i have a heap of mills for the 0r47 in amp and power supply, they come standard as 1%, but really for the source resistors i should match further by hand right? fets are matched, should i do this, or will it be thrown out by the rest of the parts tolerance and need to be trimmed out anyway?
scaiff001: which jfets do you have? its easier if you are more specific. if you actually have a j109, there is no heatsink for them unless you use a cpu sink and glue it with silver epoxy. if you are using 2 x j74 and you have matched them, it realy depends more on whether you need more drive from them depending on your build. heat stability can be managed fairly well with matched units by gluing them face to face, but if you need to get more current from them the heatsinks you get from Patrick's (EUVL) partner mark lai. message him through the forum. Peter may even have some of them. this also helps them track over temp, but i think if they are matched well glueing them will do well also
> Do the JFETs require heatsinks on them, if so dose anyone know the email address of the person who is selling them ?
http://www.diyaudio.com/forums/group-buys/135359-toshiba-dual-jfet-heatsink-6.html#post2366641
Pls also read post #282 re shipment conditions.
Will fit the PCB from PD.
We actually sent him a few.
Patrick
.
http://www.diyaudio.com/forums/group-buys/135359-toshiba-dual-jfet-heatsink-6.html#post2366641
Pls also read post #282 re shipment conditions.
Will fit the PCB from PD.
We actually sent him a few.
Patrick
.
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SCAIFF-
The IRFP240's need to be isolated from their heatsinks. Buy these. It is possible to get away with not insulating them but there are safety and capacitance etc issues that simply are more trouble than just using these insulators (which have a negligible thermal loss across them).
Further on what qusp has said: PD's boards that you have won't allow gluing the J74's face to face. EUVL's wee sinks or maybe a TO-220 clip type heatsink?
The IRFP240's need to be isolated from their heatsinks. Buy these. It is possible to get away with not insulating them but there are safety and capacitance etc issues that simply are more trouble than just using these insulators (which have a negligible thermal loss across them).
Further on what qusp has said: PD's boards that you have won't allow gluing the J74's face to face. EUVL's wee sinks or maybe a TO-220 clip type heatsink?
> Matching source resistors is not necessary; further, I'm not sure one can reliably does that easily, as 1% of 0.47R is merely 4.7mR which is too small for the general multimeter
Again I dare to disagree.
http://www.diyaudio.com/forums/grou...ima-resistors-gb-euvls-fx5-3.html#post2540241
http://www.diyaudio.com/forums/atta...anced-f5-question-power-resistor-matching.pdf
You may consider joining our Group Buy :
http://www.diyaudio.com/forums/grou...ima-resistors-gb-euvls-fx5-2.html#post2535988
Get great value for sets of 8 matched Fukushima MPC74s (as used by Accuphase), and help the Earth Quake victims at the same time.
Patrick
Again I dare to disagree.
http://www.diyaudio.com/forums/grou...ima-resistors-gb-euvls-fx5-3.html#post2540241
http://www.diyaudio.com/forums/atta...anced-f5-question-power-resistor-matching.pdf
You may consider joining our Group Buy :
http://www.diyaudio.com/forums/grou...ima-resistors-gb-euvls-fx5-2.html#post2535988
Get great value for sets of 8 matched Fukushima MPC74s (as used by Accuphase), and help the Earth Quake victims at the same time.
Patrick
Okay. While we're here, and I hate to do this:
Where are we getting 2SJ74's these days?
I'm staring at the datasheets right now of 2SJ74 and 2SJ108 and the only difference seems to be the power dissipation. It's down to me of course to determine what the power on them is going to be per application, but is 2SJ108 an okay way to go if I can't find 2SJ74's?
Where are we getting 2SJ74's these days?
I'm staring at the datasheets right now of 2SJ74 and 2SJ108 and the only difference seems to be the power dissipation. It's down to me of course to determine what the power on them is going to be per application, but is 2SJ108 an okay way to go if I can't find 2SJ74's?
Hi,
Matching source resistors is not necessary; further, I'm not sure one can reliably does that easily, as 1% of 0.47R is merely 4.7mR which is too small for the general multimeter
Hannes
i know that, wasnt planning on trying to use a meter. wheatstone bridge should do the trick. also 0.47R is 470mR
right i hadnt seen the j109 sinks Patrick,
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you can fairly easily twist them so they are face to face, but the heatsinks are a good solution
Easy to match resistors
You could use a constant current source and mesure the volt drop (LM317)
Or a bridge circuit that does not need to be realy accurate if you keep one resistor as reference and other branch to test DUT mesure the deviation
Swap DUT
resistors that give you the same mesurament are matched.
I am doing that on 100 MPC74 and is working quite well
You could use a constant current source and mesure the volt drop (LM317)
Or a bridge circuit that does not need to be realy accurate if you keep one resistor as reference and other branch to test DUT mesure the deviation
Swap DUT
resistors that give you the same mesurament are matched.
I am doing that on 100 MPC74 and is working quite well
Hi Everyone. I just ordered the aleph-jx boards from Peter yesterday and am in the early stages of planning this project. Was wondering where the state-side members are sourcing the JS inputs. Did a quick search on the Digikey site and didn't turn up anything. Also, I just replaced the main caps in my A75 with 56k/50v Mallory CGS's from Digikey. At a cost of $64 each it will blow the budget for the X amp (64 x 8 = $512). If there's a cheaper alternative / supplier anyone is using I'd appreciate suggestions. You'll probably be seeing alot more of me on this thread once I get started.
Dan
Dan
Yes, that's the best way. You also don't need any additional mounting screws to support the board.