[Clutz]

Just to say that I think the differential outputs are great. It may mean that my next amp will be a dynamid.. and then converting my K701s and HD580s to balanced.

 

[MASantos]

This is probably a dumb question, but what is the purspose of the PIC?

Also, is there a ETA on the boards?

 

[00940]

The pic is a function selector for the cs8416. It avoids using a forest of jumpers.

There is no ETA on the boards. It must be first prototyped and troubleshoot and its sound evaluated before any further development is considered.

 

[Clutz]

Quote:

Originally Posted by 00940 There is no ETA on the boards. It must be first prototyped and troubleshoot and its sound evaluated before any further development is considered.

Might I suggest posting the schematic and layout at diyhifi? They seem like they'd be good for getting some more feedback on layout / design. The more eyes that look at it, the more likely that any errors that may exist will be caught. How much do you figure it's going to cost you to get the prototype boards made?

Cheers,
Clutz

 

[SnoopyRocks]

Quote:

Originally Posted by 00940 Snoopy : don't we have a lpf anyway with C37, C40, C51, C53 ? Considering how high the first alias will appear, isn't sufficient actually ? I agree it would be best to move the pads, to avoid assymetric interaction with the output lpf.

Yes, that network gives us a single pole. A single pole will only give 20 dB per decade and consequently very little attenuation in the second Nyquist band since this is less than a decade after the filter corner frequency. Why not give the differential output drivers the same filter as the I/V? It's just 4 more caps and there is plenty of board space for them.

Does 1st order filtering seem right for the differential output when the single-ended output has 3rd order filtering?
Quote:

Originally Posted by ble0t As for the PIC, I personally think it makes the design easier and more flexible. There are many more options that can be explored and the actual board layout is simplified/improved greatly by using it. Don't be frightened by the programmable logic

Ok. I just wanted to know the thinking behind the choice.

 

[ble0t]

As 00940 has said, there really is no ETA on the boards. For that reason, I can't even begin to guess what the cost per board would be. Although the main design is complete, the tweaks are not. Please be patient

 

[Clutz]

I just noticed that there is no reverse voltage protection. If you miswire your PSU and connect the power up incorrectly it could make for a rather expensive oops. How about dropping a single diode in there - a 1N4004? Even if it isn't likely to happen (which with me, it is) it's cheap enough to implement - and if people don't want to they can jumper it.

 

[Clutz]

Is it me, or did you guys read Guido Tents' article on decoupling ICs?

 

[00940]

Good point on the reverse protection.

I've read the paper of Guido, it's somewhere on my harddrive, why ?

 

[Clutz]

Quote:

Originally Posted by 00940 Good point on the reverse protection. I've read the paper of Guido, it's somewhere on my harddrive, why ?

The way you've connected the power and ground pins up on the ICs seems reminiscent to me of what he recommends in that article. I was happy to see it, that's all.

 

[ble0t]

Quote:

The way you've connected the power and ground pins up on the ICs seems reminiscent to me of what he recommends in that article.

That was the goal

I'll put a diode in for the section ahead of the LM317....putting them anywhere else would affect the voltage on the rails.

 

[Clutz]

Well,fwiw, the more I look at it, the more impressed I am with it.

 

[ble0t]

Just to keep everyone updated, 00940 and Snoopy are working on some filter related stuff (as per the discussion previously in the thread). As soon as they square that away, I'll have what will hopefully be the final version of the board.

 

[Clutz]

Thanks ble0t,

Does anyone have any suggestion as to where I can go to read about filters?

Thanks,
Clutz

 

[00940]

there are two chapters on that in the book on opamps applications published by Analog Design under the direction of Walt Jung. I posted the link somewhere on this board to download it.