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Old 16th August 2016, 08:01 AM   #281
cu6apum is offline cu6apum  Russian Federation
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Quote:
Originally Posted by nautibuoy View Post
Sorry for the imprecision but I'm sure you know I meant something like this...

Passive output

Twas just a pin, sorry. Yes, this is possible - moreover, if you use a relatively slow triode with common grid as the load on the secondary, the result may be pretty impressive. I've been doing this for prehistoric chips like tda1541.
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Old 16th August 2016, 10:20 PM   #282
cu6apum is offline cu6apum  Russian Federation
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First sounds.
Kids are sleeping for 5h now, so listening at -60dB.

Man, I like it.
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Old 20th August 2016, 08:16 AM   #283
nautibuoy is offline nautibuoy  United Kingdom
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Originally Posted by newmatrix View Post
Now available on ebay;

Differential Version DSC1 DAC DSD decoding hardware kit Italy Amanero XMOS | eBay

I just ordered one.
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Old 20th August 2016, 08:31 AM   #284
nautibuoy is offline nautibuoy  United Kingdom
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Quote:
Originally Posted by cu6apum View Post
Twas just a pin, sorry. Yes, this is possible - moreover, if you use a relatively slow triode with common grid as the load on the secondary, the result may be pretty impressive. I've been doing this for prehistoric chips like tda1541.
Hmmm...

It's difficult to be sure from the pictures on the ebay listing but it appears that the differential board only has transformers on the output, I cant see anything that looks like an I/V resistor?

How are your listening impressions developing with your build?

Ray
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Old 20th August 2016, 03:19 PM   #285
cu6apum is offline cu6apum  Russian Federation
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First of all, there are quite a few approaches to the task. One must clearly imagine the whole track, so I'm taking a pause to think the things out.

First, I've got some advises from professionals about reworking the window filter (shift regs and resistors). There is a way to create a full-fashioned FIR filter with non-square window function, that can reduce the noise by some orders. This is the very first topic of research.

Next, I'll obviously replace the CFA to an integrating stage. Too much HF passing through is no good.
And afterwards there's some space for engineering the postfilter.

Alternatively, a common grid tube could be used as the I/V. Loaded by a neat transformer it can behave (in addition) as a first-order lowpass filter.

Also a transformer can be used as in the new Chinese design, followed by I/V resistor, or common grid/base/gate stage, or traditional conversion stage. But don't try those pea-sized modem transformers, it's waste of time.
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Old 20th August 2016, 03:22 PM   #286
cu6apum is offline cu6apum  Russian Federation
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Yes, my listening impressions.
Vinyl.
Rich, deep and thick sound, with no penalty to resolution or tonal balance. Definitely worth the money and time I spent.
But - lots of correlated noise. Actually I can hear it on high levels. This is not acceptable for the prototype of a top-end DAC.
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Old 20th August 2016, 04:09 PM   #287
nautibuoy is offline nautibuoy  United Kingdom
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Quote:
Originally Posted by cu6apum View Post
First of all, there are quite a few approaches to the task. One must clearly imagine the whole track, so I'm taking a pause to think the things out.

First, I've got some advises from professionals about reworking the window filter (shift regs and resistors). There is a way to create a full-fashioned FIR filter with non-square window function, that can reduce the noise by some orders. This is the very first topic of research.

Next, I'll obviously replace the CFA to an integrating stage. Too much HF passing through is no good.
And afterwards there's some space for engineering the postfilter.

Alternatively, a common grid tube could be used as the I/V. Loaded by a neat transformer it can behave (in addition) as a first-order lowpass filter.

Also a transformer can be used as in the new Chinese design, followed by I/V resistor, or common grid/base/gate stage, or traditional conversion stage. But don't try those pea-sized modem transformers, it's waste of time.
I'm thinking of using my Silk TVCs on the output, configured for Balanced to SE operation and of course they will act as a LP filter too.

Can I ask if you're HQPlayer? Are you using DSF files or upsampling. What DSD rate are you feeding the DAC?

Also, with your Chinese kit, did you use any of the parts provided or did you just assume they're bad and replace them parts from a known source? I would like to give the supplier the benefit of the doubt but it feels safer to replace the parts.

Cheers

Ray
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Old 20th August 2016, 05:16 PM   #288
cu6apum is offline cu6apum  Russian Federation
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Ray,

I'm using Audirvana+ on a hackintosh and JLsound's usb board as the source, then chinese AK4137 board as the DSD converter. Tried converting with A+ directly, same noise figure.
As my resistor values differ from the authors, I bought my own bag of Susumu. Caps are NP0 ceramic, Wima polyprop, Nichicon KG electrolytic. 74AHCT chips are from China, look pretty real. Do you suspect them? Opamps bought separately.
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Old 20th August 2016, 05:28 PM   #289
nautibuoy is offline nautibuoy  United Kingdom
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Quote:
Originally Posted by cu6apum View Post
Ray,

I'm using Audirvana+ on a hackintosh and JLsound's usb board as the source, then chinese AK4137 board as the DSD converter. Tried converting with A+ directly, same noise figure.
As my resistor values differ from the authors, I bought my own bag of Susumu. Caps are NP0 ceramic, Wima polyprop, Nichicon KG electrolytic. 74AHCT chips are from China, look pretty real. Do you suspect them? Opamps bought separately.
What DSD rate is the AK4137 delivering?

I've seen enough bad tales to have an inherent mistrust of Chinese parts so for a few extra pennies I replaced the chips.

Ray
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Old 20th August 2016, 05:39 PM   #290
cu6apum is offline cu6apum  Russian Federation
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11.2MHz.
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