Krell KSA 100mkII Clone

[Upupa Epops]

One of basic test at UL, VDE, etc. is test of shorting output of amp.... Have Dan d'Agostino some exemption clause ?

[kvholio]

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


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

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

Klaas

[gerhard]

Originally posted by AndrewT
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

It can cope with 0r5 for output voltages that don't require more than 1A
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

[konst]

Hallo Gerhard, verstehe Ich volkommen, freue mich schon auf die audio version

[Flodstroem]

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/attac...amp=1146061771

in the thread:

mounting of outputs to heatsink

Regards

[K-amps]

Originally posted by AndrewT
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.

[AndrewT]

Hi Kamps,
thanks for your info.
It confirms that your Mk2 was almost fully biased (about 80 to 90%) into ClassA for an 8ohm load.

Much different from the mk1.

It also confirms the dissipation of the 4pair output stage @295W, more than double the KSA50mk2

[K-amps]

Originally posted by AndrewT
Hi Kamps,
thanks for your info.
It confirms that your Mk2 was almost fully biased (about 80 to 90%) into ClassA for an 8ohm load.

Much different from the mk1.

It also confirms the dissipation of the 4pair output stage @295W, more than double the KSA50mk2

Why 80-90%, Isn't it 122%?

[AndrewT]

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?

[Stuart Easson]

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