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Old 19th September 2011, 10:09 PM   #281
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Late edit:

Quote:
Originally Posted by 454Casull View Post
So to recap yet again:

C2/C3 - please add one more hole to allow for 5.0 mm LS.

C5/C9 - I suggest that an 8.0 mm diameter cap will work, after checking with a vernier on a scale printout. Also, it seems like 6.3D/2.5LS is a more common size than 6.0 or 6.3/3.5 LS - do you agree?

C13/C17 - please add an extra pair of holes to allow for 10.0 mm LS.

Also,

C20 - please add 2 more holes to allow for 15.0 mm, 20.0 mm LS (required for polypro caps)... unless polypro caps offer no advantages vs polyester caps in this application.

C12/C16 - if you can move C11/C15 to the right a little bit, please do; a 5mm-thick cap (MKP/MFP) will be a tight squeeze here.

C10/C14/C21 - can you add a little more space between these caps? 5mm-thick (MKP/MFP) caps will not fit here... you might have to move R32 and C11 to allow that, though.

C6 - MKP box caps won't fit here, only polyester. Is this OK? There are 4.0mm-thick 0.1uF MKP caps available but even 4.0mm may be a very tight squeeze against the nearby transistor leg and resistor body.

C7/C8 - Cap ESL matters? C0G/NP0 usable here?

Last edited by 454Casull; 19th September 2011 at 10:30 PM.
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Old 20th September 2011, 12:24 AM   #282
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Quote:
Originally Posted by 454Casull View Post
Late edit:
All cap suggestions were implemented except the film caps .

2.5 to 4mm is common for .1uf /100v poly units. 250@.1uf is 5mm ....
http://www.vishay.com/docs/26009/mkt1818.pdf
Wima is similar "poly wise".

C7 and 8 are silver mica. Critical dominant pole(s) of the amp. I would not use poly's or ceramic for these. These pads are 7.5-10mm (C8 -430-470p) and 7.5mm for (C7-100p) perfect for 500v CDE silver mica's (my existing amp).

Worst case , if a certain size poly might not be available .... flexible leaded units can be used. http://www.vishay.com/docs/28132/mkt368.pdf
This would not be the case in most area's , as the vishay/wima's are very common and standardized.

PS-below is the "2.2" , same as 2.1 with a couple tweaks.
also , C5,9 ARE 2.5mm LS electro's .
Nice to be "alive" again , C2C. Tennessee was nice to me for a decade .
OS
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Last edited by ostripper; 20th September 2011 at 12:28 AM.
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Old 20th September 2011, 01:17 AM   #283
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Quote:
Originally Posted by ostripper View Post
All cap suggestions were implemented except the film caps .

2.5 to 4mm is common for .1uf /100v poly units. 250@.1uf is 5mm ....
http://www.vishay.com/docs/26009/mkt1818.pdf
Wima is similar "poly wise".
Yeah, these are polyesters though. MKPs are much bigger, though if the extra quality isn't needed then I cede the point.

Quote:
also , C5,9 ARE 2.5mm LS electro's .
I didn't check that one so I didn't notice. Your BOM had them at 3.5.

Anyway, I'll look at it again with a ruler in a bit, thanks.
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Old 20th September 2011, 01:22 AM   #284
49 - for the 18th time
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Originally Posted by ostripper View Post
Nice to be "alive" again , C2C. Tennessee was nice to me for a decade .
OS
Hey OS - it's great that you are "alive" - in all respects.
I'm transplanted here to Tennessee (my wife is a Nashville gal). I'm actually an Air Force brat that's traveled around and raised primarily in Texas and California.

I have a mess of my northern clan living in Johnstown N.Y. so you really can't get away from us!!!
Johnstown (city), New York - Wikipedia, the free encyclopedia
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Old 20th September 2011, 01:48 AM   #285
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Originally Posted by 454Casull View Post

2SA1381 is the only difficult one; also, 2SC3503 is available, but not in huge quantities.

Mouser:

KSA1381ESTU Fairchild Semiconductor Bipolar Small Signal

2SC3503FSTU Fairchild Semiconductor Bipolar Power
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Old 20th September 2011, 02:31 AM   #286
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In reply to the TO-126 sourcing (1381/3503) , I have even built this type amp with the MJE340/350 VAS. The only difference is a little more overcompensation , lower slew , a little less open loop gain. Audibly , I was unable to differentiate the MJE's from the 1381/3503's.

Another sub would be the 2sa/c (ksa/c) 1220A/2690A. At 50v rails ,still has a 50% derated Vceo (160v). I will include more "less than ideal" but adequate semi's in my updated BOM.

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Old 20th September 2011, 03:59 AM   #287
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In place of A1381/C3503 you could also use A1538, A1539/C3953, C3954. Perhaps, easy to obtain and nearly as good. I have used these and experienced a very audible difference compated to MJE340/350.
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Old 20th September 2011, 12:29 PM   #288
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Quote:
Originally Posted by 454Casull View Post
Q1,Q2 -- MPSA18/SS9014 -- MPSA18RLRAG is available at Digikey

Q10 -- 2SA1381 -- not available at Digikey, Mouser; Newark recommends MJE350G

Q11,Q12,Q13 -- 2SC3503 -- not available at Digikey; 2SC3503FSTU available at Mouser (scheduled to become obsolete)

Q14 -- MJE15032 -- MJE15032G is available at Digikey
Q15 -- MJE15033 -- MJE15033G is available at Digikey
Q16,Q17,Q18 -- MJL3281 -- MJL3281AG available at Digikey
Q19,Q20,Q21 -- MJL1302 -- MJL1302AG available at Digikey (low quantities) and Mouser
Q3,Q4,Q7,Q8 -- KSC1845 -- KSC1845 (various types) available at Mouser
Q5,Q6,Q9 -- KSA992 -- KSA992 (various types) available at Mouser

------------

2SA1381 is the only difficult one; also, 2SC3503 is available, but not in huge quantities.
2SA1381 and 2SC3503 -->> KSA1381 and KSC3503
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Old 20th September 2011, 04:21 PM   #289
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http://www.murata.com/products/catalog/pdf/c49e.pdf - page 45

http://www.epcos.com/inf/20/20/db/fc...MKT_B32232.pdf - page 8

The impedance vs frequency charts above... the C0G/NP0 caps have impedance minima at higher frequencies than the MKTs, but the MKTs (for some strange reason) show slightly lower impedance leading up to the impedance minima.
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Old 21st September 2011, 01:08 AM   #290
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Default Question for OS

Hi OS,

Good to see you back!

I did my own layout to suit components/heat-sinks/case materials on hand - hope you do not mind....

The heat-sinks are 12"x3"x1.5" flat backs, same height as my PCB, so the TO-3P packages end up close to the top/bottom edges of the heat-sink.
Power supply will be 40+40 VDC.

Based on your experience, do you think I will have thermal stability issues due to the placement of the drivers/Q13?
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