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Old 1st February 2012, 09:49 AM   #341
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Quote:
Originally Posted by jameshillj View Post
Dunno about the double insulated rated safety standards gear, but if you have 240 volt and just the usual 2 wire mains supply wire into a metal cased cd player of 15 - 20 years ago, the metal case will rarely have a chassis earth connection at all, but relies on the signal's sheild wire of the interrconnect for safety earth - with the insulated plastic cases like some of the Marantz, etc, players, this won't apply provided the lid is kept on and so on ...
No, it can't rely on an external connection for safety because that might not be provided. It relies on having more layers of insulation internally to protect against a single point failure resulting in exposure of a person to hazardous voltages.

Quote:
However, if you are into DIY and maybe using older metal chassis players (without lid, bare mains fuse holders, bare wires at the switch, etc, etc) and it doesn't have a chassis earth connected via a 3 wire cable, I would stongly suggest you add one (or an IEC socket) and tie the metal chassis to the earth pin for safety and then isolate the phono plugs from the metal case - and maybe seperate/float the original central 0 volt point on the pcb from the new chassis earth via a resistor, thermistor, etc
Use of a component - like resistor - for ground lifting is dangerous unless that component can handle any potential fault current for long enough to blow the line fuse. So you're in danger of making your equipment more unsafe, whereas it was relatively safe before you started modding it...
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Old 1st February 2012, 10:17 AM   #342
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Quote:
Originally Posted by Joshua_G View Post
I'm still looking for a DAC that will produce the recorded music as it is, without any additions and omissions…
I have achieved nice results with dual differential 1704 and AD811 as I/V - however, flat input impedance of < 1 ohm was crucial factor….. also, a lot of measurements & very low noise environment.

I almost completely wasted 3 years on 1541.

Sigma/delta DAC's in very low noise implementations served me as reference for achieving high frequency spectrum resolution with difficult to implement, but superior sounding 1704's.

Good CD transport is of equal importance as DAC, and with CD transports -> I learned that heavy plastics of an appropriate density make or break the end-result. I still have to find a single useful thread on internet that discusses this topic with due relevance to the digital reproduction (sensible ones decided to forgo CD mechanism altogether and accept flash as digital source!)


Boky
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Old 1st February 2012, 10:19 AM   #343
Previously: Kuei Yang Wang
 
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Hi,

Quote:
Originally Posted by Extreme_Boky View Post
Mains earth should not be connected to metal case -> this applies to all HiFi components in a system.
This is EXTREMELY dangerous and in many cases also very "un-sound" advise.

Unless a given piece of equipment can be shown to reliably pass all the requirements for Class II Double Insulated equipment it must be considered Class I and requires a mains earth connection to all metal parts that can be touched or reached through louvres etc. (that includes for example exposed metal binding posts on Amplifiers and RCA connector shells).

Appliance classes - Wikipedia, the free encyclopedia

Those are very serious requirements mandated by law in almost any country and strongly enforced in first world countries and even many 2nd world countries..

In the case anything happens (e.g. someone receives an electrical shock and requires medical treatment and is perhaps disabled or your house burns down) and you used equipment that did not comply with safety regulations you may find yourself without any insurance and liable for all costs incurred.

Mains electricity can kill. Often it does not kill or maim you, but others.

So PLEASE take electrical safety VERY serious.

If you have DIY Gear, build it according to applicable standards and perform a PAT (Portable Appliance Test) on it after building and regularly afterwards.

Past that, removing the Earth from any unit designed to operate with earth can cause unpredictable behaviour and poor sonics.

AMR's gear is all designed as Class I and had measures taken to avoid the common problems while passing all mandated tests. Moreover it requires the normal mains earth to "dump" any mains born noise intercepted by the transformers screens and core into this earth.

In an extreme case at a show in old hotel in the US where the mains power had no earth we had major issues with CD-Players skipping, until an earth cable was run from the metal water pipes in the Bathroom!

In other cases the inability to get rid of noise caused poor sound quality.

