Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Audio Line Level output?

Status
Not open for further replies.

pepillo

Advanced Member level 4
Joined
Jan 23, 2006
Messages
114
Helped
3
Reputation
6
Reaction score
0
Trophy points
1,296
Location
Spain
Activity points
2,382
ad1854 3.3v

I am using the AD1854 as a DAC for an MP3 player, I see the output is line level voltage, but each channel is double-ended (+ and -). How do I drive these outputs from the chip to the headphones?
Any schematic, circuit?
Thanks
 

pepillo

Advanced Member level 4
Joined
Jan 23, 2006
Messages
114
Helped
3
Reputation
6
Reaction score
0
Trophy points
1,296
Location
Spain
Activity points
2,382
Thank you I have already read the datasheet and I see the circuit the suggest. However, I wonder if I can make it with less external components.
I was about to use the AD1857 which has single-ended outputs, what's the advantage on having differential line level outputs? it's nonsense, it just adds complexity to the output circuit, need of op-amps, more passives (I see you need 1% resistances for the filter)...

Any idea to simplify the design?
 

xxargs

Full Member level 4
Joined
Jul 28, 2002
Messages
229
Helped
44
Reputation
88
Reaction score
2
Trophy points
1,298
Activity points
4,642
pepillo said:
Thank you I have already read the datasheet and I see the circuit the suggest. However, I wonder if I can make it with less external components.
I was about to use the AD1857 which has single-ended outputs, what's the advantage on having differential line level outputs? it's nonsense, it just adds complexity to the output circuit, need of op-amps, more passives (I see you need 1% resistances for the filter)...

Any idea to simplify the design?


Differental output make higher voltage swing than 5 Volt single end power supply can make. and also make lower noise and intefrence from enviroment and power supply. Make IM, noise and spurr free dynamic range above 100 dB is not easy in single end enviroment.

AD1854 output impedance is a still high (~200 Ohm) and cannot drive earphone load as 32 Ohm in loud level and high quality. But possible to make 'line level' as maximum 245 mV RMS ( -10 dBu) for consumer HIFI-equipment. For single ended output you must AC-couple output from AD1854 and after this using (resistive) voltage divide take down single end output from around 2.5 Volt swing to ~ 600-700 mV p-p for line level and make still low impedance (~300 - 600 Ohm).

You not exactly need but want low pass filtering for frequency above 96 kHz to make high quality sound and not load amplifier/stereo with high freqency noise/alising effect from AD1850 and can possible make intermodulation and mixing products in voice range frequency in your stereo. Embedded SC-filter cannot take away every thing and have periodic/cyclic suppression shape depend of frequency and describes by time discret theory.

all digital D/A-stuff need some type of sharp analog LP-filter (time continous-type) in last step on output to avoid high frequency noise/alising effect and mixing/IM-product in later step, not so good audio amplifiers.
 

    pepillo

    Points: 2
    Helpful Answer Positive Rating

pepillo

Advanced Member level 4
Joined
Jan 23, 2006
Messages
114
Helped
3
Reputation
6
Reaction score
0
Trophy points
1,296
Location
Spain
Activity points
2,382
xxargs said:
AD1854 output impedance is a still high (~200 Ohm) and cannot drive earphone load as 32 Ohm in loud level and high quality. But possible to make 'line level' as maximum 245 mV RMS ( -10 dBu) for consumer HIFI-equipment. For single ended output you must AC-couple output from AD1854 and after this using (resistive) voltage divide take down single end output from around 2.5 Volt swing to ~ 600-700 mV p-p for line level and make still low impedance (~300 - 600 Ohm).

Thanks xxargs for your reply.

I didn't exactly understand what you mean whith this paragraph. I want to drive an earphone load, I don't understand why 200 ohms is too big source impedance. What does 'line level' mean? I have seen I can easily drive earphones with single-ended line level outputs from, say, CS4340 with an easy passive filter. Do I really need the op-amp? Is the schematic in the AD1854 the only possibility? Can I simplify the design in any way?

By the way, do you know any 3.3V supply DAC (with I2S input interface)? Because I'm working on a 3.3V system and I realised that the AD1854 has 4.5 V minimum supply.
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top