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Jens Rasmussen Leach clone group buy

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#801
Nice looking cases at reasonable prices even with the US dollar as weak as it is.

Since the output devices are lumped together, the 300 mm depth is more appropriate. If you need the extra depth to fit your PSU, the 200 mm active heat sink ought to be enough.
 
#803
PCM=Printed circuit module
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Thanks(I kept thinking "Pulse Code Modulation" or something equally unrelated to our project...) !

BTW, Since my budget was used up on everything else, perhaps I should look into getting samples of the preferred model transistors, as I just need 10pcs to test the PCB with my PSU....😕

Any advice on how to approach this?
I visited www.fairchildsemi.com, and their sample policy states they do not supply to students or individuals without a corporate email account. :whazzat:

'Tis a shame, for I already have 2pairs of their nice FJL4315/4215 and need 3 more pairs to test the board in my chassis...:bawling:

TIA

-Chas
 
#804
Chas, let me try to register with my corporate email to see I can get you some samples. Are FJL4315/4215 what you looked for? Since the company that I work for is not a electronic company, don't have too much of a high hope 🙂
 
#807
The SOA is roughly equivalent to the 3281, a little bigger in the high Vce area.

The hfe curve is a bit lower than the 3281. Initially the curve is flatter, but at higher temperatures the 4315's hfe rolls off earlier, potentially meaning more distortion. It is still flat up to 2A per device, so we'd be in the flat region up to 10A (400W/4R) in this application

They are the same package.

Based on SOA I'd say they are a decent substitute for the 3281/1302, but at 75V rails the 4281/4302 are a safer bet for low impedance/reactive loads.

Hopefully someone a bit more knowledgeable will look at the data sheet and comment on the suitability.
 
#808
even cheaper

For high rail voltages it is much wiser to go for really big heatsinks, such as the Seifert type that Jens used.
A 0.35 C/W heatsink will be nearly 3/4 to blame for the max power handling and peak output current levels, something like 350W and 22.5A for 150W output devices.(200W dissipation level)
Using a 0.15C/W heatsink will raise those numbers by roughly 150% : 800W and ~55A.

If you calculate dissipation and derated output current levels for MJL4281/4302 devices you'll discover that the heatsink size is more significant than the type of output device.
Using both is even prettier of course :at 200W dissipation still +1300W power handling.(all numbers for 10mS burst)
 
#809
Skip a night out

Skip a night out and you've got enough for both channels.
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Unfortunately, I haven't had a night "out" in a while, since I'm stuck at home on diability leave(=$0 income; Thanks goodness for being able to sell some of my rare record collection on eBay-check it out!). 😱

But then, this is why I'm so excited about this project (something to do with all that time)! 😉

The reason I have the FJL4215/4315 is 'cause a member, Sean, was kind enough to send me 2 prs. to evaluate. I'll be using to test my setup. Thanks, Sean!

I appreciate all the help, guys! (Boards should arrive any day, right, Tad?).😎

-chas

p.s. I've located one or two DIY'ers in my area, so I look forward to collaborating(commiserating) on the project without hijacking the board all the time
 
#810
Sorry, I forgot you'd mentioned the disability earlier. I wish you a speedy recovery.

Get together with the local DIYers to do a mini group buy of all parts. That way you can match from a larger pool without having too many leftovers. Matching your differential and output devices will improve sonics.
 
#812
tryonziess said:
Where can you buy them at a reasonable price in the U.S. I had a hard time finding regular MKP Evox at the proper pcm.
There is not a real good source for Rifa and other high grade films in the States unless you pay audiophile rates at specialty outlets. When I ordered through RS components global the freight was murder. I tried to emulate Jens layout at Delta-Audio.
I agree with your choice I just could not find them. Someone want to run a group buy on film caps or Rifa electrolytics????
Come to a consensus on the parts and I could do this I suppose. Power supply electros in 100+ volts can get very expensive fast. I like the 47,000uf/100 volt Rifa caps as my first choice they retail at about 100.00 dollars EACH. It makes big trannies look cheap. Put 8 of those in your stereo Leach and your budget is -- what budget. We could save BIG here with a GB.

Be careful with the film caps watch the pcm closely. Speaking from past experience.

Tad
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are you referring to B 41 456

http://export.farnell.com/epcos/b41456b9479m/capacitor-47000uf-100v/dp/3878156

how really good are they
I like Idea of GB for these
 
#820
I'm going to use an 800VA 2 x 0-42V transformer per 2 channels. for ~62V rails.

Inrush limiter will be a CL30 in the mains. I'll probably also have one in each rail before splitting to the two boards. (or a 10A fuse)

Eventually I am going to have to make a sequencer to turn on all these amps and XOs (4 way OB in the works + 2 subs) in a reasonable fashion. That will probably include inrush current limiting since I will be making delays like Rod Elliot's project 39 anyway.
 
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