[ginger]

First a couple of caveats:

I've had this mod in and out of my 55N+ a number of times. I originally didn't regard it highly because it costs a little impact and slam.

My tastes have changed a bit in recent times as I played around with a batch of valve amps and I now like this mod a lot.

This mod is NOT for the unskilled.

This mod is unsuitable for the 100W due to rail voltage.

So what is it?

Replace the bootstrap cap with "Super E" connected (ie two caps in parallel but one reversed with respect to the other) Blackgate N 100uF/50Volt - yep the expensive non-polarised ones

One cap can be put in place of the existing bootstrap cap, the other needs to be tacked to the solder pads under the PCB. The Blackgate Ns have one lead longer than the other. You need to join a long lead of one to the short lead of the other and vice versa.

The amp with this mod is more "valve like" - you sacrifice a bit of impact and slam for a smoother more "polite" sound. Thus it won't suit everyones taste.

If you are a Rock and Roll "Head Banger" it probably won't suit you. If you like to listen to a bit of Jazz and Classical now and again it probably will.

Hope this is of interest to some of you.

Cheers,
Ginger

[Greg Erskine]

Replace the bootstrap cap with "Super E" connected (ie two caps in parallel but one reversed with r ...

Hi ginger

This went way over my head but may be of interest to you. I don't know if you follow GC threads but I hope you find it interesting. In this thread Joseph K was doing some analyser work testing caps/bypass caps ESL and ESR and he tested the "Super E" config.

http://www.diyaudio.com/forums/showthread.php?postid=551810#post551810

Thanks for the tips.

EDIT: I hope you can decipher my english.   Sounds like I have a fat tongue.

[andyr]

... If you are a Rock and Roll "Head Banger" it probably won't suit you. ...

Hey, hey, Ginger,

Do I detect a bit of "sniff" ... condescension about us Thrash Metal "head banger types".  Ya still need an AKSA to get off on this type of music!  

Regards,

Andy

[AKSA]

Thanks Ginger,

Very useful information for the sonic sculptors - much appreciated!

Cheers,

Hugh

[SamL]

Hi Ginger,
Thanks for the tips. Is C4 the bootstrap caps?
Did you bend the lead or drill a new hole for BG 100uf/50v N cap as it has wider pitch space?
There isn't a lot of space on Aksa55 amp pcb and having 2 x 16mm wide caps on the pcb need a lot of planning.  Another 10mm on both side of the pcb will make mod life a lot easy. Maybe I should add this to the "wish" list.

TIA,
Sam

[ginger]

Greg,
I waded thru' the DIYAudio thread. Basically what the guys there were trying to prove/dis-prove was Blackgates claim that "Super E" connecting their capacitors causes an inductance cancelling mechanism (the capictors self inductance or ESL). Most of the testing was done with other than Blackgate Capacitors BUT the results of their experiments pretty much shows that Inductance Cancelling is rubbish - it doesn't happen. What you do get is a halving of ESR (Equivalent Series Resistance) the same as if you parallel 2 resistors of equal value. So any sonic benefit is from the superiority of the capacitors themselves and not to do with any magical / mythical inductance cancelling technique. Of course if the caps have a simple non-linear response then reverse connecting a pair in parallel will tend to cancel that and give a much more linear response.

The Blackgate Tech Notes are a bit like that - they are their own worst enemy by mixing quite valid claims of better noise  and sonic performance with pure marketing Bull S..t. It makes those tech notes much less useful / valuable than they might have been because your always trying to sort the worthwhile truth from the lies.

Sam,
You are correct about the space for the bootstap cap. My boards already had some components shifted to the undeside of the PCB (the 3K3 resistor and the Vbe Multiplier Bypass cap {C7?} in particular) to make space for the 470uF/50V Blackgate Standard I was using for the bootstrap previously (Yeh I know thats not standard 55N+ either). Thats why I said this mod is not for beginners. I bent the leads in a bit  to fit the same PCB holes. Actually I put the lead ends in the holes and applied good old brute force and ignorance.

