Suggestions for upgrading C1 (coupling cap) in AKSA 55W

Fredly · « **on:** 1 Jun 2004, 02:09 pm »

Gents, I'm in the position to place an order to Part Connexion here in Toronto, Canada, and thought at the same time I'd include an upgrade to the AKSA 55W coupling cap (C1).

I've already done the original Nirvana upgrade and have replace numerous resistors and caps with Rikens and Blackgates, so this is a little tweak I want to do right.

I've heard good word about replacing this cap with Hovlands (thanx Mal), but frankly am leaning to Auricaps, since I've had very good experience with them in the past.

Also, as far as replacing this cap goes, do I need the exact same cap size (470nF) OR is bigger better for this application.

Any suggestions/feedback regarding this tweak would be GREATLY appreciated.

Take care all, thanx much in advance Fredly in Canada

Malcolm Fear · « **Reply #1 on:** 1 Jun 2004, 07:54 pm »

Hi

I used Hovlands as they were "the go" three years ago (have I had an AKSA that long?).
Since then, I have been using Auricaps. If I built another AKSA, I would use Auricaps.
I haven't compared Hovlands to Auricaps, so can't comment on which is better.

andyr · « **Reply #2 on:** 1 Jun 2004, 10:01 pm »

Quote from: Fredly

Gents, I'm in the position to place an order to Part Connexion here in Toronto, Canada, and thought at the same time I'd include an upgrade to the AKSA 55W coupling cap (C1).

I've heard good word about replacing this cap with Hovlands (thanx Mal), but frankly am leaning to Auricaps, since I've had very good experience with them in the pas ...

Hi, Fredly,

I used 470nF/400v RelCap RTXs for my 55N+s. I won't use Auricaps bcoz they have stranded leads - so I've also substituted an appropriate RelCap for the Auricap in my GK-1.

Regards,

Andy

SamL · « **Reply #3 on:** 1 Jun 2004, 11:07 pm »

Quote from: andyr

I used 470nF/400v RelCap RTXs for my 55N+s. I won't use Auricaps bcoz they have stranded leads - so I've also substituted an appropriate RelCap for the Auricap in my GK-1.

Regards,

Andy

Andy,
Did you have a chance to compare the sound of RelCap vs Auricaps in your aksa?

Sam

E TYPE PHIL · « **Reply #4 on:** 2 Jun 2004, 12:22 am »

Hi

FYI - I used MULCAP RTX 1.0uf X 100V in both my 55 and GK1 (Parts Connexion No.51295). They are a bit more expensive but were suggested as the "Best of Breed".

Phil

andyr · « **Reply #5 on:** 2 Jun 2004, 12:35 am »

Quote from: SamL

[Andy,
Did you have a chance to compare the sound of RelCap vs Auricaps in your aksa?

Sam

No, sorry, Sam - I did not (the only good wire is a solid-core wire, IMO!!)

Regards,

Andy

stvnharr · « **Reply #6 on:** 2 Jun 2004, 01:36 am »

Fredly,
I'd go for the more expensive RelCap, the $20 one. I contemplated this last summer when I built my latest Aksa's, but cheaped out with RTX instead. You could also consider an expensive Caddock or Vishay resistor for R9.
If you got the bucks, these are a thought. Not sure of the improvement, but won't make things worse.

SamL · « **Reply #7 on:** 2 Jun 2004, 01:38 am »

I am wonder if using 0.47uf 425v Auricap bypassing with 0.1uf 100v RTX cap will give the best of both world = better sound with cheaper price?

Sam

ginger · « **Reply #8 on:** 3 Jun 2004, 04:53 am »

G'day from Oz,
I have been missing in action for a few months while I built a new 120W, 4 x KT88 Ultralinear Push pull Valve Amp.

During this time I have using my AKSA 55 Nivarna Plus as my reference amp.

C1 in my AKSA is a 470nF PPS (this is the dielectric which replaced Polycarbonate when it went obsolete). I have a 4n7 Polypropylene soldered across it on the underside of the PCB.

The Capacitor Sounds articles which appeared in Electronics World (UK) last year suggest that PPS (PolyPhenylSulphide) are excellent caps and even outperform Polypropylene is some respects. This is also my experience.

I also use a PPS (1uF) in parallel with the Blackgate Standard 100uF/50V I use for C3 which helped lift the top end a little.

I used a 1uF PPS for C7 (the Vbe multiplier bypass cap) for a while but eventually decided that a Blackgate NX 22uF/6.3V was the go here.

By the way - my experience with upgrading after ftting the Nivarna upgrade was that the more I improved the capacitors the less I liked the Rikken Ohms I had fitted for the driver base resistors and the feedback resistor. I now use NO Rikken Ohms. The feedback resistor is back to the kit supplied metal film and the driver base resistors are back to the kit supplied carbon films.

Hope this is of interest,
Cheers,
Ginger

Occam · « **Reply #9 on:** 3 Jun 2004, 01:12 pm »

Quote from: ginger

G'day from Oz,
........
C1 in my AKSA is a 470nF PPS (this is the dielectric which replaced Polycarbonate when it went obsolete). I have a 4n7 Polypropylene soldered across it on the underside of the PCB. ...

