DAC output voltage

daredevil_kk · 27th August 2009, 06:15 PM

Hi guys,

My dac is giving a output of 0.3v for a 0dB 1khz. Is it too low and what is the effect down stream, beside having to crank up the vol?

Thanks,

KK

Iain McNeill · 27th August 2009, 06:33 PM

I assume you mean 0.3Vrms which would be 0.85V p-p. It all depends on your DAC supply rails so this might be reasonable for a 1.8V rail DAC. As long as the DAC is achieving the 96dB signal-to-noise that 16bit digital aspires to you should have no problem with adding clean gain.

I have seen 1Vrms as a more typical 0dBFS level. Care to share the DAC schematic and we could comment further.

daredevil_kk · 27th August 2009, 06:50 PM

Hi Iain,

Yup, it is 0.3Vrms. As for the circuit, it is a TDA1541A to a I/V 34ohm resistor to step-up transformer. It has a output impedance of 4.5kohm. My intention is to put a unity non-inverting buffer after that.

Cheers,

KK

Iain McNeill · 27th August 2009, 07:19 PM

Hmmm. Doesn't seem like it's stepping up much. Sounds like it may be mismatched somewhere. Do you have full specs on the transformer like primary inductance, turns ratio etcetc?

daredevil_kk · 28th August 2009, 03:08 AM

From my measurement, the voltage after the I/V is 0.043Vrms. Hence, the transformer is a 16.9dB gain. I don't have much info on the transformer.

KK

daredevil_kk · 28th August 2009, 03:49 AM

Oh yeah, it is an input trans for a tube amp.

Cheers.

KK

Iain McNeill · 28th August 2009, 07:41 AM

43mVrms is about right for 4mA pk into 34ohm so that's encouraging.

Without a schematic and measurements it's hard to say how it works.

daredevil_kk · 28th August 2009, 01:47 PM

The DAC is a simple I2S to the TDA1541A to the passive I/V. Nothing complex about it. The only thing that I thinking is to leave it alone with a low line out or change the value of the I/V or change to a higher step up trans.

Thanks Iain.

KK

27th August 2009, 06:15 PM	#1
daredevil_kk diyAudio Member Join Date: Mar 2001 Location: Singapore	DAC output voltage Hi guys, My dac is giving a output of 0.3v for a 0dB 1khz. Is it too low and what is the effect down stream, beside having to crank up the vol? Thanks, KK __________________ CD pro=>TDA1541AS1=>Lightspeed=>ESP crossover=>Soraya CB205=>Accuton drivers

27th August 2009, 06:50 PM	#3
daredevil_kk diyAudio Member Join Date: Mar 2001 Location: Singapore	Hi Iain, Yup, it is 0.3Vrms. As for the circuit, it is a TDA1541A to a I/V 34ohm resistor to step-up transformer. It has a output impedance of 4.5kohm. My intention is to put a unity non-inverting buffer after that. Cheers, KK __________________ CD pro=>TDA1541AS1=>Lightspeed=>ESP crossover=>Soraya CB205=>Accuton drivers

28th August 2009, 03:08 AM	#5
daredevil_kk diyAudio Member Join Date: Mar 2001 Location: Singapore	From my measurement, the voltage after the I/V is 0.043Vrms. Hence, the transformer is a 16.9dB gain. I don't have much info on the transformer. KK __________________ CD pro=>TDA1541AS1=>Lightspeed=>ESP crossover=>Soraya CB205=>Accuton drivers

28th August 2009, 03:49 AM	#6
daredevil_kk diyAudio Member Join Date: Mar 2001 Location: Singapore	Oh yeah, it is an input trans for a tube amp. Cheers. KK __________________ CD pro=>TDA1541AS1=>Lightspeed=>ESP crossover=>Soraya CB205=>Accuton drivers

28th August 2009, 01:47 PM	#8
daredevil_kk diyAudio Member Join Date: Mar 2001 Location: Singapore	The DAC is a simple I2S to the TDA1541A to the passive I/V. Nothing complex about it. The only thing that I thinking is to leave it alone with a low line out or change the value of the I/V or change to a higher step up trans. Thanks Iain. KK __________________ CD pro=>TDA1541AS1=>Lightspeed=>ESP crossover=>Soraya CB205=>Accuton drivers


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27th August 2009, 06:33 PM	#2
Iain McNeill diyAudio Moderator Join Date: Oct 2007 Location: Santa Cruz, California	I assume you mean 0.3Vrms which would be 0.85V p-p. It all depends on your DAC supply rails so this might be reasonable for a 1.8V rail DAC. As long as the DAC is achieving the 96dB signal-to-noise that 16bit digital aspires to you should have no problem with adding clean gain. I have seen 1Vrms as a more typical 0dBFS level. Care to share the DAC schematic and we could comment further.

27th August 2009, 07:19 PM	#4
Iain McNeill diyAudio Moderator Join Date: Oct 2007 Location: Santa Cruz, California	Hmmm. Doesn't seem like it's stepping up much. Sounds like it may be mismatched somewhere. Do you have full specs on the transformer like primary inductance, turns ratio etcetc?

28th August 2009, 07:41 AM	#7
Iain McNeill diyAudio Moderator Join Date: Oct 2007 Location: Santa Cruz, California	43mVrms is about right for 4mA pk into 34ohm so that's encouraging. Without a schematic and measurements it's hard to say how it works.

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