MOSFET matching
Hi Bob, et.al.
I have all of my power supply components, I can use this power supply for my MOSFET matching, I will just have to put resistors on it to limit the amount of current, is this what you are saying? I have a 600VA transformers so what whould be the resistor size to limit the current for the MOSFET matching?
The DMM I recieved has no hooks or pincers, just probes that make it imposible to get a reading out of it. I am buying hook cables for the DMM: POMONA|3782-24-0|Connector assemblies, IC clips | Newark Canada .
I have read that some people have oscilliscopes for measurements, are PC Based Oscilliscopes the cheepist way to go because some of them are expensive to like : http://www.picotech.com/document/pdf/ps3425-en-2.pdf is about $1,800.00 . Can anyone suggest a cheep PC Based Oscilliscope, I know nothing about them aside from the fact that everyone would like to have one whom(who) dose not posess one yet.
Thank You
Ian
Hi Bob, et.al.
I have all of my power supply components, I can use this power supply for my MOSFET matching, I will just have to put resistors on it to limit the amount of current, is this what you are saying? I have a 600VA transformers so what whould be the resistor size to limit the current for the MOSFET matching?
The DMM I recieved has no hooks or pincers, just probes that make it imposible to get a reading out of it. I am buying hook cables for the DMM: POMONA|3782-24-0|Connector assemblies, IC clips | Newark Canada .
I have read that some people have oscilliscopes for measurements, are PC Based Oscilliscopes the cheepist way to go because some of them are expensive to like : http://www.picotech.com/document/pdf/ps3425-en-2.pdf is about $1,800.00 . Can anyone suggest a cheep PC Based Oscilliscope, I know nothing about them aside from the fact that everyone would like to have one whom(who) dose not posess one yet.
Thank You
Ian
read the matching mosfets article at PassDIY. Count on ~4V across the FETs, look at your PSU's off load voltage, subtract 4V and that is what the resistor needs to drop at your chosen per device bias. Then use Ohm's law to determine the resistor value and power rating. Alternately you can make a CCS out of one of your mosfets or a spare TO-220 transistor set for your chosen bias.
Don't go overboard with the parts specs used in your matching jig. 10% is close enough.
Don't go overboard with the parts specs used in your matching jig. 10% is close enough.
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Hi Ian there is quite a bit of stuff on the web
I use True RTA Spectrum analiser and scope pure software duda appart from sound card
No need for Hardvare
Other USB based stuf do the Jodb for about 8o quids.
Pico scope vas a bit of a revolution 10 15 years ago now prices of hardvare cought up and Pico scope moved to the Hier end of the market still I have the price for the Pico 3424 at £399
A proper scope for Audio may set yu off £250 as they get up in prices whit the frequency( the lowest frequency do) 20MHz dual trace GW Insteck from rapid £253 but I wish now that I bought a beter one
Just think that it may not be worth buyng the cheep one as one day you may need someting better aim for the best you can afford.
Ceck prices at RS Farnell and Rapid electronics take your pick and then search same more for cheaper prices
I use True RTA Spectrum analiser and scope pure software duda appart from sound card
No need for Hardvare
Other USB based stuf do the Jodb for about 8o quids.
Pico scope vas a bit of a revolution 10 15 years ago now prices of hardvare cought up and Pico scope moved to the Hier end of the market still I have the price for the Pico 3424 at £399
A proper scope for Audio may set yu off £250 as they get up in prices whit the frequency( the lowest frequency do) 20MHz dual trace GW Insteck from rapid £253 but I wish now that I bought a beter one
Just think that it may not be worth buyng the cheep one as one day you may need someting better aim for the best you can afford.
Ceck prices at RS Farnell and Rapid electronics take your pick and then search same more for cheaper prices
MOSFET matching
Hi Bob,
I purchased 50 IRFP240s as you suggested, it came as two groups of 25 MOSFETs, I have not checled to see if the numbers are in sequence. I will re-read the PASS documentation on matching MOSFETs.
How do I attach the three pieces of ALeph J-X circuit boards together, I dont have all of the components for the middle common fromt end circuit board. What is the value for P1, I have looked over Aleph X amplifier schematics and they use either 50ohms or 200ohms 500mV pentiometers, The F5 amp uses 5Kohm pentiometer, for some reason I have 10Kohm pentiometer in my mind but I dont remember where I read this value from.
At the begining of next month I will be ordering the rest of my parts along with the Power MOSFET heat sinks which will be about $290.00 .
I still might have to wait to complete my amplifier the following month if I dont have enough money to purchase all of the parts I need on 01Nov2010. Because I still need to purchase some stuff from www.apexjr.com like switchs , DC filter caps, DPDT switchs, 8gage silver cable, 36 screw top electrolytic capacitor vertical mounting brackets, six 0.25inch thick 6in by 9in heat sinks for power supply mounting, I also still have to purchase the power supply components and three fans for each mono block amp, also I ave to puchase the hooks for the DMM and a good DMM, and other stuff I can not think of at this moment, it all adds up to over $700.00, so I will have to wait untill next month befor I have all of the components I need to complete the project. This is a very expensive amplifier I am building, I hope it sounds as good as I imagine it will with the components I have purchased, who knows mabe making an inexpensive Aleph J-X will sound the same or even better ?
