Who would I contact about building a Buffalo II DAC and Beta 22 amp? - Page 5

Well, no one really "needs" a Beta-22. And regardless of the fact that the IVY III can drive balanced headphones directly, I doubt that it can complete with the sound quality of a fully balanced Beta-22. 

Quote:

Originally Posted by jcx 

the Ivy's opa1632 output looks like it only has ~ +/-50 mA current capability - combined with the 22 Ohm series R in each output you can't drive low Z, low sensitivity headphones very well - it should be fine with higher Z HD8/6xx or similar if you replaced the R13-16 180 Ohm feedback R with higher values to provide appropiate output V gain

 

most people would be happy with the level it can drive Grados to but the combined 44 Ohms series R in the output may affect the frequency response

TPA recommend that you jumper the 22R output resistor if driving headphones directly.

Oh, and the OPA1632 is 150mA according to the datasheet, but I suspect that it would actually fry if asked to supply that continuously......

Quote:

Originally Posted by MrSlim 

Well, no one really "needs" a Beta-22. And regardless of the fact that the IVY III can drive balanced headphones directly, I doubt that it can complete with the sound quality of a fully balanced Beta-22. 

It is an interesting situation. There could be considerable benefits from not having extra connections, cabling, an attenuator, and a whole extra amp with its own distortions and non-linearities.

If you aren't pushing the IVY's OPAMPs too hard, it could be a very elegant solution.

Quote:

Originally Posted by Beefy 

TPA recommend that you jumper the 22R output resistor if driving headphones directly.

 

Oh, and the OPA1632 is 150mA according to the datasheet, but I suspect that it would actually fry if asked to supply that continuously......

the 22 Ohm R isolate the op amp output from cable Cload which can cause instability - reducing to 5-10 Ohms or replacing with properly (over) sized ferrite bead core inductors would be my recomendation for direct headphone output

for usable output current absoulute max rating isn't the right place to look, min short circuit current spec is +50/-60 mA

then look at the output V vs load R plot to see that the short circuit current also seems to be the working current limit of the (hopefully "typical") device the plot was made with

continuous power rating could be a problem for low Z loads

[edit: looks like the usable current is nearer 25-30 mA from a 2nd look a the datasheed fig 9 plot]

Quote:

Originally Posted by jcx 

the 22 Ohm R....

....could be a problem for low Z loads

All sounds reasonable!