SB4000 Support Thread

[Harpo]

I get 6.98ac at TP8 and 6.99ac at TP10.

So you're feeding the SB4000 with an above +19dBu signal.

...I get no voltage on Tp11 or TP12 when T2 is engaged, so I am assuming it's a problem within the sidechain.  I get no voltage off of U1b pin 7 unless I'm in T1 or external in. At this point, I'm not sure where to look specifically for the issue.

So the fault is in the T2 stage or -less likely- the ribbon connector at pin20 doesn't connect for whatever reason.
Might be a short at U6 between pins 5/6 or 6/7. A magnifying glass might help to spot it.

It does seem that the HPF switch is selecting freqs, just not the T2 setting.  I have checked continuity on the ribbon cable.  I have hit all solder joints in the u1 area.  No luck.

Nothing wrong in the U1 area, else other settings wouldn't show up.

 

[darnell]

I get 6.98ac at TP8 and 6.99ac at TP10.

So you're feeding the SB4000 with an above +19dBu signal.

I guess thats the case. I messed around with my audiofire 4 i/o settings until the tone generator plug was sending and receiving a signal that wasn't in the red.

I have isolated the problem to the ribbon. It was not making enough of a connection for passing audio, but enough to show continuity.

Thanks.
Daryl

 

[mativas]

Hi !

I finish my sb4000 build since couples of mounts ( all stock) but now i have a pair of dbx202c ( gold )  , and now i'm little confused in the installation someone can please advice me ?

i only need to remove all components under the vca's ,  put the two jumpers on JMP8/JMP9  and trim the vr1 /vr2 to 5k ??

or i need change any other component ?

Thanks !

we did exactly that says in the thread and bom list with my partner sea man.. but after do it we can"t se any meter action...  not in the vu meter either in the led section.. anyone could help us

 

[Harpo]

Hi !

I finish my sb4000 build since couples of mounts ( all stock) but now i have a pair of dbx202c ( gold )  , and now i'm little confused in the installation someone can please advice me ?

i only need to remove all components under the vca's ,  put the two jumpers on JMP8/JMP9  and trim the vr1 /vr2 to 5k ??

or i need change any other component ?

Thanks !

we did exactly that

Obviously not. Have a look at the schematic again. You 'have a pair of dbx202c ( gold )', not dbx202 (black).
Do Not Populate (this is what DNP stands for) jumpers JMP8/JMP9. edit: just the other way round, POP JMP8/9 for DBX202C, DNP for DBX202.
'Trim the vr1 /vr2 to 5k' (for the Quad-VCA-boards) will be 27K for DBX202C. (For DBX202 you obviously can't pretrim a 50K trimmer to 75K, so replace VR1 and VR2 with 100K trimmers for these parts.) If you tried it with 5K and a too high signal level, you might have killed your DBX202Cs by exceeding their abs.max input current.
Populate jumpers JMP1/JMP4, so you can adjust THD by VR3/VR4. (this is an error in the schematics substitution chart for both DBX202 and DBX202C).

but after do it we can"t se any meter action...  not in the vu meter

If 'meter action' is the round GR meter, this is not a VU meter but a (1mA fsd) current sensing meter, showing the generated control voltage in the sidechain section. Nothing to do with your DBX202Cs.

either in the led section

If signal arrives on output with input signal present, this might only be a build error in the bargraph section, else switch off your unit, pull both DBX202Cs out of their socket, temporary jumper VCA-in to VCA-out with a piece of wire, power on and check again. If the LED bargraph section (the LM3916 is a VU type bargraph IC, showing the level of output signal) now shows up, expect the DBX202Cs to be blown, else double check parts, parts values and parts orientation in the LED bargraph section.

 

[mamiti]

Hi,

I've built (finally, had the parts for ages) SB4000 with DBX202C's and CnB.

The thing is that dry signal from LD or RD is always 6dB louder than unit bypassed. In other words: If I connect LD directly to LO, the output signal is 6dB louder than in bypass. This kind of makes Dry/Wet blend uncomfortable. VR1/VR2 are after dry out so they doesn't have effect.

