Arcam Alpha One upgrade

[Malefoda]

Hi there!
On a famous CDP mod therad, wise guys as Simon and Brent advised me to upgarde my Acram Alpha One (not1!!).

Originally posted by SimontY
Wow, super upgradeable!! Those caps look rubbish, but... There's clearly loads of room for bigger ones, and ditto the transformer. If you could find a larger tx and physicaly larger (possibly same uF rating but better) caps (such as BHC Aerovox etc. - search the forum) then you could improve the bass (and the rest) somewhat. Some kind of service manual would help you identify which other caps could be upgraded to good effect. You could have some fun here and produce something more worthy of partnering your cd player.
Simon

Did someone have done this?
Any idea for the caps? Others?

Thanks,
Matthieu

[richie00boy]

I'd be interested on what basis the claims are made that the caps are rubbish. Dubilier is a decent enough make. What output is the amp rated at?

6800uF is on the low side for a stereo mid-power amp. It certainly wouldn't hurt to upsize the transformer either.

[Malefoda]

35W I think. I have no idea of what has to be done, I just want to know what can be easy and cheap to improve some. Not rebuild it
I'm almsot ready to invest on this one:
http://www.ornec.com/productim/100106/tw-2006-8.jpg

[SimontY]

Oh dear, you've got me in trouble! lol

You need to trust your ears with the caps. Bigger capacity ones really could hurt the sound. Feel free to try though. I say this not because it's fashionable, but from some experience with two different amps of my own. Larger caps can improve the deep bass at the expense of everything else. The often talked about "snubber" of 1ohm and 100nF across the caps can bring the "freshness" back.

The rectifier diodes could affect the sound too, so consider "fancy" types here too, schottky etc.

The passive components are important, apart from those suggestions I can't offer much more because I don't know enough about how your amp was designed. Good luck with it.

Discussion of the "snubber":
Carlos' snubberized Gainclone Power supply

Simon

[SimontY]

Originally posted by richie00boy
I'd be interested on what basis the claims are made that the caps are rubbish. Dubilier is a decent enough make. What output is the amp rated at?

6800uF is on the low side for a stereo mid-power amp. It certainly wouldn't hurt to upsize the transformer either.

I withdraw the claim! I'll change it to "they don't look impressive"!

Caps that are larger for a given capacitance tend to be better specified and sound better. Black Gate, Elna Cerafine or Silmic, Siemens Sikorel (sp?) and BHC Aerovox are all said to offer good sound.

Matthieu,

If you can get a service manual perhaps someone here can point you to the most sensible components to upgrade.

Simon

[Malefoda]

I have the service manual, Arcam is very kind and offer it by mail. I'll put a link when I'll have uploaded it.

[es44]

I must admit, that the whole construction doesn't look too impressive
What catches my eyes is the potentiometers, the tiny cooling fins, and all the jumpers on that board. I don't mean to offend anyone, but it looks a little like some "no-name board" put in a case with a "name" on it

[markk02474]

Originally posted by es44
I must admit, that the whole construction doesn't look too impressive

I would put it "rich in upgrade opportunities!"

Seriously, it looks easy to work on and improve upon. The diodes look like discrete 3A or 5A ones and not a monolithic bridge. There are some opamps there, and I hope that single in-line one has a Brown Dog adapter. The electrolytics could be replaced with Panasonic FCs on the power rails and Black Gates for signal coupling. The ammo box caps might be polyester and upgraded to polypropylene.

I would start with the preamp section first as there is the most to gain.

[richie00boy]

Originally posted by SimontY
I withdraw the claim! I'll change it to "they don't look impressive"!

Caps that are larger for a given capacitance tend to be better specified and sound better. Black Gate, Elna Cerafine or Silmic, Siemens Sikorel (sp?) and BHC Aerovox are all said to offer good sound.

It's just not that easy to gauge size on a photo like that. Maybe you studied it more

Yes a bigger sized cap of same capacitance generally has better ripple current capacity and a few other nice properties.

I do actually use Schottky diodes in my own designs.

If the amp is only 35w then 6800uF is not too bad.

Maybe upgrading the volume pot might bring benefits.

[SimontY]

Originally posted by richie00boy
Maybe upgrading the volume pot might bring benefits.

Especially if the channel matching is poor.