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Old 28th April 2009, 12:40 AM   #51
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Quote:
Originally posted by skidude
Thanks very much for your suggestions.

The feedback cap is currently a 100uF NP. I've been doing a bit of reading of this thread and now I'm not sure what to try!

http://www.pinkfishmedia.net/forum/s...ad.php?t=61242

Regarding the input caps, I guess I will need to stick to the original 10uF so I don't loose low frequency response? A poly cap of this value is physically pretty big and there's very little room on the pcb for it! maybe there's more room in the 340A?

I tried the 22uf wimas even though my amp is completey different to the Naim most of those guys are modding. It had a great effect in my amp. I much prefer the bass response with this cap over that of the 100uF Rubycon ZL lytics I had tried previously. Physically they arent that big and have a 5mm lead spacing, they should hopefully fit. The wma MKS2-XL also come in 10uF so might be worth a try for the signal path dc blocking. I used 3.3uF wimas and have no loss of bass. However I do have TL speakers so maybe that helps. Why not ask on Pinkfish?


EDIT: Just to give you an idea of the size of the wima caps. The large square red ones are the 22uF and the smaller square ones are the 3.3uF.

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Old 28th April 2009, 02:49 PM   #52
skidude is offline skidude  United Kingdom
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Thanks for the piccy, that's really useful. The standard lead spacing is 5mm so indeed they should fit.

So far I've looked in CPC and Farnell and neither sell the wima MKS2-XL.

Where abouts did you buy yours from?

cheers
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Old 28th April 2009, 02:58 PM   #53
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I got some from a friend on Pinkfish. I had trouble finding them myself. Perhaps try asking wima direct, maybe you can get some free samples?

EDIT:

some info http://www.diyaudio.com/forums/showthread.php?s=&postid=1813975#post1813975]here,[/URL] also try asking a DIYA user called 'Pacificblue'. Hes in Germany where the wimas are made and he recently got some for a guy in Russia, maybe he can get you some.
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Old 28th April 2009, 03:15 PM   #54
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The 3.3uF are available from Farnell:

http://uk.farnell.com/wima/mks2-3-3u...-50v/dp/107423

Mouser do the 10's and 22's:

http://gb.mouser.com/Search/Refine.a...mks2xl&FS=True
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Old 28th April 2009, 03:28 PM   #55
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If your concerned about losing bass (not a problem in my set up) maybe you could try 2 x 22uf in parallel? Stack one on top of the other and solder the leads with some short wire, then cover with heatshrink.


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Old 28th April 2009, 09:54 PM   #56
skidude is offline skidude  United Kingdom
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Thanks again for your help Mike.

I didn't realise just how expensive those caps were, 6.80 for the 22uF?!! The mark-up on those must be immense!

I might try for some samples, they'll get suspicious when I tell them I work for Nokia! I could always tell them they're for a charger though!

Today the Panasonic caps arrived so I've been busy fitting those. They fitted perfectly. I'm a bit disappointed with the build quality of this amp though. There are 11 wires underneath the main amp PCB!

Most of the small transistors were crooked and the assy worker must have used a whole reel of solder on it.

It looks a lot better now though. I'm just waiting for the Alps pot to come from Germany and hopefully get a few 10uF and 22uF Wimas in before reassembling. Getting the Alps to fit will be fun! ;-)

I see you changed your speaker posts in your 340. Mine are very flimsy and have horrible long thin posts that are in the signal path. They'll have to go!
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Old 28th April 2009, 10:35 PM   #57
jaycee is offline jaycee  United Kingdom
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The assembly of Cambridge amps is unfortunately very poor. They are obviously not wave soldered, as it's quite obvious manual soldering with rosin flux core solder has been used - and the flux not washed off... or the solder spatters for that matter!
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Old 29th April 2009, 12:39 PM   #58
skidude is offline skidude  United Kingdom
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Quote:
Originally posted by jaycee
The assembly of Cambridge amps is unfortunately very poor. They are obviously not wave soldered, as it's quite obvious manual soldering with rosin flux core solder has been used - and the flux not washed off... or the solder spatters for that matter!
Indeed. They look great in the catalogs and even the Hifi magazines claim they're well build but when you turn the PCB's over... I wonder how good their yield rates are? I wouldn't be surprised if customer returns are high. My amp was in a Richer Sounds Returns box labled "scrap" which was worrying at first. But it was only a blown fuse at fault.

I ran out of solder wick trying to rework the pcb, I must get myself a desolder pump! :-)
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Old 29th April 2009, 10:08 PM   #59
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Originally posted by jaycee
With no expertise, you are really best leaving well alone or you will end up with a dead amp. Sorry to be so negative about it but I have seen plenty of people kill their gear by attempting mods they read about on the internet, but they had no experience of implementing them.

If you increase the size of the caps you also increase the surge current at on time. This could blow the mains fuse.

You have to consider all consequences of changing components.
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Old 2nd May 2009, 12:10 AM   #60
skidude is offline skidude  United Kingdom
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My amp is back together now with mods 1 to 4 completed.

Fitting the Alps pot isn't easy though as the legs are in a different position and they sit very close to the surface of the PCB. I temporarily mounted the pot upside down and wired each pin to the pcb with short pieces of wire. Not ideal at all but it works. It's a motorised pot and it works well with the driver circuitry from the Cambridge. I'll improve this as I suspect it'll be degrading the sound.

No issues with blowing fuses. I had a selection ready just in case!

Apart from much better tracking (Alps) the sound appears to be fuller. The bass sounds deeper and more effortless. I'm surprised how loud it will go without sounding stressed.

Other parts of my system are;

Marantz CD63 KI sig CD, Rega Ela Mk2 speakers and some Chunky cables from eBay.
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