Arcam Alpha 5

[aquapiranha]

Well I finally dusted off the soldering iron and had a go... I replaced a total of 10 diodes in the PSU section with lovely Schottky's and also ripped out a couple of opamps and replaced them with new Burr Brown OPA134's on sockets so I can replace and roll them easily. Plus I had to replace the broken RCA connectors.

And yes, it does sound better, the transients are unbelievable and the sound now has more of a 'live' quality to it. I will be ordering some more opamps to replace a couple of OPA27's I have not yet changed, plus perhaps some boutique caps also. anyone considering doing these mods should definitely give it a go!

[DSJR]

Try to get a spare loading gear for the drawer as these fail and originals are no longer stocked.

The CDM-9 tracked too well and Arcam's implementation of it was one of the best of all for clean tracking of badly scratched discs I found. After this era, Philips mechs were almost intentionally downgraded to the 1200 series which will play a disc within spec but not ones that aren't.......

[aquapiranha]

Try to get a spare loading gear for the drawer as these fail and originals are no longer stocked.

The CDM-9 tracked too well and Arcam's implementation of it was one of the best of all for clean tracking of badly scratched discs I found. After this era, Philips mechs were almost intentionally downgraded to the 1200 series which will play a disc within spec but not ones that aren't.......

Will do, thanks!

[leo]

Don't be quick to judge OP27 on its lowish spec
This op-amp doesn't sound half bad if used with care and makes a not too bad I/V stage, it don't like DC on its inputs, Arcam implemented a nice nulling circuit on the output of the dac chip which takes care of the DC (a lot of places don't bother with nulling ), could be one of the reasons why these chips work well in this cdp

BTW, this unit is dead flimsy in build, its picky what its sat on get it wrong and it'l sound flat as pancake

[aquapiranha]

Hi Leo, and thanks for the advice. I will be using sockets on the board so will be able to swap opamps at will, as I have with the 134's. Also, I will be trying different materials underneath.

[NRG]

I was going to add Leo's yer man for tweeks on the Arcamn he helped me greatly with my DIY dac based on an Arcam DAC board which is the same cct as in the 5.

The supply decoupling to the 1541 makes a big difference as does making the voltage difference between the -5v and -15v as close to 10v as possible. IE 0.1 to 0.3 volt.........0.5v is audible.

[aquapiranha]

thanks Neal. I am afraid my knowledge extends no further than following instructions on a sheet, however my soldering is prett good! So if anyone can point me to some step by step instructions I would be grateful!

Thanks

[leo]

If theres a good clear pic of the audioboard and mainboard I could edit it and add a few easy things to try

Obviously will keep things really simple

[aquapiranha]

Hi Leo, that is very good of you! is this any good?



A bit bright due to the flash. And this one of the business end...



Let me know if they are no good. I have already changed two of the opamps as you can see, and I have two more, I just need to order the push fits.

Thanks!

[leo]

Looks good, if changing caps on the main big board would not be a pain take a pic of that too, apart from improvements in sound you get better reliability