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Output transformers for DACs

Have received today a bit redesigned version of Ian's DAC hat with "large" RCAs and receptacles usage possibility:


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Hi Ivan, I have a ES9018K2M board and I have +/- for every channel but only 4mA. Do you think I can use yours transformers? 1:4 is it enough to have 2V output?. I've read that this chip acts automatically in current or voltage mode it depends on the impedance saw. What kind of resistor could work ? and more the output impedance is around 700 Ohm!!! quite a lot. Thank you. Vito
Hi Vito,
the output impedance of ES9018K2M is 780 Ohm already. It is simply impossible to use any step-up transformers without increasing the output impedance, as transformer means impedances transformation first of all, current/voltage these are secondary properties. As ES9018K2M is similar to 38Q2M in terms of the output current, you can refer to this table for understanding the output impedance versus output signal level. Output transformers for DACs

And one question if you don't mind. What is the DAC based on 9018k2m you have which is for you want to spend ~ $ 200, buying my transformers (in theory at least)? :magnify:
Since my main DAC is TDA1541A, I could not pass by the developments of Abbas. His master clock based on EF11/EZ11 tubes, as well as a tube DEM clock, converted my DAC to an analog device. A tube clock for a digital converter - this sounds as absurd as incredible the result. And also his cables - again in the bull's eye!
Thus, I simply could not pass by his tube current / voltage converter for my beloved TDA1541A chip.

I made a sonical comparison with my version: my current / voltage transformers plus a buffer on a jfet pair 2SK170V / 2SJ74V.
Without belittling its musicality, Abbas's i/v converter has too many harmonics for mine (and those who listened too).

I would describe the difference between my version and Abbas like this: photography versus painting.

For my humble opininon that tracks where some of the art idea is missed or/and the record quality is poor sounds very interesting with Abbass'es converter.

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And one question if you don't mind. What is the DAC based on 9018k2m you have which is for you want to spend ~ $ 200, buying my transformers (in theory at least)?

I bought some years ago this pcb at diyhhk:
ES9018K2M XMOS DSD DXD 384kHz USB DAC with Bit-perfect volume control and SPDIF input - DIYINHK.

Thank you for the chart, yes I am intersted in your transformers, they have wonderful feedback and apparently input impedance is not the classic 600:10k for the 1:4 which is great! Just one question, the resistors on the chart is on the secondary or in the primary of the transformer?
Has anyone tried any of these transformers with DDDAC 1794? I have a version with 4 boards. With 4 parallel DAC chips PCM1794 in mono mode the quiescent current is 80mA, at each output it is + 2.7VDC on the 34ohm U/I resistors. The difference between the balanced outputs is a couple of mV, SO there is practically no DC offset. Each of the differential outputs is connected to the GND with a 34 ohm resistor.

I tested several different 600:600ohm transformers, the best of which was the old ISKRA telephony transformer wound on a torus core. Measured 1.5H and 20ohm are primary and secondary, the compensation on the secondary is a 2k resistor. The transformer primary is connected between + Out and -Out of the DAC, the output is balanced or unbalanced without connection to GND, about 2.3V RMS with transformer.


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