X350 Power Supply

[GRollins]

I would expect a rail closer to 40, maybe 42V. As for current limiting, Nelson seems to design (in most cases--the Aleph 3 was an exception, for instance) for maximum power into around 5 Ohms.
Just for giggles, and without having seen a schematic, I'd guess something on the order of 5-600W into 2 Ohms. That said, very few speakers go that low over an extended frequency range. Usually, it's a relatively narrow dip. In the real world, it's not much of a problem because you'll be trotting along at 5 or 10W when something occurs in the impedance dip that calls for (gasp!) something like 50W. With an amp the size of the X350, you'll have plenty of reserves.

Grey

 

[K-amps]

Would 2 ohm loadings make a MOSFET amp sound slightly tinny the way it does a BJT amp? (I know overkill BJT amps would not have issues with this but in real world it does.)

 

[AndrewT]

Sorry Kamps,
I saw "fuses" and wrongly assumed PSU.
My figures still apply except the very final one about quadruple power. Where a speaker fuse does not get a rest period as a Vrail fuse does.


Grollins,
if Kamps is blowing fuses he must be pushing a lot more than

5 or 10W

have a think.

 

[GRollins]

It's beginning to sound as though the Krell is being run into clipping. Assuming that the current amplifier is not malfunctioning in some way, there are three cures:
--A bigger amp
--More efficient speakers
--Turn the volume down
What's the wattage on the Krell? I haven't bothered to keep up with their product line.

Grey

 

[K-amps]

Grey/ Andrew:

The krell (KAV-250a) is a class-AB 250watter. Rails are about 84 each way clips at 330 watts into 8, 500 into 4. Have not tested clipping into2 ohms but as you know the speaker line fuses blew.

It has about 5 pairs of MJ21195/96 class; BJT's. (Actually krell's own special order number from ON/MOT, but curiously were introduced about the same time the 21195/96's were introduced by MOT)

The funny thing is I now run the four paralell drivers (stryke audio SA-071's) with another Nelson amp, a Forte Model 3. 200wpc into 8. It does not have speaker line fuses and has not blown the OP stage (yet ;-). Works fine... except I liked the midbass definition of the krell better.

However it's OP stage is a tad weaker than the krell i.e. four pairs of 1302/3281 vs. 5 pairs of 21195/96's on the krell.... so I muse that the krell can drive my speaker only if I increase the speaker fuse to 15 amps...

By the way I have a fast acting 10amp fuse... I do not believe I am running the Krell into clipping for 2 reasons: I might have heard the clipping and The Forte is a less powerful amp, and does not clip either...

 

[AndrewT]

Hi Kamps,
is the output fuse in the Krell or in the speaker?
Is there any protection in the Krell?

I would be tempted to try the speakers without any fuse but maybe you should play safe and go for T15A.

Tell us when you finally blow it up. And Krell's response to a warranty claim.

 

[K-amps]

Hi Andrew:

Fuse on the Krell. They really don't rate it into 2 ohms so I know I may be abusing it a little... then again, the original Adcom 555 was hyped for 2 ohms and service guys know how many got back blown amps because of that.

I have not assembled my Krell Klone yet... so perhaps design that for 1.5 ohms?

K-

 

[AndrewT]

Hi,
five or six pairs of 200W devices with Tc <55degC should achieve 2ohm rating and good resistive ability down to half that.

What temp does the big Krell run at and is the output device SOAR Ok at that combination of Tc, Vce and reactive load?

 

[K-amps]

It barely breaks a sweat!

 

[jam]

K-amps,

So when do you get the Pass...............

Jam

 

[K-amps]

Still thinking....!