Krell KSA 50 PCB

[still4given]

One more question.

In the parts list it lists resistors as;
9K1
3K39
4K7
1K5.

What do these values mean?

Sorry for the newbee questions.

Thanks Terry

 

[Stuart Easson]

check the construction wiki for this project...

I'll go read it again, I'll add what I know that isn't already there, it would be cool if everyone else could do the same...

Mark, those amps look beautiful, I hope I can get the larger one to look one tenth as clean...

Stuart

 

[Mark A. Gulbrandsen]

Actually the best place for this is on the KSA-50 web site. I will begin to gather together al the stuff and get it posted there this weekend. I may need some help getting photos and diagrams posted but hopefully Brian GT will help with that. If he's busy( and I'm sure that he is) I may need another html literate person- volunteer to help out with getting the site situated I think Brian already has at least several cups of coffee going so are there any volunteers out there just in case?

Again, I will be out of town installing new projectors in a cinema up in Idaho the rest of the week but I will have my laptop with but infortunately just via modem at what ever motel I end up at.... I will however peek in while on the road and see whats going on.

Mark

 

[Mark A. Gulbrandsen]

What do these values mean?

Terry,
Ask away! If I don't know the answer or see the post someone else will eventually chime in.

9K1 = 9.1K

3K39 = 3.39k

4K7 = 4.7k

1K5 = 1.5 k

____________________________

Thanks Stuart, This set of boards was a real pleasure to wire up! That #$$&&!!!!! broken tap....... I can't wait for Jacco's comments on the lack of wire in there.

Mark

 

[Stuart Easson]

building guide wiki...

...is at:

http://www.diyaudio.com/wiki/index.php?page=Building+guide

I have added 'normal' voltages for test purposes, plus transformer and cap info...

If finding the exact value of the resistors is difficult (I wouldn't really know I didn't try) using the standard 5% values nearest to the one specified works perfectly. You can get every value you need at radio shack if you are in a hurry...or at least I did...

Later on, for the next couple of channels, I went to the local electronics store and got some nice 1% metal film...

Stuart

 

[jacco vermeulen]

This set of boards was a real pleasure to wire up!

Very clean looking setup. I think a lot of people on the wiki will be pleased with wiring the boards and the end result, including me.
Even the strange bird from Prague is pretty quiet !
Beefy amplifiers without salad look so much better.

For the toshiba's : http://mcm.newark.com

 

[Upupa Epops]

Don't worry, Jacco 😉 , I'm waiting for end results 😀 .

 

[jacco vermeulen]

Mr Green,

i took a look at the pictures of your heat duct setup.
I counted 77 holes, if they have a 1/3" diameter airflow speed will be in the range of 27 ft/sec, with a 70 cbft/min fan.
Even if you derate the fan to 50% airflow speed through the holes will be too high.
Which will lead to turbulent flow because of the edges of all those holes, and have a serious effect on your fan efficiency,imo.
Better than adding many more holes would be to increase the diameter of the holes.
If you can i would clean the holes with a smoothing bit after you've drilled them, even better would be to smooth the edges.

(a 120mm fan has a cross section of 18 square inches, 77 holes of 1/3" diameter only add up to 6, >> 1/3d)

 

[AndrewT]

Hi,
you did say this was the bottom panel?

How about cutting the panel out & inserting one of those wire grids that cover computer fan openings? Just keep the lugs for the standoffs.

 

[pinkmouse]

The proto type amp is all up and running just fine on the bench supply so Al you can sleep now...

Yeay!

I'm glad you approve of the neatness, it's one of the things I was trying to achieve, despite the separate board strategy. One thing you might want to try to cut down distortion, is to run each board with it's own feed from the PSU caps, and of course the option is there to use Pavel's decoupling caps.

Gengis, I'll get back with the cap sizes later, or you can just print out a copy of the board layout and measure them if you're in a hurry.

 

[K-amps]

I get them from MCM Electronics in Ohio. They are dirt cheap like a quarter each. I am pretty sure its www.mcmonline.com

Mark and me and websites... I think it is www.mcmelectronics.com, another vendor I use for dirt cheap prices is www.makelectronics.com.



🙂

 

[Mark A. Gulbrandsen]

Mr. Green needs to get a sabre saw and just cut one large hole for the fan. Forget all those small holes.... that won't work very well!! Too much turbulance and you will have to run the fan at alot higher speed and the resulting noise will be very distracting.

Mark

 

[still4given]

I've got a question about the way Mr Green is using his fan as well. Wouldn't it be better to mount the fan at the bottom and blow into the tunnel rather than at the top where it is drawing hot air? Seems the life span of the fan may be seriously reduced by the heat.

Thanks, Terry

 

[VT67]

In my opinion that's the way to go Terry, as I mentioned in my earlier post (2024)

Regards

 

[pinkmouse]

Seems the life span of the fan may be seriously reduced by the heat.

I would have thought that if the air the fan is sucking is hot enough to damage it, then the amp is probably already in meltdown...

BTW, in general, you want to blow air onto a heatsink, as this disrupts the laminar flow and cools the surface more effectively.

 

[jacco vermeulen]

Wouldn't it be better to mount the fan at the bottom and blow into the tunnel rather than at the top where it is drawing hot air?

Fans have better efficiency when blowing than sucking.
Sucking they create underpressure in the duct, when blowing an overpressure.
Higher pressure means higher massflow.
Al covered the turbulence bit>> with laminar flow there is a layer of air over the heatsink that reduces friction and isolates thermally.

I think Mr Green will be sorry he chose a 70cbft/min fan

 

[lgreen]

Input Board

OK OK OK OK Enough about the fan and the vent holes! I appreciate the comments but, and you can quote me on this-

I will be the happiest man on earth if the biggest problem I faced was heat on the output stage. Must get circuit working!!! Heat can be easily fixed. Last time I show you guys anything of my work in progress


Soo, how about those driver boards?

Here are mine:

An externally hosted image should be here but it was not working when we last tested it.

oops. didn't meant to show these so soon...You all will probably make fun of my huge zener diodes.....and tiny heat sinks....

All assembled except C105 and C106...I recall a discussion about 1,000 posts ago regarding the proper values for these...they are listed as 390 pF but I think people were using 100pF??? Have I got that right?

For those of you getting parts, look at the handwriting on the parts list. You see that the resistors you can order (I used Mouser - dale CCF I think) don't match the parts in the schematic, so I wrote in the next closest that I could find in a 1% tolerance. I hope these work but if you see anything wrong, let me know.

Now, about C106 and C105???

 

[wim]

Igreen, For C105 and C106 i did see in several earlyer posts two values: 33pF and 47pF. I do not know wich one is the best.

 

[still4given]

Re: Input Board

OK OK OK OK Enough about the fan and the vent holes! I appreciate the comments but, and you can quote me on this-

I will be the happiest man on earth if the biggest problem I faced was heat on the output stage. Must get circuit working!!! Heat can be easily fixed. Last time I show you guys anything of my work in progress

Aren't the pictures of the boards "anything of my work in progress"

😀

Why don't you reduce the size of the pictures a bit so they fit on the screen?

Blessings, Terry

 

[pinkmouse]

I got down as far as 22pF, but I was checking all the way with a scope. To be honest there isn't much difference anyway, so you won't go wrong with the 47pF, and it gives you an extra margin of stabilty.