I need help cause I have somthing bothering me!
My Le Monstre has a transformer of 160VA, 2 x 12 V. I have a slow start board (DIYAudioShop) and the power supply capacitors are on total 2.4 Farad. I have tested the slow start against a package of 0.6 Farad caps and it was flawless. relay closed at about 0.3 seconds and the caps bank was filled nicely. Now when I have connected the full caps bank I blow fuses faster than you can blink with the eye.
Started off at 800 mA slow blow and it blew before even connecting the relay, now I am up at 1.6 A and still the fuse blows. At least now the relay have time to close properly but it only runs for a second before blowing the fuse again so I only get about 3 volts on the caps.
My question is, (I know that filling 2.4 Farad is tricky) if I go higher on the fuse, 3.15 A for example, will I lose the function of the fuse cause I will be well above the needed 160/230=0.695 mA that should be used??
Could I get around the problem if I install a thermistor before the slow start board or is that not advisable??
My Le Monstre has a transformer of 160VA, 2 x 12 V. I have a slow start board (DIYAudioShop) and the power supply capacitors are on total 2.4 Farad. I have tested the slow start against a package of 0.6 Farad caps and it was flawless. relay closed at about 0.3 seconds and the caps bank was filled nicely. Now when I have connected the full caps bank I blow fuses faster than you can blink with the eye.
Started off at 800 mA slow blow and it blew before even connecting the relay, now I am up at 1.6 A and still the fuse blows. At least now the relay have time to close properly but it only runs for a second before blowing the fuse again so I only get about 3 volts on the caps.
My question is, (I know that filling 2.4 Farad is tricky) if I go higher on the fuse, 3.15 A for example, will I lose the function of the fuse cause I will be well above the needed 160/230=0.695 mA that should be used??
Could I get around the problem if I install a thermistor before the slow start board or is that not advisable??
Please post your Hiraga 8 Watt Le Monstre schematic version, your Jfets BL grade and 1k resistors will create higher bias current.
Ok, I have made some investigation but I don't know if I am wiser afterwords... and yes trannies is transformer and not transistors so my wrong in earlier post (I blame the swedish).
Disconnected the different capacitor banks and started with only the one to the left in picture (I had used this one when I tested the slow start board) and as before, starting without any problem with 800 mA fuse.
Did the same with the right capacitor bank but the fuse went puhf after about 1 second so back to the left package again. Changed the fuse and started the left bank again without any problem, showing 35.87 Volts over plus to minus and then checking so I had the same from the transformer on the right side and it measure 35.88 Volts so, yes. That suggest that from transformer via the rectifier I am good but somewhere in the right capacitor bank there is an error. Obviously it should not be too difficult to find an error there but I don't and that puzzles me. Can I have one or many capacitors that are broken and in that case, how do I tell??
Bought them from Digi key last year but of cause there can be bad samples even from well renowed shops as well so how do I check a big capacitor, my DMM does only measure capacitors up to a couple of hundred uF, these are 75000 uF. Can anyone help??
Disconnected the different capacitor banks and started with only the one to the left in picture (I had used this one when I tested the slow start board) and as before, starting without any problem with 800 mA fuse.
Did the same with the right capacitor bank but the fuse went puhf after about 1 second so back to the left package again. Changed the fuse and started the left bank again without any problem, showing 35.87 Volts over plus to minus and then checking so I had the same from the transformer on the right side and it measure 35.88 Volts so, yes. That suggest that from transformer via the rectifier I am good but somewhere in the right capacitor bank there is an error. Obviously it should not be too difficult to find an error there but I don't and that puzzles me. Can I have one or many capacitors that are broken and in that case, how do I tell??
Bought them from Digi key last year but of cause there can be bad samples even from well renowed shops as well so how do I check a big capacitor, my DMM does only measure capacitors up to a couple of hundred uF, these are 75000 uF. Can anyone help??
Are you sure all of these 75,000uF capacitors are connected with the correct polarity for each rail?
Yes, double checked polarity both when connecting them and now in the evening when I got doubtful about the function, but they are all correct.
With them all disconnected, and using resistance range on your DMM, check there is no internal short on each capacitor across the +/- terminals and then check for shorts from each terminal to metal of outer case. Should all be open circuit - not a dead short. You will get a reading that slowly counts up across the terminals as the DMM battery tries to charge the cap - this is normal. You would need a sophisticated instrument to check the 75,000uF value of each cap. You can also check for shorts from the copper bus bars to GND before checking individual caps. If nothing is found with this check, then check all wiring.
Think I found it!! Have no time to verify untill in the evening but wiggling this capacitor rendered a beep for continuity between capacitor and chassi. Most likely the nut for the foot underneath have penetrated the capacitor protection cause found a small scratch just were the nut is sitting.
