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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Yeah, these are polyesters though. MKPs are much bigger, though if the extra quality isn't needed then I cede the point.
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.
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
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. 😎
OS
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. 😎
OS
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.
http://www.murata.com/products/catalog/pdf/c49e.pdf - page 45
www.epcos.com/inf/20/20/db/fc_2009/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.
www.epcos.com/inf/20/20/db/fc_2009/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.
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?
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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nice layout discrete, but, if your power transistors fit under your PCB (I am assuming this), then your emmitter degen resistor solder pads will cause a problem. You need a bit more clearance. If you are using the short version resistors, you will not have this problem.
Lazy, Bonsai,
Thanks for the feedback!
Re. the solder pads above the power transistors, I was planning to have the board on 1/4" or 3/8" standoffs, so not touching the transistors. 10mm LS radial degen resistors like OS is using would be nice, but I only have 17mm axial on hand.
i like this layout better because of its symmetry.....i have 150mm high heatsinks which will accommodate this board better....
any chance to make "more pairs" options?😀
3? 🙂
Note my board miss a few components (css trimmer, dc offset trimmer, fuse bypass resistors), and is much more limited with regards to component sizes.
It also comes with no guarantees against errors or omissions...
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Just a few "tweaks".....
I suppose one can not please everyone. 😀 BUT .... for this PCB format , I think the artwork /BOM is flawless.
Below (attached) , I have both the layout,schema and BOM. If these are "right on" (physically) , we can haggle about substitutes and/or sourcing later.
I did take Casull's capacitor recommendations , and re-positioned some components to allow for more space. 99% of the amp remains the same , as this layout still seems to offer the best "universality".
Some call for more outputs ... Crazy !!! 3 pair of NJW/MJL output devices can really "rock the house" ... 150w/8R and at 60v rails , 300w peaks.
If any can find any discrepancies between the 3 items below ......(BOM,schema,PCB) , please inform me. 100's of eyes are far superior to just 2 old ones 😀 .
OS
I suppose one can not please everyone. 😀 BUT .... for this PCB format , I think the artwork /BOM is flawless.
Below (attached) , I have both the layout,schema and BOM. If these are "right on" (physically) , we can haggle about substitutes and/or sourcing later.
I did take Casull's capacitor recommendations , and re-positioned some components to allow for more space. 99% of the amp remains the same , as this layout still seems to offer the best "universality".
Some call for more outputs ... Crazy !!! 3 pair of NJW/MJL output devices can really "rock the house" ... 150w/8R and at 60v rails , 300w peaks.
If any can find any discrepancies between the 3 items below ......(BOM,schema,PCB) , please inform me. 100's of eyes are far superior to just 2 old ones 😀 .
OS
Attachments
You still need to correct the errors in the BOM - see C3/C4 and others... Perhaps you can use my revised BOM as a reference?