Hi Bob,
I purchased 50 IRFP240s as you suggested, it came as two groups of 25 MOSFETs, I have not checled to see if the numbers are in sequence. I will re-read the PASS documentation on matching MOSFETs.
How do I attach the three pieces of ALeph J-X circuit boards together, I dont have all of the components for the middle common fromt end circuit board. What is the value for P1, I have looked over Aleph X amplifier schematics and they use either 50ohms or 200ohms 500mV pentiometers, The F5 amp uses 5Kohm pentiometer, for some reason I have 10Kohm pentiometer in my mind but I dont remember where I read this value from.
At the begining of next month I will be ordering the rest of my parts along with the Power MOSFET heat sinks which will be about $290.00 .
I still might have to wait to complete my amplifier the following month if I dont have enough money to purchase all of the parts I need on 01Nov2010. Because I still need to purchase some stuff from www.apexjr.com like switchs , DC filter caps, DPDT switchs, 8gage silver cable, 36 screw top electrolytic capacitor vertical mounting brackets, six 0.25inch thick 6in by 9in heat sinks for power supply mounting, I also still have to purchase the power supply components and three fans for each mono block amp, also I ave to puchase the hooks for the DMM and a good DMM, and other stuff I can not think of at this moment, it all adds up to over $700.00, so I will have to wait untill next month befor I have all of the components I need to complete the project. This is a very expensive amplifier I am building, I hope it sounds as good as I imagine it will with the components I have purchased, who knows mabe making an inexpensive Aleph J-X will sound the same or even better ?
Hey guys,
Just received a set of Peter's board along with PS boards. I'm just building the standard Aleph J not the X. I've got two of the PS boards and I'm trying to detirmine the capacitance requirement as there seems to be many opinions on this. From what I can detirmine one PS board supplies the + rail the other the - rail and I can source some 15000uF caps so there would be two per board or 60000uF for the amp. Do you think this is sufficient or should I be aiming for more?
Just received a set of Peter's board along with PS boards. I'm just building the standard Aleph J not the X. I've got two of the PS boards and I'm trying to detirmine the capacitance requirement as there seems to be many opinions on this. From what I can detirmine one PS board supplies the + rail the other the - rail and I can source some 15000uF caps so there would be two per board or 60000uF for the amp. Do you think this is sufficient or should I be aiming for more?
I'm just using Peter Daniel's PS boards see here http://www.diyaudio.com/forums/audio-sector/149672-universal-power-supply-pcb.html so I have room for four caps upto 50mm in diameter. There just seems to be so much varience in how much capacitance people use especially when talking about something like the J which is 2 x 25w and yet you see people with staggering amounts of capacitance and others with very little in comparison.
Those look like nice boards. Yes, one for the positive rail and one for the negative. You can so a CRC or CLC with them. Download PSU designer and model your PSU to see how much ripple you get. Obviously the lower the better, but since you are limited to two caps it becomes an issue of practicality.
There are 50 mm caps 50,000 uf and up, but they are $35+ each.
There are 50 mm caps 50,000 uf and up, but they are $35+ each.
Hi there,
I too have a couple of those psu boards that I'll also be using for an aleph -jx (or maybe just a j) build.
Is there any reason I can't to wire a couple of caps in parallel, and then wire them to the relevant points on the pcb? Ie mount the caps somewhere else and wire them into the pcb instead of connecting them up to the pcb directly?
I too have a couple of those psu boards that I'll also be using for an aleph -jx (or maybe just a j) build.
Is there any reason I can't to wire a couple of caps in parallel, and then wire them to the relevant points on the pcb? Ie mount the caps somewhere else and wire them into the pcb instead of connecting them up to the pcb directly?
Does anyone have a copy of the Schematic for Peter Daniels PS boards in the configuration used for the Aleph J as I can't seem to find one or even a copy of the simulation file to use in PSU designer? I'm afraid back tracing the circuit of the board is still a bit above me. As I understand it you don't need to fully populate the board depending on what you are using it for and being a beginner I'm unsure what I actually require for the PS to use with the Aleph.
Does anyone know where to get some matched IRFP240N's? I was on a website only the other day and he sold matched batches. It was one of the usual DIY suppliers.
I'm assuming it is best to use the IRFP240N and not this one http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=IRFP240PBF-ND ?
I'm assuming it is best to use the IRFP240N and not this one http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=IRFP240PBF-ND ?
nothing wrong with them , except the price
maybe they're made of preputium
Or Unobtainium....
I found the place i was thinking of Tech DIY Company Store would you consider those prices fair for matched sets? Otherwise do you know a reliable source at a good price and if I was to match my own Quartets how many do you think I'd need to make two matched quartets?
Thanks
Luke