So if I use this R-core 2x18VDC 120VA can I use the BiB to get +-45Vout?
http://www.selectronic.fr/catalog/product/view/id/17866/s/transformateur-r-core-120va-avec-etrier/category/172666500/
http://www.selectronic.fr/catalog/product/view/id/17866/s/transformateur-r-core-120va-avec-etrier/category/172666500/
Salas,
please explain.
On the one hand you say 36Vac nominal max and <=38Vac max.
On the other hand you state that k117 is at risk if higher PSU input voltage is fed in.
How can an output of 45Vdc be obtained from 36/38Vac with this high voltage drop regulator?
I did not subscribe to BiB and thus don't have build instructions.
please explain.
On the one hand you say 36Vac nominal max and <=38Vac max.
On the other hand you state that k117 is at risk if higher PSU input voltage is fed in.
How can an output of 45Vdc be obtained from 36/38Vac with this high voltage drop regulator?
I did not subscribe to BiB and thus don't have build instructions.
36VAC gives ~50VDC input to the regulator after it is full bridge rectified on board. That allows enough drop across the reg to reliably set for 45VDC out. The 2SK117 under the leds sees 50VDC-VfLedsTotal as VDS. ~44.3VDC with 3 leds. Its max VDS is 50V. Combined with its degeneration resistor, the Id gets small enough to take the dissipation. T-Bag's one of the two test protos was a 43VDC out affair for instance.
Yes I know Salas that CCS is set with LEDs & resistor but when I read your answer to AndrewT I wanna be sure asking you about LEDs number.
The usual advice for low Vdrop regulators is to adopt similar Vac transformer to required regulated Vdc output voltage.
At low DC volts the transformer needs to be slightly higher. At high DC volts the transformer can be slightly lower.
But for a high Vdrop shunt regulator the transformer Vac should be increased above that normally adopted. Thus why we went with 15Vac for the DCB1 which ran on 10Vdc. 12Vac can in worst case situations allow the regulator to drop out even though we are already 2V above the norm that could be adopted.
I cannot see how 45Vdc can be reliably got from 36Vac with a high Vdrop regulator.
When the question was first asked "how 45Vdc" those thoughts jumped to mind and that is why I suggested 40Vac as the minimum to obtain 45Vdc output.
The detail is, this is not a high series Vdrop regulator. It has a high need when pushed to its lower Vo regions because it needs enough drop to ground since its CCS is vertically referenced. Someone has to cater for all leds drop, plus ~1V for the K117 to develop steady IDSS. Thus the 6.3VAC min recommendation even when setting for 3.3V out. For its series drop, it can go very near Vo, but 5V are recommended to cater for transformers nominal tolerance, power ducking, mains variations. Give it sure DCin from a bench supply, say 25VDC, then trim up near that, and you will see it will go smack near before losing regulation.
The thing to know is drop across the setting resistor. That plus 1.5V maybe, will suffice for unimpeded CCS current. If it is a Vbe controlled reg (1.2 1.2R Reflektor) then its 0.6V+1.5V. About 2V and it will work. The 5V drop recommendation covers even the higher setting resistors drops when in led controlled regs (1 & 1.1, DCB1). Vrset=Vftotal-Vgs. MinDif=Vrset+1.5V. Vrset can be kept small if with red leds and small difference to Vgs is calculated. It will go even nearer than those thresholds I described without losing regulation but will start compressing CCS current after those. There is nothing more to it, given there is no big uncertainty margin for DCin value.
Due to high voltage required I can't test BiB in Simplistic NJFET RIAA
I can do the test Vs V1.2R powering my BII, I will let you know subjective opinion.
Test V1.2R vs BiB 1.1 +BJT 5.5Vout both powering BII DAC, clear winner BiB: more harmonics so better resolution & the most impressive thing more tridimensional
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