New AU-D11II

[Zekeman]

Just got an AU-D11II today. Impressive audio. Super pure and fast! I really like the sound of it.

What a bitch to work on. Took me about an hour and a half to figure out how to get the glued-in circuit boards apart (the little black vertical support clips pivot away from the side of the board)...Got the power supply board and the front board (with the turnover switches) recapped.

Pix later.

 

[Robisme]

Nice amp.

Rob

 

[Zekeman]

Progress so far:

Recapped 75% (Not a purdy cap install in terms of alignment....but they are in there solidly), Installed new opamp, and installed RCA's for preamp out.

 

[mjs1]

Great job, show us more when you're ready. I would like to read your comparison of the AU D11II, when you are through, with your AU 9900 and 717.

Marc

 

[Bigerik]

Progress so far:

Recapped 75%, Installed new opamp, and installed RCA's for preamp out.

Careful with the pre-amp outs. Apparently, it does not take very kindly to a change like that. Will talk to my friend John, probably the pre-eminent expert on these amps in North America, and find out what he had to do to make it work.
E

 

[NeilT]

Careful with the pre-amp outs. Apparently, it does not take very kindly to a change like that. Will talk to my friend John, probably the pre-eminent expert on these amps in North America, and find out what he had to do to make it work.
E

Can you please explain what you mean by "does not take very kindly" BigErik? I'm getting pre-out main-ins put in an AU-719 but would love to know if that is going to create other potential problems.

- Neil.

 

[Zekeman]

EW provided guidance on this so I feel confident in a positive outcome. I am interested in what John has to say about it as well.

Thanks.

 

[EchoWars]

Well, I've never tried it, but it ought to work.

 

[Bigerik]

EW provided guidance on this so I feel confident in a positive outcome. I am interested in what John has to say about it as well.

Thanks.

Will try to get ahold of him tomorrow. These units are Johns specialty.

How were you planning on going about doing it? I can run that approach by John and get his thoughts.

 

[EchoWars]

Connection point 38 and 41 from the preamp board to the back panel. Zekeman said he did not need full pre-out/main-in capability, so these preout jacks are stand-alone (essentially a parallel 'tap' of the preout signal).

 

[Zekeman]

That's right...I just need the signal from the new preouts to send to an active crossover which will, in turn, drive a b-2101 for subwoofers. I will run L-96's off the D11's main speaker outputs.

 

[Zekeman]

Question regarding the center photo in the third posting above: What exactly are the clear plastic components with the copper colored "foil" inside?

Thanks.

 

[gusten]

Question regarding the center photo in the third posting above: What exactly are the clear plastic components with the copper colored "foil" inside?

Thanks.

The foil is of course copper foil and the components are Polystyrene caps with very low values,like 10 to 50pF.Absolutely top quality caps.Caps like these are perfect to use as Miller-caps.
/gusten

 

[Zekeman]

Well Thanks for the info.

Below is another pic of progress....New opamp on phono eq board.

 

[bobrown14]

Hey Zekeman what opamp did you replace the original one with and why?

Bob Brown

 

[EchoWars]

He's using OPA2604.

Stock power supply rails for the AU-D11 II are +/-21V. Puts a huge limit on what you can use unless you want to redesign the regulated supply to lower the voltage.

 

[eradoncic]

Even better results can be achieved using Analogue device's OP-275; supply voltage above 19V in this opamp drasticly reduce THD below .001%, and has better input noise than 2604. (For details, please refer to fig. 5 on the page 7 of the OP275 data sheet http://hjem.get2net.dk/tkhifi/data-blade/op275.pdf ).
My 5c

 

[EchoWars]

Max rails on the OP275 are +/-22V. The specified rails on the AU-D11 II for the opamps is +/-21.2V. That's just cutting it too close.

 

[eradoncic]

Well, it is risky only in lighting area...otherwise, it works good - the mains voltage usually tend to be lower than specified:scratch2:

 

[Zekeman]

Recapped the board located in the back-left (first pic), behind the main filter caps....what a bitch that was....and then when you can visualize the board there are thirteen caps to replace....!

This amp (and I suspect like many others built at the time) is like a unibody car; each part is hanging onto the next for support.....oh well it seems worth the effort.

The other pic shows the routing of the new cables supplying the preamp signal to the newly installed RCA's on the back panel.

If all goes well I should be able to fire it up within the next day or two....