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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: Tweakomatic, I'm tweakomatic - the LHH-1000/DA-12 Sessions #1 posted by Thorsten on August 1, 2001 at 03:08:16:
Wow, great article ! Due to my limited knowlege, I can't understand all, though. I hope one day I can apply similar changes to my CDA94. For the moment, I am waiting for some OPA627s for a direct swap.> I used a 300 Ohm resistor to the DAC, a 220uF Elna Silmic Capacitor
> as filter and 7k5 Resistor to +15V, giving pretty accuratly +2mA
> offset current to compensate for the 2mA quiescent output current
> of the TDA1541 at "digital silence". I also fited a 10nF Polystyren
> Cap from the OPA637 negative input to ground.I suddenly recall that I heard about the quiescent current at digital silence for 1541. In the tube o/p stage I am building (a direct copying from your circuit in your "Thermionic Valve Analogue Stages for Digital Audio" with the values calculated for PCM63), this has not been catered for. What should I do ? Should I connect a 2.5k resistor from the +5 supply (my circuit has no +15V supply) to the DAC ouptut (i.e. pins 6 & 25 of the 1541) direct to "zeroise" the 2mA current (I suppose it is negative) ? Or, should I forget about this resistor but series a 1 uF cap (I have two good quality Sprague) between the DAC output and the tube stage input ?
I have almost completed connecting a CS8414 and a TDA1541 and their TL431 based regulations. When I finished the power supply part in the next couple of days, I can test the DAC part probably in the weekend. I would therefore appreciate your urgent advice. Thx.
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Follow Ups
- Re: Tweakomatic, I'm tweakomatic - the LHH-1000/DA-12 Sessions #1 - Tazo 08/1/0119:09:17 08/1/01 (0)