[Fredly]

Cheap Tweaks for AKSA 55W Nirvana

I’ve been enjoying my AKSA Nirvana 55W for quite some time.

I’ve also been reading the Valhalla thread with great interest over the past few weeks.

I’m anxious to do a few selective “budget” tweaks BUT could use a bit of input feedback from you people.

In summary, here’s what I want to do;

PUT MY DACT PASSIVE AKSA IN SHUNT MODE

Time and time again I read threads referencing this tweak as an inexpensive way to boost up your performance quick.

I’ve reviewed referenced shunt mode schematics BUT quite frankly I’m a not too sure how to go about it.

In normal mode, pin 1,2 & 3 hook-up to line IN, OUT and GROUND.

In SHUNT mode, the diagram has me TOTALLY confused.

I believe it shows Pins 2 and 1 joined together and the line IN connects via the shunt resistor to pin 2 AND the line IN ALSO connects to pin 3!

Am I reading this correct? I REALLY need help here.

Also with such limited space, does anyone have suggestion on the best method of hooking this all up?

I have a 20K DACT, what resistor size should I use?

I plan to ultimately use a Riken Ohm resistor here, but for experimental reasons will use a simple metal film resistor initially.

REPLACE C3 WITH BLACKGATE & R9 WITH RIKEN OHM

As I said, I’ve been following the Valhalla thread religiously with great interest.

Although there are MANY great suggestions within, I’ve scaled it down to the replacement of these key components.

Again I realize there appears to be sonic benefits in replacing C4, C10 & C12 as well. But in keeping with my “cheap” theme, have selected C3 ONLY.

Does anyone differ in their findings?
 
ANY OTHER CHEAP “MUST HAVE” TWEAKS?

Although budget plays a great rule as to WHY I’m keep things simple this time around, I also feel that smaller changes will allow me to really appreciate and review what each tweak does on an individual basis

Having said that does anyone else have any other  “must have” tweaks they’d highly recommend while I’m “in” already.

I’m hope to keep this thread simple and NOT repeat the Valhalla one, so please keep budget/cheap in mind when posting.
 
Thanx in advance for your input people and anyone that can help with the shunt mode….. this would be VERY much appreciated.

Cheers, Fredly in Canada.

[Carlman]

If you feel the amp is totally safe and stable, can you remove the fuses on the amp board and replace with a wire connection?

This would be free as long as there are no other problems.  I've never had one blow..... but, don't know if this regarded as a safe thing to do.

[PSP]

Carlman,
Once your amp is built and biased, you could remove the fuse clips and solder in 5A fuses with pigtail leads... you still have the fuse (and any slight sonic effect of the fuse wire) but you have removed the clips and any contribution from the clip/fuse interface.

Personally, I would never remove the fuses from my AKSA... gawd, if a bug with enough conductivity started crawling around in my amp or--more likely--if I slip up making a tweak 5 years from now, I would never want to blow up my AKSA baby.

Fredly,
Regarding shunt attenuators, take a look at section 1.0 on the following web page (written by VoltSecond specifically for the Bottlehead Foreplay, but the same physics applies to us), specifically the first few diagrams in that section.
http://www.siteswithstyle.com/voltsecond/12_posistion_shunt/12_Position_Pure_Shunt.html

The basic concept in running an attenuator in shunt mode is that the signal doesn't go through all of the resistive elements in the attenuator, only the signal that is shunted to ground (the extra signal that would be lounder than the volume you wish to listen to) goes through those resistors.  Step-by-step instructions are given in section 1.1 (again, for the Foreplay, but you could probably start with the recommended shunt resistor values and see how it sounds).

Also, ginger (I believe) suggested that there might be a sonic improvement (in addition to safety and convenience) from using bleeder resistors between each + and - power supply spade to the power supply ground.  For +/-36v supply in the 55w AKSA, you need four 15k 1/4 watt carbon resistors (very, very cheap).  I put mine in months ago without listening.  Maybe you could listen before/after and report back?

Good luck,
Peter