X-Can v2 Amp Board Mods.

[dhoggan]

Guys,

With the PSU board mods out of the way and the caps burning-in, I've been looking at my options for the amp board itself. As I've already replaced the tubes, pot and headphone socket, it seems the only areas left are the input, output and filter caps, oh and maybe heatsinks for the transistors. I know these have all been discussed in here, but just wanted to confirm if I understand the current views on these correctly....

For the output caps, it seems that 16v 470uF ( RS 521-1895) or 16v 1000uF (RS 521-1615) are recommended. I even read that the 1000uF are good if you have Sennheisers, which I have. In you opinion, would the 100uF give and advantage over the 470uF, or should I stick with a like-for-like replacement?

For the input caps, it seems that many people simply remove them and 'zero-ohm link' them instead, *if* there is no DC at source. If I had a multimeter I would check, but in your experience, do PC soundcard outputs have DC? If I understand correctly, there is a significant sonic benefit to omitting these caps if possible.

Finally the filter caps C104, C105, C204 & C205.... Mike recommendation seems to be Panasonic FM 35v 100uF. Can't seem to find these on RS, but they do have 150uF (526-1799). Would these be OK?

And finally finally, do you have recommendations for the type of heatsinks to use?

Hope you don't mind all the questions in such a short space of time; I've been bitten by the modding bug;-)

MIke, if you get a chance to read this, I'd prefer to buy from you if possible. Sould I PM you?

Regards,

Dave

[PinkFloyd]

dhoggan said:

For the output caps, it seems that 16v 470uF ( RS 521-1895) or 16v 1000uF (RS 521-1615) are recommended. I even read that the 1000uF are good if you have Sennheisers, which I have. In you opinion, would the 100uF give and advantage over the 470uF, or should I stick with a like-for-like replacement?

Stock output caps are 220uF non polars, fine if you're running high impedance 'phones but not optimum if you're planning on running low impedance 'phones such as Grado. 470uF is a good value and fits perfectly on the board and is MUCH better with low impedance 'phones. You'll notice that MF now fit 440uF as stock in the v3.

1000uF is a great catchall value and you will be able to run 'phones with extremeley low impedance (<32R) without roll off as well as high impedance 'phones.... so well worth fitting if you're ever planning on running 16ohm (or less) loads. Only minor niggle with the 1000uF is the size of them, they will fit but not as neatly as the 470uF. One thing is certain, 470uF or 1000uF sure do sound better than 220uF in this position with a wide variety of headphones / impedances.

For the input caps, it seems that many people simply remove them and 'zero-ohm link' them instead, *if* there is no DC at source. If I had a multimeter I would check, but in your experience, do PC soundcard outputs have DC? If I understand correctly, there is a significant sonic benefit to omitting these caps if possible.

I don't even have a soundcard in my computer so can't answer that question (I refuse to listen to my music through a computer) it's easy to check for DC though. Simply plug a set of interconnects into the output of your soundcard (with no music playing) get yourself a cheap multimeter (you'll get one for under a fiver) and set it to the DC range (200mV setting) probe between tip and sleeve of each interconnect (ie: probe between the pin and the outer body of the interconnect that's connected to your soundcard) the reading should be pretty close to 0.00mV if it's anything under 10mV then ok to omit the input caps. If it's a good quality soundcard then very likely it will employ its own output caps or a DC servo in which case the offset should be negligible.

I have a few types of non polar in stock, 1000uF 16V Nitai / 470uF 16V Nitai or 470uF 16V CapXon. Don't be fooled by the name, the "Nitai" are very nice sounding caps and were favoured by Dr. White in all his WNA amps, the CapXon are equally good but come in a slightly more compact package. They don't cost an arm and a leg either typically being well under a quid eack.

Finally the filter caps C104, C105, C204 & C205.... Mike recommendation seems to be Panasonic FM 35v 100uF. Can't seem to find these on RS, but they do have 150uF (526-1799). Would these be OK?

No. Strictly 100uF here. I have hundreds of the pana FM 100uF so will be able to supply them no problems.

And finally finally, do you have recommendations for the type of heatsinks to use?

You won't get one to fit the transistors in the v2 as the trannies are placed so close to each other, you will have to get a heatsink and then saw it to size to prevent them touching each other (and you really DON'T want them to touch )

Should I PM you?

Sure man I have everything you need, just let me know what you want.

Mike.

[dhoggan]

Mike,

Thanks for the post. I have procured a multimeter and it looks like DC on the input is pretty close to zero, with nothing playing. Jumps everywere with something playing though.

I have sent you an email for some bits.

Thanks,

Dave

[PinkFloyd]

Jumps everywere with something playing though.

Yes it will do, that's perfectly normal, it's the music.

[dhoggan]

Guessed it was;-) I was less sure of the the occasional spikes over 10mV though, but I guess that's also normal.

Dave

[dhoggan]

Well, the bits for the amp board arrived from Mike in good time for the weekend and despite a minor panic over breaking the cable that connects the PSU board to the amp board, the upgrade went pretty smoothly.

Now the odd thing is, and not in a bad way, is that the sound quality seems much improved. Improved in that the music seems much more much more defined - bass notes just stop dead when they're finished - a difference I expected with the diode upgrade, but only since I've modded the amp board does it really seem obvious.

Am I imagining this? If not. what would be responsible? Removal of the input caps or the upgrade of the output caps? Also, the the caps on the amp board benefit from burn-in the the PSU board do?

But, not matter what the reason, the sound quality has drastically improved, and that's what it's all about.

Dave