As a matter of fact, a PS that can keep music playing for 30 seconds or more is not a poor design. It's more than solid. The caps in both your pre and power amp is what keeps the music playing at power off and not just your pre-amp's caps. BTW, caps are better off fully charged all the time.
I suggest you stop worrying about it and just keep in mind to power off your Source first.
I suggest you stop worrying about it and just keep in mind to power off your Source first.
well, looking at the formulas, it doesnt look like im drawing the full power of the preamp.
i still need to get in and measure it to make sure, but here is the math...
given the previous two formulas, we get:
W = v^2/(t/C)
we know W, V, and C, we are trying to find the time it takes to discharge the caps, assuming all 2 1000uf caps, two per rail.
so, 10 = 3600/(t/0.002)
10 = 7.2t
t = 1.39 seconds.
so, sound lasting more than about 2 seconds doesnt seem like it should be happening... maybe i need to check the amp first before i start doing anything with relays
Blues,
it aint happening man. i WILL fix it and it will be how i want it. its just me. i dont half-*** anything. you may not see it as such, but i do. i dont want my dad to have to worry about turning off pressing stop, swithing inputs, turning down the volume first, or turning off the amp, etc... i want it to work exactly how it should. there is a reason i put an on/off switch. if i WANTED it to work like this, i wouldnt have bothered for 2 months making an on/off switch that i liked.
when i build something, i dont build it to be just ok, or average. i try to build it not only the best that i can, but i try to keep the standard that it should be one of the best of the bunch. and i feel that when this is done, it will be right up there with the best BOSOZ's ever made.
its the reason i dont finish my projects very quickly and often run into many problems. but, when im done, i have no regrets and am always happy with the turnout.
i still need to get in and measure it to make sure, but here is the math...
given the previous two formulas, we get:
W = v^2/(t/C)
we know W, V, and C, we are trying to find the time it takes to discharge the caps, assuming all 2 1000uf caps, two per rail.
so, 10 = 3600/(t/0.002)
10 = 7.2t
t = 1.39 seconds.
so, sound lasting more than about 2 seconds doesnt seem like it should be happening... maybe i need to check the amp first before i start doing anything with relays
Blues,
it aint happening man. i WILL fix it and it will be how i want it. its just me. i dont half-*** anything. you may not see it as such, but i do. i dont want my dad to have to worry about turning off pressing stop, swithing inputs, turning down the volume first, or turning off the amp, etc... i want it to work exactly how it should. there is a reason i put an on/off switch. if i WANTED it to work like this, i wouldnt have bothered for 2 months making an on/off switch that i liked.
when i build something, i dont build it to be just ok, or average. i try to build it not only the best that i can, but i try to keep the standard that it should be one of the best of the bunch. and i feel that when this is done, it will be right up there with the best BOSOZ's ever made.
its the reason i dont finish my projects very quickly and often run into many problems. but, when im done, i have no regrets and am always happy with the turnout.
Banned
Joined 2002
sure thing.
here is the directory listing:
guts so far:
http://www.cowanrg.mesanetworks.net/projects/images/bosoz/preamp10.jpg
shielding for xformer and psu:
http://www.cowanrg.mesanetworks.net/projects/images/bosoz/preamp11.jpg
faceplate, not quite complete, still needs work (perfection, remember)
http://www.cowanrg.mesanetworks.net/projects/images/bosoz/preamp12.jpg
faceplate upclose (recessed 1/8" plexiglass rod for lights)
http://www.cowanrg.mesanetworks.net/projects/images/bosoz/preamp13.jpg
and back (looks dirty, just dust and stuff)
http://www.cowanrg.mesanetworks.net/projects/images/bosoz/preamp7.jpg
here is the directory listing:
guts so far:
http://www.cowanrg.mesanetworks.net/projects/images/bosoz/preamp10.jpg
shielding for xformer and psu:
http://www.cowanrg.mesanetworks.net/projects/images/bosoz/preamp11.jpg
faceplate, not quite complete, still needs work (perfection, remember)
http://www.cowanrg.mesanetworks.net/projects/images/bosoz/preamp12.jpg
faceplate upclose (recessed 1/8" plexiglass rod for lights)
http://www.cowanrg.mesanetworks.net/projects/images/bosoz/preamp13.jpg
and back (looks dirty, just dust and stuff)
http://www.cowanrg.mesanetworks.net/projects/images/bosoz/preamp7.jpg
Hey Cow man, not to milk this discussion any more as it seems to have an unusually long life as it is, but here is my two cents.
