SB4000 Support Thread

[imo]

has anyone ever dealt with the same problem that i did? The l/r bargraph not being correct? I was able to balance them at the output, signal is right, confirmed both with RMS multimeter and DAW meters, but the bargraph shows disparity between left and right. When i look at the schematic i see that the reference is to ground, so possible this is the problem, as opposed to the balanced outs?

 

[kepeb]

are the audio levels different at input or just the meter?
have you checked trimmers 11-14? maybe where I would start.

 

[whomper]

Have finished my SB4000 and it sounds great!

Am using 2181A and would like to know what do people think of upgrading to quad vac board.

How much benefit will that yield?
Have people started with single and then upgraded to quad vca? Did that yield audible results?

 

[fazeka]

Hi Mike,

I sent you an email on a few parts missing from my kit. Didn't hear from you, did you get my email?

Thanks,
Chris

 

[mjahnig]

@buildafriend, some remarks.
1) Mains fuse seems missing.
2) From your profile location info you seem to be US based, so the mains transformer primary windings will be wired in parallel for 120VAC mains. Your pic seems to show the primary windings hooked up in series for 230VAC mains. This will hum, because the transformer now only transforms to half of its secondary voltages. Not enough for your PSUs regulators.
3) A toroidal transformer for usual radiates the largest field where the leads come in/out. You might twistturn it about 180 degrees, so leads are closest to your case corner. Distance is your friend.
4) Twist each pair of at least your audio-In hot/cold wires, so the balanced line receiver has a chance to cancel out common mode induced garbage.
5) Missing resistors at the audio-VCAs?

All remarks and advice are appreciated
1) I don't know where the fuse should be in the circuit. Maybe on the hot wire of the primary of the power xfrmr? as you can see I have a fuse that is separate from IEC connector. I am not sure where it should be connected.
2) Do you mean the mains transformer primary windings on the positive side(the primaries with the dots)? If anyone could rig together a fast wiring diagram it would be a huge help. It seems the one I used earlier in this thread is not for the US.
3) Thanks! Will do!
4) Hm.. I never knew that helped cancel anything out. Does that even matter though since this is an unbalanced circuit? I mean I'll do it, it seems to be something that everyone is doing. I bet they are doing that for a reason.
5) Oh it says not to throw those in somewhere in the build guide. Certain resistors on this board are only for use with certain chips. The board also accepts the original gold and black can DBX VCA's

Wow I just learned a lot.

Harpo, if you have anything to add please be my guest, but:

1)  Fuse should always go between line (L) on the IEC and the Power Switch.  Power switch is then wired to transformer primary.

2)  Your transformer will come with an instruction sheet of how it gets wired for 120V or 240V.  For 120V, you want to wire the transformer primaries in parallel.  For the VPT36-1390 transformer only - this means tie Blue/Violet together, and tie Gray/Brown together.  Blue/Violet is you Hot, and gets connected to your fuse.  Gray/Brown is your Neutral, and should be connected to Neutral (N) on your IEC.

4) It's done for the reason Harpo already explained. This is a balanced circuit, it's not unbalanced.  If you plug in an unbalanced connection on the output it will load down the 5532 output chip, eventually probably killing it.

5) Nowhere that I know of.  Those two resistors need to be installed for THAT218X chips, otherwise no compression or makeup gain will be possible.

With regards to #4: If I do need to interface with an unbalanced in/out (i.e. the insert send/return from my Toft ATB32), should I tie ring (pin3) to ground or leave it floating?

 

[bmaughan]

Hey, I finished this project a year or so ago....and just wanted to let you know that is sounds great, and is very consistent. I do have a quick question....I've been toying with the idea with putting either gold or black cans in it....what are the benifits of either vs. the cost. Any info at all would be helpful....thanks!!!!!!

 

[McAulayK]

Hey guys, it's very interesting reading through this thread. I'm really thinking about jumping on one of these and making it my first big boy DIY, besides a few mics and DI boxes. I would really appeciate it if someone who has built this would be able to anwser a few questions. I know there basic but is the SB4000 PCB Parts Kit, SB4000 PCB and Front Panel, Meter, and casing all that's needed to complete this project? Obviously besides the wire, solder, etc. And I also can't decide if the quad vca's would be worth the extra money. Sorry if it's too basic.

 

[druu]

www.serpentaudio.com/

 

[David R.]

Hi, can anyone help me troubleshoot?

