Nice & detailed account of your thoughts and actions. Keep us posted.
P.S. Shortening the output to ground has a toll on the audio fets, I hope that with the 220R buffer resistors the current will be just OK not to kill any ever. 50K pot for now keeps it back in sonics. A 10k-20k even cheap carbon will do better until you will optimize the LSPD.
P.S. Shortening the output to ground has a toll on the audio fets, I hope that with the 220R buffer resistors the current will be just OK not to kill any ever. 50K pot for now keeps it back in sonics. A 10k-20k even cheap carbon will do better until you will optimize the LSPD.
Hi.I bought Alien dac v 1.1 and it has direct pcm2702 outputs.At the output there are 47uf coupling capacitors.I do not like them.Can i short circuit the capacitors and use B1 buffer directly?What happens then?Thanks
Don't know about your DAC. Its a question for the digital forums. In general if you have a DC component free line level low impedance output, you can use any DC coupled pot & buffer after.
I don't really see why shortening the output to ground could kill a jfet. I describe what I think happens:
Q1
I could put an extra resistance to the ground during mute, but it would need to be extremely low value to protect the poweramp from DC. So in practice useless.
I checked the DC offset voltage on startup while it was not shorted to gound, there was no peak showing that both power supply sides went up simultaniously. I'll put a scope to check in detail, I'll do it with a full volume sinewave on the input.
I can as well raise the start-up delay of my poweramp, but I try to have every part self-contained and not depending on another part.
Q1
- Acts as a current source, so no issue at all, current IDS will remain at IDSS. VDS is well below limits at any time.
- Current through the fet (ID) is limited by the jfet design if I'm not wrong.
- Voltage over the jfet (VDS): never more then V+, which is +10V.
- Tension on the gate (VGS): can have full volume from the source, say between + and -2V. At 2V with Rin 220Ohm, gate-current could become 9mA which is below the spec of 10mA gate current. Although I don't see how a gate could draw such a current.
I could put an extra resistance to the ground during mute, but it would need to be extremely low value to protect the poweramp from DC. So in practice useless.
I checked the DC offset voltage on startup while it was not shorted to gound, there was no peak showing that both power supply sides went up simultaniously. I'll put a scope to check in detail, I'll do it with a full volume sinewave on the input.
I can as well raise the start-up delay of my poweramp, but I try to have every part self-contained and not depending on another part.
Hi.Firstly i will build the dac.And then i will measure.I could not see any information about dc offset of pcm 2702 outputs in datasheet.But i think B1 buffer will be good for my application(pcm2702 is not a very good dac i do not know it worths though).Thank you
* http://www.diyaudio.com/forums/pass...ymmetrical-psu-b1-buffer-111.html#post2115940
**The DC component rises during shut down.
oenboek, try to measure DC offset and then start blowing air on the board. You will see how DC offset decreases to 0 and then raises on the other polarity. In fact, DC offset of this circuit is caused by thermal drift of its components, not by the circuit design.
Nice idea of thermally coupling both transistors.
Regards,
Regi
Nice idea of thermally coupling both transistors.
Regards,
Regi
Dear salas,
Increasing the number of LEDs from D4-D8 will increase the voltage output? i am needing a good design like yours to regulated at around 15Vdc output.
Regards
chong
Increasing the number of LEDs from D4-D8 will increase the voltage output? i am needing a good design like yours to regulated at around 15Vdc output.
Regards
chong
It sure will. You can use 3v LED's instead.
Mouser pn MV5352
The typical red is 1.8v x 5 = 9v
I am not sure if they will be too noisy. Other's may comment on that. I know 12v one's Salas told me are risky.
Mouser pn MV5352
The typical red is 1.8v x 5 = 9v
I am not sure if they will be too noisy. Other's may comment on that. I know 12v one's Salas told me are risky.
out of curiousity on 15vdc with salas's shunt reg, possible? anyone can guide me in this? if possible with some calculation too, so that i can learn from you guys 🙂
there're several designs up to 60V out and even HV schems up to 300V out for tube freaks.http://www.diyaudio.com/forums/powe...listic-salas-low-voltage-shunt-regulator.html
http://www.diyaudio.com/forums/power-supplies/134801-simplistic-mosfet-hv-shunt-regs.html
Hello,
I'm in trouble with LED matching...
I must have missed something.
I've bought LEDs in v4.3 BOM (Mouser 593-VAOL-3HCE4), and measured forward voltage of each LED fed by a 9V battery and a 1K2 resistor in series (right, isn't it?).
Measures varies from 1,901V to 1,910V, in spec according to datasheet (mav 2V froward voltage) but far from the typical 1,8V expected value.😱
So no way of getting 9V or 5,4V (9,53V and 5,70 are best match)
Help!
I'm in trouble with LED matching...
I must have missed something.
I've bought LEDs in v4.3 BOM (Mouser 593-VAOL-3HCE4), and measured forward voltage of each LED fed by a 9V battery and a 1K2 resistor in series (right, isn't it?).
Measures varies from 1,901V to 1,910V, in spec according to datasheet (mav 2V froward voltage) but far from the typical 1,8V expected value.😱
So no way of getting 9V or 5,4V (9,53V and 5,70 are best match)
Help!
It will be OK. The Vout values will still track with positive somewhat higher as expected and in sweet spot range. Just find 2 similar strings.
I had the same results when matching my leds (same part number). You will get a few more tens of a volt in the supply rails. Nothing to worry about.
Other people in the thread reported to have the same values with the same part number.
Regards,
Regi
Other people in the thread reported to have the same values with the same part number.
Regards,
Regi
Thanks everyone, so it's OK 😎
Powered ON soldering iron again...
Wow! So I suppose I've been lucky...😉
Like mentioned before, it's more important to have two strings have similiar total values than the trying to get lower one's. I am using the yellow one's, and they sit @ 10v.
Well, soldering iron now is powered OFF...😀
Haargh, my R-Core transformer is still shipping from France...
I've implemented directly last mods, I think...
Vref caps are Wima MKS2XL 2,2uF, the value is ok?
Is 10 Ohm 5W the right value to replace the 68 Ohm couple?
Thanks in advance
Haargh, my R-Core transformer is still shipping from France...
I've implemented directly last mods, I think...
Vref caps are Wima MKS2XL 2,2uF, the value is ok?
Is 10 Ohm 5W the right value to replace the 68 Ohm couple?
Thanks in advance
