Brand New Super AKSA - the SAKSA 85!

[AKSA]

Hi Folks,
Today I fired up my brand new SAKSA, the next generation of the Aspen range! This amp has:
1. Heritage from the original AKSA 55, particularly the midrange and top end.
2. VAS stage enhanced from the original NAKSA 80.
3. Improved output drive system from the Maya.
4. Footprint from the NAKSA 80, identical to the pinout and heatsink.
5. Lender VAS drive with shunt compensation and phase lead - no lag comp.
6. Nested feedback like all my recent amps deliverying low global feedback - 29dB.
7. Strengthened output stage over the NAKSA 80, all complementary mosfets rated at 280W and 38A.
8. Snubbers on all gates to guard against self-oscillation, the bane of mosfets.
9. Clip indicator (RED!!!)
10. Same price as the NAKSA 80, $AUD930 including 300x75mm 0.37C/W heatsink.

Technical:
The amp has a THD of 0.06% at 12.5W, 1KHz into 8R, 97% being H2 and H4
All fuses are 10A. Slew rate is 15V/us, 1dB down at 12Hz and 150KHz (LP filter in place).
Subjectives:
Very strong bass and midrange. Top end utterly clean. Lots of speed, PRAT, and engagement. You close your eyes, and tap your foot. Very spatial, you can 'see' the instruments in place front to back on a large orchestra. HUGE soundstage and very low intermodulation on choir and orchestra.

This will last as long as the original AKSA. This is a superior amp with a huge of careful engineering and psychoacoustic detective in it. It is knocking on the door of the Maya, and that is a watershed of my amp designs.

I have my first batch and ready to roll for despatch. Wait for a bit on an old, slow guy when I respond, but I'm still the same old Hugh of yore and I will get through all of it over time........!

A very happy day for me, this year both new ground breaking designs have come to life!

Ciao,

Hugh

[thiagomogi]

just wonderful!!!!

Best Regards

[zman01]

Congratulations Hugh and wish you all the success with your new design!

Regards,
Zia

[ben123]

Oh man, you make some beautiful amps !

Can you tell us why u use, different height/voltage type of PSU elco's ?

Is speaker DC-protection necessary to ad, or is it ok to use without external module ?

Congrats

[meanman1964]

Hugh,realy looking good.

[Bigun]

Fantastic !!!

[didiet78]

Slewrate 15v/us ?

[AKSA]

Hi Zia, Thiago, Ben, Patrick and Gareth -
Thank you sincerely for good wishes! I'm very pleased with it and I'm very happy that people think it looks good. After all, if its to sell it has to look good!

1. Protection: None on the output node, but fuses sufficient. The output devices are so large (38A/40A; 250V/150V and both 280W) and so tied down with snubbers I do not expect anyone to blow it up; with heavy current it will take out the fuses, and fuse the power supply 0.15R 2W resistors between 1st and 2nd caps. That will remove the power completely. With only 42V rails I consider no other protection needed, but you can use on externally if you wish. There have been no failures in a couple of years for the NAKSA 80; I would expect this product, with much bigger output devices and stronger stability this would be as good if not better than the predecessor.
2. The smaller caps take power directly from the rectifiers, one bridge for positive, the other bridge for negative. A 0.15R resistor lies between small and large caps; the small caps smooth the mains pulses (4,400uF total) and the large caps are both speaker current bypasses and further smoothing caps. This separates some of the rectifier pulses from the caps which deal with the speaker current, avoiding intermodulation with the power supply. The large 4,700uF takes care of the speaker earth current, one for each rail. Effectively this is a bifurcated power supply, allowing me to use one 300VA toroid.
3. 15V/uS is fine and dandy for 85W. It would not be adequate for 20KHz from a 250W amp. This is imposed by the input LP filter. You need only about 5V/uS for a 80W amp.

Cheers,

Hugh

[didiet78]

Good to know.

[probbo]

Hi Hugh

Its great to read that you have released yet another fine product. I'll have to explore the possibility of slotting one into my system, to replace my 6 yer old NAKSA 70.

Regards, Peter Roberts