[soitstarts]

Hi all,
Well, soon I'll be ordering my kit. Got a coupla questions that I hope someone can help me out with. I have already ordered my torroids (for a 100 W Nirvana) but have since thought I would be better off getting 55W Nirvana plus. I will be doing a 3 channel kit (L C R) and my speakers are spec'd at 89.5dB 1W@1M. I listen to easy listening with the occasional loud rock when the feeling hits me. First question is would I be able to use the torrodials I have (300VA 33-0-33) for the 55W kit and, if so, wich way would you guys reccomend I go, the 100W Nirvanas or the 55W Nirvana plus'? thanks for your time..

[Carlman]

All things being equal, I'd suggest finesse over power.  So, 55 Plus vs. 100 Nirvana.  However, if you have a large room or speakers below 86db, I'd suggest 100w over 55.

I don't know if you can use the 33-0-33 configuration on a 55, though... my only experience is with the 100w nirv and nirvana plus.

[JohnR]

The 55 requires 25-0-25 toroids. I don't think there's any way that you can use 33-0-33 with the 55...

Where are the toroids from?

[soitstarts]

The 55 requires 25-0-25 toroids. I don't think there's any way that you can use 33-0-33 with the 55...

Where are the toroids from?

Poo.    

Ordered them from Harbuch at Hughs recommendation.

[AKSA]

Hi SIS,

Thank you for your inquiry!  You raise pivotal issues about rail voltage and this bears some explanation.

Now, for more power on an amplifier you need more volts on the rails, so you can swing more voltage across the load.  The peak to peak voltage across a nominall 8R load gives power, according to the voltage squared and then divided by 64.  So 80Vpp gives us precisely 100W into 8R.

To swing more voltage across a load, you naturally create a higher current, since current, by Ohm's Law, is volts/resistance.  More current and more volts generally means a bigger output device, or, in the case of most solid state amplifiers, more output devices of the same size.

So it is with the AKSAs.  The 55W has a single output pair, one npn and the other pnp.  The 100W has two output pairs, two matched npns, and two matched pnps, to accommodate the higher voltage and the higher current.

And here's the rub;  300VA transformers with 33-0-33Vac secondaries will generate around 50V rails on a SS amplifier, and this is too much for the single output pair on a 55W AKSA.  This high voltage will create large currents through the load, and all this current - up to about 6A - will pass through just one device at a time on the 55W, rather than being nicely shared on the 100W.  At this high voltage and current, you will invoke a failure mode called secondary breakdown, and the output devices will lay down their lives to protect the fuses.......

Don't do it!

If you have the large transformers, go for the 100W AKSA because it is designed for precisely these trafos!

Cheers,

Hugh

[soitstarts]

Don't do it..


Thats the only bit I understand..  

Thanks Hugh, Should be getting my order in the next coupla weeks   Hooray for overtime...

[Rhythm Willie]

You will be very happy with these transformers,they gave perfect voltage figures etc .

Mine have no buzz,no noise,neither do the amps & although I hav'nt heard the 55w verses 100w head to head, the sound qualities are very similar with the 100W definately having great bass control and slam when needed(running Vaf I-93's).

[Lost81]

Soitstarts,

from what I read on this forum, the 100W Nirvana Plus is supposed to be very close to a 55W Nirvana Plus

So, I don't think you will be missing out much when you upgrade in the future. I highly recommend the Nirvana upgrade.

For my current speakers, which are 90dB / 1W @ 6 ohms, the 100W Nirvanas (163.5W @ 6 ohms) are perfect for the bass, but it is overkill for the midrange / treble. I think I managed to overdrive the midrange a couple of times

Looking back now, the 55W Nirvana might be a better choice for the midrange / treble.

Then again, the 100W Nirvana gives me the headroom for more power should I upgrade to less efficient speakers (I have my eye on the B&W 800 Nautilus when I eventually get my own house   ).

Have fun constructing the AKSAs!


-Lost81