Need a krell 300i amp schematic

[mikeks]

.......Krell's business model....

Nothing wrong with Krell's business model, in contradistinction to their technical model.

On an intellectual basis, I just wouldn't pay many thousands of dollars for their designs: simply not worth it-not even close.

For a start the output is ''fused''...

 

[Ipanema]

high input impedance of 210k ohms.

Balanced/single-ended input conditioning is achieved with Krell's discrete FET-input, class-A amplifier.

http://www.stereophile.com/integratedamps/809/index1.html

Reading the Stereophile review, 210K input impedance and Fet input stage is not found in the Krell Schematic posted. Is the schematic accurate?


The feedback of KSA100 is taken from the output stage, while the feedback for 300i is taken from the predriver stage making the output stage outside the feedback loop without any feedback correction. How good will the non-feedback output stage perform? Has anyone try this by modifying the KSA board?

 

[mikeks]

How good will the non-feedback output stage perform?

Not good.

 

[Ipanema]

Krell is going backward in their design?

 

[pinkmouse]

Krell is going backward in their design?

Mikeks has strong personal opinions as to what is right and wrong in amp design

 

[Mark A. Gulbrandsen]

If the driver and output devices are well matched in hfe, bandwidth, current sharing the output stage should actually work very well.... although I personally don't see any problem with an output satge like the KSA-100 MK-2 that gives its feedback fomr the output.

Mark

 

[Bratislav]

If the driver and output devices are well matched in hfe, bandwidth, current sharing the output stage should actually work very well.... although I personally don't see any problem with an output satge like the KSA-100 MK-2 that gives its feedback fomr the output.

Mark

I think the idea is to isolate sensitive feedback circuit from any back EMF issues, or even possible RF interference.
I can confirm that well matched, multi paired output adds very little to distortion figures when left out of the feedback loop.
In fact when Nelson went to design A75 one of the suggestions was to try to leave the output stage ouside the feedback loop. It may measure slightly worse but again then in may sound better

 

[B.L.]

I can't find Q70 and Q71 on partlist. What kind of transistors are there?

 

[soundcrafters]

krell 300i parts etc.

I will check my amp to see what they are, Q70 , Q71 driver trans. It may be some time as I have to remove the driver pcb to see them.

Also my amp has OP42g [ic] and Ltc8043 [ic] on driver pcb.

outputs are krell 484081 9835 mexico
and 484002 9830 mexico.

 

[jacco vermeulen]

How good will the non-feedback output stage perform?

Pretty good, search for Reinhard Wachowiak/Audiolabor Stark.
I suppose the custom Krell device output stage is fast, like the 6 cylinder Sanken MT200 in the Stark

For the ones for whom it's not old news: such an output stage benefits from AC-filtering.
Why us overhere had Aha New Tube with a module for the 300i, aka AH Njoe Tjoeb in Cheesy Windmillo English.

 

[GK]

 

[jacco vermeulen]

Mr Kilowatt Kleinschmidt must feel it needs at least 3 rail voltages and 50 output devices more to be any good.

I recollect a snubber from Portugal who favored having more money in the outer dress and an RC than the component and circuit quality, cost of the 300i was close to $6K overhere

 

[GK]

Mr Kilowatt Kleinschmidt must feel it needs at least 3 rail voltages and 50 output devices more to be any good.

For the cost of a Krell it should have that three times over......

 

[jacco vermeulen]

Haven't you heard, Krell cherishes it's hot amp aura so much that they came up with downsizing the heatsinks to raise the temperature.
No problemo for the 300i successor, the 200 watts are just for flashing anyway.
What are the odds Carlos the snubber already bought himself a 400 ?

Maybe Al should do a board layout for a 4 to 6 MJE1503* parallel device output stage, like the 400xi has.
Combined with his KSA50 main/driver board they'd make an affordable low bias power amp kit.
10 watts in A and 50-75 in Class AB makes more sense than cloning a 200 watt budget circuit.

Shoot, why not add a ccs, cascode the input stage and revamp the Vas arrangement of the KSA50 in one go.
BSA50 : the Blame Self Amplifier

(purely by coincidence, i happen to have a stereo set of main/driver boards left from the KSA50 works)

 

[soundcrafters]

krell 300i transistors/schematic

I can't find Q70 and Q71 on partlist. What kind of transistors are there?

Hi my krell 300i does not have a Q70 or Q71 listed on the pcb.
10-9-95 100-087-01 rev- B

What is missing is from the list is, Q25,= F15030 and
Q26, = F15031 motorola tab style.

I need the schematic for the preamp with a parts list.
11-17-98 100-087-02 rev-E

 

[soundcrafters]

Re: KAV300I preamp schematic, parts list needed.

KRELL300I AMP

Please Help
Krell 300i
I need the schematic for the preamp with a parts list. The resistors are burned to black.
11-17-98 100-087-02 rev-E

Q1 - Q52
and resistors R1 - R100 ???
IC's - four are on the pcb.

Thanks you are the Greatest!!!!!

 

[pinkmouse]

Maybe Al should do a board layout for a 4 to 6 MJE1503* parallel device output stage, like the 400xi has.

Already done and running with 5 pairs.

Shoot, why not add a ccs, cascode the input stage and revamp the Vas arrangement of the KSA50 in one go.

Draw me up a schematic, and I'll give it a go. Due to my PC catching fire, I lost all my old and projects in development, so I'm looking for a fresh start of new stuff.

 

[GK]

Shoot, why not add a ccs, cascode the input stage and revamp the Vas arrangement of the KSA50 in one go.
BSA50 : the Blame Self Amplifier

Good idea. There is very little point, in my opinion, of going the class A route if you're going to stick to an overly simplistic circuit topology that will only ever perform comparably to a medicore class AB design.

Cheers,
Glen

 

[soundcrafters]

need krell 300i preamp parts list etc.

Please Help
Krell 300i
I need the schematic for the preamp with a parts list. The resistors are burned to black.
11-17-98 100-087-02 rev-E

 

[bra]

Here is very nice PCB: http://www.andiy.com/admin/pic/kav300i-1.jpg