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Output transformers for DACs

Hi Ivan,

I would like to improve my current DAC (AD1865). Now I'm using it with 100R I/V resistor, and a tube output stage.
Could you suggest me trafo for this application? I think 1:4 or 1:5 turn ratio will be enough for this application with 500-600R I/V resistor at the secondary side. According to my calculation the DAC will see around 20R. What is the iron and copper loss of your trafo in this application?
 
Hi Ivan,

I would like to improve my current DAC (AD1865). Now I'm using it with 100R I/V resistor, and a tube output stage.
Could you suggest me trafo for this application? I think 1:4 or 1:5 turn ratio will be enough for this application with 500-600R I/V resistor at the secondary side. According to my calculation the DAC will see around 20R. What is the iron and copper loss of your trafo in this application?
Hi!

Due to the fact that after trafos there will be a tube high-impedanced stage, I would suggesting to use 1:15 transformers. Such TR (turnsratio) is more profitable in terms of the load seen by the DAC. By the way, this is exactly the TRs on the recordings above.


Next. Rejection of the i/v resistor in the primary is not a good idea as well. Resistors must be used at both the primary and secondary coil sides. I recommend to use a wirewound types.

Thus, with 1:15 you will need 12 ohms across the primary coil and 2.7kOhm as a load for secondary coil to get ~70mV (level of mentioned by you 20R).
 
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My suggestions are based on my own experience. Higher TR gives steeper LPF.
No argument from me as I really have no experience with loading AD1865 . I do however have a dac board with that IC and it is fitted wit 100 Ohm I/V resistors . Through a horse trading I was able to buy Electraprint silver 1:2 input transformers on nickel cores which I though I could use as an I/V transformer with 2.4 K resistor on the secondary winding to get ~600 loading on the IC . From reading a little bit on this thread I see you don't recommend loading only the secondary winding but both primary and secondary . Sadly Jack Eliano doesn't remember the specification of this transformer so I'm a ;little bit in the dark here.
 
I recently purchased a transformer with mixed silver and copper wires from bisesik, The resolution has been greatly improved!

I listen to this pop music very often. Since I used silver and copper transformers, the sound became very "chaotic" when I first listened to it, but I listened carefully again and I heard that this pop song has a vocal harmony with the lead singer, This harmony, which was never heard before, is now all out.

When I first listened to it, I felt "chaotic", mainly because I didn't expect this song to have harmony, so at first I felt that this extra voice "interfered" with the vocals of the lead singer🤦‍♀️
 
B) Analog part:
1. TDA1541AS2' Iout -> my IV resistors -> my big trafos+jfet buffer -> my big trafos+jfet buffer ->
2. -> my interstage cables -> modified chineese 845 tubes based' SE amplifier-> my speaker cables -> acoustic panels + vintage Heil AMT1 HF speakers
Hi, your transformers are very interesting, I wish I could afford them at this moment. The recordings are sounding good on IEMs/iphone and I wanted to ask you what are your "acoustic panels"?

Thanks,
Alex
 
Some time ago I have got a task to make a splitter based on my transformers. So below is the PCB based on my transformers with buffered (jfets) outputs which realizing the simple approach of Y-splitter. Can be used either as a combined i/v stage+splitter for current-output-type DACs (using my SUTs) or as a line-level splitter solution (1:1+1). The combined SE/BAL version.


big_trafos_jfet buf_splitter.jpg
 

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I ordered a pair of the bigger transformers (1:15) that Ivan offers, for my TDA1541A dac (in simultaneous mode, with Andrea Mori external clocks). I had previously used the 'smaller' 1:22 versions, and was very happy with the timbre, depth and overall sound they provided.
I hooked them up and used a 33ohm I/V resistor that Ivan also makes and after a week of listening can only say the following:
They are Absolutely Brilliant!
The extended bandwidth is of course immediately apparent, but there is now also a richness in tone, a lot of nuance, depth,... everything you could dream for in a DAC. I have tried a lot of I/V solutions, from a simple resistor, to CEN/SEN, tube... With these transformers, I can honestly say, they bring such a pleasant, rich, deep, musical sound and so for me, my DAC is finished, I will search no further!
I can only urge you to try them, and you will most definitely not regret them.
 
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I ordered a pair of the bigger transformers (1:15) that Ivan offers, for my TDA1541A dac (in simultaneous mode, with Andrea Mori external clocks). I had previously used the 'smaller' 1:22 versions, and was very happy with the timbre, depth and overall sound they provided.
I hooked them up and used a 33ohm I/V resistor that Ivan also makes and after a week of listening can only say the following:
They are Absolutely Brilliant!
The extended bandwidth is of course immediately apparent, but there is now also a richness in tone, a lot of nuance, depth,... everything you could dream for in a DAC. I have tried a lot of I/V solutions, from a simple resistor, to CEN/SEN, tube... With these transformers, I can honestly say, they bring such a pleasant, rich, deep, musical sound and so for me, my DAC is finished, I will search no further!
I can only urge you to try them, and you will most definitely not regret them.
How to you know / calculate the turn ratio required? Ivan also made a big tranfos for me but in the conversation we didn't talk about the turn ratio.
 
How to you know / calculate the turn ratio required? Ivan also made a big tranfos for me but in the conversation we didn't talk about the turn ratio.
TR of your trafos is the same (~1:15). TR depends on several factors: initial data from the customer (desired output signal level, input impedance of the next stage, LF losses), but the main reason is my own personal experimental observations and preferences as experiments to improve the quality of transformers not stops.