Krell KSA 100mkII Clone

HI

Today I picked up a pair transformer for these project .
Each transformer has a 39.8V-0-39.8V sec. 120V prim. and 8.8A .
Any opinion about these transformers .
I know it would be better if 10A or more but these transformers were very cheap .
May be I go a bit with a lower bias .

Regards
 
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gaborbela said:
HI

Today I picked up a pair transformer for these project .
Each transformer has a 39.8V-0-39.8V sec. 120V prim. and 8.8A .
Any opinion about these transformers .
I know it would be better if 10A or more but these transformers were very cheap .
May be I go a bit with a lower bias .

Regards


twice 700VA looks good enough for me
 
HI
Thanks .
I think is bigger than 700VA even they marked for 8.8A .
It is almost the same size like 1KVA Plitron .
I payed $30CAD for each .
I just tested under power they are nice quiet , for load I hook up the 1500VA hair dryer and no hum at all .
I hope it will be OK with a lower bias for the KSA-100 .

Regards
 
Zen Mod said:



lower?
just crank it

Let me guess - you haven't had a 600W heater in your room when it is 42-43 degrees day outside ? Even with aircon on full blast I can feel the thing radiate heat from 3 meters away.
Big Krells work just fine biased at ~30W full class A (for me at least, and at least in summer).
You can always crank it up in winter if you feel like you're missing something. Mine are in fact sitting on ~1.5A bias all the time now. Can't really say I can hear much difference.
(this is with 16 pairs of 15003/4 in the output stage and with output feedback loop disconnected)
 
Not the best shot ...
 

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Hi,
what temperature does the heatsink run at?
What is the temperature difference between the sink and the aluminium spreader plate and between the spreader plate and the Q cases?

I think your transistors my be running a bit hot, particularly if you bias it up to the full value of 2.6A in the mk2 (what is the mk1 bias?).
 
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Bratislav said:


Let me guess - you haven't had a 600W heater in your room when it is 42-43 degrees day outside ? Even with aircon on full blast I can feel the thing radiate heat from 3 meters away.
Big Krells work just fine biased at ~30W full class A (for me at least, and at least in summer).
You can always crank it up in winter if you feel like you're missing something. Mine are in fact sitting on ~1.5A bias all the time now. Can't really say I can hear much difference.
(this is with 16 pairs of 15003/4 in the output stage and with output feedback loop disconnected)

my "cranking" comment was related to 700VA xformers ability to drive stock biased one channel;
nothing more......

btw- bias issue is certainly related to exact amp-spks combo ,especially when you count on temp issues.......thinking of that-I'm lucky,just because temp in my place isn't higher than 35-38 Celsius at Summer
 
How about building a few KMA 100 revII's with a 2-level Class-A bias selector switch on the PCB? This strategy would give a pretty universal amplifier solution from one common design. I think a well designed KMA100, even with reduced bias, would have better sonics than the KSA50 based upon my past experience on my Apogees. The symmetric MOS diff-pairs should provide good isolation of the speaker's back EMF from the voice coil inductance, and a voltage regulator for the driver stages should extend this separation. This is why I suggested a single PCB KMA100 design suitable for a compact monoblock.

I'm interested how the ears on this tread think the DIY KSA100 and KSA50 compare.

My latest amp has a switch for 12A or 20A of Class-A bias. My power supply is only +/- 5V, but I still need two KL-271 tweleve inch long heatsinks.
 
Krell Power Switch- Help ?

Hi

I received a quote from the local Krell agent for a replacement power switch for my Krell Mk2. Total cost - $400.00 !!

Does anybody know where one could source these switches from? It is not that I dont mind paying but $400-00 is a tad heavy for what I suspect is nothing more than a fancy trip switch.



Jozua
 
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Re: Krell Power Switch- Help ?

Jozua said:
Hi

I received a quote from the local Krell agent for a replacement power switch for my Krell Mk2. Total cost - $400.00 !!

Does anybody know where one could source these switches from? It is not that I dont mind paying but $400-00 is a tad heavy for what I suspect is nothing more than a fancy trip switch.



Jozua


mebbe this one is made of preputium?
 
I'm interested how the ears on this tread think the DIY KSA100 and KSA50 compare.

My KSA-100 biased at just 300mv blows the pants off the KSA-50 biased at spec.

Smoother mids and highs that are far better defined.
Neglagable congestion even at loud levels.
A soundstage depth and width that made my speakers virtually disappear.
A slam factor that rattles my front windows and floor!

Keep in mind that we have not actually built the KSA50 MK-2 version. I believe ours is a MK1.5 version. Until someone puts this pcb in a KSA-50 we won't have a fair comparison of the two MK-2 versions.

mebbe this one is made of preputium?

No, not quite... the metal for the contacts comes from this unobtanium mine in the west Utah desert... seceretly owned by Dan himself:D . You can go in and get the switch material if you want to but its dangerous down there... snakes scorpions and large rolling boulders(not the amplifier) and poison darts... a job for Indy for sure.... or Dan for the price he is getting!



Mark
(Live from Stockman's Casino dinning room in Beautiful Elko Nevada!)
 

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