Every power supply I ever built and continue to build is either equipped with bleeder resistors or load resistor on a relay. For dual rail applications always use two bleeders one from each rail to common ground. for 80V rails 2.2K to 3.9K @ 5W should be sufficient to drain the caps below thier ability to deliver power in a few seconds. Unloaded it can take several minutes to drain the caps, but with a load in parallel with the bleeders the caps lose thier ability to present sufficient current to the load in a hurry.
The other process I use is a DC relay holding the rails closed while power is applied, as soon as the AC is disengaged the relay shunts the load to a 10R 25Watt metal housed resistor clamped to the casing. I use this on my really big Amps.
My two cents
Regards
Anthony
Every power supply I ever built and continue to build is either equipped with bleeder resistors or load resistor on a relay. For dual rail applications always use two bleeders one from each rail to common ground. for 80V rails 2.2K to 3.9K @ 5W should be sufficient to drain the caps below thier ability to deliver power in a few seconds. Unloaded it can take several minutes to drain the caps, but with a load in parallel with the bleeders the caps lose thier ability to present sufficient current to the load in a hurry.
The other process I use is a DC relay holding the rails closed while power is applied, as soon as the AC is disengaged the relay shunts the load to a 10R 25Watt metal housed resistor clamped to the casing. I use this on my really big Amps.
My two cents
Regards
Anthony
Coulomb said:
thanks for the advice and the pun.
yeah, the thread has gone unusually long, but thats because i havent found a satisfactory answer yet
i think the relays will be the ticket, but that requires another xformerer (dont have much room left) and some more work to make it look nice. but im still concerned if the amp is drawing what it should. the PSU seems awfully small to sustain the preamp for a minute. a couple seconds i might be able to handle.
here is an idea... would it be possible to just boost the bias up a bit? i know on an amp that could be possible. i have MORE than ample heatsinking. so, if i could boost the bias up to where the PSU would only last a second or so, that could even better the sound? hmmmm.
BTW, the spring on the idler arm is to keep tension off of a power switch at the back there? Can't make out the switch from the Photo.
Oh, and I am terribly dissapointed to see you cheaped out on a plain Bridge rectifier instead of a more exotic expatial Diode Rectifier with snubbers.
Regards
Anthony
Oh, and I am terribly dissapointed to see you cheaped out on a plain Bridge rectifier instead of a more exotic expatial Diode Rectifier with snubbers.
Regards
Anthony
Coulomb said:
well, the spring is to keep the rod pushed away from the power switch, yes. the power switch itself has a spring, but not enough to sustain the whole assembly.
sorry about the bridge rectifier. it was the original design. as you notice, i always use off-the-shelf designs and PCB's. at least i upgraded the 1N4005's to MUR1520's! im not even sure what a expatial diode rectifier with snubbers is. i think i know that snubbers are small value caps across the diodes? i just used the basic design with decent parts is all. sorry! i did use south-american bubinga wood though, not cherry...
Coulomb said:
ah ok. i learned something then. oh well, there is always next time
oh, duh. forgot about an AC coil relay. so something like this:
http://www.allelectronics.com/cgi-bin/category.cgi?category=500&item=4PRLY-120L&type=store
connected to the + and - rails of each PSU and optionally connected to a bleeder resistor of some sort. i guess i would still have to worry about the caps on the main board. so, i should make the relay not necessarily disconnect the power, but connect a bleeder resistor when its off, thus discharging all the power.
Coulomb said:
nope. simpler than that.
sandwiched the wood between two other pieces of wood (for a perfect hole) and drilled a "just less than" 1/8" hole. then, took 1/8" plexiglass rod and carefully hammered it into the holes, then sanded flush. its perfectly smooth, even before it was lacquered. then, there are pockets in the back that are milled out to house the LED's. since its just a see-through rod, i can acutally position the LED's so they dont directly shine though, but rather reflect through. so, you get a bright LED, but its only really visible looking straight at it. i like this better because at night i dont want my LED's to light up the room. and if you stare straight at those blue buggers it can be BRIGHT. these are very subtle. but as you see from the pics, you can still see them even with flash from a camera.
cowanrg said:
ah ok. i learned something then. oh well, there is always next time
oh, duh. forgot about an AC coil relay. so something like this:
http://www.allelectronics.com/cgi-bin/category.cgi?category=500&item=4PRLY-120L&type=store
connected to the + and - rails of each PSU and optionally connected to a bleeder resistor of some sort. i guess i would still have to worry about the caps on the main board. so, i should make the relay not necessarily disconnect the power, but connect a bleeder resistor when its off, thus discharging all the power.
