SB4000 Support Thread

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Diamondj421

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sr1200 said:
if i recall this is discussed in the calibration procedure no?

I believe recalibrating the unity gain pots only affects the signal when the compressor is engaged. Correct? This is happening engaged and bypassed.
 

Harpo

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Diamondj421 said:
I believe recalibrating the unity gain pots only affects the signal when the compressor is engaged. Correct?
Correct.
This is happening engaged and bypassed.
So the reason of your 3dB R/L level difference is not the SB4000, because the hardwire bypass simply connects input with output.
With your signal generator engaged, measure AC voltage between XLR-Pins 2/3 of your left ch.sending device and compare measured value with your right ch.sending device. In case these L/R numbers match, the 3dB difference giving fault is in the receiving device, else it is the sending device. If you set levels only by dialing in pot settings to same optical degree of rotation or slider travel, keep in mind real world pots come with +/-20% parts tolerances.
Good luck.
 

Sinkia

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Hi all !
I still have a problem on my sb4000 build...

A friend of mine have builtthe pcbs for me, and I have wire it.
When I don't hook up the power pcb to the main PCB, all my voltages rails are correct. But when I do connect the two PCBs, r182 and 183 (10ohm) start to smokes..
I have double check everything, and nothing seems to be misplaced/bad solder...

Do you might have an idea where it can come from..?

Many thanks in advance
 

Harpo

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Sinkia said:
... But when I do connect the two PCBs, r182 and 183 (10ohm) start to smokes..
so the fault is connected to the +12VDC/-12VDC supply rails, causing a current draw exceeding parts rating (FI by one or more short/s or broken part/s).
Double check for correct part and part orientation of U9, U10 (sidechain VCAs), U13 (TL072) and U15, U16 (TL074).
If any of these chips have been placed reversed with the unit powered on, at least these reverse powered parts will be broken.
The multipin connectors J6 and J18 are placed with correct orientation ?
good luck


 

Sinkia

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Harpo said:
so the fault is connected to the +12VDC/-12VDC supply rails, causing a current draw exceeding parts rating (FI by one or more short/s or broken part/s).
Double check for correct part and part orientation of U9, U10 (sidechain VCAs), U13 (TL072) and U15, U16 (TL074).
If any of these chips have been placed reversed with the unit powered on, at least these reverse powered parts will be broken.
The multipin connectors J6 and J18 are placed with correct orientation ?
good luck

I'll have a look right now !
Thanks you !!!

Just to make it right, it's 181, and 182  8)
 

Ack

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ruckus328 said:
Adjust DTRIM Pots (VR3/VR4 on Main Board) for lowest THD.  Then turn front panel gain knob to Max (lower the input signal as required so signal doesn't clip).  Now adjust the 50K Pots on the VCA boards for lowest THD.  Return front panel gain knob to 0.  You will need to repeat this process a few times until lowest THD is achieved.
Hi,
I have 2 results with 2 ways of THD calibrating:

1. With Gain = 0, input level +4dBu, I can adjust VR3&4 to have 2kHz level around -120dBfs in the scope. But then it jumps to -75dB with Gain at Max.

2. With Gain = 0, input level +4dBu, I can adjust VR3&4 to have 2kHz level around -95dBfs in the scope.  Then it would jump to -95dB with Gain at Max.

So which result is correct ?

3. Or another calibrating way is to aim for minimum 2kHz level around 4-6dB of Gain, which is  made up for same amount of compression that I normally applied with the SSL comp type?

4. The 50k pots on both Quad VCA boards seem to change nothing to the 2kHz even being turned to both ends. I do jump all JMPs and change parts on main PCB as guided in the QUAD BOM.

(I have REW app which can measure THD+N but it is useless with Avid Thunderbolt system. RMAA is PC only and I only have OSX computers.)
 

Ack

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Hi,

In the meantime waiting for some help on calibrating the SB4000, here are photos of my SB4000 version, which is heavily modified with THAT1240 in the input section and BurrBrown OPA627+Lundahl LL5402 in the output section.

Wish you guys all the best and success with your builds!

Cheers,
 

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Blahpstick

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Does anybody still have a copy of the schematic PDF for this?  Unfortunately the old DropBox link is dead.

For the regular DIY haunts on here:
I built two of these bad boys with the quad VCA's and they have both been working great for me.  I had built one for LR (fantastic choice) and one for drums, but the quad VCA version just doesn't have enough attitude and smickety-smack for my taste on that rock drum buss.

Now I've only used the quad VCA's before, but would I be able to get that higher THD dirt if I convert one of my builds to the single THAT (or DBX can) VCA version?

Thanks for your time, ladies and gents!
Blahpstick
 

Blackdawg

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Blahpstick said:
Does anybody still have a copy of the schematic PDF for this?  Unfortunately the old DropBox link is dead.

