SB4000 Support Thread

[hammer8994]

Hey guys, finished the project! However the L channel seems to be sending 6db less signal.  This is in bypass as well.

I have tried switching ICs/VCAs, rotating cables to my interface and have been looking at the signal chain for any shorts.

One interesting thing i found was that when the Audio inputs were connected to the board, the Left positive audio  input (L+)  dropped to zero. But when the Audio inputs weren't connected to the PCB, the L+ voltage looked healthy/similar to the others.

Any tips/pointers?

UPDATE: turns out one of my XLR cables was shorting to ground, hence the 6db drop in volume, she works great!

 

[EmptyMusicBox1]

hello !

what do you think about the differents VCA ( dbx202c.X / Quad vca .... ) what is the best for the SB4000 ?

what is the most Fidelity of the original SSL comp ?

i have a quad-VCA and i want to test the dbx 202c it's an error ?

thanks for your help 

 

[weiss]

The original SSL Bus Compressor features a variety of VCA's. And each compressor sounds different. The sound is not primarily coming from the VCA being used. But you can go for it, try and compare it and share the results here if you want.

 

[EmptyMusicBox1]

The original SSL Bus Compressor features a variety of VCA's. And each compressor sounds different. The sound is not primarily coming from the VCA being used. But you can go for it, try and compare it and share the results here if you want.

HI

About the difference between Quad -Vca and dbx 202c :

The SB4000 with quad VCA is very Transparent and Low noise THD is very Good !

The SB4000 with dbx202c add more personality during the compression ("Glue" ) but the THD is Less ...

I have the impression of the Oxford mod is much "present" during the compression  with the dbx202c ....

Both of the VCA are interesting for a choice : Transparent or Not

what do you think about that  ?

Before :


After :

 

[Tschem]

hello,
having some trouble here at CV calibration stage:
feeding the unit with a 1kHz testtone, i'm measuring 2Vpp at tb8 & tb10. now tried to reach the same levels at tb11 & tb12, but no matter how i adjust VR7 or VR8, i always get 0V at tb11 & tb12.

any idea what could be the reason for that?
don't think that that's important, but  maybe i should add that i've not connected the J3 (external sidechain/key input) yet.

BR & thx in advance

 

[robertoray]

Welcome,
send and return is most often used for inserting a maybe parametric EQ for different/individual shaping of control signal.
Inserting another compresser for smoother responses might be worth a try.
Inserting a delay for always too late compressing is probably not that useful, but might allow for rythmic patterns when playing with the delays feedback, ...

Thank you.
Now it's clear.
I've done my compressor.
Seems to work fine, but I will have to test it with balanced in and outs because the levels don't match.

 

[staggerquake1]

Hi, i just started doing the sb4000 project  , and im missing a 330PF ceramic capacitor @ c101, can i get any replacement or does it have to be a certain kind?

Might not be needed at all. (LPF set for 48kHz in 1st. inverting 2.5dB gain stage of the VU-driver) Not a critical part and not in audio path. Any cap in range 100pF-330pF with 0.1" pin spacing will do, if this stage doubtfully should oscillate.

Can anybody confirm that this will work ?

 

[staggerquake1]

Hi, i just started doing the sb4000 project  , and im missing a 330PF ceramic capacitor @ c101, can i get any replacement or does it have to be a certain kind?

Might not be needed at all. (LPF set for 48kHz in 1st. inverting 2.5dB gain stage of the VU-driver) Not a critical part and not in audio path. Any cap in range 100pF-330pF with 0.1" pin spacing will do, if this stage doubtfully should oscillate.

I have the same issue, can anyone confirm that a 100pf will work?

 

[drumminkiger]

I'm just getting started on getting together all the parts for my SB4000 build, I ordered the kit, PCB's, and front panel, and now I have a couple of questions. First, what knobs do you guys like for these? And for the Key input, panel mount what TS should be used?

 

[astrosonidoespacial]

Hi you all. I made a TERRIBLE mistake. I put the violet and grey cables from the trasnformer (I use 220v so they go togheter) into ground connection. The transformer made a loud "trasnformer" rumble noise when i plugged it in. 

The readings on the transformer are: 24V on black, 23.5V on yellow,  24V on orange+red (tied). Once connected on the psu I have no more than 1.9v on the same cables. I removed the bridge diode and the reading remains the same.

