No changes, I just installed the .1 uF films instead of the 100 uF electrolytics. I mentioned this on TPA forums, and Russ White recommended not going below .1 uF in those locations. The Salas regs do not like to "see" lots of capacitance at their outputs (unless one adds additional damping to the regs themselves) nor do they seem to need it.
Easy put 100 ohms resistor in series and measure real consumption with DVM and ohms law to calculate.
Mmm, that might work on a HV low current devise.
Ohms law: U=R*I
Voltage drop over a 100 ohm resistor at 0,5 A is 50 volt. Not so good for measuring a 12 v supply
make it a 1 ohm if using that method
Thanks for this information. Yes, I suppose the TP designers were not necessarily thinking of this particular power supply when they designed the Legato.
I want to use conservative values to keep the heat down, but OK, I will go up to 100mA shunt (still at 13V).
Now could someone check my calculations, please?
The DC-in will be 18V, target DC-out 13V.
Let's just focus on the negative rail - 190mA Legato draw + 100mA shunt = 290mA CCS. Thus:
- the R101 current setting resisor should be 12.7 ohms? (But 5W resistors are easier to buy as either 12 or 13 ohms).
- In the voltage reference section I will have 2x red LED's, a 1.8k resistor, and no diode,
so the R105 initial voltage trimmer value should be 500 ohms?
Mmm, that might work on a HV low current devise.
Ohms law: U=R*I
Voltage drop over a 100 ohm resistor at 0,5 A is 50 volt. Not so good for measuring a 12 v supply
make it a 1 ohm if using that method
Will do
I need help. My target voltage is 24V, I have 30V in, but the max voltage I can get is 14v.I use 4 green leds and 2 red leds, the trimmer is 10k ohm with 220ohm. I try for r101 10ohm and 100ohms, it change the max output volatge from 14v to 13v. The jfet idss are about 4ma. Now I don't know what to do.
Do you mean the value of r106 ?
I have 9.6v across the trimmer when tunr to max with 680ohm load. When I reach the max voltage output, I can stiil turn the trimmer but the voltage doesn't increase afetr 14v. The ouptu mosfet is irf9530n. does it make a deifference ?
That one is bit beefier but has +260pF Ciss +70pF Crss above the standard. Not sure if it could create a functional problem but I don't like it for performance a least. Don't remember the designation right now, talking that resistor very near to the left most leg of the output Mosfet. Check that out for right value, make it half value, piggyback one the same, see if something changes.
Thanks for that information merlin el mago.
By the way, I will have the chance to see Barcelona/Catalonia this September!
I have another question: I'm a bit confused about the choice of capacitor for C101/C102.
For voltage reference I will be using resistance (2x 1.9V LED, R1.8k + 5k trimmer) not zener. The build guide says -
"A fully resistive choice can have smoother and lower noise spectrum to filter and lends for C102,202,302 MKT 4.7uF-10uF. 10uF filters better. Electrolytic 220uF is even more efficient a filter for sensitive digital and MC phono stages"
Given my situation - an I/V stage drawing a fairly constant 180mA per rail - at C101/C102 should I use 10uF/50V MKT or 220uF/50V electrolytic?
By the way, I will have the chance to see Barcelona/Catalonia this September!
I have another question: I'm a bit confused about the choice of capacitor for C101/C102.
For voltage reference I will be using resistance (2x 1.9V LED, R1.8k + 5k trimmer) not zener. The build guide says -
"A fully resistive choice can have smoother and lower noise spectrum to filter and lends for C102,202,302 MKT 4.7uF-10uF. 10uF filters better. Electrolytic 220uF is even more efficient a filter for sensitive digital and MC phono stages"
Given my situation - an I/V stage drawing a fairly constant 180mA per rail - at C101/C102 should I use 10uF/50V MKT or 220uF/50V electrolytic?
You are welcome to Barcelona you will not be upset with the visit and surely come back again.
With my Legato I/V I use 10uF 200V Auricap MKP and sounds wonderful
Enjoy
Felipe
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