Haha I had the same type of short where a little dent had made a short between the outside winding and the case (on a capacitor-coupled output with a SIT). Have to isolate the whole nut now.
- Nice build like my original LeMonstre was. I should restore it; is now a low-power version with regulated supply, but use SMPS next time. Many toroids have awkward start-up behaviour, can blow (trip) the mains fuse just at start-up.
I showed mine in an audio show from a Dutch magazine, beginning 80ies. Everyone . Was. Baffled. That is what they were. A LS manufacturer took my build and listened the better part of the night to his 10 cm Speakers. I had the full mounty. In nr of caps.
Note i had a slight dissimilarity in Vb (+ vs -) that may have aided the impression: different size of chokes.
Note i had a slight dissimilarity in Vb (+ vs -) that may have aided the impression: different size of chokes.
Later I reduced the caps bank, reduced everything; never the same again. So that is also a given.
Good to hear you might have found the fault on the right channel PSU - keep us updated an progress.
Yes, I was right so now I can continue.
This evening I have had the whole PSU up and running, 2.4 Farad starts up like a charm with 800 mA fuse!! And, everything is dead quiet so far. No humming, nothing, it have never been so quiet, I have always been able to hear the transformer humming before but now I have to look at the leds to check if it is in fact running.
Little high voltage compared to before but I will see what bias current I end up with cause I am accepting between 500 to 600 mA bias current so there is some slack to play with, worst case I have to get some new resistors.
This evening I have had the whole PSU up and running, 2.4 Farad starts up like a charm with 800 mA fuse!! And, everything is dead quiet so far. No humming, nothing, it have never been so quiet, I have always been able to hear the transformer humming before but now I have to look at the leds to check if it is in fact running.
Little high voltage compared to before but I will see what bias current I end up with cause I am accepting between 500 to 600 mA bias current so there is some slack to play with, worst case I have to get some new resistors.
Hi Guys,
I have a power supply which is has rail voltage of 22v (after rectification). I have some spare Le Monstre boards, is it possible to run this design with 22v? My issue is space, the le monstre boards are just the right size to fit in a chassis i want to use.
Thanks, lovely work from everyone after browsing through the thread.
I have a power supply which is has rail voltage of 22v (after rectification). I have some spare Le Monstre boards, is it possible to run this design with 22v? My issue is space, the le monstre boards are just the right size to fit in a chassis i want to use.
Thanks, lovely work from everyone after browsing through the thread.
Just finished my build yesterday! I have wanted to build this amp for about 10 years now and after doing so I am not sure why I waited so long! I have just over 1F per rail per the original article as well as dual source AC and DC battery power. I have a slight 120Hz on AC but on DC it is dead quiet. The imaging on DC is mind-boggling! This does not sound at all like a solid state amp but rather a tube amplifier. Probably one of the better amplifiers I have ever heard. it is not very far behind my Korneff 45 with EML 45's! I'll share pics soon once I get it cleaned-up a bit.
Congratulations and well done, 10 years in the making and now complete. Will be looking forward to some images, and a real pity you can't share a sample of the audio output but I know and understand exactly what you mean about mind-boggling, it got me too the same way the first time I turned it on. Absolutely dead silent, in fact I thought it wasn't working and no output, then connected an iphone, oh my God, I still remember that moment, probably my single greatest moment in DIY Audio and there are no words to explain it. The depth, width, detail, clarity, separation, and soundstage was beyond anything I heard before and this was an iphone and 92db visaton speakers. I later paired it up with the fantastic Salas DCG3 Preamp (it's here on another thread as a kit) and a pair of 100db Altec 604-8G speakers. No fancy cables or wires, just plain DIY stuff that we all have. Now I just listen to the music, loud or low, and change nothing else other than the music. For me I've reached the place!!!
As I just stumbled over this thread: It is remarkable that people are still building this great amp after so many years! My first one was an order by some friends who needed a presentable build for an exhibition in 1984. It still lives and is operational ...
After quite some time a pair with a somewhat reduced CRC supply ended as „drawer"-amp in a high efficiency speaker setup.
A stand-alone mono version ist also still in use, incorporating a budget CRC supply with a total of 120 caps with 4,700µF each.
Each of these amps uses the original PCBs and Transistors, each is still a real pleasure to listen to!
After quite some time a pair with a somewhat reduced CRC supply ended as „drawer"-amp in a high efficiency speaker setup.
A stand-alone mono version ist also still in use, incorporating a budget CRC supply with a total of 120 caps with 4,700µF each.
Each of these amps uses the original PCBs and Transistors, each is still a real pleasure to listen to!
Did you have to make any parts changes to the Jim’s audio board to use the original transistors? I have both but my amp is not assemble fully yet, looking for a reasonably priced case that looks nice.