Yes quite, the rails or output from the power supplies would be the common contacts and at rest would connect to the shunt resistor through the (N/C at rest) contacts. The (N/O at rest) contacts is where the preamp power would be supplied from when the coil is enegizedl
Edit:
Add a 10,000pf cap across the AC contacts to the coil for noise suppression.
ok, im satisfied with that.
i can mount it on the front wall of the metal plate the isolates the PSU from the preamp. so around a 3k, 5w resistor? ill give that a go tomorrow, but first i will measure the current draw on the amp to make sure all is going well. i need to wire up my volume control too. i finally mounted the front panel (all those front panel pics were just hot-glued togehter).
if i want it to "power down" quicker, can i just get a 10W resistor of a lower value?
well, time for bed now. i probably wont get back to this until the weekend because ill be working hard until then. unfortunately i didnt make near the progress i wanted to today.
thanks everyone. if it wasnt for you guys, i wouldnt know what im doing, and i wouldnt care about it because i wouldnt have anyone to say "nice work". i really do appreciate it. one of these days i will get back to my idea about a design contest. but i need to work on my entries first
i can mount it on the front wall of the metal plate the isolates the PSU from the preamp. so around a 3k, 5w resistor? ill give that a go tomorrow, but first i will measure the current draw on the amp to make sure all is going well. i need to wire up my volume control too. i finally mounted the front panel (all those front panel pics were just hot-glued togehter).
if i want it to "power down" quicker, can i just get a 10W resistor of a lower value?
well, time for bed now. i probably wont get back to this until the weekend because ill be working hard until then. unfortunately i didnt make near the progress i wanted to today.
thanks everyone. if it wasnt for you guys, i wouldnt know what im doing, and i wouldnt care about it because i wouldnt have anyone to say "nice work". i really do appreciate it. one of these days i will get back to my idea about a design contest. but i need to work on my entries first
I'm still unclear on how you arrived at the conclusion that running after the switch is cut is somehow bad...but this is DIY and we're all allowed our eccentricities. Still, I think you might want to review the circuits of existing designs that you're comparing this to. I think that you'll find that what I said earlier is true: High end designs run after cutoff or use relays to drop the signal (meaning they're still running--you just can't hear it). Ah, well.
You're on a "bandersnatch hunt," also known as "looking for the nonesuch." That's your right. Just try not to be dissappointed when you discover that there's no magic way to accomplish what you're trying to do. A number of things have been proposed in this thread, but they're all just bandaids. I still recommend doing what the high end designers do.
Technically, 800VA is way overkill, but I happen to like using oversized transformers. Secondary impedance is lower, which means that the circuit doesn't have to snarf so hard on the rail to get current.
...However...
Note that the transformer has absolutely nothing to do with the amount of time the circuit runs after it's turned off.
Boosting the bias on the circuit suits me just peachy. Keep in mind two things:
--voltage and current ratings for the devices
--rated heat dissipation
Don't be surprised if increasing the bias still leaves the music running longer than you might like.
If I can come up with another suggestion, I may drop back in on this thread, but right now I'm all out of bandersnatches and my shipment of nonesuches has been delayed once more.
Good luck.
Remember to have fun.
Grey
You're on a "bandersnatch hunt," also known as "looking for the nonesuch." That's your right. Just try not to be dissappointed when you discover that there's no magic way to accomplish what you're trying to do. A number of things have been proposed in this thread, but they're all just bandaids. I still recommend doing what the high end designers do.
Technically, 800VA is way overkill, but I happen to like using oversized transformers. Secondary impedance is lower, which means that the circuit doesn't have to snarf so hard on the rail to get current.
...However...
Note that the transformer has absolutely nothing to do with the amount of time the circuit runs after it's turned off.
Boosting the bias on the circuit suits me just peachy. Keep in mind two things:
--voltage and current ratings for the devices
--rated heat dissipation
Don't be surprised if increasing the bias still leaves the music running longer than you might like.
If I can come up with another suggestion, I may drop back in on this thread, but right now I'm all out of bandersnatches and my shipment of nonesuches has been delayed once more.
Good luck.
Remember to have fun.
Grey
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