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Old 6th September 2011, 12:03 PM   #191
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Quote:
Originally Posted by Ciu View Post
Hello Joe

Newbie question
Each output (+ , -) can sink or source the signal ....
So why the center 3R connected to ground ?
What's the value of the current from +- to Gnd ?

Thanks!
Richard
Hi Richard

The idea is to achive current mode.

The otput of the DAC needs to see only a small fraction of it 195 Ohm output impedance otherwise it will not be working "current" mode.

If you don't ground, you would have a single 6R and it would be in voltage mode and most of the two phases would cancel out and you'd get 30mV RMS approx. Just no point doing it that way.

Note that internal 1.65V offset, the Sabre DAC is unique in that you can still ground it to 0V (don't try this with any other current DAC - it may not survive - and don't do it to conventional voltage DACs since they all have about 2.5V). So essentially shorting the output to virtually ZERO Volt, means the offset now become a current offset of 8mA.

But getting a high ratio 193R/3R = 65 - is the only way to get current mode.

Other than that, the suggested idea is pretty straight forward.

Much simpler to use twin 330R as suggested with 1:1 transformer, even if the fancy Japanese kind exotic transformer.

Cheers, Joe R.
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Last edited by Joe Rasmussen; 6th September 2011 at 12:06 PM.
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Old 6th September 2011, 03:17 PM   #192
Bunpei is offline Bunpei  Japan
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Quote:
Originally Posted by fulken View Post
I will look into a way with Bunpei and Feastrex Japan.
Dear joemana,

Please send your PM to "fulken".
He may arrange an opportunity for you in U.S.

Bunpei
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Old 7th September 2011, 02:03 PM   #193
fulken is offline fulken  United States
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DAC Transformer for ES9018 is ordered for touring around North Ametica. I will update detail when all the detail is worked out!

Kenji@AudioFeast
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Old 9th September 2011, 01:39 PM   #194
Marek is offline Marek  Poland
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What signal level is achieved on secondaries using this trafo with Buffalo II? what is turns ratio?
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Old 9th September 2011, 01:56 PM   #195
Bunpei is offline Bunpei  Japan
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I assume you are asking on Feastrex Finemet transformer.
As explained in staccatiss' review post, he obtained 2.0V rms at 0dB FS of Buffalo II output with 4.02k ohm load resister in secondary. Turn ratio is 1+1:1+1.
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Old 9th September 2011, 02:06 PM   #196
Marek is offline Marek  Poland
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Buffalo II DAC conected to Feastrex transformer will work in voltage mode because secondaries load + secondary DCR will transform to primaries with 1/N ratio so DAC will see more than 4kohm load effectively.
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Old 13th September 2011, 11:37 AM   #197
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Default Feastrex Urushi coated finemet transformer, brief impression

Mr. Yukihito of Feastrex Japan kindly allowed me to borrow a pair of their Finemet transformer "FLT-ES1" (designed mainly for ES9018DAC).
I had installed them directly to BII's output and listened last week.

That's my first experience of transformer output stage, so I have no idea how they are sonically superior/inferior to the other trafos.
I usually have used discrete opamp I/V stage designed by Mr. Fujiwara, that's highly regarded among Japanese DIY people.
(That I/V stage is originally designed for pcm1794, but I think works well with other high current output dacs like ES9018 in 2ch stereo mode)


Compared to discrete opamp, the Finemet transformer has less bass dynamics and less wide soundstage,
however I feel those "degradations" are not so audible and better than I expected.
I think some people might prefer other active I/V stages such as Legato in this regard.


Each instruments, Voices are somewhat more naturally presented and detailed, and have better textures with Finemet transformers.
e.g. - I felt I could realize each notes much easier, especially with mixed choruses.

Besides, as Mr. Yukihito mentioned in his blog, metalic percussions - especially symbals - are most realistic and enjoyable without being harsh.


Mr. Yukihito explained in e-mail, their transformer filters HF noises out of audio band very well, so can reproduce these "realistic" HF characteristics,
however this cause some people might feel somewhat earlier HF roll off. I felt these "roll off" are totally acceptable for me, but some might prefer "brighter" "more opened" HF characteristics.
I think that's a matter of taste.


That's my humble impression of BuffaloII + "FLT-ES1". I decided to ordered one pair of them after the loan period...
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Old 14th September 2011, 05:56 PM   #198
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Interesting post, Wktk_smile-san.

