Sound Skulptor forums
Build help and troubleshooting => CP554 Diode bridge compressor => Topic started by: Amek on January 14, 2023, 12:26:27 PM
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Hi everyone, I am calibrating two CP554 and the values all come back to me except when I get to step 13: it is not possible for me, on both CP554 modules, to get with trimmer TR3, with bypass on, to read 0.165 Vac, I get to about 1.42/1.3 Vac minimum with input at 6.15Vac and thresold at -6db: what am I doing wrong? Same thing with input at 1.55 Vac, thresold at -18db, I can't get down to 0.155 Vac: my output voltage stays much higher. I tried CP554 with a music track and it seems to work.... Can you help me? Thank you very much
Amek
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Can you check the following values with the same setup as in Step 9 (initial settings)?
With input signal 6.15VAC, THRES@-6,
JMP1 removed --> TP4 = TP5 = 2.8VAC
JMP1 on 1-2 --> JMP1-pin1 = 4.7VDC.
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Hi,
With input signal 6.15VAC, THRES@-6,
JMP1 removed--> TP4=TP5 = 1,0 mVAC
JMP1 on 1-2--> JMP1.pin1= 3,65 VDC
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TP4 and TP5 must be measured against 0V.
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Ok sorry....:-)
TP4-->0V= 1,336 VAC
TP5-->0V= 1,336 VAC
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Some gain is missing.
What is your AC voltage level (against 0V) on R43 top pin, JMP1removed ? It should be around 0.3VAC.
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yesss:
0,291 VAC from 0V to R43 top pin
Amek
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So the signal is good before U5.1 and too low after, on TP4.
You must check the resistors that set the gain of this stage : R44 to R56 and the trimmer TR3 (values and solder joints).
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Hi, I double-checked everything you told me and everything seems okay. I asked myself a question: but both modules with the same problem???? Almost impossible!!! I am really an idiot, it was simply the position of the thresold switch: I had mounted the Marconi knob turned.....Put it in the right position all measurements are now correct....I got confused the position of "0"....Thank you very much for everything and for your patience, have a good evening
Amek
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I am using the two CP554 modules and I must say that the sound is really great, much more than I expected to hear: congratulations!!!!!!!! I am left with a very small problem, so I take the opportunity to ask: I have a very small level difference between the two modules of 0.7 db: where is it best to act to put them equal? Thank you very much again and congratulations on the project!!!!!
Good night.....
Amek
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Thank you for the kind words.
If the difference remains when the sidechain is off then you must adjust with TR1.
If the difference is when compressing, then try adjusting TR3. If it doesn't work you should redo the whole setup.
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Perfect,
All work fine!!!
Thanks you
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Hi @JPK
I am also struggling with step 13 but with different issue.
After setting the unit threshold to -6 and the tone from DAW to 6.15VAC, I switch on the bypass and nothing changes on the DMM and I get no change when I adjust TR3. I kept going curious about what was going on there. -18db behaved the same. When I try the last step at +9Db thresh and switch by pass on there is also no change to the 6.15VAC tone doesn't change to 2.6VAC.
The rest of of the setup up to this point has been really good.
I have two CP554's and have tried each side chain card in each unit and got the same results with all options.
Be grateful for any guidance.
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Make sure the sidechain switch is on INT.
Check the sidechain as shown here (https://www.soundskulptor.com/forum/index.php?topic=389.msg2169#msg2169).
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Side chain was on int.
I tried both compressors without board 2 on a drum track and to me they didn't sound like they were applying any compression. Maybe I'm tired but if there was a difference it was barely audible even on extreme settings.
How subtle is the unit? How delicately do I need to listen to hear a 12/1 ratio across any given threshold? There was little to no change. I've used plugin versions and they have great range so I'd suspect this does too and I've made an error. The same error on both units is surprising. They sound the same.
I tried the side chain set up again and was still having issues with the last step which I feel may be related to the above.
I've lost track a little as this level of trouble shooting is giving me serious brain fog!!
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The side chain circuits are on board 2. So it is normal that you don't get any compression without board 2.
Can you do the measurements on the side chain shown here (https://www.soundskulptor.com/forum/index.php?topic=389.msg2169#msg2169)?