having that before.  Maybe it was always there.  Sometimes there is a click other times there isn't I guess it just depends on the material going through the filters. 

Is there anything else I should check after re-calibrating to make sure everything is working correctly.

I am one very lucky guy, so lucky it could have been a lot worse so always reread the build thread when you take something apart.  Lesson learned!!!!!!!!!!!


-Scott

 

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