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Output transformers for DACs
Output transformers for DACs
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Old 23rd September 2018, 07:07 PM   #1
bisesik is offline bisesik  Kazakhstan
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Join Date: Sep 2008
Default Output transformers for DACs

Hello everyone who looking for Sound!


After years of expirience the output transformers for current output DACs have been developed. Transformers tested with following DACs: ES9018/28/38, PCM63/58, PCM1702/04, AD1862/65, PCM1792. Speaking in general, transformers can be suited for any current DAC both in SE or PP modes. Transformers for TDA1541 and 1543 in such dimensions - are in process (available but without shielding, even for paralleled up to 8x1543)...

These transformers are made on high permeable cores, have an excellent ratio of the low DC resistance of the primary coil to the inductive resistance to achieve for best frequency response of the DAC. Transformers provides significant sound quality improvement compared to other outputs. Your music will begin to live a new life, it will sparkle with a naturalness without plastic nervousness :-)

Xfrmer.jpg

Xfrmer_bottom.jpg

Specification:
Core type - toroidal, core material - nanocrystalline
Can (mumetall) dimensions: OD=47mm, H=24mm, thickness=0.3мм
Available turns ratio: 0.5+0.5:2+2; 0.5+0.5:4; 1:2+2; 1:4
Typical primary inductance: 17H (for 1:4, 1:2+2 types)
Typical primary DC resistance*: 10 Ohms
*Can be down to 5 Ohms on request
Typical secondary DC resistance: 240 Ohms

Frequency Responce of transformer with ES9038q2m at 1.4VRMS (~8kOhm in secondary loaded on 100pF cable): 20Hz=-0.3dB, 20kHz=-0.2dB (rel.1kHz):
ES9038_4Vpp_1m_cable.png

Same, but with 470pF in parallel with secondary:
ES9038_4Vpp_1m_cable+470pF.png

The possible output level depends on the output current of the DAC (and I/V resistance). In practice it sounds without problems on LF and HF with +/-2mA DAC types such as PCM63\TDA1541 at 2Vp level (1.4VRMS). Less powerfull DACs like PCM58 with +/-1mA have good enough HF even with 1.3Vp witout next buffers.

Here is an example of connection:
Schem of connection.png

The price for matched pair is 110 USD + worldwide shipping ~10-15USD. Lead time depends on order. Thanks.

BR, Ivan.

Last edited by bisesik; 4th October 2018 at 02:43 PM.
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Old 2nd October 2018, 07:14 PM   #2
bisesik is offline bisesik  Kazakhstan
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Join Date: Sep 2008
Have done some THD measurements of ES9038Q2M with transformers.

Output transformers for DACs-es9038q2m_bis25_1-2vrms-png

Output transformers for DACs-es9038q2m-bis25_0-21vrms-png

Output transformers for DACs-es9038q2m-bis25_1-2vrms_20hz-png

Output transformers for DACs-es9038q2m-bis25_0-21vrms_20hz-png
Attached Images
File Type: png ES9038q2m_bis25_1.2VRMS.png (347.1 KB, 194 views)
File Type: png ES9038Q2M+bis25_0.21VRMS.png (90.5 KB, 234 views)
File Type: png ES9038Q2M+bis25_1.2VRMS_20Hz.png (99.8 KB, 233 views)
File Type: png ES9038Q2M+bis25_0.21VRMS_20Hz.png (93.9 KB, 239 views)
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Old 4th October 2018, 09:43 AM   #3
schultzsch is offline schultzsch  Europe
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Join Date: Mar 2009
Very nice work you have done here!
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Old 4th October 2018, 02:13 PM   #4
bisesik is offline bisesik  Kazakhstan
diyAudio Member
 
Join Date: Sep 2008
Thank you!

Here is the FR for a popular SMPCB ES9038Q2M board (ver.1.06, LPF=slow roll-off linear) with transformer:

Spectrum_ES9038q2m.png
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Old 4th October 2018, 07:47 PM   #5
bisesik is offline bisesik  Kazakhstan
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Join Date: Sep 2008
Thanks to and with permission of schultzsch here shown some approximative ("remote") comparison with LL1684 transformer (that was connected to Buffalo es3 9018 based DAC).

bis25vsll1684_20hz_200mvrms_out.jpg

bis25vsll1684_300hz_200mvrms_out.jpg
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Old 5th October 2018, 06:17 PM   #6
androa76 is offline androa76  Slovenia
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Join Date: Mar 2007
Location: Maribor
Excellent,
I have tested a lot with this Transformers. You did nice work. They are really optimized for current output dacs. I have not used any cap at output because at test is used 1.5 long cable with capacity of around 100pf or even more. Adding cap reduced 20khz response in my configuration. After a lot of testing we also added B1 and Tube buffer. I had a feeling that in some configurations dac couldn*t handeled load. Similar is seen in Audio note dacs.
For me this transformers are better than opamp stage. Highly recommendet.
At es9038q2m you can save a lot of time with testing opamp stages if you use this transformers.
It is pitty that this design is not intend for voltage out dacs, as far i know both constructors can*t do it because of large input impedance. Ak449x can handle till 1kohm...can*t be done something?
Congratulation this is not easy job what both of you did.
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Old 5th October 2018, 07:07 PM   #7
bisesik is offline bisesik  Kazakhstan
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Join Date: Sep 2008
Thanks for the feedback! Our transformers are still in the enhancement process. That is why this new version should be even better in terms of Load Capability compared to what you have right now.

Regarding transformers for voltage types of DACs - in process.
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