Yes, it is really going to happen: a modified Duet.
I just sent out the first evaluation unit this afternoon. A few more to follow shortly. We have several different power supplies that we are looking at making, so some guys are going to have to listen to more than one. No, I don't listen to anything that I design, as it is never a good idea for the designer to evaluate it. (We know what it did, and what we expect it to do. So, we let others do that job.)
We are still aiming at making this a $500 mod.
If we decide to go with one of the larger supplies, that may be hard to do. Another thing we have decided on is what will be included in the basic offering.
Ok, for $X (whatever "x" will be), this is what we will do:
Low-noise oscillator, powered by its own low-noise regulator inside the unit. Not only will it be separate from the rest of the Duet, it will be fed from a separate pre-regulator inside the remote supply.
The remote supply will not only replace the stock SMPS, but will not be interchangeable with it. Or any other power supply. The Duet will have a power cord sticking out of the back, with a connector that will only mate with the supply that we supply with it.
The clock and SPDIF stages will no longer share the same chip. Each will be independent of each other. (They will share the same supply, as that is essential for proper operation, but they will be isolated in that respect.)
The output will be transformer coupled, with a 75 ohm BNC connector. The output return loss of this output will be <-36 dB. (IOW, pretty damn accurate.) The SPDIF will be reclocked to assure low jitter.
And the power supply, as mentioned above.
The Duet will now only work on 44.1 kHz source material. Not knowing enough about the architecture of the unit, I can not say with certainty that it will work with 32 kHz 'Net radio. We have reports that it seems to work ok. Perhaps it is smart enough to figure out the 48 kHz clock is disabled, and somehow resamples to 44 kHz instead. I have no idea. It seems to work, but we do not promise that it will for that application.
Now.............there will be one level of upgrade above this. Probably for an additional $100.
This mod is only for those who use the analogue outputs. In order to keep the cost down, this will only be provided for those who actually use those outputs. No sense gouging folks who have no use for it. And frankly, the mod I came up with is a bit of a pain. So. the less folks who want it is fine by us.
Here is what it will entail:
Separate supply for the DAC chip.
Clean clock signal applied directly from the clock, instead of some giant chip. (Which is never good for jitter.)
The post filter will be slightly altered, mostly to add some better parts. And get rid of some others that I feel should not be there (Sorry, Sean!) We do take steps to address the purpose of those parts, so rest assured that we did not sacrifice one feature for another.
The output caps will not be changed. I know, caps do sound different. But seriously, we have no intention of listening to a bunch of SM caps, only to find out that most of them sound as lousy as the other one. We do not play the "politically correct parts game", and have less desire to find a way to shoe horn a cap that is larger than the case into one of these buggers. Sorry, you have to accept what is in there. We have improved it enough to more than justify the price. If you are the type that loses sleep over what brand of cap that is used, then please, either accept what there is or look elsewhere. We are not going to get involved in that realm.
Ok, that is the good news. Here is the bad news:
You should all be aware that our company is not in the modification business. I will end up doing these on my spare time. (Yes, I can get the hired help to make the PCBs and drill the holes in the supply chassis. But I will have to do the actual job of shoving the mod inside the Duet.) As I have more than enough things to occupy my day, these will be done on a limited basis. IOW, if you request to have your unit done, you will be assigned a number, and contacted when I am ready to proceed. Anyone who sends one to us without being assigned a number or jumps the gun will have their unit sent back. Stock condition, and COD. Ok, got it? I'm serious.
OK, maybe not the best business model to use, but again, we are not in that business. So, "we" will only proceed as my time allows. Sorry, but I don't want to have my other functions bogged down by this type of work. I will provide it as a service, but I hope that you all understand that this has to be at my discretion.
Ok, here is the preliminary view of what to expect.
With one of the "small" supplies that we are thinking about
OK..........questions............?
(I sure hope that I don't live to regret doing this.)
Pat
