Da-capo issue (John W?)

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#181
Hi Steve,

The HDCD mastering process allows an extra 6dB peak signal level. If the DAC's output is to remain at 2V then normal Non HDCD encoded material would have an average 6dB higher playback level.

Therefore, as HDCD vers non HDCD would have a "Average level" of 6dB less - this would put HDCD recordings at a disadvantage in quick A/B listening test (If levels are not matched - most people would prefer the louder source), So Pacific Microsonics (HDCD developer) required non HDCD playback to be scaled by -6dB, under the HDCD licensing terms.

This could be done in the Digital domain (Internal Scaling) - but loosing 6dB of DAC Dynamic range, or in the Analogue domain (Ext Scaling).

So as we don’t really care about the need to keep the average playback levels matched between HDCD and Non HDCD, we can loose the scaling by setting to Ext Scaling (As the Dacapo & Ordinal where designed well before HDCD was developed, they have no provision for -6dB scaling in there analog design).

Also, the HDCD digital filter also has a about -0.9dB attenuation to cope with transients compared to more standard filters - so in total the HDCD filter could be attenuated by just under -7dB compared to the other filters (18Bit, 20Bit, 22Bit, 24Bit, TDA1307) – so around 1V.

Hope this helps,

John
 
#182
Hi John, thank's for the info.The reason i asked about the output levels was because i recently read an article on CD player attenuation which stated that levels can range from 2.4v to 4v. HDCD compatible players having 4v output on HDCD. As i'm sure you are aware there is nothing in the literature that accompanies Dacapo or on the casing to say what it's output is. I have been thinking of experimenting with attenuation to give me greater use of volume control on my amp, as it only has 200mv input sensitivity. I was thinking of the Rothwel inline attenuators or such like which offer -10db. Any thoughts?
Regards, Steven.
 
#184
I was thinking of the Rothwel inline attenuators or such like which offer -10db. Any thoughts?
Click to expand...

Save yourself a load of money and and make your own attenuators.

Simply buy four 0.25 or 0.6 watt metal film resistors from Maplin for a total of about £0.52. For -10dB try two 4k7 Ohms and two 1k9 Ohms.

Depending on the nature of how your interconnects are terminated you could unsolder the signal wire inside each amp end phono plug and solder in a 4k7 in series with a 1k9 after it going to earth.

Or you could buy two phono plugs and sockets and a little bit of wire and make little additional attenuating interconnects.

I used to do it this way. But I used Vishay resistors and silver wire. I also have no preamp. The DAC goes direct to the amps.

You could also take the lid off the amp and unsolder the signal wire in there for each channel from the chassis phono socket and insert the series resistor between the signal pin and the wire then fit the shunt resistor after it going from the signal wire to the chassis socket earth tab.

That's a better way as adding another phono socket and plug to the signal path does have a deleterious effect on the sound quality similar to changing from a Vishay resistor to a metal film resistor.
 
#185
Hi John, finally worked out how to upload pictures of my damaged Dacapo pcb. What do you think? Is this easy to repair?
Regards, Steven.



http://usera.imagecave.com/scubaboy/DACAPOPCBTOP50.JPG[/img][/IMG]
DACAPOPCBBOTTOM50.JPG
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#189
Quote:Save yourself a load of money and and make your own attenuators.

Thanks' for the info Ian, i'll give it a go.
Does anyone know where to source replacement batteries for the DC? Can they only be found in specialist retailers? If anyone out there has bought new one's and replaced them themselves, i would be really interested to know how you got on.

Steven.
 
#190
Puffin said:
John. Some months ago you said that you would look at my Isomagic board that I had fried. Any chance ? Send me a PM.
Click to expand...


Puffin said:
sonusthree. Are you offering to look at the board ?
Click to expand...


Sorry for any confusion. I was just trying to remind you that your PM's are switched off. Therefore, John (I'm loving your design of the CD4SE by the way) could only contact you via your email if he has it.

All the best,
 
#191
Puffin,

No problem to take a look at your IsoMagic, However within a couple of months I will be releasing a sub US$300 DAC that is far superior to IsoMagic, Ordinal and even Dacapo - yep better then Dacapo for less then US$300!!!

This is cheaper version of the Dacapo MK2 which will also be released later.

Basic Specs. of the unit are:-

Optical, AES Balanced & BNC 75R SPDIF support to 192 KHz

96 KHz 24 Bit USB support

Balance and Single-ended Audio outputs

Digital Volume Control

LCD display

Class A Output

Remote Control

HQ Headphone amplifier

Steven,

As I mentioned above, I will be releasing a sub US$300 DAC that output performs the original DACAPO in a big way within a couple of months (I just issued the PCB files). While this is not officially the Dacapo replacement from me – I suspect it will cost less the repairing you’re Dacapo – and you can enjoy your music once again without feeling pain over the demise of your current Dacapo!

If you can not wait two more months, then I can send an engineering unit within a month (maybe sooner than I could turn around the Dacapo repair) electronics will be production grade, Um – just casework leaves a little to desire…


Sonusthree

Thanks for your nice words about the CD4SE, if I had to grade my designs that have been released I would say:-

Dacapo with DC, HDCD & Cardinal

IsoMagic with modified Output stage, PSU + Clock-Locked (Ok this is not fully production)

Ordinal with HDCD & Cardinal

CD4SE

Then the rest.

I never much cared for my design's that used the TDA1305 - it was an OK DAC, but not neutral, a heavy kind of Bass - However back in 1995 there where very few "Budget" DAC’s to choose from - nowadays its quite the reveres, there seems to be even fewer High-End DAC’s to choose from.

For the Money, even today the CD4SE is very hard to beat.

John
 
#196
John. Thanks for yoiur response. Eons ago you suggested that some of us might like to test pre-production samples of your intended products. Any chance of trying the new Dac ?

I write reviews occasionally for Affordable$$Audio so it might benefit both of us ?!

Rob.
 
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