Where should I start tracking / anything can be done? What I've done wrong?

I've modded the usual suspects when using DBX2020C: R76/R96 are 1M, JMP1-6 unpopulated (of course), JMP8/9 populated, R77/R121/R83/R125 not populated.

Thank you,

Mikko

 

[Harpo]

The thing is that dry signal from LD or RD is always 6dB louder than unit bypassed. In other words: If I connect LD directly to LO, the output signal is 6dB louder than in bypass. This kind of makes Dry/Wet blend uncomfortable. VR1/VR2 are after dry out so they doesn't have effect.

That is what the schematic says. Easiest fix seems to be doubling up the input resistors at the C&B.

I've modded the usual suspects when using DBX2020C:

probably a typo. From your 1st.line this might be a DBX202C. Maybe read my previous post.

R76/R96 are 1M, JMP1-6 unpopulated (of course)

JMP1 and JMP4 populated (of course), otherwise R76/R96 would be one side connected and your THD trimmers VR3/VR4 would do nothing.

JMP8/9 populated

There is a reason, the schematic shows the line 'FOR DBX202 ONLY' for these type of VCAs 6mV/dB control law. For the DBX202C, coming with a 50mV/dB control law, different control port impedances, different i/o-current capabilities, different..., you'll have JMP8/JMP9 not populated. The nearly only common to all these VCA modules (DBX202, DBX202C, DBX202X, DBX202XL, THAT2001, THAT2002N, THAT2002R, THAT2002T, THAT202R, THAT202XT, THAT202XTC) is the packages pin spacing and pinout function. You'd need to adapt the surrounding circuit to meet the modules requirements, to not exceed modules limits or to trim for modules optimal performance.

 

[mamiti]

The thing is that dry signal from LD or RD is always 6dB louder than unit bypassed. In other words: If I connect LD directly to LO, the output signal is 6dB louder than in bypass. This kind of makes Dry/Wet blend uncomfortable. VR1/VR2 are after dry out so they doesn't have effect.

That is what the schematic says. Easiest fix seems to be doubling up the input resistors at the C&B.

That really is an easy solution, works well. Thank you for helping a beginner.

R76/R96 are 1M, JMP1-6 unpopulated (of course)

JMP1 and JMP4 populated (of course), otherwise R76/R96 would be one side connected and your THD trimmers VR3/VR4 would do nothing.

You're right again, JMP1 and 4 populated now. I only read the table for different VCA's and didn't compare to schematics. Should have...

JMP8/9 populated

There is a reason, the schematic shows the line 'FOR DBX202 ONLY' for these type of VCAs 6mV/dB control law. For the DBX202C, coming with a 50mV/dB control law, different control port impedances, different i/o-current capabilities, different..., you'll have JMP8/JMP9 not populated. The nearly only common to all these VCA modules (DBX202, DBX202C, DBX202X, DBX202XL, THAT2001, THAT2002N, THAT2002R, THAT2002T, THAT202R, THAT202XT, THAT202XTC) is the packages pin spacing and pinout function. You'd need to adapt the surrounding circuit to meet the modules requirements, to not exceed modules limits or to trim for modules optimal performance.

The table in the schematics says JMP8 and JMP9 populated for both DBX202C and DBX202. If those are removed then I don't understand where to get control voltage (CV_VCA / L_CV202) into DBX202C. Did you really mean Do Not Populate JMP8 and 9 when DBX202C's are in the circuit?

Thank you for your help!

 

[Harpo]

JMP8/9 populated

There is a reason, the schematic shows the line 'FOR DBX202 ONLY' for these type of VCAs 6mV/dB control law. For the DBX202C, coming with a 50mV/dB control law, different control port impedances, different i/o-current capabilities, different..., you'll have JMP8/JMP9 not populated. The nearly only common to all these VCA modules (DBX202, DBX202C, DBX202X, DBX202XL, THAT2001, THAT2002N, THAT2002R, THAT2002T, THAT202R, THAT202XT, THAT202XTC) is the packages pin spacing and pinout function. You'd need to adapt the surrounding circuit to meet the modules requirements, to not exceed modules limits or to trim for modules optimal performance.

