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Old 3rd June 2011, 09:43 PM   #3691
Sven257 is offline Sven257  United States
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Hi,

I agree with you Ryan when I have listend to some very high priced CD/SACD players with oversampling filter and upsampling they don't sound as natural as NOS especially with SACD the 'highs' sound "homogenized" for lack of a better word...

Peter
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Old 5th June 2011, 07:48 AM   #3692
brubeck is offline brubeck  Netherlands
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I listen to John's MK7 DAC and had a lot of listening experience with OS Dac's. I suppose Lossless haven't heard John's MK7 DAC approach with Double Crown chip ;-)

My own listening experience is that OS dac's can sound impressive for about 15 minutes, then i get tired and bored, Up-sampling creates little phase-shifts (faults) which, i suppose, makes the brain nervous. Maybe not all human ears are sensitive for phase-shift...
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Old 5th June 2011, 06:52 PM   #3693
roger57 is offline roger57  Canada
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John,

Could you please let us know which manufacturer is on the tunable coils in the schematic? And to confirm, are they 100uH?
I've checked on Coilcraft's website, I cannot find a 100uH in this style.

Thanks!
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Old 6th June 2011, 10:05 PM   #3694
Sven257 is offline Sven257  United States
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Hi Brubeck,

Can you tell us a little more of your listening impression of Johns MK7 DAC compared to other digital or analogue sources that you have heard?

Thanks,

Peter
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Old 6th June 2011, 11:48 PM   #3695
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Hi roger57

Quote:
Could you please let us know which manufacturer is on the tunable coils in the schematic? And to confirm, are they 100uH?
I've checked on Coilcraft's website, I cannot find a 100uH in this style.
These are custom made, multi-segment air chokes (non tunable). They consist of two dual half core formers glued together (intended for use with ferrite pot cores). Turns are equally divided over these 2 formers (4 x 50 windings). These chokes are then screened using a brass IF transformer screen.

The photograph shows an early prototype.
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File Type: jpg airchokes.jpg (56.6 KB, 1620 views)
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Old 7th June 2011, 05:43 AM   #3696
roger57 is offline roger57  Canada
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Sorry about this, John - I was looking at the schematic for Mk 7 and a picture for Mk 6, which looks like tunable coils! Perhaps let us know if you ever decide to sell just the PCB, I wouldn't mind taking a shot at building one (with 100% of the risk at this end!)

Gary
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Old 7th June 2011, 11:10 AM   #3697
brubeck is offline brubeck  Netherlands
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Quote:
Originally Posted by Sven257 View Post
Hi Brubeck,

Can you tell us a little more of your listening impression of Johns MK7 DAC compared to other digital or analogue sources that you have heard?

Thanks,

Peter
What I can say more about this DAC that it just sounds ‘right’ in all aspects. You can listen –even with a very, very critical ear- to this DAC without detecting any flaw or fault in the jitter, noise en phase area. That makes the sound truly natural, undisturbed and most close to the master recording. No other DAC i heard comes even close to this.

The way of implementation (amp) and the type/year of TDA1541 can give little variations in the perceived sound character.

Beside of phase issues, a major issue with DAC design is the maximum bitdepth they can reach on the analog output. Even with MK7 it will be hard to get the very last LSB’s as an purified analog differentiation on the output. Here we talking in the microvolts area. I am sure that The MK7 is technically the closest possible approach to get the most of the bits on the output.

My experience is that this micro information of the LSB’s is the next step to make a DAC a real musical performer. There are several ways to achieve this after the DAC. Using an very, very clean AMP like John’s Circlotron to keep the bits alive. If that isn’t enough it is possible to create some white noise (signal correlated), which simulates the micro information of the missing bits. I am are experimenting with graphite from a pencil or a carbon composite resistor after the DAC. Graphite gives remarkable results on this.
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Old 7th June 2011, 09:45 PM   #3698
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is it possible to use the graphite resistor for the I/V 500 Ohm resistor?
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Old 8th June 2011, 08:23 AM   #3699
brubeck is offline brubeck  Netherlands
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Quote:
Originally Posted by marconi118 View Post
is it possible to use the graphite resistor for the I/V 500 Ohm resistor?
Good question.

John, is that an option?
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Old 8th June 2011, 03:22 PM   #3700
roger57 is offline roger57  Canada
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I'd like to pop in my thoughts. Graphite resistors exhibit different characteristics, but none that I could see would be detrimental - other than size. Carbon resistors are typically large, used in higher power rating applications such as speaker crossovers because of their temperature vs power curve. At 500 ohms, the only option may be to make them. I haven't been able to locate any manufacturers in the USA (yet) Maybe someone knows?
As for sound quality, they should be great, with no inductance to speak of, and none of the harshness of metal types.

Last edited by roger57; 8th June 2011 at 03:23 PM. Reason: fixed
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