Any good TDA1541A DAC kit? - Page 34 - diyAudio
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Old 27th January 2012, 05:24 PM   #331
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Hello T,
Do you still use the LCR filter for NOS used in the old E88CC buffer in the 8072 discussed above?
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Old 27th January 2012, 05:32 PM   #332
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Hi,

Quote:
Originally Posted by revintage View Post
Do you still use the LCR filter for NOS used in the old E88CC buffer in the 8072 discussed above?
Yes, suitably scaled.

I have abandoned this style in my commercial designs, but there I have extra complexity to exploit and other requirements, for DIY I'd stick to LCR EQ...

Ciao T
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Old 27th January 2012, 06:11 PM   #333
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Quote:
Originally Posted by regal View Post
Thanks for trying to help but I don't see this has any bearing on this discussion to the discussion at all, Do you know what an opamp I/V input impedance vs rf curve is or its revalance to pre sigma-delta switcher "DAC's?
It's lower than the resistors that are needed in order to raise the voltage level enough to get some decent SNR.
Don't like the output dynamic impedance of naked OpAmps, add in the loop a discrete stage with MOS-FET. Would be less cucumbersome than any tube concoction.
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Old 31st January 2012, 01:51 PM   #334
mekr is offline mekr  India
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Quote:
Originally Posted by ThorstenL View Post
Hi,



Yes, suitably scaled.

I have abandoned this style in my commercial designs, but there I have extra complexity to exploit and other requirements, for DIY I'd stick to LCR EQ...

Ciao T
HelloThorsten,
I have been following this thread with interest as i have read about the lifelike and musical sound of NOS DAC,s and have also read rave reviews of your AMR CD77 based on TDA1541 DAC,Which i cannot afford, I am asking you a commercial question,as being from a country where i will have to import every component from abroad and being not a DIYer myself, I want to buy a NOS DAC with tube outputs,say if i buy a DAc from source like EC designs and the rest of the other components from other sources to complete the DAC,can you recommend how and where i can source and build parts for such a DAC.
Thanks
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Old 31st January 2012, 02:30 PM   #335
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Hi,

Quote:
Originally Posted by mekr View Post
I want to buy a NOS DAC with tube outputs,say if i buy a DAc from source like EC designs and the rest of the other components from other sources to complete the DAC,can you recommend how and where i can source and build parts for such a DAC.
I do like to help, however I really cannot help with this.

There are a number of DAC's and CD-Players that use the TDA1541A and India has many DIY'ers and capable technicians.

I suggest you try to find a suitable "donor" Machine (may be even in india) and then have someone talented and capable do the modification work.

Ciao T
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Old 31st January 2012, 03:11 PM   #336
mekr is offline mekr  India
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Quote:
Originally Posted by ThorstenL View Post
Hi,



I do like to help, however I really cannot help with this.

There are a number of DAC's and CD-Players that use the TDA1541A and India has many DIY'ers and capable technicians.

I suggest you try to find a suitable "donor" Machine (may be even in india) and then have someone talented and capable do the modification work.

Ciao T
Thanks thorsten,I have a friend who is a master technician,but difficulty is in sourcing different components and he does not use net,so that otherwise i may have asked him to join this forum to ask for different inputs from forum members to DIY a DAC,now he is repairing my CD player which since last 6 months is lying with him for repirs,as i have to source components from the manufacturer in US ,first i imported lens assembly ,then full drive and when i bought the player home after these fitments sometime back,i found one channel not working ,now i am waiting for the DAC from manufacturer
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Old 1st February 2012, 12:29 AM   #337
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mekr,

Suggest you look for 2nd hand older machines - I do my "playing about" with the old Rotel RCD855 and 955 units as they are cheap and a good simple build with enough room for mods and less SMD components like many of the same age Marantz, Phillips, Grundig machines (that are still good source of the player mech (CDM4/19) common to nearly all) - Arcams also good to upgrade.

If you do get one - 2 suggestions ....

When shipping, insist on having the red plastic transport "catches" fitted (underneath) or have the lid removed and a foam cushion to hold down the mechanism - the top part (on spring suspension) of the mech (CDM4/19) easily falls out of its spring mounts when turned on it's side or upside down and it's a PIA to refit.

Also, suggest replacing the standard 2 wire power cord with a 3 wire power cable that does include a chassis earth and add a "100 ohm floating resistor" between 0volt point on the pcb and the chassis earth - back then, they just left off the chassis earth for various reasons - very common, but quite unsafe!

... 2 cents
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Old 1st February 2012, 05:00 AM   #338
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Quote:
Originally Posted by jameshillj View Post
Also, suggest replacing the standard 2 wire power cord with a 3 wire power cable that does include a chassis earth and add a "100 ohm floating resistor" between 0volt point on the pcb and the chassis earth - back then, they just left off the chassis earth for various reasons - very common, but quite unsafe!
Is this mod designed to make the unit more safe? There's nothing particularly unsafe about the original configuration - its typical for Class II (double insulated) appliances. Having a ground via 100R might turn out to be more unsafe - not to mention the 3 wire mains cable might be only Class I rated.
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Old 1st February 2012, 09:49 AM   #339
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Sorry abraxilito,
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 ...

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

I see a ridiculously large percentage of diy gear that's dangerous, mainly thru ignorance, and a strange belief that "they won't get bitten" or that the earth leakage safety switches fitted to the house switch board will save them from a lethal jolt.
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Old 1st February 2012, 10:35 AM   #340
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hmmmmm.... metal case should be DC coupled to PCB ground at single point, via low impedance connection (large contact area & low contact resistance between PCB ground and metal case) - best place is PCB ground area with lowest noise, i.e where the RCA's are located - at inputs / outputs.

The rest of the PCB ground should be AC coupled to metal case at as many points as possible, using parallel combination of 0.1 and 0.01uF capacitors with very short leads - surface mount capacitors are perfect -> this requires some planning -> proper PCB layout at design phase.

Mains earth should not be connected to metal case -> this applies to all HiFi components in a system.

Mains earth is VERY noisy...... AND it contains induced 50Hz artifacts caused by close proximity and long parallel run of 240V phase lead, and earth lead -> which includes power cables as well as the house wiring.

Boky
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