Peter Daniel said:
If you call that theoretically fine you slept during lessons I think
There is something like safety margin. With such small headroom spikes on the net can cause your electrolytics to fail. They won't last very long for sure.But with batteries there won't be a problem.
minus forward voltage of diodes and plus overvoltage of an unloaded transformer. Forgot the correct english words but especially the smaller transformers can give a lot higher voltage when unloaded. A 1 VA 12 V can give 18 V or even higher unloaded. I overdimension the working voltage of the cap with the unloaded voltage in mind.
jean-paul said:
If you call that theoretically fine you slept during lessons I think
You obviously slept when Hugo posted this: http://www.diyaudio.com/forums/showthread.php?s=&postid=356575#post356575
I've been using caps at their max rating voltage, without problems, but in my preamp, they didn't last that long indeed. When I checked them after 6 or 8 years, they were completely dead
Contradictive, don't you think ? I wonder why those manufacturers write max. ratings on those caps if you can safely ignore them The parallel with smokers that tell their granddad was 90 and still smoking comes to mind.
Good engineering means also that components are calculated well within their safe operating area, not at max. ratings. Some manufacturers are conservative in their ratings whereas others are more strict. Try ( or better don't try ) running tantalum caps just some Volts over their max. rating and BOOM
In the fictive case of running 35 V caps on 34 V at idle I would call that plain unsafe. I just repaired a Proton AP-1000 preamp that had 100 uF 3V ( yes, they exist ) between stages that run at +/- 35 V and it was capable of 20 V output easily. Guess what was broken...
IMHO an amp or whatever device should not break down on underrated components ( be it boutique parts or not, remember the discussion about failing BG's in 300B amps ? ) as I feel responsible for what can happen in case of failure. Suppose a fire breaks out when shortcircuit happens because a wire is not soldered well... Years ago when I had more time to develop and build gear my practice was that an amp should be able to fall down from a table and still function. Safety first. Hence my obsession of the possibility for mounting boards with standoffs etc. I am not a soldier in the meltglue army
On the other hand: breakdown because of sometimes stupid user errors is more difficult to cope with for me.
The parallel with smokers that tell their granddad was 90 and still smoking comes to mind.Good engineering means also that components are calculated well within their safe operating area, not at max. ratings. Some manufacturers are conservative in their ratings whereas others are more strict. Try ( or better don't try ) running tantalum caps just some Volts over their max. rating and BOOM
In the fictive case of running 35 V caps on 34 V at idle I would call that plain unsafe. I just repaired a Proton AP-1000 preamp that had 100 uF 3V ( yes, they exist ) between stages that run at +/- 35 V and it was capable of 20 V output easily. Guess what was broken...
IMHO an amp or whatever device should not break down on underrated components ( be it boutique parts or not, remember the discussion about failing BG's in 300B amps ? ) as I feel responsible for what can happen in case of failure. Suppose a fire breaks out when shortcircuit happens because a wire is not soldered well... Years ago when I had more time to develop and build gear my practice was that an amp should be able to fall down from a table and still function. Safety first. Hence my obsession of the possibility for mounting boards with standoffs etc. I am not a soldier in the meltglue army
On the other hand: breakdown because of sometimes stupid user errors is more difficult to cope with for me.
As a sidenote: extreme overrating can give less good results i.e. running 100 V electrolytics on 3V is not good practice sonically. Technically there is nothing wrong AFAIK, just economically there could be a point.
Overdimensioning voltage ratings 25 to 50 % calculated with max. possible voltages is safe. Only an hour ago I repaired a device that broke down because of an underrated electrolytic cap ( continuous 15 V on a 16 V max. cap ) killing fuse, diodes etc.
Sorry for hijacking the thread, back to the subject.
Overdimensioning voltage ratings 25 to 50 % calculated with max. possible voltages is safe. Only an hour ago I repaired a device that broke down because of an underrated electrolytic cap ( continuous 15 V on a 16 V max. cap ) killing fuse, diodes etc.
Sorry for hijacking the thread, back to the subject.
