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-   -   Cambridge Audio A1 mk3 upgrade mods (http://www.diyaudio.com/forums/chip-amps/174022-cambridge-audio-a1-mk3-upgrade-mods.html)

Honda Z50M 21st September 2010 11:37 AM

Cambridge Audio A1 mk3 upgrade mods
 
Does anyone know of any component upgrades or a mod for bypassing the audio controls?

Thanks in Advance

Best Wishes
Tom

sardonx 29th November 2010 02:58 AM

i once replaced the power supply caps with two DNM (BHC) slit foils (not the t-network, the normal ones). I'm sure they could be had quite a bit cheaper there since they are UK company i believe. And the opamps in the preamp to burr brown opa2604's and let me tell you the amp turned into a monster while retaining all of it's typical strengths. It made it super punchy and sent heaps of energy out the speakrs. In fact i'm on the lookout for a used one here in Canada so I can do that mod to it. Best amp i've had. I do'nt know why you wanna take out the tone controls.. they are useful and sound great.

Honda Z50M 29th November 2010 07:34 AM

Thanks for the reply, do you happen to know the cap and op amp ID's on the PCB?

It is a cracking amp even in it's standard form and well built, too much HiFi snobbery around if you ask me.

Generally I don't use the tone controls so would like to bypass them and maybe fit a switch so I have the option.

Best Wishes
Tom

sardonx 30th November 2010 01:01 AM

Well when you open the case, the board closest to the front plate is the preamp circuit. There are two gold rectangular covers which will have to be removed to get to the opamps. These covers don't really serve any purpose other than looking cool. I think i cut mine off with some heavy duty wire cutters. There is one opamp under each cover.. you cannot miss them. They are ne5532's.

As for the power supply caps, you cannot miss them either. They'll be the biggest in the amp. I have to mention though that I've had two of these amps at different times and one of them had two large filter caps (around 5000 to 10000 uf each) and the other had two banks of four 2200 uf caps. I hope for you it's just the two caps as it'll make it easier to wire up.

You will have to take out both the circuit boards (the amp and preamp) to work on them. Which in this amp involves taking the knobs off, severing the power wires, taking out quite a few screws and i'm sure other things i cna't think of now.. but if you do it all in order and keep it neat it's not that difficult at all. Well worth it.

I actually remember wanting to do the same as you with the first amp i had.. to bypass the tone controls but i never got to it. You may be able to bypass the preamp board altogether by rearranging the jumper cables that connect the boards. But I'm really not sure of that, so do that at your own risk!

Honda Z50M 30th November 2010 07:29 AM

Thanks very much Sardonx, it's very much appreciated.

Hopefully I'll get round to it this side of Christmas, I'll let you know how I got on.


Tom

Honda Z50M 1st December 2010 07:23 AM

Had a look last night my amp has two groups of 4 caps all 2200uf 35V.

Had a look at BHC slit foil caps and they don't appear to do anything less than 10,000uf (excluding the large 200v + ones).

I suppose I should look for low or ultra low ESR caps as BHC slit foil are aprox 0.06m'ohms and low ESR are aprox 0.1m'ohms, so anyhting less than 0.1m'ohms should be almost as good unless you know of anything.

I haven't removed covers from op amps as they look soldered from underside but I assume they are DIP and not surface mount??

Tom

sardonx 2nd December 2010 02:35 AM

Hey.. that's unfortunate.. I don't know of any caps that fit that bill. I'm actually not sure what's so special about the DNM ones. I just know they sounded great. Here at the parts connexion they call them premium power supply caps. And I don't recall any DNM markings on them either.. just BHC. I also am not sure if you could somehow just use two 10,000 uf ones and somehow rewire into the existing places.. a circuit diagram and someone more knowledgeable in electronics might be able to help.

The covers are indeed soldered from underneath and yes the opamps are DIP not surface mount. I just installed adapters so you can plug in different chips easily. If i could get this amp here in Canada I would. But now you got me thinking i might have to damage my bank account and get the one i can get cheapest here which is the azur350 now. It has lm3886's i believe not tda1514's. It worries me a little.. i think the lm3886s are mosfet output and the tda1514s are bipolar output which may have something to do with its gutsy sound. I could be wrong though.

Mind you.. i did both these mods at once and i always assumed that it was the caps that made the amp sound bigger but now that i'm actually recommending it to someone maybe i should suggest that if you are going to do a mod that you do the op-amps first as it's the cheaper and easier mod. I suppose it is possible that they were responsible for the majority of the difference. Let me know how it goes if you go ahead with it... Mladen

Honda Z50M 2nd December 2010 07:20 AM

Thanks, I'll leave at the op amps which I hopefully will be ordering today as I'm also ordering parts to make a Kwak Clock 7 (low jitter clock) for my CD player.

I'm also going to fit a schaffner mains filter to the rear of the amp.

Fitted one to my cd player, seemed to help wiht the sound but not sure could have been placebo effect.

I have one lying round so it's not going to cost me anything to fit it.

Will let you know when done.

Thanks,

Honda Z50M 2nd December 2010 11:17 AM

I am actually going to use op amp LM4562 instead of opa2604 as it is much better apparently than the opa's, looking at the data sheets it produces a qaurter of the noise as the opa's (double the price though)

Tom

shepperd 2nd December 2010 12:45 PM

The LM4562 is a very good choice although some find it a bit clinical but in fact it needs some time to settle in. (my 2cts!)


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