duantro said:Anyone have tips for assembling the ribbon cable connectors? When I pressed mine together the female connectors exploded. I have more on order.
Thanks for the reply! R31 has 15.41vdc on trimmer side, the same as the working one. And 0vdc on the other side. I took most all voltages and only posted the ones that differ from the working one.12afael said:What voltage do you have at the set gate pot? Does it change??
jasonallenh said:Here's my calibration procedure per the SSL documents and Igor's schematic. Please feel free to correct anything I got wrong, because I am far from 100% sure I've done this correctly...
2. Send a +14 dB 1k sine wave (this is the first part I may have done wrong... I'm assuming this is in dBu, which according to my console manual is -4 dBFS. I set my DAW sine generator to -4 in this case to make the +14 dB).
jasonallenh said:5. Turn your threshold control all the way down (-20) so that you're seeing the GR maxed out. Back your sine wave off until you see no compression. Clear your meter peak in your daw.
6. Raise the sine level until you see the first GR meter LED come on. Take a look at the peak reading in your DAW at this point. (Mine was -25.5 at this point).
7. The SSL Docs say that the level should stay fairly constant (within +/- 1 dB) as you raise the sine level from here (because your ratio is at infinity). Mine did not do this at first- Once my compressor started limiting at -25.5, the level made it up to like -23.9 or something like that. This is how you know you need further adjustment...
8. ...in which case, the documents tell you to adjust the "gain preset" (I guess 'preset' means 'trimpot' in British... I speak American =P). The trimmer in this case is VR1... You'll adjust VR1 to correct this. Lower your sine level until there is no more Gain Reduction, then clear out your DAW peak meter again. Raise the sine until you see some GR, make note of the peak level at that point, then continue raising. If the output level doesn't go past 1dB, you've made the correct adjustment. If it got WORSE, you need to turn the trim pot the other direction =P
9. Once you've met the condition that the output stays within +/- 1dB of where it is when GR begins, your compressor is set! Change your ratio to the lowest setting (1:1)
10. Set the expander settings to those specified in the SSL docs.
jasonallenh said:12. Adjust VR3 until the signal passes through the gate. (this was easy). Once this is done, put your range control to its minimum setting.
13. Sym Adjustment. I stumbled upon this by accident! The output, when viewed in the cubase channel settings, showed multiple harmonics of 1k (2k, 4k, etc). This is the distortion that the SYM trimmer is supposed to remove (I guess... tell me if I'm wrong!) I'm including an image of what it looks like before adjustment.
14. Adjust the SYM preset until those extra harmonics go away. If you go too far, they begin to creep back up. Find the happy medium.
Electrobumps 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.
11.Send a 1khz test tone to the compressor to see 1.55rms at TP4.
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