I actually have the impression that the feastrex transformers+TX2352+10nF PS load have more energy in the trble than the Legato.

Could you tell us a bit more about how you loaded the transformer?

Where can I find Mr. Yukihito´s blog?

BTW,
I ordered an urushi-coated pair of Feasterex transformers and they arrived a -few days ago. Attached are some photos.
I am now awaiting some 10nF Teflon and tin foil caps from Percy Audio and cryo treated mono crystalline copper wire. Then, I will hook everything up to my B2.

The champagne I have to sell to finance the transformers...

Quote:
Originally Posted by wktk_smile View Post
Mr. Yukihito of Feastrex Japan kindly allowed me to borrow a pair of their Finemet transformer "FLT-ES1" (designed mainly for ES9018DAC).
I had installed them directly to BII's output and listened last week.

That's my first experience of transformer output stage, so I have no idea how they are sonically superior/inferior to the other trafos.
I usually have used discrete opamp I/V stage designed by Mr. Fujiwara, that's highly regarded among Japanese DIY people.
(That I/V stage is originally designed for pcm1794, but I think works well with other high current output dacs like ES9018 in 2ch stereo mode)


Compared to discrete opamp, the Finemet transformer has less bass dynamics and less wide soundstage,
however I feel those "degradations" are not so audible and better than I expected.
I think some people might prefer other active I/V stages such as Legato in this regard.


Each instruments, Voices are somewhat more naturally presented and detailed, and have better textures with Finemet transformers.
e.g. - I felt I could realize each notes much easier, especially with mixed choruses.

Besides, as Mr. Yukihito mentioned in his blog, metalic percussions - especially symbals - are most realistic and enjoyable without being harsh.


Mr. Yukihito explained in e-mail, their transformer filters HF noises out of audio band very well, so can reproduce these "realistic" HF characteristics,
however this cause some people might feel somewhat earlier HF roll off. I felt these "roll off" are totally acceptable for me, but some might prefer "brighter" "more opened" HF characteristics.
I think that's a matter of taste.


That's my humble impression of BuffaloII + "FLT-ES1". I decided to ordered one pair of them after the loan period...
Attached Images
File Type: jpg DSC03166-3.jpg (121.7 KB, 973 views)
File Type: jpg DSC03169-2.jpg (390.6 KB, 920 views)
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Old 15th September 2011, 09:13 AM   #199
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Hi, staccatiss,

I had simply inserted load resistor in secondary as their recommendation.
I used 2.4k ohm generic metal film I just found in my junkbox.

I felt "brightness" in treble decreased with Finemet transformer in comparison to previously used I/V stage. That's not always, but with some recordings.


Later I realized this kind of brighter treble of previously used discrete op amp I/V tend to have fogginess - this actually masked details in some extent - at the same time.

Here's related article in Mr. Yukihito's blog. (in Japanese only)

Feastrex????????????????? | SD????????????????

Cheers,
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Old 15th September 2011, 02:10 PM   #200
waltube is offline waltube  Italy
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One very good solution, in my opinion, is to use the 3575 OCC from Sowter (http://www.sowter.co.uk/pdf/3575.pdf); it is 1:1.
I use the output from buffalo to feed a 15 ohm resistor (current mode) for + and -.
Then I connect each end of the primary, and the center to ground.
On secondary I put a 3k3 or 4k7 ohm in palallel, unbalanced mode, then a CF of 6922, tube power supply with a good filtering.
Trimming this resistor I can change the frequency response with a little change on signal amplitude.
In attach you can find a frequency response with a 24bit/192Khz come from a AP x585; the ressitor on secondary is 10k , I got 0,7 db of increment at 70 kHz.
With 4k7 I got -1 db about 40Kz, also good for signal at 24/192Khz.
The S192_70, is a signal 1 Khz, -70 db 24bit/192Khz; good performance
The S96_diff is a test, 24/96Kh,z with two signal at 40Khz and 44KHz, also in this case a good perf.
This before a little modification on tube power supply to have a better residual noise.

Bye

Walter
Attached Images
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File Type: jpg S192_70D.jpg (82.5 KB, 802 views)
File Type: jpg S96_DIFF.jpg (80.1 KB, 778 views)
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