50watt into 1ohm load with KAPPA 9

[tinitus]

Hi,

Does anyone remember SONNY discussing his MIRAND amp on this forum ?

I have made mono amps version with less output and stronger transistors, supply is about +/-30V, 500w trafos and a single pair "average" 15.000uf (Jensen) and switchdiodes, bias is 29mv and has needed adjustment from time to time, but seems to have settled now, it affects sound and must be very accurate

It has been playing quite a while now, and a friend who liked it asked if we could test it on his speakers - KAPPA 9
He has tried a lot of amps without much luck, but found a old PS.Audio, and at the moment he is is using a cheap NAD 60watt, anything else have failed

SURPRISE !
At start I was a bit nervous being told that KAPPA 9 impedance can drop below 1ohm
SOUND was impressive right away, and we could hear this was something special
And amps didnt even get hot, even at loud levels - very impressive

KAPPA 9 has a bass servo, which my friend didnt use because his amps couldnt drive it
But we heard instantly that sound improved a lot with bass servo
But NOW amps got hot, but not too much, and they didnt get any hotter even when driven into clipping

Unexpectedly we could play pretty loud, but ofcourse not insanely loud
What surpised me the most was the quality of sound - I have always thought that amps would sound better if driven into 8ohm load
And this was into 1ohm load, and propably strange phase angles

At all times music was presented with unbelieveable ease, liquid and airy

MIND YOU, this is done with a single pair of transistors - I find that pretty amazing - it should be able to drive a ribbon with VERY low impedance - just what I have been looking fore !

[lineup]

Originally posted by tinitus

Does anyone remember SONNY discussing his
MIRAND amp on this forum ?

--------------------
MIND YOU, this is done with a single pair of transistors - I find that pretty amazing - it should be able to drive a ribbon with VERY low impedance - just what I have been looking fore !

Standard edition
Q1 MJL3281A
Q2 MJE15030
Q3 2SC2911
Q4 MJE15031
Q5 MJL1302A
Q6 2SA1209
.

TOPIC diyAudio: http://www.diyaudio.com/forums/showt...496#post324496

Sonnya Website: http://mirand.dk/index.html
Brochure, Data: http://mirand.dk/brochure-miranda1v11.pdf
Schematic PDF: http://mirand.dk/miranda1v11.pdf

...............................
lineup

[tinitus]

I am not sure if Sonny is active at the moment

[jacco vermeulen]

The Extended position, your "bass servo" , is where the K9 dips to 0.8 Ohms.

Unless my memorybank is ready to be flushed down the drain, the "common" budget power amplifier for the Canine was an HK Citation 22.
Buttugly, nevertheless a $2000 power amplifier in the Infinity K9 years. And to make the K9 sound really good was to go bi-amping.

Maybe your miracle amp can survive the K9s with the Extended bass switched Off.
I can also understand you can get a moderate volume out of loudspeakers that can blow the roof off your home with the proper set of power amps.
But getting a decent volume out of the Infinity's with only a single pair of output devices and 30Vdc rails ?
Stronger transistors ?

In Extended mode the K9 was called the AmpKiller

[tinitus]

Clarification,

Amps did survive with K9 in extended bass mode, and that was over hours of listening at VERY high volume levels close to clipping

And it did not only survive, but sounded absolutely amazing - although I dont like the K9 it was pretty impressive - music had magic even at high levels

Furthermore the amps was driven at clipping levels fore a while with no other problem that distortion, but no exscessive heat at all

BTW, I should mention that amps has enough cooling to be driven in class-A

[AndrewT]

Hi,
I wonder if two pair of Krell 50Klone monoblocks could match or better that single pair of 3281/1302s?

You'll need to borrow 2pair and tell us.

[tinitus]

I expect that I have to build amps to my friend and his beloved K9

They will probably be with some 300watt modules - BUT with lower voltage rails to do about 100watt

[jacco vermeulen]

Tinitus,

Reads as a good example of how much 1 pair of output devices is capable of if they have plenty of cooling, thanks.
Your friend should try to find one of those Infinity boxes for bi-amping

[tinitus]

Biamping would be fine - But what do you mean by "infinity boxes"?

His K9 are the original with emit tweeters

I think they are with double speaker terminals for biamping

[jacco vermeulen]

Infinity crossovers for the RS series are still very frequently for sale.
Not the very best electronic crossovers, but i bet it beats the standard filter setup of the classic Kappa 9 for bi-amp mode, and they're cheap.