SB4000 Support Thread

[rdubgt]

Hi all,

Just finished my build- everything works great audio wise and it sounds amazing!

I'm having some difficulty getting the bargraph to work properly. I've sent a +4dBu test tone from my DAW (confirmed with fluke showing ~1.228VAC on XLR inputs) and my input bargraph shows well above the maximum of +2dB. I attempted to calibrate but don't have enough room in my VR15 trim pot (I would need <0 Ohms to get it to work).

I've experimented with just the Left/In part of the circuit. I changed VR14 from 13k fixed to a 25k trimpot and even then didn't have enough resistance in the pot. I found that a ~30k resistor gets it in the roughly correct spot. My question is why these could be off so much- I've double checked all values in the bargraph section of the schematic... I'd rather not have to replace all 4 (L/R & In/Out) VRs with trimpots that are ABOVE spec (5k or 20k on schematic --> 10k and 30k?), but if it's that simple, please let me know.

And FYI- I've jumped JM7 (for bar mode instead of dot) and my 12v rail is dead on @ +/- 12.01VDC while 15V is acceptable @ +/- 15.33VDC. No other noticeable strange behavior except this bargraph issue.

Thanks to all for the earlier responses and pictures, they were a huge help with the assembly, machining, and wiring.

 

[Harpo]

R106, R107, R108, R134 fitted with correct parts value ? (there are other as well and you mistakenly might have read a resistors colour code backwards).
Easiest fix seems to be either increasing R108 or decreasing R107 or R134.
(maybe use your 25K trimmer in parallel to R134, trimmer initially centered, to have this resistor variable from 0...18K3 instead of 68K).

 

[rdubgt]

R106, R107, R108, R134 fitted with correct parts value ? (there are other as well and you mistakenly might have read a resistors colour code backwards).
Easiest fix seems to be either increasing R108 or decreasing R107 or R134.
(maybe use your 25K trimmer in parallel to R134, trimmer initially centered, to have this resistor variable from 0...18K3 instead of 68K).

Re-checked all values and they were correct. Went with your suggestion - increased R108 from 10k to 20k, fixed it. Still not sure why that issue came up for me, but since R108 just drops the voltage between U14A and U14B (the 2 parts of the TL074), I guess it shouldn't cause any significant extra wear on the chip.

Thanks all, it works and sounds great!

 

[mamiti]

Hi,

has anyone else faced this kind of issue with SB4000:

- Unit is on for few hours compressing happily
- Suddenly something like 10dB's of more compression appears; Output gain is really low, GR meter hits ceiling constantly.
- Even in bypass mode the GR meter shows ~10dB of compression (Audio is fine in bypass)
- If the unit is off for half an hour, it works fine again

Power Supply voltages are ok all the time. Regulators have bigger heatsinks than the 'stock' model.

I'm suspecting some opamp may be 'on/off' e.g. U13 or U16 but this issue is not nice to track down... and I don't know what are typical issues with these type of opamps.

Thanks in advance!

 

[Rlucas41]

Hello All,
I am new to the DIY thread here but I need some help... Doing my first SB4000 build and have all boards populated and mounted in enclosure. I have hooked up transformer and am getting good dc readings from power supply when I measure with my multimeter i.e. +15 (15.33), +12 (11.99) and the exact corresponding negative values as well. When I hook into the main pcb I am blowing the main fuse and am seeing r182 & r183 smoking. I get 12v to power indicator but nothing to meters before the main fuse blows. Thanks for any help in trouble shooting!

 

[sr1200]

Did you try hooking up just the main board and power up?  You have something open thats drawing too much.  If you can power teh main board without the control board, there's something wrong on the control board.  If you're blowing fuses with the main board hooked up.  take out all your chips and re-power up and see if you're still cooking.  Process of elimination will go a long way.  One of my builds was doing this, i had a chip in backwards.  Chip finally exploded which lead me to the problem, but not before some other damage was done.

 

[Rlucas41]

Did you try hooking up just the main board and power up?  You have something open thats drawing too much.  If you can power teh main board without the control board, there's something wrong on the control board.  If you're blowing fuses with the main board hooked up.  take out all your chips and re-power up and see if you're still cooking.  Process of elimination will go a long way.  One of my builds was doing this, i had a chip in backwards.  Chip finally exploded which lead me to the problem, but not before some other damage was done.

Thanks for the reply, going to try that as soon as I get back home!

 

[Rlucas41]

Did you try hooking up just the main board and power up?  You have something open thats drawing too much.  If you can power teh main board without the control board, there's something wrong on the control board.  If you're blowing fuses with the main board hooked up.  take out all your chips and re-power up and see if you're still cooking.  Process of elimination will go a long way.  One of my builds was doing this, i had a chip in backwards.  Chip finally exploded which lead me to the problem, but not before some other damage was done.

Thanks sr1200! I have isolated my problem I think... had the TL074 chips in backwards and narrowed it down to the bargraph driver section TL047. when that chip is out... I have good voltages (replaced r182 & r183 on power supply board), but when I put the TL047 back in the bargraph driver circuit... I get a negative voltage and the voltage regulaters u20 & u21 began to get hot and of course immediately shut it down. I am guessing (and ordering new TL047 chips) is bad. I am learning as I go and greatly appreciate the help in getting my unit working right 

 

[Rlucas41]

Thanks again to sr1200! Got my unit working and is compressing nicely and sounds really good... but I have a few issues and while I am searching through old posts would love some input from you folks. My bargraph is not working at all... so please give me some ideas on what to check. I am getting 12v to the led.

