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DAC as Preamp

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#1
Now that many DACs provide the option of volume controlled outputs, in a digital system, the DAC can potentially be used as a preamp. Unfortunately, the sensitivity of many amps is too low to be fully driven by a DAC's RCA/XLR outputs.

I haven't seen this issue mentioned anywhere.

It's worth noting that the Topping A90 completely resolves problem. If you have a current DAC with digital volume control, the A90 can be set at mid gain and near/at max volume. The result is a preamp with SOTA performance and a DAC's perfect channel-matched volume control; plus, you also get a SOTA headphone amp for free.
 

Nathan_A

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#2
Are you sure about that? I've found it pretty hard to find a power amplifier with a sensitivity less than 2V to full gain out there. Most seem to be somewhere between 1.25V and 1.85V that I come across, which means that any DAC that puts out 2V on RCA can easily drive the amp to clipping.

My Yamaha MX-1 is full power at 1.47V, and when I was driving it directly from a Topping D50s I had to run the digital volume control around -40dB or attenuate the amp input using its input gain controls to keep things in a listenable range, and I don't have particularly efficient speakers (4 Ohm, 88dB).
 
OP
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Thread Starter #3
The MX1 happens to have a lower input sensitivity than most amps.

As one example, this amp[1] - Input Sensitivity 8ohm 2.52Vrms 10.24dBu. In fact, this is true for all Nord Amps. Ditto for all Apollon amps. March Audio doesn't list the input sensitivity of its amps.

Most amps expect to be driven with a preamp that provides 15-20 db voltage gain. Here is a note from PSAudio stating this[2].

A DAC with volume control doesn't provide the voltage gain provided by a typical preamp.

[1] https://www.nordacoustics.co.uk/nord-one-up-nc500-power-amplifiers
[2] https://forum.psaudio.com/t/preamp-output-voltage-question/13974
 

March Audio

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#4
The MX1 happens to have a lower input sensitivity than most amps.

As one example, this amp[1] - Input Sensitivity 8ohm 2.52Vrms 10.24dBu. In fact, this is true for all Nord Amps. Ditto for all Apollon amps. March Audio doesn't list the input sensitivity of its amps.

Most amps expect to be driven with a preamp that provides 15-20 db voltage gain. Here is a note from PSAudio stating this[2].

A DAC with volume control doesn't provide the voltage gain provided by a typical preamp.

[1] https://www.nordacoustics.co.uk/nord-one-up-nc500-power-amplifiers
[2] https://forum.psaudio.com/t/preamp-output-voltage-question/13974
Gain of our stereo amps is 26dB and is stated in the specs. This is an extremely common value for power amps. Very few are as low as 15 to 20dB.

Sensitivity as a spec isnt always helpful as its value depends on the load impedance. Speakers are a complex load and not a constant impedance, let alone a fixed "8 ohm" value. Majority of speakers these days are leaning towards 4 ohm loads.

Typical single ended (RCA) dac output of 2 v rms will yield a 40 volt rms output with a gain of 26dB. Assuming the amp can deliver, that would equate to 400 watts into 4 ohms.
 
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Thread Starter #5
I had said the voltage gain of a preamp is typically 15-20db.

I have verified that a DAC with volume control will not drive a Nord amp to full output.
 

March Audio

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#6
I had said the voltage gain of a preamp is typically 15-20db.

I have verified that a DAC with volume control will not drive a Nord amp to full output.
Sorry, misread that. However Im not sure I see the logic behind stating that power amps "expect" to be driven by a pre amp with x voltage gain. Its too much of a generalisation.
 
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Thread Starter #7
I believe that many amps are designed to be driven by a preamp with voltage gain, i.e. they are not designed to be directly connected to line-level devices. I don't believe there is any controversy on this point.

A DAC with volume control produces a balanced output voltage of 4.0Vpp.

An amp's input sensitivity determines the input voltage required to drive it to max output.

As this link[1] notes, computing this depends on a number of factors.

Someone, who understands this better than I, can tell us whether, spec-wise, a line-level DAC can drive a Nord amp with Input Sensitivity 8ohm 2.52Vrms 10.24dBu to max output.

I've done the experiment - it can't. An A90 preamp can.

[1] https://www.audioholics.com/audio-amplifier/amplifier-voltage-gain
 

Eetu

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#8
I believe that many amps are designed to be driven by a preamp with voltage gain, i.e. they are not designed to be directly connected to line-level devices. I don't believe there is any controversy on this point.

A DAC with volume control produces a balanced output voltage of 4.0Vpp.

An amp's input sensitivity determines the input voltage required to drive it to max output.

As this link[1] notes, computing this depends on a number of factors.

Someone, who understands this better than I, can tell us whether, spec-wise, a line-level DAC can drive a Nord amp with Input Sensitivity 8ohm 2.52Vrms 10.24dBu to max output.

I've done the experiment - it can't. An A90 preamp can.

[1] https://www.audioholics.com/audio-amplifier/amplifier-voltage-gain
The majority of power amps seem to have a spec'd input sensitivity below 2V though.
 
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Thread Starter #9
Some amps don't publish an input sensitivity. Some are 1.38Vrms or lower. Some are higher.

Interpreting input sensitivity for a specific combination of amp and speakers is somewhat complicated.

Many Hypex/Purifi amps have high input sensitivity.

The Mark Levinson No536[1] input sensitivity is `2.83VRMS output at 142mVRMS input`. Can a line-level input produce max output at 2/4/8 ohms?

Audio Science's amp tests don't measure input sensitivity.

All of this argues that the statement 'Most amps can be driven to max output by a line-level input` is false.

[1] https://www.marklevinson.com/produc...6-_color=Black-GLOBAL-Current&cgid=amplifiers
 
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#10
hi , everyone can anyone recommend a dac that acts as a pre-amp for my Avid Integra amp, as I like to control the volume of the amp with a remote control

Avid Integra amp

http://www.avidhifi.com/electronics_integra.htm

i like to have a dac/pre-amp that suits my tonal preference, organic musical, and not cold or analytical sounds such as the Gustard A20H DAC , which was really not my cup of tea in regards to tonality. my mojo sounded way better than my gustard
 

Harmonie

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#12
hi , everyone can anyone recommend a dac that acts as a pre-amp for my Avid Integra amp, as I like to control the volume of the amp with a remote control

Avid Integra amp

http://www.avidhifi.com/electronics_integra.htm

i like to have a dac/pre-amp that suits my tonal preference, organic musical, and not cold or analytical sounds such as the Gustard A20H DAC , which was really not my cup of tea in regards to tonality. my mojo sounded way better than my gustard
I had the Gustard A22 and found it very pleasant, singing/involving in every aspect, piano, organ, strings (down to contrabass, voices good output stage 3/6 volts. I believe it could drive your amp .

PS- Why do you need a Dac with preamp function if you have an integrated amp ? Or you mean it lacks IR ?
 
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#13
I had the Gustard A22 and found it very pleasant, singing/involving in every aspect, piano, organ, strings (down to contrabass, voices good output stage 3/6 volts. I believe it could drive your amp .

PS- Why do you need a Dac with preamp function if you have an integrated amp ? Or you mean it lacks IR ?
yes it lacks a remote control
 
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#14
I’ve moved away from a tube pre-amp toward using a Benchmark DAC3 as the pre-amp, as it has easily changed jumpers to modify its voltage output. With that, it can pretty much drive any amp directly and bypass amp input buffers. It also has a remote control. I do sometimes miss the tube glow.
 
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