So you leave us for a few months and come back just to tease us? And those Polypropylenes bypasses might be???? MKP1837s? KP1830s? Or those film and foils wound on the inner thighs of those few remaining 'maidens' in Brooklyn? From your subjective evaluations these poly bypasses provide/improve what characteristics?

Thanks in advance.

PS- for any Yanks wishing to experiment with PPS caps, Digikey carries the Panasonic ECHS caps.

SamL · « **Reply #10 on:** 3 Jun 2004, 10:58 pm »

A bit off topic. How do you all manage to solder and desolder your parts on/off the pcb so many times wihout damaging/lifting the track?
How do you do it?

Thanks,
Sam

AKSA · « **Reply #11 on:** 4 Jun 2004, 12:55 am »

Sam,

I'll have a go at this one......

I use a professional solder sucker. (This is a high end sex-aid for a pcb.....

)

These machines cost several hundred dollars; mine is a cheapie from Micron. You place the tip of the gun over the pad, with the hole centred on the end of the lead, and pull the trigger. It makes a dreadful noise, like a machine passing wind (the sonics of the expensive ones, like the Hako, are MUCH better!) The pad is heated, the solder removed, and minimal heat remains because it mostly comes off with the solder itself, and the pad has very low thermal inertia. This works well, and with care you can do this about ten times before the track/pad lifts.

Pcb tracks are held to the substrate with a special adhesive. This adhesive loses effectiveness with repeated application of heat.

The other way, not so wonderful, but the technique I used until about a year ago, is to go to Dick Smith Electronics (in Wellington) and buy a handheld manual solder sucker. This is about 15cms long, 2cms in diameter, with a large, spring-loaded piston inside. You set it against a little plastic stop, and when the nozzle is positioned over the molten solder joint (you need an iron, of course) you press the stop. The piston flies forward, creating low pressure at the joint, and the solder, now molten, flies up the nozzle, leaving the pad clean.

This technique heats the pad more, and you'll get maybe five applications only if you are good.

Pcbs are indeed perishable. It's a problem. But they've served the industry well, and I must admit I love to design them!

Cheers,

Hugh

ginger · « **Reply #12 on:** 4 Jun 2004, 01:46 am »

The Capacitors:
The Polypropylene parallel caps I use are garden variety WIMA FKP2 Series (Film and Foil).

The parallel caps across C1 (4n7 Polypropylene) and across C3 (1uF PPS) I thought added some top end "air" and improved imaging. Note I stick to the 100:1 rule of thumb for parallel caps, 4n7 across the 470nF and 1uF across the 100uF.

CAUTION:
As always when paralleling caps, be aware that sometimes the results will be worse not better. When the big cap turns inductive at higher frequencies and the small parallel cap takes over you can effectively end up with a inductor in parallel with a capacitior ( a tuned tank circuit) which can resonate and cause ringing. This will sound harsh. If this happens, either remove the parallel small cap or try to damp the ringing by adding a 1 to 2.2 Ohm resistor in series with the smaller cap.

PCB Rework:
Reworking of PCBs is something I've been doing for 30 years at work. I've access to the latest and greatest Radio Frequency Heated De-soldering stations costing more than I make in a month, seriously "flash" solder suckers etc. and have tried them all.

After all this time the method I find works best for me is Solder Wick. Its not cheap but it works a treat and its certainly cheaper than destroying a PCB and having to start over. Its not the "Silver Bullet", its still quite possible to lift pads and tracks from the board BUT its the best of a mediocre bunch of methods.

The simple truth is that PCBs just are'nt suitable for reworking over and over. With care you can perhaps rework one component up to about 10 times. This applies to sophisticated 16 layer PCBs as much (possibly more) than simple single sided PCBs like the AKSA board.

IMPORTANT:
A large percentage of PCB problems (lifted pads in particular) I have seen from my techo's and apprentices over the years (and from myself too if I'm going to be honest )have been due to getting frustrated and applying mechanical force either from the iron tip or by pushing/pulling on the component itself and were NOT directly attributable to heat damage. Its one of those jobs you just have to take a deep breath and "talk to nicely".

Cheers,
Ginger

Fredly · « **Reply #13 on:** 4 Jun 2004, 02:40 pm »

Thanx all for your input regarding C1 coupling suggestions.

It’s obvious by the replies that everyone has very different opinions and ideas of the BEST coupling cap. (But that’s what makes DIY amps like the AKSA so damn exciting!).

At the end of the day, I have to admit, I’m cheap. And looking at some of the prices of the caps available at Parts Connexion is swaying me towards the Auricaps, due to their price and my personal experience.

To retrofit these caps into place, I thought it would be very easy to simply snip the existing cap leads, and solder the new ones to the stubs. This avoids the whole solder sucker removal business, and saves me easily an hour of work dismantling and reassembling my AKSA.

