Hi Pavel
Yes, they will be beefed up, but I left them as is for clarity.
It does, sort of...
The size of the board lead to some limitations in placement, and as I go along I will be optimising it, hopefully to make it look a bit more symetrical, and clean it up a bit.
Yes, they will be beefed up, but I left them as is for clarity.
This amp have quite symetrical connection, PCB not. Why ?
It does, sort of...
The size of the board lead to some limitations in placement, and as I go along I will be optimising it, hopefully to make it look a bit more symetrical, and clean it up a bit.
With the free version of Eagle, the size of the board is limited to 50mm by 75mm.
The layout may be "weak", that's why I'm asking for opinions, I want to make it better!
Anyway, is the use of a ground plane a good idea for designs like this, or should I be looking at starring the grounds?
The layout may be "weak", that's why I'm asking for opinions, I want to make it better!
Anyway, is the use of a ground plane a good idea for designs like this, or should I be looking at starring the grounds?
Upupa Epops said:I have any comments to this connection, I see it at the first time. Is interesting, how mostly of amateurs have delay in thinking - Hood, Hiraga, Leach etc. - all this connections are 20-30 years old, while hottest news like Halcro ( patented
Upupa - I think this mostly is coming from the fact that newer amps are 99% more complex inside i have found!....
The Krell has a SIMPLE simple simple mainboard...... the leach is simple too, but the likes of M.L. have massively complex circuit boards on the newer ones, several boards... this makes construction harder and harder, we don't have the money to spend to build something like that... Krell is very very simple and also "sounds very good"..... This i now have evidence of
...I've taken my H/K surround sound amp (which i always thought sounded VERY good for what it was) and added preouts for the fronts and centre and the difference is AMAZING.... using the krell and a peavey amp to run it all the sound is totally different!
Halcro is unlikely to release their schematics to anyone... and we are unlikely to buy one to pull apart and copy....
We may open it up and find a few Krell KSA-50's lying in there
Aaron
NUTTTR said:
This one
Why should you avoid it? Was there something wrong - or is the schematic questionable? There is a LOT of varying values, etc for the parts, which makes me wonder who's right
I have been using the drawing you refer to and it dose not tie up with my amp krell ksa 50 mk1 about 1983 number 543. it also sugests the bias is set to 620mv. does any one now the correct bias value or should I say the factory recomended setting.
after a little mishap I have now replaced the original roe caps with black gate 1000uf 16v then set the bias to about 600mv. but on testing the amp it sounded terrible, no base and a very bright treble something is far wrong! any ideas as to what has happened. before I changed the bias it was about 440mv. I have also tryed changing it back to 44mv.
Iain
Iain
Well, this is all very interesting. It seems strange that schema is wrong, as it comes from a guy who fixes them for a living.
Anyway, definitely don't use that layout I posted earlier, some of the transistors have the wrong pin-outs. I have just been spending time learning how to build new components, so I haven't progressed either board yet. Not quite sure how to proceed, but then I have to go to work in a bit, so I might do some more research whilst I'm there.
BTW, very nice amp Pavel!
Anyway, definitely don't use that layout I posted earlier, some of the transistors have the wrong pin-outs.
I have just been spending time learning how to build new components, so I haven't progressed either board yet. Not quite sure how to proceed, but then I have to go to work in a bit, so I might do some more research whilst I'm there.BTW, very nice amp Pavel!
bias...
The level of bias is set in mv against a certain emitter resistance. The ultimate goal is to achieve a certain current, so the exact level of mv is not critical in performing comparisons from one amp to another. As far as we can tell from input from lloyd and others the KSA50 has ~1.9A total bias, so the voltage across emitter resistors of the following values would be:
0R22 : 209mv
0R50 : 475mv
0R68 : 646mv
1R00 : 950mv
If you are choosing emitter resistors, I wouldn't go much lower or your idle current may not be too stable thermally speaking, much higher and you will lose some damping factor and a few volts of output...
So don't fixate on mv as reported by other people, what matters is your idle current. If you have different emitter resistors than those I listed you may have to do a little math, but ultimately you are looking to get about 0.95 amps through each transistor.
Stuart
The level of bias is set in mv against a certain emitter resistance. The ultimate goal is to achieve a certain current, so the exact level of mv is not critical in performing comparisons from one amp to another. As far as we can tell from input from lloyd and others the KSA50 has ~1.9A total bias, so the voltage across emitter resistors of the following values would be:
0R22 : 209mv
0R50 : 475mv
0R68 : 646mv
1R00 : 950mv
If you are choosing emitter resistors, I wouldn't go much lower or your idle current may not be too stable thermally speaking, much higher and you will lose some damping factor and a few volts of output...
So don't fixate on mv as reported by other people, what matters is your idle current. If you have different emitter resistors than those I listed you may have to do a little math, but ultimately you are looking to get about 0.95 amps through each transistor.
Stuart
schematics
Hi Pink,
I think there's a good chance all the scematics are 'correct' in that they were used at one point or another. I think in the early days of Krell they were making changes as they went through batches of boards, components etc. Many of the schematics on the net are hand drawn from the board layout. Since the values of components, ie the compensation caps etc can be misread pretty easily, we may end up having to tweak those, but the overall topology is the same for all the schematics I've seen. I have a PC based measuring system, as soon as I get a chance I will be measuring what I've built to determine whether any of the values we have yield bad results, but thus far people reporting back after building are pretty darn happy, so it can't be too far wrong.
Stuart
Hi Pink,
I think there's a good chance all the scematics are 'correct' in that they were used at one point or another. I think in the early days of Krell they were making changes as they went through batches of boards, components etc. Many of the schematics on the net are hand drawn from the board layout. Since the values of components, ie the compensation caps etc can be misread pretty easily, we may end up having to tweak those, but the overall topology is the same for all the schematics I've seen. I have a PC based measuring system, as soon as I get a chance I will be measuring what I've built to determine whether any of the values we have yield bad results, but thus far people reporting back after building are pretty darn happy, so it can't be too far wrong.
Stuart
trying to figure out how he does it 
