It is usefull if we have opinions about those measurements.
Keep in mind that two amplifiers have the same Power Supply ,linear +/-32v ,36000uf/rail when inputs is in parallel.Outputs are under scope control at 6,9v RMS on a dummy load=6R
Each unit tested alone.
These measurements was repeated 4 times for each module
Keep in mind that two amplifiers have the same Power Supply ,linear +/-32v ,36000uf/rail when inputs is in parallel.Outputs are under scope control at 6,9v RMS on a dummy load=6R
Each unit tested alone.
These measurements was repeated 4 times for each module
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Interesting results thimios. Looks like the peak levels of the harmonics are similar, but the 'grass' is taller with the CCS. Looks like empirical evidence that the simple version might be the better way to go if you are willing to accept its limitations.
Hi thimios, I made VSSA with CCS too. CSS will make the PSRR higher.
I see PMI version have higher noise. THD should be same. I think Shaan version have better PCB layout.
Hi bimo.
Hearing the PMI version with headphones you can hear higher noise than Shaans version.
I made 2 prototype PCB, before I can not hear anything if my ear 1 cm away from speaker with opened input. PCB layout for CFA is difficult.
Another Shaan peeceebee using ksa1381,ksc3503E
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ATTENTION all these measurements must be read as WITHOUT any load.
Dummy Load was disconnected unexpectedly.
Now i must repeat all these.
Dummy Load was disconnected unexpectedly.
Now i must repeat all these.
Hi thimios, the thread title is interesting, I have attached my pcb lay-out of Shaans PeeCeeBee but employing PMIs component. If you wish to go deeper into the comparison test I guess the PCB might unlock some mystery 😀 😉
..just a thought though..🙂
Regards!
BTW The assigned component on the PCB was my own mod, provided also was PMIs original schematic and can also be followed "as is" using my PCB lay-out. The PCB lay-out is tested and is fully functional, this is my VSSA unit at home.
..just a thought though..🙂
Regards!
BTW The assigned component on the PCB was my own mod, provided also was PMIs original schematic and can also be followed "as is" using my PCB lay-out. The PCB lay-out is tested and is fully functional, this is my VSSA unit at home.
Hi Abetir,
I am etching your layout as I type. I don't see a place for the trimmers on your layout. Did you do something different there?
Thanks, Terry
Terry,
Man that was fast! I assume you are referring to the dc offset trimmer (PMIs original), this was replaced by 2 resistor in parallel (for better regulation- LCs recommendation) placed just below the fet ccs. Try to work with the resistor from values of 750k to 920k depending on your PSU rail. I find lower values to be near zero dc offset but sonic distortion may arise and higher value, higher dc offset.
Regards!
Man that was fast! I assume you are referring to the dc offset trimmer (PMIs original), this was replaced by 2 resistor in parallel (for better regulation- LCs recommendation) placed just below the fet ccs. Try to work with the resistor from values of 750k to 920k depending on your PSU rail. I find lower values to be near zero dc offset but sonic distortion may arise and higher value, higher dc offset.
Regards!
BTW which component have you installed? my mod or PMIs original. I wanted to replace the 2sk246gr with 2sk117 but I still can't locate these type in my area. In my build I removed the VAS heatsink I find it to be non-necessary at 27vdc rail voltage. Also just in case work with the cdom values from 22pf-47pf.
Yes that is correct, as I am using different components. I think VAS was settled at about 15ma. You can also install a 2k trimmer via jumper wires during test.
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I basically followed your silk. I changed a few things based on what I had in my parts bin. I used 220uf for the 100uf. I used 2SK246. I have 2SK117 if they are necessary but I figured for use in the CCS it wouldn't matter. I'll try using some pots to find the best value and then pull them and install resistors. I used BC546C/556C because I have a lot of them and I wanted to be able to try higher rails. I'll let you know how they work out.
Blessings, Terry
Blessings, Terry
I think your components should work just fine, just be sure to change the current source resistor for the CCS if you happen to change the component, it will also needs adjusting depending on your PSU rail voltage.
😉
😉
I have 4 other VSSAs. A regular Peeceebee built on a veraboard, a TO-3 version, PMI version and a Jkuetemann version. They are all running on +-36V rails. I want to try this one on higher rails. I'll try it in the morning and report back.
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