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Old 26th February 2010, 12:32 PM   #1
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Default ARCAM A75 help

I recently picked up a used ARCAM DiVA A75 integrated (50WPC) for a song because it had a problem. Seller stated the amp would not go out of protection mode on turn on, relay would just keep clicking. I contacted ARCAM about this and to my surprise got a response same day. Probable cause according to ARCAM was cold solder joints on the output transistors. Sure enough that was the problem. I re-soldered them and that particular problem was solved.

Which brings me to the purpose of this post. Right off the bat this amp sounds like s**t...boring, lifeless and veiled. I've owned several ARCAM integrateds including the Alpha 9, which I'm currently using, the Alpha 10, A65+ and the A70. Everyone's aural memory is short but I do remember the A65+ (40WPC) sounding better than the A75. To my ears the Alpha 9 is the best sounding of the lot and the A75 the worst. ARCAM also made a A75+ which I haven't heard. I contacted ARCAM three times asking what the difference between the A75 and the A75+ was to no avail. Does anyone have any idea what the difference is? They obviously tweaked the plus version cause the other sounded like crap.

For those of you who don't know the Alpha and Delta series of amps used MOSFET outputs and the DiVA range, which followed the Alpha's, use bi-polar outputs. The A75 uses for the pre amp section one BurrBrown OPA2134 DIP op-amp and the phono stage uses one Philips NE5532 DIP op-amp. Are there any serious tweakers out there that can help to make this amp sound better?
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Old 16th June 2010, 10:51 PM   #2
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I don't know what the differences between the A75 and A75+ were but I'd guess things like better quality coupling capacitors, opamps, electrostatically shielded transformer perhaps with uprated power rating. I wouldn't expect anything radical though - just better components in a few selected areas. What was the different in new price between the two ?
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Old 8th July 2010, 09:36 PM   #3
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The bias in the A65/A75 is set to 37mV which equates to 84mA , the A65+/A75+ has the bias set to 12-15mV which equates to 27-34mA . The Sanken recommendation is 40mA which would be 17.6mV across the bias test points. This might also explain why the A75 sounds worse than the A65+.
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