Typed this up in a hell of a hurry during lunch before dashing off to fix some laser timing issues on the laser depth sounding aircraft at Adelaide airport so I hope it makes sense and you will forgive spelling and grammar. No time to proof read it.

Cheers,
Ginger

[SamL]

Greg,
Typed this up in a hell of a hurry during lunch before dashing off to fix some laser timing issues on the laser depth sounding aircraft at Adelaide airport so I hope it makes sense and you will forgive spelling and grammar. No time to proof read it.

No problem here
Since you have tried quite a few components, you maybe able to help me.
On my aksa100, I used Kiwame resistor over the stock 5w 47R. As I did this on day one, I am not sure if there's any sonic advantage. I now have the aksa55n+ and wonder if stock sandcast resistor is good enough?

Sam

[Greg Erskine]

ginger,

Thanks for explaination of what they were doing on DIYA. I was following the thread but I must admit, it was going a bit over my head. Your summary of the "Super-E" part was pretty much what I thought they were getting at. I'm only just starting to understand these more technical issues and looking forward to the day when these things become obvious.  

I may start trying some of your modification tips on my AKSA. At the moment I don't mind modifying my other amps but my AKSA is used for listening and doesn't get touched.  

[ginger]

I've had this mod out and back in since last post and spent some time critically listening. I also spent time with one channel with mod in and the other with it out on a mono source and swapping a single speaker between channels.

With the 2 x 100uF/50 Blackgate Ns the sound is more natural BUT subjectively weaker in the bass. The top end however is much lovelier. Dwell on cymbols etc is far better controlled - transient response is better. Balance across the frequency spectrum sounded better gving a more natural "live" sound. Also imaging was improved. There is no music from the two speakers - just a wall of sound which seems to extend for ever in all 3 dimensions.

I did most of the critical listening with Norah Jones and similar BUT I did shove on Spiderbait's Black Betty and cranked the wick a fair bit. This also sounds better (less covered and less "intermodulation" products) so maybe the comment above about it not suiting "headbanging" rock and rollers is wrong. On the other hand there is a small loss of warmth along with the loss of the "covered" sound. Consistent with reduced 2nd harmonic distortion.

Cheers,
Ginger

[PT914]

Thanks Ginger, this was an excellent mod.  I love listening to choir pieces.  With this mod, I can almost count the number of members in each section; bass, tenor, altos, and sapranos.
I also found a device to brake in the Black Gate caps before installing them.  Found at http://www.geocities.com/rjm003.geo/rjmaudio/diy.html under "The Cap Rack"  It works!  I also added more noise to the rack with a frycleaner through a 100 uF protective cap.  When I installed the BG's, I instantly new the mod was great.  Not like other mods that take 400 hours!

Thanks again,
Philip

[ginger]

Philip,
Glad you like it. It's always good to get a second opinion on mods. What suits me (or you) won't necessarily suit the next fellow. I've had my AKSA out of the system for a while working on a couple of new valve amps.

BUT even when working on valve amps costing as much as 5 or 6 AKSAs (or more) I still chuck the AKSA back in reasonably often as a sanity check, that is: it remains one of my reference amps. What I was looking for with this mod was the stereo imaging, "tingly" highs and the stunning vocal treatment of a top of the line, no global feedback Single Ended Triode (SET) valve amp. (The cheaper SETs tend to be 2nd harmonic distortion generators which do the above BUT accompanied by overly rich, flabby, covered bottom end). Asking that from Solid State is asking a LOT - its a credit to the AKSA design that it delivered the goods.

AndyR - Report Card when you try this mod on your tri-amped system (just do the top amp and maybe the mid) ????

Cheers,
Ginger

[andyr]

Philip,
Glad you like it. ...
AndyR - Report Card when you try this mod on your tri-amped system (just do the top amp and maybe the mid) ????  ...

Yessah!!  

But it won't be for a while.

Regards,

Andy