Fitting caps to X-Can v2 PSU Board

[dhoggan]

Well, I've just received a bag of goodies from Mike so it'll be out with the soldering iron this weekend. I've already got the v2 out of it's case as a pair of EH23-EB valves arrived (via eBay) the other day and so I've been sitting listening to how they perform whilst examining the circuit board.

I done a fair bit of reading on the forum and on Mike's How-To guides and have a couple of questions about the capacitors. Back in 2003, I upgraded them (the PSU ones) to Panasonic FC 63V 1000uF. Now after reading a lot of the stuff here, I'm thinking about changing these. And that's where my problems lay... what do I change them to?

From reading the forums, it seems that I have two recommended choices: Panasonic FC and Panasonic FM series. One of Mikes Articles shows an upgrade using FM 1200uF 35v caps. I've also read in these forums that it's perfectly safe (indeed better) to go 2200uF 35v caps. The question is: what would be better FM 1800uF or FC 2200uF? (RS components only go up to 1800uF in the FM range.)

The second question is: After changing the 10 caps on the PSU board and the ultrafast diode mod, are there any other PSU board mods I should do?

Thanks,

Dave

[FauDrei]

Hi Dave,

FM's have better specs (lower ESR, longer life) than FC series. Can not tell about the differences between them cause I've tried just 1500uF FMs and that was a DEFINITE improvement over stock caps. If you already have FCs inside, it is questionable what and how much difference it Will make.

If you still are willing to try more capacitance - be aware that the maximum cap height in V2 (as Mike warned me in my investigation time) is 35mm and that in a couple of positions you can not go wider than 12,5mm. I've settled for 1500uF FMs (RS: 526-1806) and in places they just fit in.

As for other PSU changes: I went for change of brownish 470nF thing on PSU board for blue rectangular PHE426 polypropylene equivalent (RS: 414-7721) and I think (could be placebo though) that it made a positive difference. Since I had 9 of them left (min. RS order is 10) and Rick in one of my inquiry suggested that THE LAST capacitors on PSU are the most important ones (the ones that audio electronics actually "sees") I've used three "blue ones" to bypass the three lines that are feeding power from PSU board to lower audio board. Followed the tracks and bypassed capacitors: C7 (pins 2 & 3 of the connector), C8 (pins 4 &5) and C11 (pins 1 & 6). In my subjective opinion - not as big as ten FMs, but sound improvement it is.

For the last PSU stab I am planning to go for even faster (20ns) Schottky STTH102 diodes (RS: 486-2896) and experiment with X7R ceramic bypasses on them.

...and here the V2 PSU story ends for me... Hope anything mentioned here helped you...

V3

[FauDrei]

Thanks Miguel...

...it would have been even better if I knew how to post pictures

(know I've seen the explanation somewhere on the board, but in the time of writting I just couldn't and couldn't find that explanation)

[PinkFloyd]

From reading the forums, it seems that I have two recommended choices: Panasonic FC and Panasonic FM series. One of Mikes Articles shows an upgrade using FM 1200uF 35v caps. I've also read in these forums that it's perfectly safe (indeed better) to go 2200uF 35v caps. The question is: what would be better FM 1800uF or FC 2200uF? (RS components only go up to 1800uF in the FM range.)

I've tried quite a few values in this position and the Pana 1200uF FM give just as good sonic results as the Pana 2200uF FC plus (and it's a BIG plus) the Pana 1200uF fit perfectly into position... there's nothing worse than an amp with capacitors sprawled about at all angles (funky angles) I'm a great believer in caps being fitted securely onto the PCB with as little "lead" floating about as possible.... there are even sonic gains to be had by adding mass in the form of hot melt glue, I tried this on a few V3's and the bass department and overall clarity certainly benefitted from it.... of course, remember to check everything is firing on all four cylinders before damping the caps

Here's one with the hot glue tweak in place:







Basically just pump the stuff between the caps (from the top) and it will settle very neatly between the caps adding mass and a good degree of damping.... a cheap but most effective tweak.

[PinkFloyd]

mrarroyo said:

Mike, on the hot glue mod do I need to put something around the caps to prevent the glue from going all over the board? How hard would it be remove one of the glued caps in the future?

Thanks for trying new things. If guys like you did not experiment then the above improvements would not have been achieved.

