I'm curious about this as well.
I started looking up parts for the BX1.3VB board at Digikey, and apart from Q1/Q2 all the other transistors are either unlisted or non-stocked. Mouser has the 2SA1381, but it is flagged as "end of life".
It would be nice to build an amp around readily available (standard) parts, but I don't want to re-design the whole thing, or have to wonder why my amp ends up sounding bad.
I think I recall reading that the mongrel design was pretty tolerant of part substitutions, but I may be confused.😛
Any input would be most appreciated !
Okay, I'm confused.
Are 2SA1381 and KSA1381 are the same thing ? After skimming the data sheet, the only diff between the two is ... the package marking.
???
A few more questions about BX1.3BV as I continue part-shopping :
1) Resistors : Any special type (apart from power ratings specified) ? Should I go for low tempco ? I assume precision isn't necessary, since trim pots are included.
2) C1 : I picked this one : ECW-F2475JA Panasonic Electronic Components Polypropylene Film Capacitors
Is this okay ? I'm no golden-ear, just want a Mouser-stocked part that won't ruin things.
1) Resistors : Any special type (apart from power ratings specified) ? Should I go for low tempco ? I assume precision isn't necessary, since trim pots are included.
2) C1 : I picked this one : ECW-F2475JA Panasonic Electronic Components Polypropylene Film Capacitors
Is this okay ? I'm no golden-ear, just want a Mouser-stocked part that won't ruin things.
In answer to all the above questions... I have used 2sa733/945 for the higher voltage cascode and CM devices , everything worked out perfect. I even tried MJE340/350 for the VAS , both amps sounded and performed the same... just a slight change in CCS current. Just observe the Vceo ratings. VAS 250+ Vceo , CM and cascode 80-120V Vceo. The input pair can be as low as 30V as it is cascoded.
All devices are E-C-B lead wise... except for the input pair. I have tried MPS8089 / mpsa18 and all the "ss"'s (fairchild ss9012/9014) these are E-B-C .. lead wise.
Just a slight CCS adjustment was all these needed. The input pair emitter resistors should be 1-2% tolerance. With this you should be +/- 2mv offset with basic DMM hfe matching of the IP pair. Make shure the "OFFSET" trimmer is 500-500 (right in the middle) , 1/2 to 1 turn should get you .5mV and under offset wise.
Same goes for any of the power boards. I have 3 amps now , 1 uses NJW21193/4's , the second uses NJW0281/0302's and the "little dog" uses 2sc3263/2sa1294 (sanken). ALL the popular BJT OP's would work fine in the power boards as long as Vceo = 250v+ Hfe+ 60+ and B-C-E (leads). VERY universal projects.
ALL the ksa/ksc fairchild models are direct clones of the original 2sa/2sc parts - perfect ,if not improved replacements. 🙂
OS
All devices are E-C-B lead wise... except for the input pair. I have tried MPS8089 / mpsa18 and all the "ss"'s (fairchild ss9012/9014) these are E-B-C .. lead wise.
Just a slight CCS adjustment was all these needed. The input pair emitter resistors should be 1-2% tolerance. With this you should be +/- 2mv offset with basic DMM hfe matching of the IP pair. Make shure the "OFFSET" trimmer is 500-500 (right in the middle) , 1/2 to 1 turn should get you .5mV and under offset wise.
Same goes for any of the power boards. I have 3 amps now , 1 uses NJW21193/4's , the second uses NJW0281/0302's and the "little dog" uses 2sc3263/2sa1294 (sanken). ALL the popular BJT OP's would work fine in the power boards as long as Vceo = 250v+ Hfe+ 60+ and B-C-E (leads). VERY universal projects.
ALL the ksa/ksc fairchild models are direct clones of the original 2sa/2sc parts - perfect ,if not improved replacements. 🙂
OS
Hey, OS, Thanks for the reply.
After learning about the "name change", I found all the transistors in stock at Mouser. (But not Digikey ???)
Just to be sure, the trimmer (R13) is 500 ohms total, right ?
After learning about the "name change", I found all the transistors in stock at Mouser. (But not Digikey ???)
Just to be sure, the trimmer (R13) is 500 ohms total, right ?
The offset trimmer can be either 500R or 1k , your choice. I use 500's on my BX and 1k's on my AX's (I have 4 of them). Either way , Just a slight change in input stage degeneration and offset trimmer precision (1/2 turn vs 1 turn ).
OS
Ostripper,
Question what's the RMS output power of the PB250N when I use a +- 75Volts supply?
Question what's the RMS output power of the PB250N when I use a +- 75Volts supply?
Hi,
with a very stiff PSU expect close to 70Vpk at the output.
With a poor to medium performing PSU expect 60Vpk to 65Vpk at the output.
60Vpk into 8r0 is equivalent to 225W
70Vpk into 8r0 is equivalent to 306W
You won't be disappointed , I have gotten so loud that it's given me the "sweats". Even with this output , no sign of strain ... clear as a bell with the AX(PS "sagged" to 73-0-73V) ripple at main rails was 1+V p-p , ripple at cap multiplier output was 10mv. At this level I was averaging 32-35V rms , my woofer "tapped" (bottomed out) and I took out a tweeter , (fried it) on one channel. THAT's is why I just bought some real mids and tweeters(below 1) .. I need speakers that can really handle this amp ... OEM's can't do it !!
If you want the 250H (mine) .. it is below (2 and in .zip).. different layout...
That one has 10mm copper strips soldered on top of the massive rail traces(18mm). 125mm(5") heatsink required !!
I will complete the 250H package monday (BOM ,stuffing guide)
PS - I also reached 32-35Vrms with 2 PAIR of those OEM speakers In my initial burn-in , this worked well (a little warmer) and caused law enforcement to come... 😱 😱
OS
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I have sold them locally and in the (traded) US (USPS - 5$). If you have a HP based toner , it is SO easy to make perfect copies from the artwork provided. with just glossy magazines and a Iron , I was able to get 6 pair 250H's- 8 pair AX/BX voltage boards and 7 PS100's perfect (no errors at all). I don't know about oversea shipping ??? 😕 (VAT .. customs ?? )
Quality wise , my FR-4 is better than most board houses (no traces come off) and the etch quality is about the same (600DPI standard).
OS
Ship it as a gift write electronic parts included
Can you provide a PDF file of this layout?
Can you provide a PDF file of this layout?
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Unfortunately , I am OUT of $$ and FR-4 as of now (poor man). 🙁
Layout above in .zip is a perfect 600dpi 250mm X 100mm .JPG. I have found that a PDF is inferior to the original .BMP or .JPG. You could install the "bloated" adobe package and convert from the above original - it is directly outputted from sprint layout.
OS
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If you can provide me PDF files of the PB250N amp and the AX boards or Sprint layouts I could let them make in Holland
But then I would have to install adobe (yuk!!!) maybe Monday. You could do it , search my "ZIP2" folder ,you may just find something (AHEM - adobe 5 , old .. but it works).
OS
OS
Sprint layout... Below is the original. With the free sprint viewer - http://www.abacom-online.de/uk/html/sprint-layout.html, gerbers and all that "jazz" is available (board house).
Below = .zip with the sprint layouts for PS100,ax/BX, PB250n/H
OS
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