For the regular DIY haunts on here:
I built two of these bad boys with the quad VCA's and they have both been working great for me.  I had built one for LR (fantastic choice) and one for drums, but the quad VCA version just doesn't have enough attitude and smickety-smack for my taste on that rock drum buss.

Now I've only used the quad VCA's before, but would I be able to get that higher THD dirt if I convert one of my builds to the single THAT (or DBX can) VCA version?

Thanks for your time, ladies and gents!
Blahpstick

I saved all the data from the DB links so i have it. I've attached it below.

Yes even going to just a single THAT should raise the THD. To what you want? Not sure.

 

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buildafriend

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Hi guys,

How should I populate the main PCB VCA area for old school DBX 202 or DBX 201 cans?
Info is on table in schematic.

Are any mods needed to add input and output transformers?
^still curious about this though ^

All the best,
-JP
 

jcgriggs

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May 20, 2017
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I'm building an SB-4000 using the 8027-B 1mA meter from Hairball.  Can someone confirm that I need to adjust R133 to 275R-300R (from 1K) for the lamp with this meter?  The Hairball link from where this advice was originally given is dead, so I want to confirm and get it right the first time  :).  Also, any advice on an exact value to use with this meter would be great.

Regards,
  John
 

jcgriggs

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More questions:

Power for the Livingnote Crush'n'Blend board, is that J19?  If so, what is the pin out?  If not, where are the connections for this?  I can see the points for RD, RW, RO, LD, LW and LO on the PCB, just not V+, V- and ground (0).

I am not planning to implement the external side chain and I believe that would allow me to re-purpose the Ext In switch as the Crush'n'Blend bypass switch - is there any problem doing this?  My understanding is that leaving the Ext In switch unconnected will just disable the external side chain but I wanted to confirm this.

Regards,
  John
 

buildafriend

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Its a current limiting resistor. Google that, how many mA do you want to the LED? How many VDC are going to it? Sounds like you might already have 2 parts of a three part formula.

https://www.sparkfun.com/tutorials/219

I'm building an SB-4000 using the 8027-B 1mA meter from Hairball.  Can someone confirm that I need to adjust R133 to 275R-300R (from 1K) for the lamp with this meter?  The Hairball link from where this advice was originally given is dead, so I want to confirm and get it right the first time  :).  Also, any advice on an exact value to use with this meter would be great.

Regards,
  John
 

jcgriggs

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Thanks for this.  The hairball site only lists the voltage (5.6-7.6 VDC) so I had to dig around a bit for what the current number should be - there are no real details on the site (that I could find, anyway) regarding the number of LEDs or how they re connected, but elsewhere people are saying there are 2, in series.  Assuming 20mA gives me 220R-320R, which seems to be in the ballpark of the original suggestion.

Thanks again,
  John

buildafriend said:
Its a current limiting resistor. Google that, how many mA do you want to the LED? How many VDC are going to it? Sounds like you might already have 2 parts of a three part formula.

https://www.sparkfun.com/tutorials/219

I'm building an SB-4000 using the 8027-B 1mA meter from Hairball.  Can someone confirm that I need to adjust R133 to 275R-300R (from 1K) for the lamp with this meter?  The Hairball link from where this advice was originally given is dead, so I want to confirm and get it right the first time  :).  Also, any advice on an exact value to use with this meter would be great.

Regards,
  John
 

jcgriggs

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May 20, 2017
Messages
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PING:

jcgriggs said:
More questions:

Power for the Livingnote Crush'n'Blend board, is that J19?  If so, what is the pin out?  If not, where are the connections for this?  I can see the points for RD, RW, RO, LD, LW and LO on the PCB, just not V+, V- and ground (0).

I am not planning to implement the external side chain and I believe that would allow me to re-purpose the Ext In switch as the Crush'n'Blend bypass switch - is there any problem doing this?  My understanding is that leaving the Ext In switch unconnected will just disable the external side chain but I wanted to confirm this.

Regards,
  John
 

jcgriggs

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May 20, 2017
Messages
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Yes - I know I can work this out with a DVM but at the moment I am waiting on parts (transformer, etc.), so I figured I'd ask and possibly save myself some effort.  Also, like most folks (I think), I have more faith in the opinions of strangers than my own surmises...

Thanx,
  John

Blackdawg said:
I don't know your answers per say..however a volt meter will tell you if its the case with J19 pretty quickly.

As for the switch, just unplug it and test it out to see what happens!

Monte
 

justinvm

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Dec 13, 2011
Messages
5
Can someone please upload the SB4000 schematic.

All the links online are all dead.

I need to know resistor / jmp values for the dbx202c gold can VCAs.
 

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