SSR01 as direct feed for 3.3v + supplies for sabre dac

[qusp]

Hi everyone, I recently bought some of the PCBs for the SSR01 and 02 to serve as regulators for AVCC (L and R) and DVCC (B and T) and VOSC. well at least 3 of these positions and I may use another as a prereg for supplying the other 2. I have bought enough parts for 3 5V supplies, because at the time I had planned on using them all as preregs, but thought they may be good enough to supply direct, as I have changed tack. anyway as there is no BOM for anything below 5v, so i'm wondering which parts I might have to change to get them down to a stable 3.3v i'm assuming the red LEDs are still the best reference??

I have all parts for the trimpot version as well, so I have pretty much every option for DZ1 and DZ2 as well as N1 , N2, IC1 etc etc. I basically covered myself for a few 5v 1 or 2 trim pot builds and a couple + - 15v so I have most values to play with. i'm a bit of a noob in power supplies, as far as setting voltages with R values. any ideas on what I need to change from the strandard 5v BOM to get 3.3v?? should I be working with a pot here til I find the right value and then switch out the pot for a matching value resistor?? also I had to grab some 5% resistors as digikey did not carry all the values needed in the 1% .6w, will this cause me issues, most likely would surface in the form of noise right?? i'll be working till I find the right values and then replacing the vital points with vishay S102 or Z102 for lowest noise eventually, but I wanted to grab everything needed to build some up and save a little on shipping as a temporary measure.

and yes I have had a look around the threads here, but the only time it was mentioned there was no definitive answer other than it was possible, so hopefully I can get something a little more concrete. Perhaps since its possible, it could be added to the BOM since its such a common voltage for digital devices and from what I can tell these supplies should be quite well suited to such a low noise situation

any help would be much appreciated, thanks for reading

[qusp]

oh yeah i'll be using 240v/20VA transformers with dual 15v secondaries with preregulators supplying ~ 8v or so DC or a 240v 15va with dual 10v secondaries also preregulated. in a related question for the 15v rails for the I/V section of the same dac, can I use a bipolar preregulator to supply a ssr01/02 pair??

[peranders]

I have experimented with 3.3 V out but I haven't tested it particularly much.

What is did was this:
Reference set to 2.5 V
Gain set to 1.32
The opamp was fed after the prereg, appox. 6 V
The DZ1 was a red LED

The opamp should be a rail-to-rail type or at least be able to handle the common mode voltage you have here. I used an AD825 (if I remember correctly) and it is specified to work at more than 9 volts.

If you try a 10-15 V/us opamp you should very much likely succeed but a AD825 or similar could be tricky.

[peranders]

also I had to grab some 5% resistors as digikey did not carry all the values needed in the 1% .6w, will this cause me issues, most likely would surface in the form of noise right?? i'll be working till I find the right values and then replacing the vital points with vishay S102 or Z102 for lowest noise eventually

The sensitive locations for the noise performance are the LP-filter R12, R9, the feedback, all resistors around the inverting input of the opamp, pin 2.

[qusp]

I have experimented with 3.3 V out but I haven't tested it particularly much.

ok, well lets see if we can come up with something solid then, I may tinker away at it for a little as I already have a couple of options for powering this dac, but I really want to use these, I think they will work quite nicely if I can get them stable

What is did was this:
Reference set to 2.5 V

ok, so to do this I find a reg within operating range and at 2.5v (LM317??), alright i'll see what I have here; or are you suggesting I do this by use of the trimming resistors??

Gain set to 1.32

OK

The opamp was fed after the prereg, appox. 6 V

ok, so the onboard prereg at 6v, check

The DZ1 was a red LED

cool, got some

The opamp should be a rail-to-rail type or at least be able to handle the common mode voltage you have here. I used an AD825 (if I remember correctly) and it is specified to work at more than 9 volts.

If you try a 10-15 V/us opamp you should very much likely succeed but a AD825 or similar could be tricky.

ok, well I have all manner of opamps here and i'm a fan of rail to rail buffers in my dacs, so I got a few that should suit, but the problem is that many may be too fast for this situation. some of the single channel opamps I have here are
OPA211, OPA1611,  LME96410, OPA827, AD825 of course, AD744, and quite a few others, but with the info you supply there, i'm not sure any suit?? from a quick search as i'm making orders anyway, how about OPA37 or OPA743 (this looks promising). i'm assuming dual types cannot be used?? because I have craploads of dual rail to rail type low noise/low supply and thanks for the tips on psitions to watch for noise. will take note and once I have a working value i'll order in some nice R's to suit.

thanks muchly ;)

[peranders]

The reference is the LM431 and set it to 2.5V or you could use 1.2V ref or higher.

[qusp]

lol, yeah ok of course  :? ; looking at the wrong part, I have all of them open in excel. cool ok, like I said I have pretty much all the parts for all the configurations, so i'll work something out. i've got some smd lt1763 1.2v too, but thats no good in this package. anyway i'll report back when i find some time to start and have a few more parts here.

[zz1969]

lol, yeah ok of course  :? ; looking at the wrong part, I have all of them open in excel. cool ok, like I said I have pretty much all the parts for all the configurations, so i'll work something out. i've got some smd lt1763 1.2v too, but thats no good in this package. anyway i'll report back when i find some time to start and have a few more parts here.

Were you successful with 3.3v finally?