I was talking about an old Phase Linear 700B http://hometown.aol.com/phasetek2/pl20.jpg . Sorry if I confused anybody but this is reality. The actual rail voltage is +/-102V. As I said, I would buy higher rated caps if they had to be replaced. Something like 20% + or so.jean-paul said:I wonder why those manufacturers write max. ratings on those caps if you can safely ignore them
Nevertheless, this amp works fine and to be honest I can't remember his age.
You might want to read this as well: http://hometown.aol.com/phasetek/filtercap.html
Oops, plain off topic too but maybe useful.
jean-paul said:
Luck maybe ? Luck can be reality too
.Seriously, it depends from brand to brand what "headroom" they add to their published max. ratings. It is possible if you replace those caps with new 100V caps that they fail in a shorter time. Did you ever measure the original ones ? I think you'll agree with me that running 100 V parts at 102 V is playing with fire. The link you gave describes that replacement caps for some Phase Linear models are overrated 25V as it should be IMO ( mmm, when I think of it; why would they offer replacement caps
)Folks, maybe this should be in a new thread ? I am sorry for polluting the thread but safety was the reason for doing so. IMO a valid reason. Probably new inexperienced GC builders read this thread and they should be informed on safety and precautions. It is better to practice safety engineering by the rule instead of trial and error.
I fired it up to see what it sounds like. It sounds good... very good. Nicely detailed and punchy, without being harsh or too etched. Things should smoothen out even more after I've run it in some more. It's pretty quiet too, even with the chips less than 1" from the transformer. In fact, I can now hear the noise added by my subwoofer crossover more clearly. DC offset came to about 3mV on one side and 1mV on the other - can't ask for better IMO.
Right now it has just a little too much gain for my 96dB speakers. On more conventional speakers, this would work perfectly.
Note that these are all very early impressions, with just 30 minutes of burn-in and listening.
Thanks a lot for putting the group order together, Brian. And thanks to everyone else who helped out. I took some more pictures, I'll post those later.
Right now it has just a little too much gain for my 96dB speakers. On more conventional speakers, this would work perfectly.
Note that these are all very early impressions, with just 30 minutes of burn-in and listening.
Thanks a lot for putting the group order together, Brian. And thanks to everyone else who helped out. I took some more pictures, I'll post those later.
Brian,
All hell is breaking loose on the power supply front:
http://www.diyaudio.com/forums/showthread.php?s=&postid=359504#post359504
How about right here - who's right Lieven or me?
I'd bet on lieven, but I need your blessing- or do both ways work?
Clearly the hardest part is hooking up the transformer!
There are 3 cases it seems to me:
- trannies with dual secondaries: that's covered in the manual
-trannies with center tap - you can resove this right now-see above.
- 2 trannies with 2 wires how to combine them to create equivalent of one or t he other of the above.Probably not as urgent... and has beeen discussed elsewhere a little.
All hell is breaking loose on the power supply front:
http://www.diyaudio.com/forums/showthread.php?s=&postid=359504#post359504
How about right here - who's right Lieven or me?
I'd bet on lieven, but I need your blessing- or do both ways work?
Clearly the hardest part is hooking up the transformer!
There are 3 cases it seems to me:
- trannies with dual secondaries: that's covered in the manual
-trannies with center tap - you can resove this right now-see above.
- 2 trannies with 2 wires how to combine them to create equivalent of one or t he other of the above.Probably not as urgent... and has beeen discussed elsewhere a little.
OK, I wired up my transformer to AC and connected it to my power supply pcb. Everything went fine and the smoke stayed in the components. Now I get ~35V dc when I check V-/PNGD- and V+/PNGD+.
Thanks for replying Brian, although I'm not sure what you were doing online the day after "The Big Day". Your better-half must be much more forgiving than mine.
