how should the 2sj74's be soldered to the board?
Check this post and the attached pic: http://www.diyaudio.com/forums/showpost.php?p=1855541&postcount=85
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Thanks Peter, I've missed this point.
With 1.8A bias per side about 180 watts per ch.
do you think that 2 per channel of SK56/200SA http://www.fischerelektronik.de/fischer2002/_2002/pdf/einzel_pdf/A_42.pdf will do the job
I would like to mount them 2 on each side of the stereo box
do you think that 2 per channel of SK56/200SA http://www.fischerelektronik.de/fischer2002/_2002/pdf/einzel_pdf/A_42.pdf will do the job
I would like to mount them 2 on each side of the stereo box
I would use the SK157/ 150, two per ch.
I tested a single Aleph J channel today and everything works fine.
300VA, 2 x 18V Plitron transformer produces approx 28V unloaded and 26V after connecting to the amp.
Loosely matched SJ74 give approX 35mV offset.
Next thing will be J-X setup.
300VA, 2 x 18V Plitron transformer produces approx 28V unloaded and 26V after connecting to the amp.
Loosely matched SJ74 give approX 35mV offset.
Next thing will be J-X setup.
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I wasn't actually correct, the DC offset was approx 2mV, I forgot about the offset produced by the generator.
The amp runs hot: the 8x8 heatsink with 1.75 fins was way too small for 2 x 18V transformer.
For AJ-X configuration, front end components (inside white border) should not be installed. I just removed them from test channel and I'm slowly getting ready for an X
The amp runs hot: the 8x8 heatsink with 1.75 fins was way too small for 2 x 18V transformer.
For AJ-X configuration, front end components (inside white border) should not be installed. I just removed them from test channel and I'm slowly getting ready for an X
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Heatsink effectiveness vs. length
I am considering using 2 lengths of the barredboss's (Russ) new 10.25" heatsinks per mono J-X channel, with the daughter board spanning across them. I thought about getting 9" or even 12" lengths, but was wondering if the 4 Mosfets are distributed and centered across it, at what point does additional length become much less effective as it exceeds 6" high ... 9"? 12"? My trusty Conrads are 12"l x 6"h but the fins are not nearly as long, so I was hoping the deeper fins and added height would do the job.
The dimensions of these extrusions are:
.375" BASE THICKNESS
2.5" FIN HEIGHT
10.125" WIDE
2.875" TOTAL HEIGHT
.400 FIN SPACING C-C
24 TOTAL FINS
12.5 POUNDS PER FOOT
I am considering using 2 lengths of the barredboss's (Russ) new 10.25" heatsinks per mono J-X channel, with the daughter board spanning across them. I thought about getting 9" or even 12" lengths, but was wondering if the 4 Mosfets are distributed and centered across it, at what point does additional length become much less effective as it exceeds 6" high ... 9"? 12"? My trusty Conrads are 12"l x 6"h but the fins are not nearly as long, so I was hoping the deeper fins and added height would do the job.
The dimensions of these extrusions are:
.375" BASE THICKNESS
2.5" FIN HEIGHT
10.125" WIDE
2.875" TOTAL HEIGHT
.400 FIN SPACING C-C
24 TOTAL FINS
12.5 POUNDS PER FOOT
An externally hosted image should be here but it was not working when we last tested it.
I believe it is R-Theta that has an extrusion identical to Russ' extrusion. I did the calculations a while ago and two 6" pieces were ideal for a stereo J amp, so they would match an XJ monoblock perfectly.
Rule of thumb, when you double the length the capacity goes up about 50%.
For instance, if a 3" piece is .600 C/W, then a piece 6" long would be about .450 C/W.
Bill
Rule of thumb, when you double the length the capacity goes up about 50%.
For instance, if a 3" piece is .600 C/W, then a piece 6" long would be about .450 C/W.
Bill
Thanks very much for that tip. I didn't know there was a profile he was working from already, so I'll look through their site and try to locate the specs.I believe it is R-Theta that has an extrusion identical to Russ' extrusion. I did the calculations a while ago and two 6" pieces were ideal for a stereo J amp, so they would match an XJ monoblock perfectly.
Rule of thumb, when you double the length the capacity goes up about 50%.
For instance, if a 3" piece is .600 C/W, then a piece 6" long would be about .450 C/W.
Bill
Tom
I believe it is R-Theta that has an extrusion identical to Russ' extrusion. I did the calculations a while ago and two 6" pieces were ideal for a stereo J amp, so they would match an XJ monoblock perfectly.
Rule of thumb, when you double the length the capacity goes up about 50%.
For instance, if a 3" piece is .600 C/W, then a piece 6" long would be about .450 C/W.
Bill
would you please give an info about heatsinks you gonna use for your X - J (what rails and bias)
cheers
Yes, it's solder dispenser, one of the most useful accessories I have, you can read more about it here: http://www.diyaudio.com/forums/showthread.php?t=3981&highlight=tools
would you please give an info about heatsinks you gonna use for your X - J (what rails and bias)
cheers
I have built two Aleph Js, one is standard design and one has three fets per rail. The standard design has a more organic sound than the higher powered one. I have no immediate plans to build an X amp, but if I did I would stick very closely to the Master's design for each half. 22-24V rails and .900A/fet bias.
Best, Bill
tms0425,
I have 4 of the barredboss 12+ inch heatsinks in one foot lengths. These are HUGE pieces of aluminum. I bought them from the initial lot before he removed the outer fins. Am I to believe that this little amp is going to generate that much heat? What lelvel of output will 22-26 volt rails yield in the j-x configuration. The j is like 30% efficient?
I am about to order the transformers and would like some input.
Maybe some fans might not be such a bad idea here.
Peter,
I Never got around to thanking you for the boards. Nice. Thanks I will be purchasing the solder thing this weekend.
Tad
I have 4 of the barredboss 12+ inch heatsinks in one foot lengths. These are HUGE pieces of aluminum. I bought them from the initial lot before he removed the outer fins. Am I to believe that this little amp is going to generate that much heat? What lelvel of output will 22-26 volt rails yield in the j-x configuration. The j is like 30% efficient?
I am about to order the transformers and would like some input.
Maybe some fans might not be such a bad idea here.
Peter,
I Never got around to thanking you for the boards. Nice. Thanks I will be purchasing the solder thing this weekend.
Tad
Well, yes it should be plenty hot . It's more so than the F4 and F5 since I believe you're looking at about 1.8A bias with 4 devices on the same rails.tms0425,
I have 4 of the barredboss 12+ inch heatsinks in one foot lengths. These are HUGE pieces of aluminum. I bought them from the initial lot before he removed the outer fins. Am I to believe that this little amp is going to generate that much heat? What lelvel of output will 22-26 volt rails yield in the j-x configuration. The j is like 30% efficient?
I am about to order the transformers and would like some input.
Maybe some fans might not be such a bad idea here.
Peter,
I Never got around to thanking you for the boards. Nice. Thanks I will be purchasing the solder thing this weekend.
Tad
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