Krell KSA 100mkII Clone

gerhard:

Why not, if the voltage & current ratings are right?
Quality-wise, standard industry transformers probably won't be inferior to that thing that sits in my Krell KST 100 and that annoys me with its loud hum.

Take a look at my last post, the link will tell you why I suggested a custom transformer though it could be very difficult to find a transformer like the ones used in Krell originals (all the output voltage, shielding, potted in a can, low noise etc..etc). The issue of a custom is relevant if the power supply will be similar as to the KSA 80/160/200..................otherwise you are probably right.

Regards :cool:
 
AndrewT said:
Hi,
is anyone else having trouble downloading the PDF in post 80?

works here. Firefox 1.5.0.2, Acrobat 6.0



and no, I won't kill the KST100. Ignoring the mechanical hum, it's completely ok. Sounds good, controls the speakers oooh so tightly etc. If necessary, I'll have someone wind me a new transformer or overhaul the old. Should be no problem here in Berlin.

Buying a working Krell and killing it for parts is not cost effective and shows some hybris. Glueing pre-existing kits together is boring, as far as I'm concerned.

I'm not interested in soldering per se but more in design, simulation and learning new tricks. A few years ago, I built an amp for applications in geophysics that could spit out +- 650V, 1A, w/o bridging, no time limit, open, short and funny loads allowed. Sooner or later I'll redo it for audio with bipolars, without having to stack lots of p-channels to make them safely withstand 2 KV.

regards, Gerhard
 
few years ago, I built an amp for applications in geophysics that could spit out +- 650V, 1A, w/o bridging, no time limit, open, short and funny loads allowed. Sooner or later I'll redo it for audio with bipolars, without having to stack lots of p-channels to make them safely withstand 2 KV


Now this i have to see, have you got a schematic, perhaps we can do a little sideline from the krell :smash: :smash: :smash:
 
Also, I never understood why the drivers were on a separate board in Als version of the KSA50.

Its been covered before.

1. The JAN board had the tabs of the two drivers reversed form each other.... not a user friendly way to mount them and difficult for newbies to deal with.

2. Most also did not like the addition of current limiting..... Krell never used any.

3. 1/2 watt Vishay resistors just barely fit between the holes.

4. No bypass options.


With Al's board design you have the option to leave the driver board attached, or break it off and mount it in the main sink. what ever is your pleasure........


Al,

Dave does have Eagle but I don't know what version. He uses PADS for all his design work though so a gerber translator will be necessary.

Gerhard...

I've heard the KST-100 before. The KSA-50 is far better.

Mark
 
Since we're talking ridicilous numbers anyway...
How about using 6 x 100kw/12.7 Vac transformers in series to get +/50Vdc...at my job we use them to kick out 10Vac (600Hz) and roughly 3500 AMPS. They weigh about 200lbs. each and need watercooling.Also "a few" extra OP-devices would be needed and some nice C's after rectifying(with what ?????).
But it would drive a 0.002 ohms load without problems.

FYI: we use them for welding thin metal sheet (0.16 mm) at "walking speed" (65 meters/min).If you approach welding-circuit at 2 feet with magnet in hand it'll vibrate at 600hz :D


http://www.soudronic.com/metal/114-1_canbody_welders.html

Since i get my "amps-kick" at work i just need music at home

Klaas
 
AndrewT said:
Hi,
could it cope with the 0r5 load that Krell say they can do?

now 650V divided by 0.5 ..... hey, that's a big number! >420kW :hot:

It can cope with 0r5 for output voltages that don't require more than 1A :cool:
Thats not very loud. I burnt a lot of FETs until the current limiting worked and until the amplifier did not oscillate at the onset of limiting. Having isolated differential scope probes is important and developing the habit of having one hand in the pocket helps to survive.


They used the amp to pump current into the soil, measured potentials every few meters and then could oracle what was down there 20 meter deep.Rubber boots are essential, worms don't like it. I wonder why nobody has died.


Konst, I won't publish the circuit of this HV amp. The audio version is a different story but will not happen before autumn. It's quite Self-ish, so many people here will miss the euphonic distortions :) It will not current limit but instead remove both rail voltages with transistor switches. These might double as capacitance multipliers to improve PSRR, I have not yet made up my mind.

regards, Gerhard
 
Mounting To-3 to heat sink?

Here is a link to my suggestion (have tested it in practice) for to mount To-3 devices to a flat surface of a heat sink. Because of the mounting solution it is very easy job to design a PCB for whole power/output stage (one board for all components including copper strips for the rails)
Could be useful if this is the way to design a power device board (a sort of a surf mount board)

http://www.diyaudio.com/forums/attachment.php?s=&postid=901814&stamp=1146061771

in the thread:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=78412

Regards :cool:
 
AndrewT said:
Hi Mark,
do you have access to Krell specifications?

160W into 8r needs an output of 50v6pk. This is impossible on a dual polarity Vrail= 50Vdc and even less possible if the +-Vrail=48Vdc when fully biased.

A maximum of 120W into 8r is more likely for +-48Vdc and possibly 130W for +-50Vdc. These maximum powers would be at clipping level when distortion is likely to be quite high.

What are the bias settings for the 100pre83 and 100Mk2?
Is there a later (Mk3) release? How do the KMA numbers compare?

I (we) could do with a full set of comparative data before we second guess how the Klone should be designed. It's like selecting the timber to build a bridge but then discover we haven't measured the width of the river.

Awpagan,
a little bit of ingenuity can keep the options open, a bit like Jan's Klone with the VI limiting (use it if you feel the need) or All's piggy back add ons for the very high voltage 50Klone.


Just saw this thread... I am not getting emails again!!!

I owned the KSA-100mk.II. Thought it sounded a little dark and limited HF extension. Had tight bass/ midbass. personally I think the KAV-250a (which I still have) sounds much better... but thats my opinion...

I measured the loaded rails on the KSA-100 mk.II

with 118v mains, the DC rails were +/- 53.5vdc. 690mv across the 1 ohm emitter resistors meant it was biased to 122 watts pure class-A into 8 ohms.
 
Hi Kamps,
not quite, your measured Vrail supports the contention of Mark that the peak output of the 100Mk2 is nearer 160W (50.6Vpk) into 8r.

0.69V bias gives Iq=2.76A.
Peak voltage in ClassA will be just below 2*2.76*8= 44.16Vpk.

I would expect the KSA100mk2 to manage quite a bit than 44.1Vpk into 8r.

ps what is the rated input voltage for the rated (specification) output voltage?
 
voltages...

Hi All,

Not been keeping up so I'm going to jump in here with a potentially ill informed comment....

The peak voltage required to get 100w RMS (200w peak) (class A or B) into 8 ohms is 40v...so the peak current is 5A, so the idle current needs to be a minimum of half that, ie 2.5A...now if I read the comments thus far the contention is that 2.76a bias is not a 'real' ie 100%, 100w Class A amp, I think it is...assuming you have a resistive load, and the fact that Krell used 2.76A gives a 10% margin for slightly weird loads.

The extra voltage and extra current are gravy, Krell promised 100w RMS Class A into 8ohms.

Please point out the flaws in the reasoning....

Stuart