Zen -> Cen -> Sen, evolution of a minimalistic IV Converter

[RollE2k]

John, did you put 1R between the voltage-output and circuit, or did you put 1R on both v-output (+F) and gnd-out (+O) (ok, it's not really ground since the circuit is floating, but you understand where i mean).
I'm doing a custom SSLV-PCB right now which sig two circuits per board, which i will us - so it would be great to know before i send to manufacturing. :-)

[John Luckins]

I think either would do, I put mine in the positive (+F). It isn't a balanced supply so it doesn't matter.

John

[RollE2k]

Thanks alot, i'm making compact SSLV1.1 PCB's which is same size as the originals, but with two regulators on each board (since it will be low current here), and also included is common mode chokes 100mH. And i will make them as you run them right now - only two wire output, and a dedicated place for the output resistor, which you can bridge if you don't need it.

[RollE2k]

I'm setting together a list of components that i will order from mouser for my SEN-board, and i have room for one 10mm Electrolytic cap, and one small film cap.

I will use 150R R-iv resistor, and i started thinking - what would be better using, Muse ES 220u Bi-polar (-3dB @ 9.64Hz) vs Elna Silmic II 220u polarized (4.82Hz)? Also, would it for me be better to bypass it with a 4.7uF film (225Hz) rather than 1uF (~1KHz)?

In the first question i would think bi-polar would be better, because it pretty much wouldn't cut anything at 20Hz, but this is just my guess. but at my other question - Would there be any downside in the higher frequencies by choosing the larger bypass cap?

[bcarso]

According to Bateman and others, there are reasons to use bipolar electrolytics over polar parts, independently of the bias voltages. And a friend said that even better are back-to-back bipolars, although that gets pretty bulky.

[samoloko]

Originally Posted by RollE2k

I'm setting together a list of components that i will order from mouser for my SEN-board, and i have room for one 10mm Electrolytic cap, and one small film cap.

I will use 150R R-iv resistor, and i started thinking - what would be better using, Muse ES 220u Bi-polar (-3dB @ 9.64Hz) vs Elna Silmic II 220u polarized (4.82Hz)? Also, would it for me be better to bypass it with a 4.7uF film (225Hz) rather than 1uF (~1KHz)?

In the first question i would think bi-polar would be better, because it pretty much wouldn't cut anything at 20Hz, but this is just my guess. but at my other question - Would there be any downside in the higher frequencies by choosing the larger bypass cap?

what Is your dac - why you will use low value R- IV resistor with Sen - does lower value decrease distortion with that circuit - Isn't recomended 1.5K for pcm63 and around 2K for pcm1704

[RollE2k]

Originally Posted by samoloko

what Is your dac - why you will use low value R- IV resistor with Sen - does lower value decrease distortion with that circuit - Isn't recomended 1.5K for pcm63 and around 2K for pcm1704

I will run it with ES9018 and three pairs of 2SK369V per phase. Since output of the dac is approx 8mA, and i have differential line-stage with 6dB gain per phase thereafter i will have enough gain for shure. My Pass X250 is full power at approx 1.5Vrms.
And as i have understand from the article (without having built the circuit myself) then yes distortion seems to be less with a smaller R-IV. But this maybe Patrick can clear out for us even better.
If i want higher gain, i still think 200R will be enough for my case.

[samoloko]

In article I can not see that lower R IV brings lower distortion
It Is said that can be used 500 - 2.7 K
I have read that when doing passive I/V It Is Important to have lower valuse If using pcm63 which has protection diodes but like to know how Is the case when using active stage - does lowering 1.5 K brings sound Improvement

[RollE2k]

You cannot compare lowering gain of the SEN cirucuit with lowering R-IV at the output of a DAC. That you should rather compare input impedance of SEN.
But lets go back to the circuit, according to Patricks article i find this:

The Zen IV is the original circuit as published, and the Cen IV has a Riv of 500R for the same transimpedance gainas the Zen. The results are somewhat
surprising. For a current input signal of +/-1mA, 1kHz sine, THD is 0.000257% for Zen, and 0.000066% for Cen.

And later down the same text you'll find the following:

Using Riv of 2.7k in the Cen circuit, THD is 0.0019% at 1kHz.

So, when i read it i at least take it as with Riv=2.7k THD 0.0019%, and with Riv=500R THD 0.000066%
And this is even with the Cen circuit, which by default does have a bit higher THD than SEN. But then again, it's possible that lowering the Riv even more pretty much wouldn't do anything for THD.

I wonder if Patrick have done any measurements with lower Riv than 500R?

[LuisMCP]

I have build a Sen I/V with a PCM1704 nos DAC.
I have two different power supplies, one for PCM1704 and other (floating) for Sen I/V.

DAC and Sen IV works fine, but there is a big hum noise.

I have experimented with and find:

1) Switching off the power don't remove hum !!
2) Disconnecting the DAC to Sen connections and noise don't changes.
3) Unplugging the USB does lower noise
4) Unplugging the power cord kills completely the noise.