However, Auricaps are renowned for their sensitivity in direction. When used in a signal path the signal must enter through the black lead and go out through the read lead. So, looking at the AKSA 55W PCB board can anyone help me as to which is the input and output lead for C1?

And on a somewhat related note, I have to mention the improvement in sound I experienced last night when introducing Auricaps as coupling to my Vinnie/Swenson modded Toshiba 3950 DVD player last night.

Like many of you on this forum, I have been patiently waiting for Hughs DAKSA to become available, and in the interim started modding this much talked about mega budget player.

Folks, although I’m sure it’s not the final word in redbook CD playback, for approx $100 US for the player and tweak parts, I’m getting sound that EASILY blows away my heavily modified ART DI/O DAC.

I strongly suggest you check this player and its suggested tweaks out.

Again, thanx to all for your input, Fredly.

Malcolm Fear · « **Reply #14 on:** 4 Jun 2004, 06:36 pm »

Hi Fredly
You don't mention where you live. If Australia, then Hugh Dean has Auricaps at the best price.
I wouldn't be snipping the old leads. You should remove the old cap and perhaps even drill the board to get the thicker leads through. Otherwise you are introducing 2 extra solder joints.
I can't remember which way round the cap should go.
Hugh??

cmscott6 · « **Reply #15 on:** 5 Jun 2004, 12:43 am »

If you do go the route of Auricaps, then try paralleling them with small polystyrene caps. (I use Ginger's suggestion of bypassing with 1/100 the value of the main cap.) I did this in the GK-1 and found a slight but noticeable improvement in the high frequencies and imaging.

Just something else to obsess over...

Occam · « **Reply #16 on:** 6 Jun 2004, 03:45 pm »

Quote from: cmscott6

Just something else to obsess over...

Well, iff'n you're gonna obscess over signal path bypass caps.... my vote is for the ROE MKP1837 .01uf 160V -
http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=381412&e_categoryid=496&e_pcodeid=75023

As to why this metalized polyprop cap is more expensive and prefferable to a film and foil polyprop (ROE 1830, EVOX PFR5, Wima FKP02....), it eludes me. I've not tried them, but some folks who's opinions I respect seem to think they're the best thing since sliced bread.

All the caps mentioned are 5.08mm pitch caps, which happens to be the spacing for the MMK presently there. Their use as bypass caps make it convenient for attaching the (which could be the extant MMK) 'to be bypassed' cap on the other side via the bypass cap's leads. As this use is for signal coupling as opposed to PS bypass, the leads inductance isn't of great concern.

PS - Iff you're interested, if you've not a large enough order at Mouser to justify a MKP1837 order, PM me and we could combine an order.

PPS - Fredly, thanks for headsup on the Toshiba DVD, I too have a heavily modded DI/O.

SamL · « **Reply #17 on:** 7 Jun 2004, 11:09 pm »

Quote from: AKSA

I use a professional solder sucker. (This is a high end sex-aid for a pcb..... )

These machines cost several hundred dollars; mine is a cheapie from Micron. You place the tip of the gun over the pad, with the hole centred on the end of the lead, and pull the trigger.

Hi Hugh, is this the type you referring to? Well, it is not cheap but compare that to my AKSA... I think I should get one. Just not sure if the one from DSE is any good?
http://www.dse.co.nz/cgi-bin/dse.storefront/40c4ef600e52e9da2740c0a87f99075d/Product/View/T2500

Quote from: ginger

After all this time the method I find works best for me is Solder Wick. Its not cheap but it works a treat and its certainly cheaper than destroying a PCB and having to start over. Its not the "Silver Bullet", its still quite possible to lift pads and tracks from the board BUT its the best of a mediocre bunch of methods.

Hi Ginger, are you referring to the copper braid like this? http://www.aputech.com/Produits/phototresse.htm
I am currently using them in combination with a disordering pump. However I find it a challenge to use in a tight area and after sometime I get frustrated.

Quote from: ginger

By the way - my experience with upgrading after fitting the Nivarna upgrade was that the more I improved the capacitors the less I liked the Rikken Ohms I had fitted for the driver base resistors and the feedback resistor. I now use NO Rikken Ohms.

Is this got anything to do with rhythms and mid-range clarity? I have a bit of Rikken Ohms in my AKSA100n and since mine is build with them on day one, I am not sure what impact they make. I do find the rhythms a bit off (always in a rush) and the mid-range got berried by the high and low. Maybe mine is not fully burn in yet.

Cheers,
Sam

stvnharr · « **Reply #18 on:** 20 Jun 2004, 01:44 am »

Just curious about this C1 cap.
Is this cap worthy of a pricey upgrade, as per some of the suggestions?
I don't recall any previous mention of tweaks for C1.
Or have I just missed them?

Malcolm Fear · « **Reply #19 on:** 20 Jun 2004, 02:48 am »

I think you just missed them. I stuck Hovlands in mine probably before AudioCircle was born, so never talked about it.
I have since mentioned them. Can't remember when. Somewhere in the Aspen group.