Krell KSA 100mkII Clone

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#2,741
Ricren said:
io, looking for the best thermal pads for the TO3 devices. Would this be the best choice?

SP900S-0.009-00-02 Bergquist | Fans, Thermal Management | DigiKey

thanks.
Click to expand...

Regarding the thermal pad performance, you want a high thermal conductivity. However!!! this has a direct relationship with cost😀...what a surprise!!!
So here is a short list of available products...

1)BERYLLIUM OXIDE +- 330 W K−1 m−1

4003G Aavid Thermalloy | Fans, Thermal Management | DigiKey

2)Aluminum Oxide +-15.06W K−1 m−1

4103G - AAVID THERMALLOY - Thermal Insulator, Thermal Insulator, Aluminium Oxide Ceramic, 15.06 W/m.K, 2.03 mm | Newark element14

3)Silicone elastomer +-6W K−1 m−1

DC0001/01-H48-6G-0.3-2A t-Global Technology | Fans, Thermal Management | DigiKey


There is also an excellent product made in Germany, if you can find a source. Keratherm Red +-6.5W K−1 m−1

http://www.kerafol.com/fileadmin/us.../01-standardfolien/Datenblaetter_TM_86_82.pdf

Hope this helps,

Cheers Eric
 
#2,742
konst said:
What is the maximum voltage the driver boards can be ran at? I have a Krell KMA200 PSU including regulator, but it runs -+80v for the driver board and -+70v for the output devices.

What changes would need to be made to adapt this to those voltages?
Click to expand...
you should be looking at the current through all the devices to see which will change when you change the voltage.
Then ask yourself:
Do I need to change any value to maintain the SAME currents?
Then you need to look at the maximum voltage ratings of all the devices and see whether the higher voltage takes any device too close or past it's rated voltage.
The you need to look at power dissipation in all the devices.
Again you need to ask yourself:
Do I need to change any value/devices to maintain the SAME temperature de-rated SOAR used?
 
#2,743
AndrewT said:
you should be looking at the current through all the devices to see which will change when you change the voltage.
Then ask yourself:
Do I need to change any value to maintain the SAME currents?
Then you need to look at the maximum voltage ratings of all the devices and see whether the higher voltage takes any device too close or past it's rated voltage.
The you need to look at power dissipation in all the devices.
Again you need to ask yourself:
Do I need to change any value/devices to maintain the SAME temperature de-rated SOAR used?
Click to expand...

Sounds like a plan, I might need some help here.... Anyone want to have a go, I am very happy and willing to put in the time, but the math will fail me!?
 
#2,746
konst said:
What is the maximum voltage the driver boards can be ran at? I have a Krell KMA200 PSU including regulator, but it runs -+80v for the driver board and -+70v for the output devices.

What changes would need to be made to adapt this to those voltages?
Click to expand...

I for example took max capcitor voltage as reference.
Depends on what you want to sacrifice , capacity or Voltage.
I guess it would run fine even with 50vdc
 
#2,749
After some queries I received there seems to be a revival of interest in this amp. I still have the original design source and can make the Gerbers available for those wishing to have their own boards made (much cheaper and easier nowadays via China than back in 2006).
I can also include a couple of small changes if required. Silkscreen and some pad geometries can definitely do with improvement and (despite being a different visual look to the original) changing the driver heatsink to an COTS model instead of relying on customized heatsinks that deterred many builders.

If there's enough interest for a GB I will be happy to provide Gerbers but will not manage the GB myself though.
 
#2,754
PWatts said:
After some queries I received there seems to be a revival of interest in this amp. I still have the original design source and can make the Gerbers available for those wishing to have their own boards made (much cheaper and easier nowadays via China than back in 2006).
I can also include a couple of small changes if required. Silkscreen and some pad geometries can definitely do with improvement and (despite being a different visual look to the original) changing the driver heatsink to an COTS model instead of relying on customized heatsinks that deterred many builders.

If there's enough interest for a GB I will be happy to provide Gerbers but will not manage the GB myself though.
Click to expand...

maybe you can post the files for the 8 output driver version (MJL´S) too?
thx
 
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#2,755
#2,756
I have a design done for 8x TO264 output pairs per channel (1x PCB with 8x NPN or PNP) that was intended to flank the mainboard on a uniform flat heatsink. Nothing special about it, but the dimensions were a visual match for the mainboard and laid out for wiring to be optimally short and symmetrical.

I would primarily like some feedback from past builders about what could be improved within reasonable effort while keeping the main original parameters (dimensions, mounting hole compatibility, 2layers) the same.
 
#2,757
@PWatts

Looking through the KSA-100 files stored in my computer made me realize I don't have a copy of the schematic you used to create the PCB. I have a copy of the one Lloyd MacLean posted on his web site, but it does not have the alternate devices you introduced. Would it be possible for you to post your schematic?
 
#2,758
grimberg said:
@PWatts

Looking through the KSA-100 files stored in my computer made me realize I don't have a copy of the schematic you used to create the PCB. I have a copy of the one Lloyd MacLean posted on his web site, but it does not have the alternate devices you introduced. Would it be possible for you to post your schematic?
Click to expand...
I have a source schematic but I don't really see why it's necessary since I kept all the parts and even designators the same, so together with the clone BOM there is no real need for another schematic.
 
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