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Old 19th March 2010, 04:59 PM   #1
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Post KrellClone KSA100-MKII Power Supply

I am building a KrellClone KSA100-MKII amplifier and need help deciding on the power supply design. When you make recommendations try to keep within the following scope:

1) Overkill - Keep every part with the thought of "over designed" if it says within the chassis dimensions
2) Quality Number One Importance - I am not concerned with the price, I am concerned with the quality of each part
3) Internal Chassis Dimension 258mm W x 143mm H x 358mm D

Does anyone have a schematic to help me choose the correct parts?

What Transformer do you recommend? What are the "perfect" values on the secondaries?

What Capacitors do you recommend?

What Rectifiers do you recommend?

Thanks!
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Old 19th March 2010, 05:10 PM   #2
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Post Krell KSA100 MKII Schematic

I just wanted to add the schematic I was using just in case it changes anything.

How does the schematic look? I bought the boards from Honk Kong, really nice quality boards with Gold Traces.
Attached Images
File Type: jpg Krell KSA50 MKII main board Sch.jpg (75.8 KB, 965 views)
File Type: jpg Krell KSA50 MKII output board Sch.jpg (31.2 KB, 928 views)

Last edited by xerocomm; 19th March 2010 at 05:12 PM. Reason: Spelling Error
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Old 22nd March 2010, 04:17 PM   #3
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This is a bad sign, no response. I guess no one has spent time on this design in a while? Can anyone direct me to a forum that has recently built a KSA100 MKII?
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Old 22nd March 2010, 05:19 PM   #4
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Krell KSA 100mkII Clone

Biased to 100W (aka 2.5A) you'd need 700VA/40Vac per channel minimum.
Option 2 is biasing to full output, on 1000VA/ch.

Preferred electrolytics are CG type big cans, 100C minimum, 125C if you can spare the extra dollars and cents.

Superior rectifier bridge diodes are fast/soft recovery types, TO247 package.
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Old 22nd March 2010, 05:32 PM   #5
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The subject of Krell clones and their construction has been well visited in another series of threads. You can use the search function to find the details.

In most cases people opted for the same capacity and quality as stock or better. My personal preference is to keep the capacity of the power supply at or lower than the de-rated thermal capacity of the output transistors. My last build (with Neil Kaye) for 100W class A/8ohm, was a 600W toroid with ~40000uF with 6 output pairs per channel. With fan assisted cooling each channel weighed #35...

In this instance you have not provided enough info for anyone to make informed comments. For instance what goals do you have for this amp? Not deciding this up front will cause you a world of hurt later on...

Some items for you consideration:

Class A output power into what load? (idle current)
Lowest impedance load (peak current)
Class B output power? (rail voltage)
Stereo build, or dual mono? (transformer capacity)
Do you plan on using fans? (mass and volume)

AFAICT your chassis is just large enough for internal passive cooling of a single ~50W channel for 8ohm use or stereo 50w if fans are used.

If you make a stereo 50W amp, in addition to making beautiful music, it will be a very heavy space heater. They only get bigger, heavier and hotter from there.

None of the above is about sound 'quality' per se, rather quality of engineering for the given task.

You can select the 'best sounding' components once you know what values are appropriate for the task you are attempting.

HTH

Stuart
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Old 3rd April 2011, 05:37 PM   #6
xslavic is offline xslavic  Moldova
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hello,im interested in building myself one amp,please tell me the site where you bought the boards,or if you have a spare kit for mer...thanks
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Old 18th February 2012, 02:09 AM   #7
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Quote:
Originally Posted by xerocomm View Post
I just wanted to add the schematic I was using just in case it changes anything.

How does the schematic look? I bought the boards from Honk Kong, really nice quality boards with Gold Traces.
I use same circuit for my KSA50... it sound nice. I use it to replace my Aleph 5. Of course, I am not sure if the circuit is good for the KSA100
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Old 25th February 2012, 10:29 PM   #8
spurlte is offline spurlte  United States
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Default Chinese PCBs

Quote:
Originally Posted by Stuart Easson View Post
The subject of Krell clones and their construction has been well visited in another series of threads. You can use the search function to find the details.

In most cases people opted for the same capacity and quality as stock or better. My personal preference is to keep the capacity of the power supply at or lower than the de-rated thermal capacity of the output transistors. My last build (with Neil Kaye) for 100W class A/8ohm, was a 600W toroid with ~40000uF with 6 output pairs per channel. With fan assisted cooling each channel weighed #35...

In this instance you have not provided enough info for anyone to make informed comments. For instance what goals do you have for this amp? Not deciding this up front will cause you a world of hurt later on...

Some items for you consideration:

Class A output power into what load? (idle current)
Lowest impedance load (peak current)
Class B output power? (rail voltage)
Stereo build, or dual mono? (transformer capacity)
Do you plan on using fans? (mass and volume)

AFAICT your chassis is just large enough for internal passive cooling of a single ~50W channel for 8ohm use or stereo 50w if fans are used.

If you make a stereo 50W amp, in addition to making beautiful music, it will be a very heavy space heater. They only get bigger, heavier and hotter from there.

None of the above is about sound 'quality' per se, rather quality of engineering for the given task.

You can select the 'best sounding' components once you know what values are appropriate for the task you are attempting.

HTH

Stuart
Class A output power into what load? (idle current)--Whatever it
takes to power at 100watts.

Lowest impedance load (peak current)--4ohms, but all my speakers are 8 ohms.

Class B output power? (rail voltage) -- Trying to stay at Class A.

Stereo build, or dual mono? (transformer capacity) The Chinese PCBs are for two MONO main boards and four for each main board (each driver PCB has either 2 each 2SC2240s or 2SA970S). I attached a photo of the PCBs.

Do you plan on using fans? (mass and volume)--I hope not. I read that fans break down easily and spread dust everywhere.
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File Type: jpg IMG_1366.jpg (705.6 KB, 627 views)
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Old 26th February 2012, 04:41 AM   #9
spurlte is offline spurlte  United States
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I meant 4 driver boards for each of the 2 main boards. 2 driver boards are either V+ or
V- oriented. You can use only 2 driver boards for each main board if you want a KSA50 setup. I really wanted to try for the KSA100 MKII setup. I want to "FEEL" the music in my bones. I am wondering if anyone might have a schematic and parts list for a workable power supply and where I might obtain a soft-start for this setup.
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Old 26th February 2012, 11:54 AM   #10
xslavic is offline xslavic  Moldova
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Default offer

hi
ive read youre posts but,dont buy these boards thery are not ok for the task
i have 2 pairs very well made,that were perfected here on diyaudio.com
an i saw on ebay, look for it
i will sell these for 100 usd free shipping, -they can take pwoer caps on the pcb

ive built mine using 1x 2kw transformer ,and very good resistors
2sa1943 2sc5200 ,excellent choice ,buy the right one not that cr,p
you will have problems and youll be forced to do it from the begining
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