dac I/V convertion with very low distortion

[smms73]

files of the TAGUS project.

[Joachim Gerhard]

Well, i am confused, U2 is connected to V1, V2.

[qusp]

Originally Posted by smms73

last week i visited a audio show with a lot of high end products, and that make me want to build an amplifier without feedback, and i am already testing some ideas to attain that. so a I/V converter design exclusively for ess9018 is not a priority right now.

But i have modified the pcb like i said in prior post, to use this I/V with the ess9018, but each pcb can only be connected to 2 dacs from ess9018 maximum, the ideal is one I/V pcb for each of the 8 dacs.
The output of the I/V converter boards will be paralleled, and only one servo and one buffer per channel will be needed the others 3 or 7 tagus pcb will run in slave and dont need the servo or the output buffer. I will post the connection schema for this.

In resume: is possible to use this pcb for the ess9018 , but we need at least 4 pcb per channel running in parallel. The ideal is 8 pcb per channel.

so this makes it not possible to use es9012? is it the current thats an issue?

edit, I see why, too low output impedance with the dacs in parallel, so yes it does seem that 9012 will be a problem.

oh well, I didnt actually NEED to build another IV convertor anyway, they just fascinate me

[smms73]

it is possible to use ess9012. there is no problem.

[smms73]

Originally Posted by Joachim Gerhard

Well, i am confused, U2 is connected to V1, V2.

u2, v1, v2 forms a variable power supply for u1( class a)
v1 and v2 are floating power supplys, you can imagine that they are batteries.

[qusp]

Originally Posted by smms73

it is possible to use ess9012. there is no problem.

hmm but you say its preferred to run 1 x IV for each dac, or pair of dacs, because of the low impedance output of the dac current source. there is no way to separate out the dacs with the 9012, so you are stuck with the equivalent of running 9018 in stereo mode

[smms73]

Qusp what is the output impedance of ess9012? I was thinking it was in the 700 ohms region.
You can parallel also the input of the tagus to bring down the input impedance of the i/v converter.

[qusp]

no, thats the output impedance for a single DAC channel in the es9018 ie ~780ohms with ~3.9mA p2p current and ~3.05V pp (with standard datasheet operating voltages, some like myself like to run AVCC at 3.5-3.6vdc instead of 3.3vdc) both es9018 in stereo mode, or es9012 in stereo mode are the same ~195ohms outputZ and ~15.6mA. 9018 in stereo and 9012 in stereo are basically identical

that rules out the use of some devices, so paralleling is needed for more than just impedance depending on which are used ie. K170 is no use unless you have a sneaky stash of K170V. this is why K369V is used in Patrick's SEN for ES901X

[smms73]

thanks for the correction qusp.
with that value of impedance and current output, using 4 parallel pcb per channel will be a good soluction. tomorrow i will post the schematic of the connections for running tagus in parallel.

[qusp]

no problem, look forward to it. I suppose all efforts would need to be made to keep traces/wires the same length to avoid smearing?