Hi,
What is the heat dissipation in those driver transistors (Q14-Q17)?
My calculations shows 3.3W each if using: U(R38)=1V and if I (output devices)=1.3A (a pair)@Hfe 25 min. U(CE-Q14) ca 50V.
If this calculation is right the total power dissipated by the drivers would be ca 13.07W total. Rather hefty dissipation for a small heat sink. If assuming a K-value of 2.8 degrees C/W (ref. by Marks heat sink#2) and an ambient of 40-50 degrees C (inside chassis) the temp on the heat sink would be from 76.6 to 86.7 degrees C when stabilized.
Its not hard to believe you guys when you told us that the original (smaller than this) heat sinks got VERY HOT.
Could somebody tell if this calculation is wrong or not?
Regards
What is the heat dissipation in those driver transistors (Q14-Q17)?
My calculations shows 3.3W each if using: U(R38)=1V and if I (output devices)=1.3A (a pair)@Hfe 25 min. U(CE-Q14) ca 50V.
If this calculation is right the total power dissipated by the drivers would be ca 13.07W total. Rather hefty dissipation for a small heat sink. If assuming a K-value of 2.8 degrees C/W (ref. by Marks heat sink#2) and an ambient of 40-50 degrees C (inside chassis) the temp on the heat sink would be from 76.6 to 86.7 degrees C when stabilized.
Its not hard to believe you guys when you told us that the original (smaller than this) heat sinks got VERY HOT.
Could somebody tell if this calculation is wrong or not?
Regards
Gotta include the drop across the diodes but then the size of the cap bank can scale it off either higher or lower.I got the preliminary pricing back on the boards. This is not nailed in the wool pricing and does not include any gold plating. It is well under $10.00 per board in 100 quantity. It does however include the board being RoHS compliant. If it were not I doubt we'd be able to ship them to any European Countries since the compliance is now mandatory. UL rating is also included in the price. This is quite a bit less than the KSA-50 boards were and it may be due to there being no routing at all for any snap off pieces... although I don't remember there being a seperate price for that on the bill for them, may have been an extra tooling charge for that.
We need some input!
I need to know exactly how you boys want em......
Gold plated pads or not....
PWatts suggested a black solder mask and white silk screen...
See below posted PDF.....
Type of board material: FR-4, FR-406, or Teflon
Two things I won't budge on are RoHS as I need to be able to ship these all over the world... and 2 oz copper foil.
If I don' get any feedback on this then they will come with bright yellow solder mask and purple silkscreen
Mark
We need some input!
I need to know exactly how you boys want em......
Gold plated pads or not....
PWatts suggested a black solder mask and white silk screen...
See below posted PDF.....
Type of board material: FR-4, FR-406, or Teflon
Two things I won't budge on are RoHS as I need to be able to ship these all over the world... and 2 oz copper foil.
If I don' get any feedback on this then they will come with bright yellow solder mask and purple silkscreen
Mark
Mark A. Gulbrandsen said:
I like that; it would match one of my Saturday night prom dresses!
Seriously, black & white or Blue & white would be cool. I read earlier that money could be saved by not including the silkscreen of components on the bottom? I'd rather have everything labeled top to bottom for ease of construction? Even if it cost an extra buck or two.
I don't need gold plated pads.
Teflon is not required on the boards.
Lots of thick copper is the essential ingredient. Every thing else is secondary.
Cheers,
Shawn.
There is indeed no silkscreen on the bottom. Most places only charge for that for the initial tooling cost, but seriously, those who manage to screw up the three resistors on the bottom would have screwed up something else anyway.
It shouldn't be a problem for most, but just bear in mind that ROHS-compliant boards are a bit harder to solder and require more heat.
I kinda forgot about the output transistor boards, but I think we should rather have a parallel run of them made (a large panel of just them), since many people either already have an output stage, upgrading an existing KSA or use TO-3 packages. No need to design a new board, Al's design is perfectly acceptable, unless people think the traces were really too thin. BTW anyone in dire need of TO3 boards such as on the original or should that just be ditched?
I've started on a BOM, and should have it posted before the weekend.
It shouldn't be a problem for most, but just bear in mind that ROHS-compliant boards are a bit harder to solder and require more heat.
I kinda forgot about the output transistor boards, but I think we should rather have a parallel run of them made (a large panel of just them), since many people either already have an output stage, upgrading an existing KSA or use TO-3 packages. No need to design a new board, Al's design is perfectly acceptable, unless people think the traces were really too thin. BTW anyone in dire need of TO3 boards such as on the original or should that just be ditched?
I've started on a BOM, and should have it posted before the weekend.
Another few things:
Since there is enough space, are there any requests to support the largest possible electrolytic that can fit on the board? I can replace the big one at the bottom with a bigger one, and I'll be able to fit a 10,000uF 63V right between the mounting holes on each side. This is the size for a RubyCon snap-in, but I know the Elnas have the same footprint. I can also place concentrically smaller caps in its centre.
