You can use the 0C3 as a replacement for the zener string, which is what I was talking about. It does regulate the voltage as it provides the gate voltage of the Q11 which is working as a follower. The keyword is follower. Q11 output just follows the voltage of the 0D3 (or zeners). With the mosfet follower, the current is only limited by the maximum dissipation of the mosfet.
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One advantage of the zener stringer is that you don't need to have a 133V power supply. The zeners only need enough extra voltage to deal with variations in the line voltage.
If the 0C3 replaces the zener string, the extra voltage that needs to be dropped is included in the Vds of the mosfet, which increases its dissipation, which may then require a bigger heat sink for the mosfet.
Since the preamp operates in Class A, there is very little current variation so perhaps the 0C3 in place of the zener string and mosfet could be viable. The 40mA maximum for the 0C3 is the maximum shunt current through it to provide regulation. So if the line voltage does not vary much and if the preamp circuit's current does not vary much, then the shunt current will not vary much, and is set by the value of the dropping resistor and chosen based on the expected minimum and maximum voltage and expected current demand.
If the 0C3 replaces the zener string, the extra voltage that needs to be dropped is included in the Vds of the mosfet, which increases its dissipation, which may then require a bigger heat sink for the mosfet.
Since the preamp operates in Class A, there is very little current variation so perhaps the 0C3 in place of the zener string and mosfet could be viable. The 40mA maximum for the 0C3 is the maximum shunt current through it to provide regulation. So if the line voltage does not vary much and if the preamp circuit's current does not vary much, then the shunt current will not vary much, and is set by the value of the dropping resistor and chosen based on the expected minimum and maximum voltage and expected current demand.
Just seeing this about the VR tube.
I have a bunch of those and wondered if they would be better than the zener string.
They are noisy but in a line stage they might be OK. Romy uses them in his phono stage and thinks they add a great something to the sound. He has not mentioned the lack of or presence of noise. His circuit is based on the entry level Paravicini phono stage. I cannot remember what it is called. It is in a very small box as it comes from the factory. The VR tube is not part of the original circuit.
Being a dangerous dilettante who has to do things differently - I am using four 28 volts 5 watts zeners. I looked at the ESR of various zeners, I have no idea how the ESR affects the operation of the zener, but I figured lower ESR would, maybe, bring about lower noise. This string has a greatly reduced ESR for what that is worth. Certainly will do no harm. In addition I am using
My string has a Zz (esr) of 24 Ohms versus the suggested three with 207 Ohms. I looked at the first diode with a 1N prefix that appeared after the search at MOUSER for the 75 and 15 voltage zeners. About two dollars of overkill at worst.
I have figured I will have a 124 volts raw supply - one never knows until it is built. TOROIDY said they would send my transformers this week.
My AC is from an inverter and stays very constant - actually rises two volts as the battery is depleted. It will spend the majority of its time at 123 volts AC which gives me the 124 volts DC. The supply has a choke and if my assumptions turn out to be wrong I can raise the voltage by changing the choke and lowering the value of the resistor on the board.
I have a bunch of those and wondered if they would be better than the zener string.
They are noisy but in a line stage they might be OK. Romy uses them in his phono stage and thinks they add a great something to the sound. He has not mentioned the lack of or presence of noise. His circuit is based on the entry level Paravicini phono stage. I cannot remember what it is called. It is in a very small box as it comes from the factory. The VR tube is not part of the original circuit.
Being a dangerous dilettante who has to do things differently - I am using four 28 volts 5 watts zeners. I looked at the ESR of various zeners, I have no idea how the ESR affects the operation of the zener, but I figured lower ESR would, maybe, bring about lower noise. This string has a greatly reduced ESR for what that is worth. Certainly will do no harm. In addition I am using
My string has a Zz (esr) of 24 Ohms versus the suggested three with 207 Ohms. I looked at the first diode with a 1N prefix that appeared after the search at MOUSER for the 75 and 15 voltage zeners. About two dollars of overkill at worst.
I have figured I will have a 124 volts raw supply - one never knows until it is built. TOROIDY said they would send my transformers this week.
My AC is from an inverter and stays very constant - actually rises two volts as the battery is depleted. It will spend the majority of its time at 123 volts AC which gives me the 124 volts DC. The supply has a choke and if my assumptions turn out to be wrong I can raise the voltage by changing the choke and lowering the value of the resistor on the board.
Rick, be sure to put a transformer between the inverter and the board input.
While zeners are noisy, there is cap right next to it to kill the noise. There is also a cap after the follower to provide decoupling from the regulator. In my testing, this PS sounded as good as a full-fledged Salas shunt reg. Build with confidence. I am even using it for the DAC supply and it is several orders better than the chip-based reg it replaced. Lastly, take a look athe BOZ and BOSOZ articles. Same supply—Papa approved.
While zeners are noisy, there is cap right next to it to kill the noise. There is also a cap after the follower to provide decoupling from the regulator. In my testing, this PS sounded as good as a full-fledged Salas shunt reg. Build with confidence. I am even using it for the DAC supply and it is several orders better than the chip-based reg it replaced. Lastly, take a look athe BOZ and BOSOZ articles. Same supply—Papa approved.
Since this brought confusion before I made a point of saying AC and DC. The inverter outputs AC which will go to the aforementioned TOROIDY transformer to be rectified.
I do not think the "regulator" is flawed - I like the idea of no feedback just fine. The inverter keeps a steadier AC voltage than the line so there is less work to be done. Always trying to gild the lily and hope I do not waste too much gold.
I do not think the "regulator" is flawed - I like the idea of no feedback just fine. The inverter keeps a steadier AC voltage than the line so there is less work to be done. Always trying to gild the lily and hope I do not waste too much gold.
Today marks the one year anniversary of the first post in the thread. Makes me really happy to see that others have built the circuit and enjoyed it and more of them will be built. It has been an amazing ride so far with all of you! Thank you for the support. I have gained many friends and learned many things! 
Totally by coincidence, but really apt, that today is the day when the SCG documentation is published. See attachment. Inspired by Papa of course! It has the following parts:
Totally by coincidence, but really apt, that today is the day when the SCG documentation is published. See attachment. Inspired by Papa of course! It has the following parts:
- Major circuit blocks and how they work
- Operating points
- Power-up procedure
- Gain calculations
- Heatsinking
- Measurements and specs
Magnificent. Nothing less than an early Christmas gift. Of course, the whole THING has been a gift.
For you this should eliminate lots of questions being asked one hundred times.
We could never expect everyone who offers up a project to do something like this which is what makes it all the better and worthy of appreciation.
Thanks, ra7
For you this should eliminate lots of questions being asked one hundred times.
We could never expect everyone who offers up a project to do something like this which is what makes it all the better and worthy of appreciation.
Thanks, ra7