Further, the concept that "mains earth is noisy" is in many ways meaningless.

It must be "noisy" in reference to something. This could be the local "true earth", however HiFi Gear on a stand and on (electrically) isolating feet will have extremely low capacitance to this earth, so bonding the chassis to mains earth for safety is unlikely to introduce any appreciable problems.

If neccesary a mains earth connected metal plate could be placed under especially sensitive equipment to screen this out, but normally the metal case already performs this function very well.

Problems arise when multiple earthed appliances are interconnected and the earth/ground interface is not managed correctly and possibly circulating chassis currents are introduced.

There are many ways in which the situation may be improved without violating electrical safety codes though and they should be tried first.

If it is ABSOLUTELY essential to lift the earth, the safe way to do this is to convert your equipment to 115V Power Supply and use a Building Site Balanced Safety Isolation transformer. These contain a centre tapped secondary with a total of 110V but the centre-tap earthed and usually additional screens to minimise leakage.

They are big portable yellow boxes normally designed to supply power tools. This way should a worker drill through a power cable, drive a nail through a power cable or otherwise connect himself to one of the power lines (preferably while working wet cloth, in the rain and standing in a puddle) will not be permanently hurt (beware of pacemakers though)

This way the maximum voltage available referenced to earth is 55V which qualifies as SELV (Safety Extra Low Voltage) and anything on the "safe" side essentially becomes Class III equipment. This may be a good choice for DIY gear anyway.

Ciao T
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Old 1st February 2012, 10:33 AM   #344
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Quote:
Originally Posted by ThorstenL View Post
Hi,



This is EXTREMELY dangerous and in many cases also very "un-sound" advise.

Those are very serious requirements mandated by law in almost any country and strongly enforced in first world countries and even many 2nd world countries..

you've obviously no clue whatsoever.... the only appliances that must be mains earthed are those that contain motors / solenoids where windings shorting to metal frame can bring the same to mains potential.

all hifi / video components are double insulated at mains transformer-end, they are not required to be earthed – and are better left un-earthed.

.... good laugh though, just before the bed time....

Are your "high-end" designs mains earthed? Ha ha ha….

Boky
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Old 1st February 2012, 10:41 AM   #345
Previously: Kuei Yang Wang
 
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Hi,

Quote:
Originally Posted by Extreme_Boky View Post
I have achieved nice results with dual differential 1704 and AD811 as I/V - however, flat input impedance of < 1 ohm was crucial factor….. also, a lot of measurements & very low noise environment.

I almost completely wasted 3 years on 1541.
Good you found something you like. It seems however you never got anywhere close to the potential of the TDA1541, OR you like a very different sound to many in this thread.

When dealing with CD signals I have yet to hear anything beat a fully optimised TDA1541 design.

Quote:
Originally Posted by Extreme_Boky View Post
Good CD transport is of equal importance as DAC, and with CD transports -> I learned that heavy plastics of an appropriate density make or break the end-result. I still have to find a single useful thread on internet that discusses this topic with due relevance to the digital reproduction
If the CD-Drive has been competently implemented and integrated there no issue.

It is important that the CD cannot resonate by itself and that the system can read without errors that cannot be corrected (note - CD-Error correction does 100% correct errors), so concealment is not required.

Error concealment happens when error correction is impossible due to too much missing data and one or more samples are interpolated to avoid extremely audible pops or clicks.

If the drive can reliably read good data AND we can make sure the clock driving the DAC remains unaffected by any transport activity or other issues (varying RFI due different processor activity during error correction) then one will find that all transport differences magically disappear.

Unfortunately very little if any CD-transports/players consequently implement the necessary power supply separations, ground separation, shielding etc., in fact looking at most they seem to be designed to maximise these problems instead, certainly in many cases I could not do worse then what we see implemented.

Ciao T
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Old 1st February 2012, 11:00 AM   #346
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Quote:
Originally Posted by ThorstenL View Post
Further, the concept that "mains earth is noisy" is in many ways meaningless.