As I say Miguel, if you pump the hot glue from the top downwards into the spaces between the caps the glue will not run out..... it will form an almost perfect "fill" between the caps and will set providing superb damping and mass. It would be relatively easy to remove one of the caps in future (if need be) you'd simply desolder the pad the cap leg was soldered onto and "crack" the cap off the top of the board..... this glue doesn't bond like epoxy it just nestles up to the capacitor and shear strength is very low compared to an epoxy..... you could also run a craft knife on an unglued section of the capacitor sleeve and pluck the cap out effortlessly... think about it, the glue is only tacking onto the cap sleeve and not the capacitor itself

With the likes of Panasonic FC / FM you won't be looking at replacing them for many many many years, they are 105C rated and will last a lifetime in the X-CAN environment... the likes of the Samwha VA series caps (130C rated) will last even longer, I still haven't experimented with the Samwha VA series in the X-CAN but will be doing so shortly, there's a V2 on it's way from Italy and, with the owners kind permission, I'd like to try the Samwha's in his amp and see how they sound compared to an X-CAN v2 fully decked out with Pana FM caps..... if he's not up for it I'll fire some VA series caps into one of my own v2's and compare them with the Panasonics.

I've been intrigued by the Samwha VA series for some time, these guys have been designed to perform within very hot and demanding environments (such as car engines etc.) People seem to get excited about "mil-spec" valves so only right I should get excited about a cap that can withstand mechanical and temperature extremes

There's a large box full of them sitting in the workshop and, dammit, I'm going to make sure I try them in an X-CAN very soon! The weather's getting better and time to start some cap rolling

Gone a bit off topic here, sorry, but I got to give myself a kick up the bum and actually get round to trying these rockgrotto.proboards39.com/index.cgi?board=m&action=display&thread=1172003105&page=1

[dhoggan]

Very interesting indeed!

Well, the hot glue mod is an easy one to do as I already have the gun/gluesticks.

As for the caps.... I am torn between the FM 1500uF (35mm * 12.5mm) and the FM 1200uF (30mm * 12.5mm) RS seems to have two 1200uF (526-1783 and 526-1777) but it looks as if the only difference is form factor.

Another question; those white felt cap thingies on the caps... are they cosmetic or do they assist in damping?

As for the bypass caps, I am intrigued, but must admit to not really following. Are you saying that you that you have attached the (blue) cap to board tracks that lead to pins 2 & 3 etc. I'll have a look in the work-in-progress gallery to see if it becomes clearer, so may have more questions :-)

Thanks for all the advice so far.

Dave

[dhoggan]

Ahhhhh, the mods are to a v3? I'm using a v2!!

Dave

[FauDrei]

As for the bypass caps, I am intrigued, but must admit to not really following. Are you saying that you that you have attached the (blue) cap to board tracks that lead to pins 2 & 3 etc. I'll have a look in the work-in-progress gallery to see if it becomes clearer, so may have more questions

Exactly. Used (both side) adhesive tape to put "blue rectangulars" in place and soldered them on the under side of the PSU board. "Put in place" means that you tape them in a position from where their leads can reach desired soldering points. You may have to bend the leads to get them where you want them - I surely had to do so because the blue polypropylene 470nF PHE426 that I used had lead pitch of 15 mm and length of just 5-6 mm.

One "blue" was soldered directly to the pins of C7 as C7 was the last cap feeding the pins 2 & 3 of the cable connector. Other "blue" went under C8 because C8 was last in power line on pins 4 & 5 of the cable connector. C11 was a bit trickier because I had a heatsink on the lower (audio) board that prevented to install "blue" directly under C11. But, since C11 was last in line on pins 1 & 6 I just soldered "blue" directly under connector on connector pins 1 & 6. I also considered placing them directly on the connector pins of the lower audio board, but my PHE426s are relatively big and there is a central rail in the inner lower part of the X-Can V2 cylinder that prevents attaching anything that would stick more than 3-4 mm from under the central part of the lower board.

So, first use adhesive tape and put "blue ones" into their positions and check whether you can assemble back upper and lower board without anything from under the upper board touching anything else from the lower board (bad and expensive side effects). When you are satisfied with the layout of the"blue ones" - solder them.

...and yes, it is recommendable that before playing with "blue ones" on the underside of the PSU board you have already changed/placed/soldered electrolytics on the upper side of the same board

I can take a picture or two of the installed blue polypropylenes under the PSU board of my V2 with my mobile phone if someone could teach me how and where to upload them.