I can also try to fit in an axial cap for something such as a Solen bypass.
True, such a large cap isn't really necessary for only the main board, but with a series resistor (5-50ohms or even an inductor) between it and the main supply it will produce a nice lowpass filter and provide some isolation from sharp current draws by the output stage... not so critical for a class-A amp but still.
It's not too hard to fit them in, but I don't want to add stuff that nobody will use.
Furthermore, people should check if the other decoupling electrolytics are large enough to their liking - I used the same as on the PinkMouse boards i.e. 10mm diameter & 5mm lead space, but since this board will need 63V caps it may perhaps be too small.
Also, since they are good value for money and Krell used them in all their designs, how are the sentiments for adding a set of Dale resistors to the board group buy? This may help a lot for overseas buyers who have to place international orders. There are 41x 0.5W resistors per board, which works out at $8.20 per board. Ultimately it all depends on Mark since it will increase his initial payment.
A little audiophile drivel: I just read on a website somewhere that "audiophiles agree than red soldermask sound better than green". Forgive me I'm not going to make all my boards red in the future
Since there is enough space, are there any requests to support the largest possible electrolytic that can fit on the board? I can replace the big one at the bottom with a bigger one, and I'll be able to fit a 10,000uF 63V right between the mounting holes on each side. This is the size for a RubyCon snap-in, but I know the Elnas have the same footprint. I can also place concentrically smaller caps in its centre.
I can also try to fit in an axial cap for something such as a Solen bypass.
True, such a large cap isn't really necessary for only the main board, but with a series resistor (5-50ohms or even an inductor) between it and the main supply it will produce a nice lowpass filter and provide some isolation from sharp current draws by the output stage... not so critical for a class-A amp but still.
It's not too hard to fit them in, but I don't want to add stuff that nobody will use.
Furthermore, people should check if the other decoupling electrolytics are large enough to their liking - I used the same as on the PinkMouse boards i.e. 10mm diameter & 5mm lead space, but since this board will need 63V caps it may perhaps be too small.
Also, since they are good value for money and Krell used them in all their designs, how are the sentiments for adding a set of Dale resistors to the board group buy? This may help a lot for overseas buyers who have to place international orders. There are 41x 0.5W resistors per board, which works out at $8.20 per board. Ultimately it all depends on Mark since it will increase his initial payment.
A little audiophile drivel: I just read on a website somewhere that "audiophiles agree than red soldermask sound better than green". Forgive me I'm not going to make all my boards red in the future
Bias pot number
PWatts:
Why is bias pot. numbered to VR3!!?? I can only see two potentiometers (V1+V3) on this board. Was it a third "summer" pot. you where speaking of?
Regarding the board production:
FR-4 (not Teflon those are for MHz/GHz frequencies or 200 degrees C, very expensive)
70µm (2 oz) Cu
Gold plated for easy soldering without excessive heat
Blue color and white silkscreen should be fine (not yellow and purple 
)
Regards
PWatts:
Why is bias pot. numbered to VR3!!?? I can only see two potentiometers (V1+V3) on this board. Was it a third "summer" pot. you where speaking of?
Regarding the board production:
FR-4 (not Teflon those are for MHz/GHz frequencies or 200 degrees C, very expensive)
70µm (2 oz) Cu
Gold plated for easy soldering without excessive heat
Blue color and white silkscreen should be fine
(not yellow and purple )Regards
PWatts,
Isnt it a benefit to add extra caps rather than to make one bigger? Thinking of Irac, ESR and Lest. (you will halves or doubles those values)
Its a benefit to add more caps, not bigger caps. Also its often easier to mount a couple of smaller caps rater than one big one. I vote for an extra pair of the CP1,CP2.
I liked your suggestion for a GB for those resistors (hard to get in EF)
Regards
Isnt it a benefit to add extra caps rather than to make one bigger? Thinking of Irac, ESR and Lest. (you will halves or doubles those values)
Its a benefit to add more caps, not bigger caps. Also its often easier to mount a couple of smaller caps rater than one big one. I vote for an extra pair of the CP1,CP2.
I liked your suggestion for a GB for those resistors (hard to get in EF)
Regards
You guys are way too sharp I noticed the VR3 (that's what happens if you add another component before deleting the old one first; it auto-increments. It's been fixed yesterday already but I didn't even think people would notice so I didn't repost hehe.
I also moved the silkscreen at the bottom for the Ground and Signal since it was covered by the connectors.. this happenned when I moved the whole board down to conserve space and they didn't travel along. At the current location (sides) they don't make as much sense as on Al's board, but those who are confused can just look at his for guidance. Unfortunately vertical space is very limited so I cannot move their silkscreen to be at the bottom of the connectors.
Two smaller caps doesn't necessarily have less ESR. A bank of say 10 smaller ones may, but if you look at the datasheets it's ofen the case that it's more or less the same. But, it's not too hard to just add a lot of cropcircles on the silkscreen for various shapes and sizes.