It must be "noisy" in reference to something.
All earth wires terminate at the planet at some point. So its noisy relative to itself - the near end is noisier than the end buried in the ground. Nothing magical about that.

Or we could just say that the earth is noisy relative to the aether. It radiates when noisy, it doesn't when its not.
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Old 1st February 2012, 11:16 AM   #347
Previously: Kuei Yang Wang
 
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Hi,

Quote:
Originally Posted by Extreme_Boky View Post
you've obviously no clue whatsoever.... the only appliances that must be mains earthed are those that contain motors / solenoids where windings shorting to metal frame can bring the same to mains potential.
First, before providing such "advise", you may wish to review the relevant standards applicable, I believe for you this would be:

AS/NZS 3820:2009 Essential safety requirements for low voltage electrical equipment

Quote:
Originally Posted by Extreme_Boky View Post
all hifi / video components are double insulated at mains transformer-end, they are not required to be earthed – and are better left un-earthed.
Double insulation is not conferred by the presence of a mains transformer, but requires the observance of specific clearances, insulation requirements etc.

AMR Equipment conforms to the most stringent (German) electrical safety regulations though we generally cross-check against other legislation to make sure we are compliant with all relevant electrical and other safety requirements. Most countries are now trying to harmonise electrical safety in like the with IEC Standards, though over time expect convergence on these.

I am hardly an expert on Australian regulations, however they do have provisions for multiple equipment classes and require the attachment of a safety earth for some classes.

Ciao T
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Old 1st February 2012, 11:46 AM   #348
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Hi,

Quote:
Originally Posted by abraxalito View Post
All earth wires terminate at the planet at some point. So its noisy relative to itself - the near end is noisier than the end buried in the ground. Nothing magical about that.
Yes, or as I pointed out, if you drove a suitable local earth stake (or several) into the local PHYSICAL earth you could measure that there is noise on the mains safety earth.

However, as long as you do not complete any circuits between this physical earth and the mains earth this noise does not matter. The circuit completed through parasitic capacitances is very minimal and should (competent design given) complete only through the actual earth wires and not through the signal circuit.

Quote:
Originally Posted by abraxalito View Post
Or we could just say that the earth is noisy relative to the aether. It radiates when noisy, it doesn't when its not.
I have not heard the term æther used in a long time. I though the concept was discredited over a 100 years ago? You still adhere to the view that this alchymical element is actually real? Or have I missed the article in nature where æther was re-instated as real?

Ciao T
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Old 1st February 2012, 11:58 AM   #349
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Quote:
Originally Posted by ThorstenL View Post
However, as long as you do not complete any circuits between this physical earth and the mains earth this noise does not matter. The circuit completed through parasitic capacitances is very minimal and should (competent design given) complete only through the actual earth wires and not through the signal circuit.
You seem to have omitted something vital here - all noisy earths are noisy in their own individual ways. Thus a noisy earth at the CD player will differ in potential from the noisy earth presented to the preamp. Ditto preamp to poweramp.

Quote:
I have not heard the term æther used in a long time. I though the concept was discredited over a 100 years ago? You still adhere to the view that this alchymical element is actually real? Or have I missed the article in nature where æther was re-instated as real?
I take the view that the vacuum is in fact a plenum yes - after all it has properties. Quantum physicists nowadays talk of 'quantum foam' or some such rather than aether.
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Old 1st February 2012, 01:58 PM   #350
mekr is offline mekr  India
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Default Any good TDA1541A DAC kit?

hello,

Thanks everyone for their kind suggestions.

Regarding power safety, here in india ,we are dependent on electrician for safety,as there is no govt manual or instructions for the safety of power supply lines
I am on the 6th floor of the building and have direct dedicated power line for my audio system.the dedicated power line is cryoed and runs from utility company,s meter on the ground floor to the output recepctacle of Maestro used in tripoint power conditioners,with a circuit breaker in between for safety.
the background of the music i hear is very black.
Now i will start hunting for TDA1541 based Cd player and it has to be with 220 or 240V electric input.
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