V3

[bennyboy]

That stock pic of your V3 makes me want to gag! if fact, O my Gawd...Gag me with a spoon!

[dhoggan]

FauDrei,

A photo would be useful - as they say, a picture paints a thousand words!

Thanks,

Dave

[PinkFloyd]

I've reached the conclusion after many hours of listening that "less is more" when it comes to the output caps on the V3 so am now only fitting one 16v 1000uF non polar per channel instead of the 2 x 470uF per channel (or 2 x 220uF as stock) I no longer bypass the non polars.

Fitting bypass caps "changes" the sound but I'm not convinced they improve the sonics, just make them slightly different and purists will tell you that the less capacitors there are in the signal path the better. Nothing wrong in tuning the sound to your personal preferences with film bypass caps and if it sounds good to your ears then it is good, there's no denying that, but strictly speaking one cap per channel is better than a cornucopia of assorted film caps tacked on all over the place..... Rick goes into depth in another thread about this (I can't remember the thread) and his conclusion was less is more in the signal path.

Ideally we'd have no output caps at all but in this design they're pretty much essential as a belt and braces safety measure against excessive DC.... I was running a v3 without input / output caps and she sounded absolutely gorgeous until the moment (some weeks later) my AKG K-501 let out an almighty CRACK!! (I nearly shit my pants) turns out one of the valves had suddenly failed and there was 12 volts running into the headphones.... not good, not good at all! back in with the output caps ;D

There are quite a few things I've tried that have made the v3 sound better but no way am I going to mention them here as they all involve a certain degree of risk should the amp go into fault conditions..... the output caps are one thing I wouldn't remove.... of course, if you like living in the fast lane and prepared to chance it then................................................ ;D

[dhoggan]

Well, thanks for all the advice and recommendations.... I have just placed an order with RS for the FM 1200uF caps and some PHE426 (blue) caps. I would have tried the 1500uF, but RS were out-of-stock.

If I've read correctly, opinion seems to be divided on using bypass caps (on both the v2 and v3), so for the moment, I'll leave them out. So I guess that once the 11 caps are upgraded on the PSU, and I've already done the diode mod, the PSU board is complete.

Is the recommended 'break-in' period approx. 200 hours for caps?

Dave

[PinkFloyd]

I have just placed an order with RS for the FM 1200uF caps and some PHE426 (blue) caps.

You should have given me a shout Dave I can do these for you cheaper than RS and only £2 for postage too..... no worries though, the deed is done ;D If you need non polars for the output I have these too (either 470uF 16V or 1000uF 16V)

Yup, around 100 - 200 hours before she really opens up.

[dhoggan]

Mike,

It's always the way! But I will be looking at modding the main board after this so, I will still need to order some components. Out of interest, do you know where I can get hold of the felt dampers for the caps? Maplins/RS don't appear to sell them.

Dave

[dhoggan]

Just an update to my quest for the Holy PSU....

Out came the previous mod of 8 * 63V 1000uF FC series and 2 * 63V 470uF FC series and in went 10 * 35V 1200uF FM series. Also the brown lump was removed and replaced with a nice blue one. Hot glue was then trickled in between the t banks of 4 caps. And 'cos it wouldn't hurt, 2 holes were drilled in the board above the transistors below.

Now begins the loooooonnng burn-in period, but despite the glue still being warm, I think it sounds better.

Thanks for all the advice and views - really learnt something. Hope you guys won't mind me asking about amp-board modding once I've been through the forum a couple of times :-)

Dave

[dhoggan]

Just an update to the mods I made to the PSU board in my v2. Open the unit up today to mod the amp board only to discover that some of the hot glue had melted all over the place - even down down the rear valve. It'll be a bugger to remove that sometime in the future!

The hot glue on the front group of four caps is fine, just the rear group which are spaced slightly further apart. If you're thinking of using hot glue... be careful.

Dave

[dhoggan]

Hi,

A good question , but one I don't know the answer to. The glue & gun was bought years ago during my computer modding phase and all packaging has long since disappeared. Admittedly, the glue was still warm (though solid) when I put the PCB back inside the 'can'. Temperature is nowhere even close to 250 - it's warm, but not hot, to the touch.

Dave

[PinkFloyd]

You've possibly used a low melt glue stick, essential that you use a hot melt glue stick it will never melt inside the amp and will stay rigid always.