The table in the schematics says JMP8 and JMP9 populated for both DBX202C and DBX202. If those are removed then I don't understand where to get control voltage (CV_VCA / L_CV202) into DBX202C. Did you really mean Do Not Populate JMP8 and 9 when DBX202C's are in the circuit?

Sorry, corrected previous posts. For the DBX202C (gold can) type of VCA the chart is correct. Populate JMP8 and JMP9.
(for DBX202 (black can) the table should say DNP JMP8 and JMP9 and jumper not fitted opamps U12 pins3/6 and U18 pins3/6 to get the attenuated control voltages thru by voltage dividers R77/R83 and R121/R125 to this type of VCA)

 

[mamiti]

Sorry, corrected previous posts. For the DBX202C (gold can) type of VCA the chart is correct. Populate JMP8 and JMP9.
(for DBX202 (black can) the table should say DNP JMP8 and JMP9 and jumper not fitted opamps U12 pins3/6 and U18 pins3/6 to get the attenuated control voltages thru by voltage dividers R77/R83 and R121/R125 to this type of VCA)

Yes, I kind of figured that out and SB4000 is now compressing well, CnB acts like it should, everything works. Well, except RMAA that chrashes at 85% during THD measurements... I'll take it to AP bench at work to get THD trimmers set.

A couple of photos:
http://tillander.kapsi.fi/Temp/Temp/SB4000_1.JPG
http://tillander.kapsi.fi/Temp/Temp/SB4000_2.JPG

Thanks!

 

[EmptyMusicBox1]

hi ! what's the schema do you have follow for your C'nB circuit ?

the CnB REV 1 ?



thx

 

[sage]

It appears that one side is 1/2 dB louder than the other, to be exact the LEFT side is louder.

Once in Bypass there's no problem so it's not the patch bay or cable...

1/2 dB is not much but really it should be that way considering it's a MASTER BUSS Compressor  - what could be the culprit?

Anyone has any idea?

sage

 

[Harpo]

Once in Bypass there's no problem so it's not the patch bay or cable...

1/2 dB is not much but really it should be that way considering it's a MASTER BUSS Compressor  - what could be the culprit?

Assuming you're talking of the hard bypass, sure. Use the soft bypass (switch to external key with no (0.0 V) external signal feeding your unit) for unity gain calibration by trimmers VR1 and VR2.

 

[sage]

THANK YOU HARPO - You are always on point - i love it !

Will do today and let you know !

sage

 

[Gijsvanwel]

Hello everybody,

I just completed my SB4000 build (ordered the complete parts kit). It is my very first build so I'm still quite nooby.

I am in the calibration stage at the moment and i encountered a problem:
When i try to set the right Unity gain my left channel seems to work perfectly, but there is something very wrong in the right channel. When i increase the volume of my test tone (1 khz test tone), the output signal hangs at a value and then immediately turns red. There is no in between.

Please help me with isolating the problem. I measured all my resistor values and they seem to be in order. Can this be caused by a broken/faulty vca?? (using that2181c)

Thanks in advance,

Gijs van Wel

 

[jamesn81]

Hi All,

I'm always very reluctant to make a post, as I try my best to be very thorough and read the whole thread. 

My unit sounds and performs fantastically.  Definitely as useful as the real deal and some great features - so thanks ruckus for the great project.

I have a few small issues!  I have the Quad VCA version of this project.

[list type=decimal]
[*]I realise the bargraph is VU, but I get the same reading for input and output even when I engage the makeup gain option (it increases on the bargraph reading for both input and output when I turn the gain knob up and down
[*]When I switch the L/R to R, I get no reading at all even though audio is working in both bypass and compression mode.  The L mode is working great.  I'm not using VR's at the bargraph in/out stages, just the 2k49 and 13k resistors supplied and they test out ok.
[*]I can't seem to accurately calibrate the compression Meter by adjusting VR17.  It works but the closest I can get is about 3-4db off.  I run out of space with the VR.
[/list]

I hope somebody can shed some LED light!