Loek: For the axial caps I was referring to MKP's such as a 1uF 400V Solen or such. The elctrolytics will be standard radial (through-hole, or snap-in for the very large ones).
I noticed the VR3 (that's what happens if you add another component before deleting the old one first; it auto-increments. It's been fixed yesterday already but I didn't even think people would notice so I didn't repost hehe.I also moved the silkscreen at the bottom for the Ground and Signal since it was covered by the connectors.. this happenned when I moved the whole board down to conserve space and they didn't travel along. At the current location (sides) they don't make as much sense as on Al's board, but those who are confused can just look at his for guidance. Unfortunately vertical space is very limited so I cannot move their silkscreen to be at the bottom of the connectors.
Two smaller caps doesn't necessarily have less ESR. A bank of say 10 smaller ones may, but if you look at the datasheets it's ofen the case that it's more or less the same. But, it's not too hard to just add a lot of cropcircles on the silkscreen for various shapes and sizes.
Loek: For the axial caps I was referring to MKP's such as a 1uF 400V Solen or such. The elctrolytics will be standard radial (through-hole, or snap-in for the very large ones).
Improvements?
Hi
If you look at the schematics of the famous "A-40"class-A amp ano 1978 by Nelson Pass the "A-40" was equipped wit a big tantalum cap where the C-7 is located in the KSA 100mkII schematics. Would it be a benefit to use same solution as Pass did in this Clone amp?
I dont remember what was the reason for to use such a big cap in the A-40 (there must have been some), but could it lower total all over distortion and have a benefit for sound quality I vote for same solution:
http://www.passdiy.com/legacy.htm
Any wise comments to this issue or is it "to shoot over the targets"?
Regards
Hi
If you look at the schematics of the famous "A-40"class-A amp ano 1978 by Nelson Pass the "A-40" was equipped wit a big tantalum cap where the C-7 is located in the KSA 100mkII schematics. Would it be a benefit to use same solution as Pass did in this Clone amp?
I dont remember what was the reason for to use such a big cap in the A-40 (there must have been some), but could it lower total all over distortion and have a benefit for sound quality I vote for same solution:
http://www.passdiy.com/legacy.htm
Any wise comments to this issue or is it "to shoot over the targets"?
Regards
PWatts has also requested gold pads and it doesn't add hardly anyting to the cost of the boards so it ill be so.
Also is everyone hell bent for leather on using Dale(vishay) resistors? If so we can add those to the group buy if there is enough interest. They have always been my favorite resistor. Otherwise you guys will all have to fend for yourself in the resistir department. Perhaps you all have some other favorites to use.....
To the first person that checks the schematic against the board
design and posts back here he/she gets a free set of proto boards sent PPD. Then if the amp goes up in smoke we can all blame you
.
Mark
Also is everyone hell bent for leather on using Dale(vishay) resistors? If so we can add those to the group buy if there is enough interest. They have always been my favorite resistor. Otherwise you guys will all have to fend for yourself in the resistir department. Perhaps you all have some other favorites to use.....
To the first person that checks the schematic against the board
design and posts back here he/she gets a free set of proto boards sent PPD. Then if the amp goes up in smoke we can all blame you
.Mark
Guess I don't qualify for checking it
BTW Mark, before you have it made I'll send you an updated version; I've made a few additional changes and will probably keep on doing so every now and then. It will be nice if I could get the final dimensions of the original before then, so that if the prototypes work the tooling cost for new boards will not have to be repeated. Please also check the footrpints - The resistors were made for Dales to fit nice and snugly with their leads bent almost straight down, so anything larger may be problematic to fit. The current hole diameter is 1.2mm, which will shrink to 1mm after plating. This should be enough. Some of the larger Wima caps have very thick leads so I'll try to increase the pad size of the 100nF's.
I've had good results with a combination of Dale, Holco and Riken resistors in the KSA50, with the Rikens used in the most critical applications, but at $4 each they're hardly group buy material.
I'll also try to stuff the unused areas as full as possible with various sized electrolytics for a nice solid local power bank for those who want it.
BTW Mark, before you have it made I'll send you an updated version; I've made a few additional changes and will probably keep on doing so every now and then. It will be nice if I could get the final dimensions of the original before then, so that if the prototypes work the tooling cost for new boards will not have to be repeated. Please also check the footrpints - The resistors were made for Dales to fit nice and snugly with their leads bent almost straight down, so anything larger may be problematic to fit. The current hole diameter is 1.2mm, which will shrink to 1mm after plating. This should be enough. Some of the larger Wima caps have very thick leads so I'll try to increase the pad size of the 100nF's.
I've had good results with a combination of Dale, Holco and Riken resistors in the KSA50, with the Rikens used in the most critical applications, but at $4 each they're hardly group buy material.
I'll also try to stuff the unused areas as full as possible with various sized electrolytics for a nice solid local power bank for those who want it.