C3 should have the shorter legs because it is the most influential part for stability. But its also the smallest capacitor among the three.
Those small LEDs are sensitive to soldering and little leg allowance keeps them safer during the procedure. If they are soldered carefully and work well with no legs left above board then they will keep on working in a not too hot environment as they do not produce significant heat themselves. You could even put the LEDS and other parts at bottom side if you will have the board facing in a way that you can have better access if so.
Tomorrow morning, I will run the iron on the joints again to be sure. The voltage is pretty constant, so I think it is stable now.
Thanks Salas! C3 should fit in there, will see which cap I'll buy.
And I've forgotten to ask, where is it best location to steal power for a remote power indicator LED, at C1?
I plan to put a positive+negative UltraBib in a 19" case (I think from ~1mm thick steel) for a Soekris DAC. I wonder whether I would need additional heatsinks, or could just use the bottom plate for cooling of M1/M2.
I use a 15 Vac transformer, so I would end up with ~20V at the input. A quick calculation...
Pos Neg
Vin 20 20
Vout 12 12
CCS 0,27 0,18
Load 0,18 0,06
M1 (W) 2,2 1,4
M2 (W) 1,1 1,4
So the dissipation of M1&M2 should be <= 2,2 W. Would you need additional heatsinks for this case? If yes, what thermal resistance (K/W) would be appropriate?
One question more, is the lead length of M1&M2 relevant? Would it be ok to use 8mm or 10 mm high spacers under the PCB assuming that M1&M2 are mounted to the base plate? I may consider ceramic insolation plates for additional height and reduced vibrations BTW.
Fedde
I use a 15 Vac transformer, so I would end up with ~20V at the input. A quick calculation...
Pos Neg
Vin 20 20
Vout 12 12
CCS 0,27 0,18
Load 0,18 0,06
M1 (W) 2,2 1,4
M2 (W) 1,1 1,4
So the dissipation of M1&M2 should be <= 2,2 W. Would you need additional heatsinks for this case? If yes, what thermal resistance (K/W) would be appropriate?
One question more, is the lead length of M1&M2 relevant? Would it be ok to use 8mm or 10 mm high spacers under the PCB assuming that M1&M2 are mounted to the base plate? I may consider ceramic insolation plates for additional height and reduced vibrations BTW.
Fedde
Your chassis will suffice for that dissipation. Has been used before that way for the DAM.
Ceramic plates would be nice for additional reasons but bit longer Mosfet legs will not be critical.
That's a 45mA bias per polarity preamp. For two channels makes 90mA. The UBiB at 150mA shunt current (spare) is working good enough. 90+150=240mA. Most builds around here give 0.58V across R1. For 240mA CC such drop voltage takes 2.4R R1. Since there is also an input stage of enough bias in the BA3 use 2.2R R1 for 260mA.
I am working on a BA-3 as a preamp too. For the 2.2R should it be at least 3w for heat dispensation or do I need a 5w there.
Thanks
Dave
Hello Salas, just powered up a new install right now, that's 5v. supply for a still brand new DAC Topping D50, but MY FAULT, I forgotten to solder vrr resistor (75k) to the pcb. A bit eager for sure.
LEDs lighted only for 5 sec and turn off.
Now I soldered that resistor to their place. But somewhere is a faulty, Where may I check? No shorts on MOFSET legs, but not sure, do I must desolder in first to test their gate?
LEDs lighted only for 5 sec and turn off.
Now I soldered that resistor to their place. But somewhere is a faulty, Where may I check? No shorts on MOFSET legs, but not sure, do I must desolder in first to test their gate?
I powered it unloaded, I used a 5k. pot as VR1, close to minimum, I lucky found 5v. value, but very picky. Then I play with R1, a variable resistor 3 ohm 2w pot plus a 2 ohm Caddock in series, so in first was Ok. at 5R, buy I try to see if increase CC whould change output voltage, and lowered the pot at half 1,5 ohm (still + 2 ohm = 3,5 ohm R1) and still same 5v. output. Suddently less than a sec. fried up.