When I used I/V resistors for PCM63 Shinkoh tantalum or Charcroft Z-foil resistors was the best ones.
Now I exclusively use I/V transformer, and loading (Caddock TF os Z-foil resistor) on the secondary side.
Now I exclusively use I/V transformer, and loading (Caddock TF os Z-foil resistor) on the secondary side.
Wich I/V trafos?Sowther,Lundahl or something else?And what R value did you put on secondary?
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I use Sowter transformers (tried custom wounded nano core ones, but Sowter is more balanced), and loading only the secondary (Sowter 8347, 2k2 loading).
Now 8347 is obsolete.
Now 8347 is obsolete.
I also use Sowter's 9545* on my dual balanced TDA1541 dac but I've not tried it yet with no I/V resistor. I'd need to use about 1K on the secondary to get 40r reflected onto the primary,
(The 2ma output offset of the dacs doesn't need current injection to cancel it because the bifilar windings mean the magnetic fields cancel since the 2ma flows in opposite directions. For a single 1541, you would need to inject 2ma as no DC is allowed through the transformer to avoid long term magnetisation)
* 9545 now obsolete and replaced with 1465 which seems identical. https://www.sowter.co.uk/dacs.php
(The 2ma output offset of the dacs doesn't need current injection to cancel it because the bifilar windings mean the magnetic fields cancel since the 2ma flows in opposite directions. For a single 1541, you would need to inject 2ma as no DC is allowed through the transformer to avoid long term magnetisation)
* 9545 now obsolete and replaced with 1465 which seems identical. https://www.sowter.co.uk/dacs.php
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I have been working on DACs for almost 15 years, I used various schemes with tubes, I rejected the OP-amp at the beginning, although I inserted the AD811 into the old player as an I / V stage.
A couple of years ago I tried a grounded grid with 6S4P and that’s when I realized I had lived in delusion all the years before.https://www.diyaudio.com/forums/tubes-valves/360960-help-tube-iv-3.html#post6363513
The sound has changed drastically, it has gained that liveliness and reality that is hard to hear from a digital source.
The disadvantage of this scheme is that it needs a capacitor between the output from the DAC chip and the tube.
I haven't tried the transformer as an output stage, but I can say that the tubes are great for the I / V stage, but only if they are applied well.
There are a lot of schemes on the internet that are a complete failure so one should carefully choose and calculate for a particular DAC chip.
A couple of years ago I tried a grounded grid with 6S4P and that’s when I realized I had lived in delusion all the years before.https://www.diyaudio.com/forums/tubes-valves/360960-help-tube-iv-3.html#post6363513
The sound has changed drastically, it has gained that liveliness and reality that is hard to hear from a digital source.
The disadvantage of this scheme is that it needs a capacitor between the output from the DAC chip and the tube.
I haven't tried the transformer as an output stage, but I can say that the tubes are great for the I / V stage, but only if they are applied well.
There are a lot of schemes on the internet that are a complete failure so one should carefully choose and calculate for a particular DAC chip.
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Euro21,
are you using a pre after the transformer or are you going directly to your 300b driver (D3a/E280F)?
S.
After the (secondary loaded) I/V transformer about 200-250mV RMS presents, so about 20dB gain active buffer needed. I use E88CC (Siemens CCa) SRPP.