[nightanole]

Im having trouble finding a 5v supply of good quality. Ive found like 4 from old cell phones that have the right cable end. However they are all like 5.5-5.7v when measured. Would it be easy to just make one? All i want is a normal linear regulated unit. I have a wall wart case and the cable.

 

[Beefy]

Cell phone chargers will all be REALLY cheap switchers. Probably far worse than USB power.

Why not build a TREAD?

 

[nightanole]

I thought that might be over kill to make a $30 shipped ps for 5v.

 

[Beefy]

If you want something better, that is the price you pay.

 

[cobaltmute]

A σ11 can provide 5V.

Remember in you search that you're dealing with the PSRR of the regulators and then how much noise the regulator itself generates. You could drive yourself nuts to get an ultra quiet supply only to be adding noise with the TPS reg.

 

[nightanole]

Uh what does tps mean? rejection ratio i got.

 

[Beefy]

Cobaltmute means the onboard 4.5 and 3.3V regulators.

 

[grenert]

Quote:

Originally Posted by cobaltmute /img/forum/go_quote.gif Remember in you search that you're dealing with the PSRR of the regulators and then how much noise the regulator itself generates. You could drive yourself nuts to get an ultra quiet supply only to be adding noise with the TPS reg.

True, but the regs specified for the DAC have some pretty good noise figures for fixed regulators:
LP2985AIM5-4.5 30uV
TPS79333DBVR 32uV
So, you want to be at least that quiet if you're going to go all out with the PS. The ripple rejection of the regs is not so great at higher frequency, and that is something I think you can improve upon. I use an "optimized" LM317 supply with RC filtering with my gamma-1. You can read about ideas for improving the LM317 at:
Using 3-pin regulators off-piste: part 1
Simple Voltage Regulators Part 1: Noise - [English]
and in the Bob Pease book "Troubleshooting Analog Circuits" available here:
Amazon.com: Troubleshooting Analog Circuits (EDN Series for Design Engineers) (9780750694995): Robert Pease: Books

Whether or not you can _hear_ a difference with a better supply is unclear, but DIY is all about overkill, right?

 

[cobaltmute]

Let's use my example:

The σ11 is very low noise - 12µV per amb. Now take a look at the datasheet for the TPS regs. It only states output noise for the TPS79328 @ full output, but it is spec'ed at 32µV best case. So you are dealing with the fact that the on-board regulators are adding noise to the line.

So you can supply super clean DC to the board and your ultimate limit on noise is the on-board local regulators.

 

[cobaltmute]

Quote:

Originally Posted by grenert /img/forum/go_quote.gif True, but the regs specified for the DAC have some pretty good noise figures for fixed regulators: LP2985AIM5-4.5 30uV TPS79333DBVR 32uV So, you want to be at least that quiet if you're going to go all out with the PS. The ripple rejection of the regs is not so great at higher frequency, and that is something I think you can improve upon. I use an "optimized" LM317 supply with RC filtering with my gamma-1. You can read about ideas for improving the LM317 at: Using 3-pin regulators off-piste: part 1 Simple Voltage Regulators Part 1: Noise - [English] and in the Bob Pease book "Troubleshooting Analog Circuits" available here: Amazon.com: Troubleshooting Analog Circuits (EDN Series for Design Engineers) (9780750694995): Robert Pease: Books Whether or not you can _hear_ a difference with a better supply is unclear, but DIY is all about overkill, right?

When you're building one, overkill is good.

The datasheet only spec's noise on the TPS79328, not the TPS79333. We can hypothesize or measure, but it is not on the datasheet.

Dual secondary transformer with separate regs supplying 3.3V and 5V bypassing the on-board regs?

 

[amb]

Quote:

Originally Posted by cobaltmute /img/forum/go_quote.gif The σ11 is very low noise - 12µV per amb.

That was measured on a σ11 with 30V output, which runs its error amp at 2.5x gain. For 5V output, the gain is 1x, so expect even lower noise.

 

[mattcalf]

Just a quick question AMB, how many gamma2 pre-made front panels are left? If you don't mind divulging.

 

[amb]

Not many...

But I usually pre-order a few sets at a time to avoid running out completely. This of course doesn't guarantee anything.

 

[mattcalf]

Okay, swell.

Probably going to have to wait until December (school holidays) to kick start this build but I'm very excited!

Cheers,
Matt.

 

[Shahrose]

Has anyone found SQ differences among the different outputs? ie. coax, optical, usb.