 

[sr1200]

make sure the unit is actually compressing and engaged (the bar graph only lights up when the compressor is working). Also, make sure you put the bar graph driver in the correct way and that all the legs are properly soldered.  That way my only complaint with the entire build (soldering that chip in and then soldering the standoffs... very tight job there.  But since Mike is a mad genius when it comes to putting 10lbs into a 5lb bag... thats what you run into.  check that your switches are properly wired as well (the i/o and l/r switches for the meter).  If everything looks right, pull the chip and see if the chip got fried when you were having the other issues.

This is seriously the best bus comp i've ever heard or used (including the center sections of SSL and Neve consoles).  I have 2 (one for mix bus and one to slam my drum bus, might even be getting a 3rd some time soon...)  Once you get it sorted out, you're gonna love it!

 

[Rlucas41]

make sure the unit is actually compressing and engaged (the bar graph only lights up when the compressor is working). Also, make sure you put the bar graph driver in the correct way and that all the legs are properly soldered.  That way my only complaint with the entire build (soldering that chip in and then soldering the standoffs... very tight job there.  But since Mike is a mad genius when it comes to putting 10lbs into a 5lb bag... thats what you run into.  check that your switches are properly wired as well (the i/o and l/r switches for the meter).  If everything looks right, pull the chip and see if the chip got fried when you were having the other issues.

This is seriously the best bus comp i've ever heard or used (including the center sections of SSL and Neve consoles).  I have 2 (one for mix bus and one to slam my drum bus, might even be getting a 3rd some time soon...)  Once you get it sorted out, you're gonna love it!

Thanks again sr1200!!!
I fully intend to build another one of these as mine does sound great! But alas I am still not able to get the bargraph working... I have changed the 100ohm resitor (r163), the LM3916, touched my socket solder points on the control board to make sure they were good... of course replaced the TL074 (U14) in the bargraph driver section of the main board, as well as the other TL074 that I had in backwards, but still no bargraph illumination. I ordered another LED just in case that was the culprit but it is on backorder from Mouser right now. Everything else is working great though, left to right on the controls... gain reduction VU > makeup gain control... it sounds great on the mixes I am running through it.
Worse case scenario, I have to take it to one of the real electronics gurus here in Nashville to help me track down my error... which is usually really cool cause I always learn something new from those guys when I get to hang around them... but I hope to solve it myself with you guys help! Thanks again!!!

 

[Rlucas41]

HALLELUJAH! IT IS ALL WORKING!!!!!
MANY THANKS TO SR1200 FOR YOUR HELP!!!!
I have to admit my ignorance... I didn't know the LED had an anode/cathode side to it and I had it upside down too. While I am still very much a newbie at this, I am so excited this works and that it is a great sounding piece of gear and am ready to build my next one! This is so very satisfying and I am ever so grateful to SR1200 for the help and Mike for this great project! MERRY CHRISTMAS EVERYONE!

 

[sr1200]

You're welcome, dont think i really did anything, but enjoy it, its a beast!!!  Don't forget to calibrate it.

 

[djvibe]

Is is common to be missing a set of resistors and have a few extra resistors in the kit from Serpent Audio? I am missing the 680K resistors for R76 & RR96 and I have a few left over that just seem to be extra. Does anyone know if this is just an error in the kit? Thanks again.

 

[Rlucas41]

Did you get the quad VCA upgrade as well? If so you don't use the 680k resistors (according to mike) and when I got my kit from him I ended up with a few extra resistors. I will look back through my emails with Mike and clarify about that, cause I had the same question about the 680k resistors early in my build too.

 

[djvibe]

Thanks Rlucas41, please let me know what he said in your emails as I did get the VCA upgrade with my kit. Thanks again!

 

[Rlucas41]

Thanks Rlucas41, please let me know what he said in your emails as I did get the VCA upgrade with my kit. Thanks again!

Hi djvibe,
this may be anticlimactic but here is what Mike responded with...
" follow quad BOM on support thread for changes on main board when using
quad VCA's, 680K not used."

The quad vca BOM is on the first page of this thread and gives you the list to follow for changes in the main board as you begin to populate the boards. Make sure you dont populate any area of the vca sections on the main board and put your jumpers in on the back side of the main board.

Hope this helps!

Best Regards,

-Mike

 

[djvibe]

Would someone please explain or link me to some documentation on how to "pretrim the pots to 1K33?" Are the fixed resistors also soldered in place with the pots?

Additionally, would someone please explain or link me to a tutorial on how to build the ribbon cable and attach the headers to hookup wire? I'm sure this is fairly basic to most DIYers but I haven't come across this before. Any help is greatly appreciated!

 

[TheJames]

Spoon-feeding time for me...

Which crimp tool do I need to get for crimping the inserts for the white header connectors included in the Serpent parts kit?  I believe it's Molex header...KK maybe?

Thanks!

 

[sr1200]

I dont recall needing a crimper at all (built 5 or 6 of these now).  The only thing that was annoying was the ribbon cable which i just used a vice clamp to evenly push down.