Based on Hugh Dean's AKSA 55

[e_fortier]

Hi Farjon,

Thanks a lot, this is perfect !!

BR
Eric

 

[farjon]

Hi Farjon,

Thanks a lot, this is perfect !!

BR
Eric

Well... Why not put the artwork here? 😉

Rgds.

 

[e_fortier]

Also, here is the minor differences between your schematics and Greg's schematic, this is copy/paste and translated from Google translate.

I believe there are more differences in components values like C2 and C4 but the rest looks the same.

I have asked Greg if he has some PCB left, if he doesn't then I'll go ahead with your PCB.

Thanks a lot.

 

[farjon]

Also, here is the minor differences between your schematics and Greg's schematic, this is copy/paste and translated from Google translate.

I believe there are more differences in components values like C2 and C4 but the rest looks the same.

I have asked Greg if he has some PCB left, if he doesn't then I'll go ahead with your PCB.

Thanks a lot.

Anyone can use this artwork and follow Greg's original BOM, if desired.

Please, post photos later.

Rgds.

 

[e_fortier]

What are you guys using for Q1,Q2 (LTP), the 2N5401 seems hard to obtain besides one manufacturer I've never heard about, see link below. If someone can confirm this is the real thing, I'll buy some. I want to remain as close as possible to the original AKSA 55.

These don't seem to be sold in Cut-tape format, it's usually easier to get a matched pair. Buying bulk is much more difficult.

2N5401 Central Semiconductor Corp | Discrete Semiconductor Products | DigiKey

Thank you,
Eric

 

[JOHN BALI]

The original AKSA maybe use 2SA970 & unfortunately it is out of production...
why we don't use another high hFE transistor, BC560C or KSA992FTA(same pin as 2SA970)

I found that 2N5401 is low hFE transistor (<200)

Regards
John

 

[Greg Erskine]

I am fairly sure all the AKSA amps used 2N5401 for input transistors. 😉

 

[AKSA]

Yes, Greg, they certainly did..... I bought thousands of them and matched them for the AKSA all those years ago......

Hugh

 

[e_fortier]

OK, thanks Greg and Hugh, I'll stick w 2N5401 via Digikey and try to match a few pairs.

Eric

 

[rabbitz]

To rabbitz.
My question is: what is the mongrel aksa 55N+? Thank you very much.
GEirin

GEirin

Sorry about the 2 year delay in replying as I don't usually go to the SS forum.

The mongrel AKSA 55N+ was built using amp PCBs supplied by Hugh and used components of my choice as well as a few value changes (some supplied by Hugh). It used Nichicon Muse KZ for the bootstrap (C4??) and Nichicon Fine Gold, Nichicon Muse BP elsewhere. The power supply used a single 300VA 25-0-25 transformer instead of the dual mono supply of the 55N+. This used a C-type supply similar to that used on the purchased ESP P101 details as it differs from the one at ESP. This used 6 Nichicon Gold Tune caps plus MKT by-pass caps.

I don't have the amp any more or a pic but it's similar in layout to the BAKSA I built.

 

[e_fortier]

Hi,

I'm having problem sourcing the original Drivers (Q5, Q6); 2SC4793 and 2SA1837, they are available through Mouser just like Q1, Q2 but the drivers are backordered and expected late October. As anyone tried with different drivers and was the sound impaired vs the original transistors ?

Your experience and feedback would be great, worse case scenario I'll have to wait for the drivers to be available..patience..patience..

Thanks,
Eric

 

[AKSA]

Eric,

You could use MJE15030/15031 from On Semi, they work very well, but at a pinch you could try the old standby BD139/140.

Cheers,

Hugh

 

[e_fortier]

Hi Hugh,

This is perfect, I will order the above but stick with the original for Q1, Q2.

Thanks a lot,
Eric

 

[farjon]

Eric,

You could use MJE15030/15031 from On Semi, they work very well, but at a pinch you could try the old standby BD139/140.

Cheers,

Hugh

Eric, just remember that the artwork (based on Greg layout) was made for TO-126 drivers, as BD139/140.

TO-220 drivers, as MJE15030/15031, need to be reversed. See attached photos.

Although I'm satisfied with BDs, nothing wrong with testing others.

Rgs.

 

[e_fortier]

Thanks Farjon, Greg had already warned me about this.

Just passed an order for some MJF15030/31 and some MJL4302AG/MJL4281A even though I have plenty of NOS 2SC5200/2SA1943. Based on a few opinion from this site it seems that the newer MJL from ON Semi sound better (whatever that means..YMMV)

What is the small cap on the BD139 that sits on 2SC5200 ?

BR,
Eric

 

[AKSA]

Eric,

That is a 22uF Black Gate across the BD139 Vbe multiplier.
It smooths the voltage variations across the bias generator, ensuring the output quiescent current is constant at audio levels and helps to turn off and on in the output devices. The drivers all stay on through the full signal waveform. I found that a really good cap in this role enhanced the sound quality. The Black Gates are very, very difficult to buy now; I had quite a few back them........

Hugh

 

[Bigun]

Instead of BlackGate you can use Nichicon MUSE/Gold or Elna Silmic (silk).

 

[farjon]

Instead of BlackGate you can use Nichicon MUSE/Gold or Elna Silmic (silk).

Elna Silmic under board.

Rgds.

 

[Bigun]

Nice capacitor 🙂

I guess you'll use some alcohol on that board and clean off the flux before you close the case.

 

[farjon]

Nice capacitor 🙂

I guess you'll use some alcohol on that board and clean off the flux before you close the case.

These boards came with pre-applied varnish. A mess after same time... Consider these as prototypes.

It would be easy to clean before applying extra components under board. 🙁

I have another pair. Thinking about another build.

Rgds.