Krell KSA 50 PCB

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troystg

troystg

Member
Joined 2004
Hey Jan-

As you might have seen, I have gotten a reasonable quote for good PCB's, and have created the wiki.

I hope to place the order for PCB's next Friday the 14th.


Your pair of boards will be complementary from those that order some to show our appreciation.

Please excuse me for this but I will post this link constantly so it is easy to find.

http://www.diyaudio.com/wiki/index.php?page=KSA-50Wiki
 
V

Vesa

Member
Joined 2004
PSU?

I wonder is there any 'final conclusion' of this amplifier PSU? I have seen there a few thoughts about transformer. Secondary voltage and power.

For example 30-0-30VAC and 300VA / channel? Maybe that is quite minimum power?

How low and how high secondary is suitable?

Sorry about my dummy question, but I'm not 100% sure with this :confused:

And many thanks to Jan. Fine work :yes:
 
Coulomb

Coulomb

Member
Joined 2002
diyaudio.com/wiki/index.php?page=Active+Group+Buys
Re: check here...

Stuart Easson said:
Hi,

In the discussion around post 230, I think it was concluded that 26v AC secondaries at approx 250va per channel would be close to what the KSA50 had from the factory. By the time you get to 30v AC and above you are in KSA100 territory and generating more heat etc.

Stuart
Click to expand...

Oh, I have a Plitron 750 VAC dual 30VAC I was planning on using!

Too much?

Regards

Anthony
 
Stuart Easson

Stuart Easson

Member
Joined 2002
too much?

As far as I know there is no electronic problem using the 30v AC secondaries. The key is to make sure you have enough heatsinking and outputs. The extra voltage translates into more power, both in the load and in the outputs, so depending on your specific needs, 30v AC may be better.

The amount of class A power depends on the bias (and therefore heatsinks), the amount of class B power depends on the voltage of the rails (and therefore heatsinks).

The discussion in the posts before number 230 describe the biasing and voltage demands of the various power levels, specifically detailing the known values for a ksa50 and ksa100, voltage and bias current.

Hope that helps

Stuart
 
K

K-amps

Member
Joined 2003
Re: too much?

Stuart Easson said:
As far as I know there is no electronic problem using the 30v AC secondaries. The key is to make sure you have enough heatsinking and outputs. The extra voltage translates into more power, both in the load and in the outputs, so depending on your specific needs, 30v AC may be better.

The amount of class A power depends on the bias (and therefore heatsinks), the amount of class B power depends on the voltage of the rails (and therefore heatsinks).

The discussion in the posts before number 230 describe the biasing and voltage demands of the various power levels, specifically detailing the known values for a ksa50 and ksa100, voltage and bias current.

Hope that helps

Stuart
Click to expand...

I have a KSA-100 Mk. II be glad to make basic measurements. The rails are +/-53.5vdc. The bias is set at 690mV across each 1 ohm emitter resistor. Thats makes it biased to 120watts Pure class-A.

You could still use the 30-0-30 AC Plitron, just don't bias it too high, let it ride into A/B or B after that. As Stuart says it all depends on your heatsinking.

On the KSA-100, the drivers and regulators also run hot and are heatsunk separately. :)
 
N

NUTTTR

Member
Joined 2004
Power Supply

I'm using 30vac toroids, 800va each....
I'm doubling the output transistors and there will be massive heatsink area... Potentially i'm looking to get 150w+ @ 4 ohm of full class A, obviously though this may produce stupid amounts of heat, so may have to resize!
I'm using 112,000uf of capacitance per channel... I'm building a 3 channel and a 2 channel (with/for a mate) :)
I'm ordering 8 boards just in case i need a spare or two!
Aaron
 
M

Mark A. Gulbrandsen

Member
Joined 2001
Thanks for creating the WIKI!! I added 10 boards and the total is now up to 65. If we can get it higher perhaps the price could be lowered.... but 10 bucks is pretty low already.

If question I have is that I sometimes travel.... Would it be possible to e-mail everyone and let us know when the fuinds are due? I don't want to niss out because I'm out of town somewhere!!

Thanks,

Mark
 
W

wim

Member
Joined 2003
There is one thing i dont understand. The original schematic from the Krell KSA50 (and the earlyer schematics from Jan) shows 2 outputtransistors per rail per channel. The outputboards jan designed show 3 outputtransistors per rail per channel.

Why is this?? To get more outputpower??
 
K

K-amps

Member
Joined 2003
wim said:
There is one thing i dont understand. The original schematic from the Krell KSA50 (and the earlyer schematics from Jan) shows 2 outputtransistors per rail per channel. The outputboards jan designed show 3 outputtransistors per rail per channel.

Why is this?? To get more outputpower??
Click to expand...


Call me crazy but I will bridge 2 channels of the KSA50 to get about 200 watts. 50 class-A rest AB. Woohoo!

By the way I too plan to use 30-0-30 as I have 10 Adcom 555 toroids lying around that are 60-0-60, I will just conncect primaries in series.

Point I was trying to make, for some unknown cosmic reson, SS amps with lower rails sound better.... so 30-0-30 will not quite have the magic of 20-0-20 etc.
 
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