DEQ2496 direct transformer out - diyAudio
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Old 16th June 2008, 04:38 PM   #1
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Location: HK
Default DEQ2496 direct transformer out

Hi,

here a pic of my deq2496 with direct transformer output.
I directly solder wire from the ak4393 pins to the tranny with 120ohm in series.
I use a Tamura tpc-101 that I have on hand and connect 600:600.

I reference the cs4396 circuit in the jensen notes below.
http://www.jensen-transformers.com/as/as093.pdf

The sound of cause is a huge improvement from the original output.
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Old 16th June 2008, 09:09 PM   #2
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Interesting project!

A couple of questions. When I looked at the AKM 4393 data sheet. It said the the unit needs to be loaded by at 1Kohm resistor and I noticed you only had a much smaller resistor in your circuit (as shown in the Jensen schematic). Did you play with this value at all?

Also the AKM sheet mentions a "built in" anti-aliasing filter on the chip. Is this why you and others can get by with only a single pole filter? Or are using the transformer is part of the low pass circuit?

thanks
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Old 16th June 2008, 09:53 PM   #3
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Can not find anything in the datasheet that says it must be loaded with 1kohm (or 600ohm). Only that it should not be loaded with less. But they do not recommend an optimal load either.

But is easy to adjust the loading with a transformer as the load on the secondary is reflected over to the primary with the addition of the DCRs.

This is an elegant solution also discussed in

http://www.diyaudio.com/forums/showt...53#post1540153
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Old 19th June 2008, 08:52 PM   #4
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Lars, The loading is mentioned on page 5 & note 11 of the AKM datasheet.

I am guessing there could be considerable distortion if the next piece of equipment presented a low input Z and tried to draw power from the DAC.
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Old 19th June 2008, 09:52 PM   #5
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Hi,
The data sheet says min load. Still nothing about recommended or optimal load :-(.
It is to bad AKM does not publish such info. We will have to judge by our ears.
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Old 19th June 2008, 11:22 PM   #6
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Well, I guess anything above the minimum is okay. At that point the issue is dependent on the input Z of the equipment later in the signal path.
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Old 19th June 2008, 11:26 PM   #7
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Yepp, it will be an easy task to terminate the transformer secondary to get it right. Funny we asked nearly the same thing at the same time over at the K&K forum.
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Old 20th June 2008, 12:00 AM   #8
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Quote:
Originally posted by revintage
Yepp, it will be an easy task to terminate the transformer secondary to get it right. Funny we asked nearly the same thing at the same time over at the K&K forum.
My DCX and DEQ projects have been been on hold for several months. So now is the time to get it done. Good luck on your version
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Old 20th June 2008, 06:29 PM   #9
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Sorry for the slow reply.

I didn't try other values, I have 4 120R on hand and that is what I used.
It seem to be ok and I didn't heard distortion in the sound.
I didn't terminate the secondary other than the 20K seem in the amp input.
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Old 21st June 2008, 09:16 AM   #10
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I am a little puzzled about the min. 1kohm DC spec. But I came to the conclusion that the serial resistors plus the RDC of the transformers primary should not be less than this value. I will go by that with my DCX, with Lundahl LL1544A connected as 600:600. In that case the serial resistors will be 430ohm as the RDC is 130ohm, totals 990ohm. Another option is to connect them as 10k:10k with 240ohm serial with the 520ohm RDC. The eventual problem then is that the load should be well above 100k.
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