Krell KSA 100mkII Clone

[AndrewT]

Hi Line,

KRS-200 mono power amplifier .....5.6 cubic feet

what size was/is it?

Can you add the Mk2 dates into your time line?

I had not realised that Krell are the young whipper snappers of the industry. Just goes to show how quickly they built up their reputation.

Pwatts,

the LTP face to face can be achieved for both cbe pins and for ecb pins but not for the reversed ebc pins of the MPSA types (but nobody with any sense will use these low gain low fT devices).

layout the pin holes as follows:-

ecbe
ebce

connect the respective e to e in the gap between the facing transistors.
Only one trace from the remote side collector (for the right hand pair) needs to be on the top side to lay directly into your PCB layout.

the base can be set back to form the traingular layout often found in To92(x).

[AndrewT]

Hi Pwatts,
can you arrange a little space around each electrolytic so that larger footprint types can be substituted (either because a builder has them available or as a larger value modification)

Could the DC blocking caps (the back to back pair) have pin locations added for 2 series inverse parallel protection diodes (4 required for 1.4Vmax) and a pair of 0.1inch pitch pin locations for a shorting plug for easy DC coupling experiments.

What about space for a second Iq adjust pot for lower standby dissipation (or summer use)? and again a pair of 0.1inch pins to connect to a remote relay or heatsink switch.

And some holes for attaching test probes to loops or single pins.

[Flodstroem]

And some holes for attaching test probes to loops or single pins.

Yes this is a good idea to make holes for test pins Very beneficial idea (remember days when all went wrong: trying to fit "big" test pins on small transistor legs when doing repair work ending with MORE repair work, sometimes also with that famous "phshhhh-----poff" and there came the smoke )

I will leave it to you for to decide location and number.

Regards

[jacco vermeulen]

Originally posted by LineSource
sets the world standard for substance, 5.6 cubic feet and 240lbs!

Add the price to your list ($30K in 1990 overhere, 22,5K for the KRS-100)
No SS amps that were more expensive, only a couple VTs.

KSA-80B/KMA-160: 23" x 9" x 21"
KSA-200B/KMA-400 : 23" x 9" x 28"

[jacco vermeulen]

Theoretically bridging should give a 4x increase into the same load (ignoring losses

Bridged amplifiers have power figures based on 4 Ohms output with regard to distortion.
A lower load impedance leads to higher distortion, a general characteristic.
Theoretically it is twice the 4 Ohms continuous output at the same distortion level.
The most important downside of bridging amplifiers(imo)

[AndrewT]

Hi Pwatts,

Could the DC blocking caps (the back to back pair) have pin locations added for 2 series inverse parallel protection diodes (4 required for 1.4Vmax)

could be melf (smd) diodes on the back and use no extra board space.

[PWatts]

Hi AndrewT,

I'll see what I can do about the diodes and capacitor size. I used the same size electrolytic as on the PinkMouse boards, and for people using 6.3, 10 or even 16V it should be big enough though. The SMD diodes may be a problem and will probably look a bit tacky for those using them, but I doubt if it will be a popular mod. The shorting jumper may be a good idea though.

The low-bias switch option was added to the Delta Audio boards, and nobody I knew actually used it. Is there anybody here who SERIOUSLY think of using it? Since there is some space at the side of the board I can perhaps even include footprints for a few popular relay sizes, but please don't overcomplicate things if nobody's going to use them.

Regarding probe hooks: I use them in all my designs, but why bother with this one since all the components are leaded? Just lift the legs slightly up when soldering the resistors and there you have your hook free of charge. However, name the nodes you want hooks and I'll see if I can fit them in. One hook I always use is a nice big fat hole for a proper ground pin for the scope ground. I've had enough smoke from a crocodile clip escaping from a dodgy connection and shorting out something to ground that shouldn't be

I'll try to see what I can do about the transistor facing. At the moment it's configured for the cbe transistors such as BC546/556 which IMO are good, simple and easily available.

[Jozua]

Pierre

The concept boards looks excellent and the speed this project seems to be developing is most impressive.

I am pretty certain that everyone agrees that this project must be considered as a no-holds-barred attempt at improving upon the original KSA100 mk2 sound quality whilst retaining the longlivity of the orginal amps.

Jozua

[Flodstroem]

Does anybody thought of a proper power transformer for this amp? Are you going to use the common mains transformers sold by Farnell/RS Component/Mouser/ Digi-Key/ or what ever or have you consider a custom design?

Why Im picking up this question now is because the long lead-time for a custom production (maybe 4-8 weeks after order is placed).

I will consider a group buy for this part as same as for the other parts. I have a Contact at the Avel Lindberg (first company to supply Krell with transformers).

If there is someone else who have a contact or know a cheap supplier for a mains transformer GB, you may step in here.

Specification for a main transformer would be same as Krell´s (main criteria was: DEAD SILENT @ full load = , Potted in a can for aesthetic purpose and enough power to the amp= high efficiency)

In March this year I got a quotation for a such a transformer from Avel (ca £ 100.00 net each for a one: 2 x 38, + 2 x 45V 600VA minimum, including a relay drive voltage of 12V @ 1.2Amps if ordering a min. of 10 pcs) This type meant for use in mono-blocks, not for a stereo amp)

I know more regarding this issue in next week......................

Any comments would be appreciated

Regards

[AndrewT]

Hi,
if the KSA50 had a pair of 400VA, I cannot see the KSA100 having less than 750VA.

I suspect it would perform better with at least 1kVA and close to 3% regulation.

A gauss band and electrostatic screen might elevate this custom job above the regular off the shelf items.