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Old 5th January 2005, 09:42 PM   #411
Vesa is offline Vesa  Finland
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OK. Thanks Stuart

-Vesa-
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Old 5th January 2005, 09:47 PM   #412
Coulomb is offline Coulomb  England
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Default Re: check here...

Quote:
Originally posted by Stuart Easson
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
Oh, I have a Plitron 750 VAC dual 30VAC I was planning on using!

Too much?

Regards

Anthony
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Old 5th January 2005, 09:56 PM   #413
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Default 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
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Old 5th January 2005, 11:32 PM   #414
K-amps is offline K-amps  United States
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Default Re: too much?

Quote:
Originally posted by Stuart Easson
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
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.
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Old 6th January 2005, 12:42 AM   #415
NUTTTR is offline NUTTTR  Australia
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Default 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
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Old 6th January 2005, 02:14 AM   #416
Coulomb is offline Coulomb  England
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Thanks for the responces, I will re read through the trhead for the Biasing tips.

Regards

Anthony
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Old 6th January 2005, 02:44 AM   #417
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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
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Old 6th January 2005, 06:34 AM   #418
Jozua is offline Jozua  South Africa
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Hi

Please add me to the list- I need boards for two stereo amps.

Please advise how and when payment is required ?

Maybe somebody can organise a group buy of top notch quality parts for boards and output devices as I am sure most of us can source the tranformers , caps and cases locally ?


Thanks.


Jozua
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Old 6th January 2005, 09:48 AM   #419
wim is offline wim  Netherlands
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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??
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Old 6th January 2005, 01:06 PM   #420
K-amps is offline K-amps  United States
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Quote:
Originally posted by wim
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??

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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