With the bridge installed, readings on the rails are below 0.1v

What did I blow up? should I rebuild the entire psu again?


Any help would be appreciated.

Thanks!

 

[Harpo]

Welcome,

I put the violet and grey cables from the trasnformer ...

Colour code of transformer wires between different manufacturers is not standarized. What type and model do you use ?

(I use 220v ...

Maybe update your profile with your location data.

into ground connection

Whatever you might call 'ground' (chassis ground, safety ground, psu ground, ... all different with differing potential and meaning).

The readings on the transformer are: 24V on black, 23.5V on yellow,  24V on orange+red (tied).

These AC voltage numbers don't make much sense without quoting their reference (and this will not be 'ground').
Assuming these transformer secondary winding wires might be connected correct and from your wire colours, with AC mains connected, you will measure about 24VAC between black and orange+red, about 24VAC between yellow and orange+red and about 48VAC between black and yellow. These numbers will drop by about 10-15% with load connected.

 

[drumminkiger]

Well, since I just knobbed my project, I will answer my own question in case it helps someone else. These 31mm Elma collet knobs seem to be about the right size for the stock serpent faceplate, and I love the original feel they have.

 

[astrosonidoespacial]

Hi! i'km getting incorrect readings on the psu. Any ideas?
This is what i have:


+31.7 on positive rail
- 32 on negative rail

+14.3 on +15
+17.8 on +12
- 21.4 on -12
-17.7 on -15

Hope you can help me out. Don' know anything about debbuging.
Cheers

 

[astrosonidoespacial]

Hi! i'km getting incorrect readings on the psu. Any ideas?
This is what i have:


+31.7 on positive rail
- 32 on negative rail

+14.3 on +15
+17.8 on +12
- 21.4 on -12
-17.7 on -15

Hope you can help me out. Don' know anything about debbuging.
Cheers

Hi again, my multimeter wasn't reading well (and it isn't a cheap one!). I plugged in my old chinese multimeter and voltages are fine.

Still have -18 where it shoul be  -12 though. Already replaced the bridge diode and it wasn't the cause.

Any ideas?

 

[mrkrawn]

Hi
just a simple question.
The return is 1 or 2 trs female jack.
there is 2 wire for return on the mainboard.
Is it one wire for each trs jack
Or take the two wire 
one go to the tips the other to sleeve of the trs jack female input

Best

 

[mrkrawn]

hi
my sb4000 working fine but unable to detect any external key.
It's really annoying.
I have trying all the possible wiring for external key and no success.
Is there a trimmer which can block the external signal?

best

 

[mrkrawn]

Today i finaly solved the problem.
what a pleasure to hear the sidechain function.
I did the send & return with trj jack female stereo used as mono and i soldered the wrong pin side.
Result no signal could pass before.
Best

 

[synthlink]

Hello !
I've the quad VCA otion.
On the BOM, it's written "R76 and R96 was 220K, now 56K".
Yes, but on the board R76 and R96 are marked as 680K.
Is this an error on the board? Because R76 and R96 are 220K in the BOM.
There's something I don't understand !

 

[Bowie]

Hello !
I've the quad VCA otion.
On the BOM, it's written "R76 and R96 was 220K, now 56K".
Yes, but on the board R76 and R96 are marked as 680K.
Is this an error on the board? Because R76 and R96 are 220K in the BOM.
There's something I don't understand !

Welcome to the board!
You need to refer to the VCA chart in the Serpent schematic to determine which resistors you use in R76/R96.  For instance, I used DBX Gold Cans so I had to use 1meg.  Some of the THAT chips are 680k, 220k, 120k, or Do Not Populate, depending on which VCA you're using.  In fact, there are a lot of things in that chart that you need to be referencing.

BTW, here's a link to mine in case you can't find one;
https://www.dropbox.com/s/ltxznsz09y02t8j/SB4000_schematic.pdf?dl=0

 

[iomegaman]

I cannot for the life of me get the 12 volt rail to be less than 14-15 volts, I have changed regulataors double checked my transformer wiring about a hundred times and rechecked all the resistor/caps...everythign is as it should be...

Even under load it remains at like 14.57 volts...

I know this is not a huge deal but I do worry about the life of the regulator since it is getting hot...

I did use the 50mA transformer so there's that...

Any thoughts or comments?