Thanks

James

 

[Harpo]

1. I realise the bargraph is VU, but I get the same reading for input and output even when I engage the makeup gain option (it increases on the bargraph reading for both input and output when I turn the gain knob up and down

Meter is always reading right side output. Relais K7 doesn't change over from its default setting. Check for missing solder connection at K7 and cathode side of D7 and/or K7-pin1 getting +12V when you activate the i/o meter toggle.

2. When I switch the L/R to R, I get no reading at all even though audio is working in both bypass and compression mode.  The L mode is working great.  I'm not using VR's at the bargraph in/out stages, just the 2k49 and 13k resistors supplied and they test out ok.

Double check solder connections at K8. Might as well only be a followup from K7.

3. I can't seem to accurately calibrate the compression Meter by adjusting VR17.  It works but the closest I can get is about 3-4db off.  I run out of space with the VR.

Measure resistance of VR17. (you left out R111 for your not 100uA meter?)

 

[jamesn81]

1. I realise the bargraph is VU, but I get the same reading for input and output even when I engage the makeup gain option (it increases on the bargraph reading for both input and output when I turn the gain knob up and down

Meter is always reading right side output. Relais K7 doesn't change over from its default setting. Check for missing solder connection at K7 and cathode side of D7 and/or K7-pin1 getting +12V when you activate the i/o meter toggle.

2. When I switch the L/R to R, I get no reading at all even though audio is working in both bypass and compression mode.  The L mode is working great.  I'm not using VR's at the bargraph in/out stages, just the 2k49 and 13k resistors supplied and they test out ok.

Double check solder connections at K8. Might as well only be a followup from K7.

3. I can't seem to accurately calibrate the compression Meter by adjusting VR17.  It works but the closest I can get is about 3-4db off.  I run out of space with the VR.

Measure resistance of VR17. (you left out R111 for your not 100uA meter?)

Harpo - you are a life saver (I'm sure many people have said this)!  You've made my weekend.  Thanks so much for the quick, detailed response.  I hadn't populated an entire side of K7! What the?!

Bargraph L/R and I/O are all perfect now - thanks so much again. 

Yes, I have Hairball's 1mA meter .... VR17 is at the far end of its spectrum - it measures 5.05K. I have not populated R111 at all.  Is the correct procedure to jump R111 or leave it blank if I have a 1mA meter?  On the schematic it seems to go off on its own tangent so I would think leaving it out is the way to go.

When I engage the compressor and adjust threshold to achieve a 10db drop in my DAW, the meter reads 12db ... and that's as close as I can get it.

Any ideas?

James

 

[Harpo]

Yes, I have Hairball's 1mA meter .... VR17 is at the far end of its spectrum - it measures 5.05K. I have not populated R111 at all.  Is the correct procedure to jump R111 or leave it blank if I have a 1mA meter?  On the schematic it seems to go off on its own tangent so I would think leaving it out is the way to go.

Yepp. Leave out R111 for a 1uA FSD meter.

When I engage the compressor and adjust threshold to achieve a 10db drop in my DAW, the meter reads 12db ... and that's as close as I can get it.

This is only half of the story. What is your dBFS reading to get a +0dBV readout ? Might be in range -12....-18dBFS.

I'd calibrate the sidechain section following signal and the schematic, so order will be different.

Initially power on the unit, engage compressor (disable the hard bypass), set the unit for no makeup gain, set HPFilters to off position and set ratio to 2:1.

For step 2 adjust audio path unity gain setting by trimmers VR1 and VR2 with unit set to soft bypass (engage External key with no signal (nada millivolt, niente dB, nuthin' whatever) on external sidechain input. Maybe short out tip and sleve at your external SC plug to ensure this). The 'with the unit in bypass' might be confused with the hard bypass relay that simply connects input to output.

For step 3 with 1kHz sine signal present, External key disabled and unit switched to default SSL-mode adjust VR8 for TP11 reading the same as TP8 and adjust VR7 for TP12 reading the same as TP10. Note these readings for the following step.

