that's some great info jon, and I wish more people could view it.
at8533 > mp-2 > modsbm-1 is a bit bulky, but it works like a champ.
I thought you plan was to do something like PM4/PS-2/AD-20 all in one box with stepped gain. Either way, thanks for trying this and listening to our opinions.
My plan was first to provide the PM4/PS-2 function in a truly small box (AT PP9). That is, I'd leave it to the customer to find a gain stage. Then my plan was to work in blissful serenity on a suitable gain stage & basscut in the smallest possible package (AT PP9-Pre). With the knowledge then acquired porting to a say AD-20 would be no challenge. But using the AD-20 as host is just one of several possibilities for running the AT mics in full performance mode.
Now I have come to realize that the first unit will be used with a D100 (and a UA-5). And a jb3 owner is interested. So I realize I have to jump right on the development of the AT-PP9-Pre. The challenge isn't in creating the functions but the limited space into which I want to do it.
The plan I have with the AD-20, again due to limited space, is to install a dual continouos volume control with gain 10 to 45 dB. Then use the stock rec. level controls for independent l/r fine control.
This project now hangs as I can't get the AD-20 to run at 48 kHz. (The DA-P1 accepts it as 48 kHz data but the M audio DIO 2496 does not see the ouput from the modded AD-20 as valid SPDIF data?. And my frequency counter is broken ... and, well...). The mod for 48 kHz is something the owner wanted. I might undo it till I get the right tools up and runnng.
Seems like this wouldn't be an issue for putting those circuits in a mod AD-20, since it will have that lower signal right now anyway, but it definitely poses a problem for those going without a pre.
For the direct to line people, it seems like some kind of gain stage would be best. The JB3 gain can be noisy, so the common reccomendation is to leave it at 0 and either adjust the input or bring it up later on your PC. So if you could do a variable gain stage that may be even better for the jb3 line in users.
Agreed, with the AD-20 f. ex the low levels pose no problem.
I don't know the jb3 first hand. Care to just tell me what are the know issues and specifics with line-in and gain settings? Or point me in the right direction?