SSL 4K channel dynamics. (And more in future). PCB's/kits: Available!
- Thread starter Igor
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Ricardus
WILL SOLDER FOR FOOD
Since I've been building SSL preamps, and I'm involved in an SSL channel EQ project, I was wondering if anyone had done the channel dynamics module. So I guess here is my answer!
Ricardus
WILL SOLDER FOR FOOD
duantro said:
I messed one up when I tried to make one by hand not long ago. I'll be getting the crimper one of these days.
Well it looks like my stand-off measurements won’t work. The ribbon cable connectors are too close. It appears the the standoffs for the main pcb need to be real short! I tried 5/16” and it looks like it needs to be almost 1/2 that.
Edit, it looks like 1/8" on the bottom and 1" between the main board and the meter board.
Edit, it looks like 1/8" on the bottom and 1" between the main board and the meter board.
Attachments
I have one of my units working and calibrated, the second one passes audio but can't calibrate compression to register anything on the meter or audibly. Also the gate seems to be registering on the meter, but can't hear anything happening. I did have CPS1 (220uf) cap in backwards that wasn't happy. I replaced that and seem to be getting proper voltages on sockets. Any thoughts on where to check? maybe I'll see if I have any extra 78L05's around and swap those.
Electrobumps
Well-known member
jasonallenh said:
Jason, thanks for your explanation of the alignment the procedure while it creates a working compressor which sounds good I’m not sure the reference levels are correct.
If we look at the our 500 series schematic compared to the original schematic we have a newly designed i/p and o/p section. Our i/p and o/p circuits do not exist in the same way in a console as there is much more complex routing and signal flow.
If we look at Igor’s schematic it is states next to TP2 SET -5VDC @ 1.55 RMS. If we reference 1.55rms at TP 4 and then align the compressor It does not matter if we use dBm, dBu or if our DAW is -18dbfs or -14dbfs or any other reference level, we just need to reference 1.55rms.
When I line my compressor up to +14dBu I see -4.33VDC at TP2 and 3.84rms at TP4.
I also found that when referencing +14dBu the trims were very close to the extent of their ranges. Aligning to 1.55rms also seems to make more sense relative to the trim pot.
In operational terms if you are recording signals at close to 0Vu in your DAW. I find lining up to +14dBu does not give as much range on the compression threshold.
My method is as follows.
1. Set the compressor as the per the SSL manual. *
2. Send a 1khz test tone to the compressor adjust the level of your tone in your DAW to see 1.55rms at TP4. (take a note of the tone level in your DAW or save the setting to recall later at step 11)
3. Adjust VR2 to get -5VDC at TP2. This sets 0dB
I then continued as per the manual / Jason’s notes but with 1.55rms reference to set gain VR1 and set gate VR3.
jasonallenh said:
11.Send a 1khz test tone to the compressor to see 1.55rms at TP4.
jasonallenh said:
For Symmetry I used a plugin in my DAW called SPAN https://www.voxengo.com/product/span. Waves PAZ will also work.
*settings of compressor do not effect TP2 VDC level. However these setting make sense to test the attack switch and then to follow on and setup the gate.
SSL manual link https://pdfslide.net/documents/611-calibration.html
jasonallenh
Well-known member
Wow, I came back to reference this to recalibrate my cards and I return to find your significantly better instructions!
I do have a couple questions though-
1) what do you do if you don't have VR2?? I used the THAT chip instead and the schematic references the other chip in the notes you're referring to.
2) I was able to set the same reference level, but I cannot reduce VR'2 to get -5VDC at TP2. Instead, I just set my reference level per your instructions, and then used the SSL procedure to set 0DB (Create a 4db decrease when switching in). The THAT portion of Igor's schematic does refer to this point as "set 0db, so I am assuming this is still ok even though this ended up giving me about 4.8VDC at TP2 instead of -5VDC. I thought maybe the PCB was arranged so that either option you choose uses one half of an opamp, but the schematic says that's not the case. It's behaving like a compressor though! and you're right, the comp does behave better.
3) Cubase's default channel eq will show the harmonics so you can set the SYM pot, no plugins needed!
I'm entirely self taught, so if you have any other thoughts, please jump in. I think between the two of us, the SSL manual, and igor's docs, we have a full calibration procedure for either option ;D
By the way- to the person asking about standoff sizes for the meter board: I never got standoffs for my meter board............. I just put a couple machine screws through the pcbs with nuts on either side to hold the meter board in place. At least this way it's infinitely adjustable. I would rather use standoffs though...
I do have a couple questions though-
1) what do you do if you don't have VR2?? I used the THAT chip instead and the schematic references the other chip in the notes you're referring to.
2) I was able to set the same reference level, but I cannot reduce VR'2 to get -5VDC at TP2. Instead, I just set my reference level per your instructions, and then used the SSL procedure to set 0DB (Create a 4db decrease when switching in). The THAT portion of Igor's schematic does refer to this point as "set 0db, so I am assuming this is still ok even though this ended up giving me about 4.8VDC at TP2 instead of -5VDC. I thought maybe the PCB was arranged so that either option you choose uses one half of an opamp, but the schematic says that's not the case. It's behaving like a compressor though! and you're right, the comp does behave better.
3) Cubase's default channel eq will show the harmonics so you can set the SYM pot, no plugins needed!
I'm entirely self taught, so if you have any other thoughts, please jump in. I think between the two of us, the SSL manual, and igor's docs, we have a full calibration procedure for either option ;D
By the way- to the person asking about standoff sizes for the meter board: I never got standoffs for my meter board............. I just put a couple machine screws through the pcbs with nuts on either side to hold the meter board in place. At least this way it's infinitely adjustable. I would rather use standoffs though...
Electrobumps said:
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