I have done a few mods to my Chiarra. I know a few people have similar kit and though it would be worthwhile posting the changes with a photo; I am very new to changing components and so this is a bit of an idiots guide with an idiots comments. A lot of thanks go to Frans for pointing me in the right direction.
I went through the various opamps and stuck with an Audio GD (moon) – circa £25. I did not try the Burr Brown recommended by. The Moon is attached with flying leads and is glued out of the way.
I while back I did a lot of rewiring and fitted new Audio Note plugs. The wire was from HiFI Collective and is silver/gold. To me it increases the highs. It can be bought here
www.hificollective.co.uk/catalog/advanced_search_result.php?keywords=mundorf+wireNext I purchased two Ansar capacitors as follows,
www2.cricklewoodelectronics.com/Cricklewood/product.php?productid=2050&cat=155&page=1Their code was CPW2U2 and overall it was £11.40 with postage and VAT.
Mike had used these in his Chiarra. I soldered one in the wrong way around and had to add a bit of wire !! to get it right. Mike had commented that they increased the sound stage. In my view this was spot on and after 50 hours they have a very transparent quality. The odd things is that they place the sound to the point that at times there are eerie gaps between the centre, left and right, but it doesn’t sound in any way wrong. Given the outlay they are a real bargain.
The bulk of the changes were done when I had a spare 20k TKD pot handy; the original (ALPS) one was a 50k unit but I paid a lot for the TKD unit and wanted it in the Chiarra. The TKD was swapped out when I fitted a DACT Attenuator to another amp. The TKD is better/different than an Alps (noticeably to me) but the DACT is in a different league. I would not now invest in a TKD but would save up for the DACT if looking to upgrade.
The problem with the TKD was the limited volume control. Frans recommended,
"gain: you need to change R4 (not R1, that's a so called 'stopper' resistor to avoid oscillations when the volpot is turned all the way down.)
each halving in value will lower the gain by 6dB
so 15k will give lower gain, 47 k will increase gain."
The Chiarra has 28k so I picked 6k8 resistors, and bought them from HIFI Collective. Frans was viewing one channel of the amp and thus R4 and the left channel equivalent were changed (PM me if you want a copy of the build manual I have).
Frans also suggested,
"here's an idea since you have 2 output sockets.
replace R8 and R28 for 100 Ohm and your amp now has 1 low Ohmic and 1 high Ohmic output.
Very easy to switch but don't get fooled by the drop in volume !"
I picked 120 ohm resistors as I was using HD595s which are 120 Ohm headphones.
I had asked Frans about changing the capacitors
“C5 and C6 can be increased in value if you want.
What's more important, certainly when rolling is to create decoupling at the opamp.
Now it isn't present and fast opamps will oscillate (may be inaudible)
Simply mount a ceramic cap of 100nF between pin4 and pin8 directly to the pins of the socket at the underside of the board.”
I ungraded the C5 & C6 capacitors to 1000uf (from 470uf) and bought the ceramic cap from Maplin (for peanuts). The C5 & C6 initially increased the bass but they have now mellowed in.
In addition to Frans’ recommendations I replaced R1 & left equivalent with the same 3K3 resistor as Rick had posted that “as it was in the signal line it should be as good as possible”.
My overall spend at HIFI Collective was therefore as follows,
2 x NKZ-220 - 1000 uF 25V Nichicon KZ type, UKZ1E102MHM £2.28
2 x (AMRG0.75-390) 3K3 0.75W Amtrans AMRG Resistor £7.08
2 x (AMRG0.75-430) 6K8 0.75W Amtrans AMRG Resistor £7.08
2 x (AMRG0.75-220) 120R 0.75W Amtrans AMRG Resistor £7.08
The combination of the new resisters was to bring volume level back to how they were with the 50k pot.
I am not sure if the flashy resistors made much of difference. The amp sounds great however. I am in no doubt the vol pot, Ansars, and resistors made a real difference overall and I would recommend them all. It is getting better by the day. Best of all I found the Chiarra a joy to work on. The case I have dates back to 1995 and the bottom plate can be removed. It is easy to use a solder sucker to free the original components and then a matter of slotting the new ones in and dropping a new bit of solder in from the underside.
The amp is still short of the White Noise Audio I have. There are a number of reasons the WNA should sound better including a better DAC source and very careful CPlay setup. A comparison would be unfair and I can’t be bothered moving kit around to do so accurately. What I can say however is that the above changes have made the amp much better, I am very happy listening to it, and I feel a sense of achievement having carried them out. I now intend working on my old Cyrus One to do a capacitor replacement for that.
Finally, CPlay is great, free software. It is well worth setting up a windows installation and stripping it down as per the Cplay forum.