Hopefully I'll have time to connect up at least one channel this week.
widman
Variac said:
For the center-tapped transformer, I haven't tried using dual bridges with it, but I would just stick to a single bridge. Say that transformer is 25-0-25, and you are using a single bridge, tie the 2 - 25v lines (50vac total potential) to the AC2 N and AC2 H pads on the power supply board. You will get roughly 70vdc on the outputs (V+ and PG+). You can then use V+ and PG+ outputs as +V and -V. The center-tap can then be used for the PGND connection, running a single ground wire to each pcb from this. The main issue with this is the capacitor on the power supply board, you will have to use a higher voltage cap (100v), or else wire up the 2 - 50v caps from the +V to PGND and the -V to PGND (using P2P wiring).
It might work just fine running the center-tap into both the AC1N and the AC2H pads, and using dual bridges, and running a single ground connection to each board (not both the +PGND and -PGND), but I haven't verified this. It might be worth trying, as this is the easiest solution.
Anyone else have any input?
--
Brian
widman said:
I was getting ready to check out of the hotel this morning, checking my e-mail before packing up my laptop. I just checked the site for a second and replied to your mail. (hotel had ethernet)
Good luck getting your amplifier working. I hope to see pictures and a finished amplifier soon from you.
--
Brian
i'm not sure anybody not knowing how to wire a simple dual secondaries toroid to a simple integrated rectifier bridge (obviously without using a fuse) should be building amplifiers.
sorry for this bold statement but hey, shoot me.
Oh, and before I forget, congrats, brian! (still wondering why on earth you were checking your email this morning in stead of being in bed with your lady and ... ah well, you know, errr, emmm ahh last edit before bed: why bring your laptop? )
sorry for this bold statement but hey, shoot me.
Oh, and before I forget, congrats, brian! (still wondering why on earth you were checking your email this morning in stead of being in bed with your lady and ... ah well, you know, errr, emmm
ahh last edit before bed: why bring your laptop? )
matjans said:
I am 100% with you. When I first get into the DIY scene thanks to Geoff's site and Rod.E 's site. I have no idea at all. But I read and read and check and read to try to understand not the amp schematic but the power supply first. Thanks to this forum I have learn a lot of safety issue, a particular one like NOT using two separate single pole switches for the netrual and hot a/c line instead of one DPST. To all newbies out there like myself, please listen to matjans advise. When we talk about the GC kit it is so easy to make a amp but I guess we take it for granted that basic electricity circuit knowledge is assumed. Please do yourself a favour and learn the power supply first before the amp. Seasoned diyers please forgive my dah dah dah.....
IMHO
Chris
matjans said:i'm not sure anybody not knowing how to wire a simple dual secondaries toroid to a simple integrated rectifier bridge (obviously without using a fuse) should be building amplifiers.
sorry for this bold statement but hey, shoot me.
Oh, and before I forget, congrats, brian! (still wondering why on earth you were checking your email this morning in stead of being in bed with your lady and ... ah well, you know, errr, emmm
Well, I got up earlier this morning, as we had originally planned to go to brunch at 10:30 with the family. Meredith had to leave earlier to say goodbye to her parents since they had an early flight, so I was left to myself for a bit.
As for your initial comment, everyone has to start at some point. I didn't specify in the manual what to do if you have dual primaries (made for using in 120vac or 240vac regions), so it was a valid question. My first transformers only had single primaries, and I was initially quite confused when I got one with dual primaries.
Variac: Here is an easier idea for wiring up the single bridge and still being able to use the existing capacitors. A single ground will be run to each channel pcb, instead of the dual grounds. This should work out good for the grounding.
--
Brian
Attachments
chris ma said:
I am working on the manual to make it clear enough for even a beginner to be able to wire up the power supply. Initially, I brushed over it quickly, but I will add to it, as I think that this is a project that a beginner can do, and probably the easiest project for a beginner wanting to build an amplifier.
But clearly, common sense and basic knowledge of electronics should be a pre-requisite, as hazards exist whenever you are dealing with electricity.
--
Brian
I would like a little advice. I have two 300VA torroids with 18V secondaries. Should I go for a full dual mono or build two stereo amps? Is the performance increase of a dual mono over single tranny significant enough to justify? I have enough components for either case. I would like decide so I can finalize my case design. Thank you in advance.
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