For step 5 (the 2nd. of the 3x step5), still in SSL mode, set HPFilter to T1 and adjust VR5 and VR10 for same reading as in previous noted readout when measuring at TP11 and TP12.
Set HPFilter to T2 and adjust VR6 and VR9 for same reading as in previous noted readout when measuring at TP11 and TP12.

For step 5 (the 1st.) Drop feeding signals by 10dB below 0dBV (0.316V AC, something in range -22...-28dBFS) both L/R reading the same level. Turn threshold full CCW (probably always compressing). Note the L/R meter readout of your return signal in your mixer, DAW or measure return signal AC voltage. Now increase feeding signals by 10dB to 0dBV. Tweak VR16 for best average for
+5dB more (or noted voltage times 1.778, probably about 0.562V AC) than previously noted return level in 2:1 ratio setting,
+2.5dB more (or noted voltage times 1.259, probably about 0.398V AC) than previously noted return level in 4:1 ratio setting,
+1dB more (or noted voltage times 1.122, probably about 0.355V AC) than previously noted return level in 10:1 ratio setting.

For step 4 increase threshold to about -10dB and adjust VR17 to reflect the GR meter showing the same amount of compression at differing ratios.

 

[jamesn81]

This is only half of the story. What is your dBFS reading to get a +0dBV readout ? Might be in range -12....-18dBFS.

Yep - it's -13.8dBFS

I'd calibrate the sidechain section following signal and the schematic, so order will be different.

Initially power on the unit, engage compressor (disable the hard bypass), set the unit for no makeup gain, set HPFilters to off position and set ratio to 2:1.

For step 2 adjust audio path unity gain setting by trimmers VR1 and VR2 with unit set to soft bypass (engage External key with no signal (nada millivolt, niente dB, nuthin' whatever) on external sidechain input. Maybe short out tip and sleve at your external SC plug to ensure this). The 'with the unit in bypass' might be confused with the hard bypass relay that simply connects input to output.

For step 3 with 1kHz sine signal present, External key disabled and unit switched to default SSL-mode adjust VR8 for TP11 reading the same as TP8 and adjust VR7 for TP12 reading the same as TP10. Note these readings for the following step.

For step 5 (the 2nd. of the 3x step5), still in SSL mode, set HPFilter to T1 and adjust VR5 and VR10 for same reading as in previous noted readout when measuring at TP11 and TP12.
Set HPFilter to T2 and adjust VR6 and VR9 for same reading as in previous noted readout when measuring at TP11 and TP12.

For step 5 (the 1st.) Drop feeding signals by 10dB below 0dBV (0.316V AC, something in range -22...-28dBFS) both L/R reading the same level. Turn threshold full CCW (probably always compressing). Note the L/R meter readout of your return signal in your mixer, DAW or measure return signal AC voltage. Now increase feeding signals by 10dB to 0dBV. Tweak VR16 for best average for
+5dB more (or noted voltage times 1.778, probably about 0.562V AC) than previously noted return level in 2:1 ratio setting,
+2.5dB more (or noted voltage times 1.259, probably about 0.398V AC) than previously noted return level in 4:1 ratio setting,
+1dB more (or noted voltage times 1.122, probably about 0.355V AC) than previously noted return level in 10:1 ratio setting.

For step 4 increase threshold to about -10dB and adjust VR17 to reflect the GR meter showing the same amount of compression at differing ratios.

Hi Harpo,

Thanks again for your very detailed guide.  Hopefully it can assist someone else too because it was good to do everything in that order for me.

When I went through it just now, most of this process worked extremely well right until your last step!  (Step 4 in the guide).  Ratios are all looking good (measured with dBFS as well as double checking with AC) ... all of the various test points voltages match up ... but the compression meter still only gets as close as 12db when the compressor is knocking down 10db.  It is quite accurate at the end of the scale however - 20db on the meter equates to pretty much 20db of compression measured in my DAW.

Ah well!   I think it's just one of those things that may not work out perfectly.

Thanks again for your advice!

 

[jamesn81]

Out of interest guys - I've followed the NKK datasheet to print out some labels on the Sidechain and Compressor buttons with transparent film.  It's just stuff you can run through a laser printer.

I'll attach an PDF vector format file in the next post.