Problem seems to be with the right channel only.  When the SB4000 is bypassed, all is good.  Signal passes through L & R, sound is good.  With the unit engaged, the left side is compressing, responds to the threshold and gain properly.  The right side drops about 10 db and does not respond to any change from the front panel knobs.  The lack of responsiveness shows in the bargraph as well.  If I push the signal going through, it distorts badly.

I can not find any problems doing a visual inspection.  I got through the first few calibration steps. I am not sure where to look.  Should I try swapping some chips?

Thanks in advance for any help.

-David R.

 

[fazeka]

Have a (hopefully not terribly uneducated) question...

If I have a TRS jack I want to use for the insert send/return, i.e., tip = return and ring = send, mainly because I don't have any TS jacks and don't want to "waste" two TRS jacks for this and don't want to place an order at Mouser/Digikey, etc. for only two TS jacks... 

I will be tying both sends and both returns, as per Mike's suggestion earlier in this thread (I only need to access the sidechain as mono).

Because 90% of the time I expect to use the return rather than the send to access/utilize the sidechain (e.g., ducking), my thought was that the tip should be used for the return.

However, will there be a problem if the compressor's output is grounded should I use a source's unbalanced output (i.e.,  via a TS plug) to feed the sidechain (because the send would be tied to the TRS jack's ring)?

I think I explained my concern right... apologies if it doesn't make sense or if I need to elaborate.

P.S. I know I can use a TRS plug to get around this and create a 'Y' cord to two TS connectors. But just wondering otherwise, trying to NOT blow anything and even trying to learn something in the end.  ;D

Thanks for any insight.

 

[sage]

Hi there

it seems like the 9 resistor in the kit measure 46.4k to 45.9k but none is closer to 47k. Is that a problem, bad parts or an error in the kit?

Please let me know -

sage

 

[sage]

same problem for the 56k resistor - it is deadlocked at 55k on my meter - what shall i DO - this is for R116

 

[Harpo]

it seems like the 9 resistor in the kit measure 46.4k to 45.9k but none is closer to 47k. Is that a problem, bad parts or an error in the kit?

Don't care for this 1.3%-2.3% parts low tolerance. (FI R30,31,44,53 low will rise this HPF from 0.034Hz to 0.035Hz or R34,57 low will rise this HPF from 0.354 to 0.356Hz. Other spots have trimmers/pots to catch these tolerances.)

same problem for the 56k resistor - it is deadlocked at 55k on my meter - what shall i DO - this is for R116

Don't care for this 1.8% off. The Threshold pot might have far bigger parts tolerances to catch it.

 

[sage]

THANK YOU very very much ! I will proceed in stuffing !

sage

 

[sage]

One more question.... what's the final verdict of the 47k or JUMP ?

I read a bit thru the posts but here are 50 pages of posts...

shall I jump or should I go....

 

[sage]

another thing i noticed that R130 and R131 the 200R in the PCB next to 200R there are 3 asterics

200R***

does it mean something special?

 

[Harpo]

another thing i noticed that R130 and R131 the 200R in the PCB next to 200R there are 3 asterics
200R***
does it mean something special?

Yeah. Snowflakes. To make it operate, you'll have to fit these parts in winter while it is snowing. Be thankful there wasn't a switch symbol as well for the additional burdon of 'only on leap years'...

More seriously, these voltage dividing/current limiting 200R values should increase if you use relays with a lower than 12V coil voltage.

And yes, you shall read ...

 

[sage]

Thanx Harpo

I am using the Kit from Serpent so it should be all fine -

YEs I will spend the next hour or so reading thru the posts on this forum and cut and paste all the info that can help -

This is definetely more complex than the SA3A I just built !

Sage

 

[bieckmusic]

I have a tech question..

My SB4000 works pretty well, except I have never been able to fix the issue I tried to resolve back a while ago.

The unit still slams like crazy when I get near 7-8dB of compression.  I've fixed all the solder joints, checked the diodes, checked all the tantalum cap orientations...  I just cant seem to figure it out.  Anywone have any additional thoughts??

I've checked everything post summing point on the control board, is there an point where the signal is summed on the main board?  Since this anomaly is happening equal to the left and right side it must be somthing that's summed.

I checked every component prior to installation, except diodes and ics...

any help would be majorly cool!!  thanks 

greg

 

[ruckus328]

Guys, will try to get on tomorrow to help with some questions, was hoping to get to it today but I have to leave in an hour for the airport for AES, so running around like a nut right now.