Are pre-amps necessary

[Nick Laslett]

I wouldn't base my decisions on the moronic actions of other people. NC500MP is 47K ohm, and NC400 is 104K ohm

Does this mean that it is easier to feed an NC500MP direct from a DAC or harder?

I try my best to follow the discussions, but I’m unclear of the basic equation I trying to solve. I appreciate that whining and complaining is not the answer and I need to educate myself. Any pointers would be greatly appreciated.

 

[restorer-john]

Does this mean that it is easier to feed an NC500MP direct from a DAC or harder?

With a 47K input impedance, you could drive it with anything without issues.

The thing about driving a power amplifier direct from a D/A converter is ensuring 100% that the level of the D/A converter never has the chance to default to 0dB on reset or turn on...

 

[Nick Laslett]

With a 47K input impedance, you could drive it with anything without issues.

The thing about driving a power amplifier direct from a D/A converter is ensuring 100% that the level of the D/A converter never has the chance to default to 0dB on reset or turn on...

Thank you. That makes sense from what else I’d been reading. In the Okto DAC8 thread there was talk about getting the output set lower to match your power amp. I also read about the R141 resistor mod to the NC400 to address the same issue. I glad you spelled out the warning about 0dB.

 

[Severian]

ok maybe i dont understand phase and time delay.
If my L+R speaker is perfectly even from my main listening position and my subs are about 3-5 feet further away from my listening position do I need to be concerned with time delay? I am planning on setting a crossover for my subs to be below 40-50hz.
Do i need to care to delay the fronts to line up with the subs or at that sub 50hz frequency you cant even tell the difference.

is this time delay I am referring too any different from phase?

Do all I need to set this up is just a crossover to only pass the low frequencies to the sub and some soft or dsp or eq for the whole frequency range to kill any peaks?

You will be able to notice the difference from getting the delay correct.

I use a JDS Labs Atom as a preamp. I run the line out to a Dayton Audio DSP-408 that handles the crossover and room correction. The DSP is connected to my power amps.

I would love to eliminate the additional ADC/DAC step with the DSP by implementing software-based crossovers and outputting from a multichannel DAC or pro audio interface to my power amps with balanced interconnects. I've managed to implement my crossover in both Voicemeeter Potato and JRiver as a proof of concept, but it's pretty cumbersome. Volume control is a challenge - I ended up MIDI mapping an unused knob on a DJ controller to control Voicemeeter's gain faders. More significantly, latency is much, much higher than with the external DSP. Not a big deal for music, but any videos on my PC are way out of sync.

As such, I've pretty much given up on the idea of implementing my crossovers in software. I think the best I can do is improve my external DSP setup by upgrading to something with digital input, volume control, and balanced output (my Dayton Audio DSP has none of these). miniDSP 4x10 HD appears to fit the bill perfectly. I haven't found anything else suitable.

 

[RichB]

With a 47K input impedance, you could drive it with anything without issues.

The thing about driving a power amplifier direct from a D/A converter is ensuring 100% that the level of the D/A converter never has the chance to default to 0dB on reset or turn on...

This is exactly why I do not trust using a PC as a preamp.

- Rich

 

[Kal Rubinson]

This is exactly why I do not trust using a PC as a preamp.

Both my server/player (Jriver) and DAC default to preset volume values......................................and I do check them.

 

[dualazmak]

What would be a good way to do systemwide digital volume control in Windows if one was doing a sub crossover in software, such as EKIO, and outputting to a multichannel DAC, (say for example a USB pro audio interface using ASIO drivers? One of those big knobs would be great, I'm just not sure what it should be controlling.

Hello Severian,
If you would have your relaxing occasion, please visit;
https://www.audiosciencereview.com/...oftware-crossover-and-multichannel-dac.12489/
"Multi-Channel, Multi-Amplifier Audio System Using Software Crossover and Multichannel-DAC"

 

[flaviowolff]

I use a minidsp ddrc-24 as dac/dsp/digital volume control directly to a power amp. Tidy setup and I don’t notice any degradation from the digital volume. I thought about adding a passive pre on the path, just for the pleasure of turning a knob, but the potential channel imbalance made me dump the idea

 

[watchnerd]

I use a minidsp ddrc-24 as dac/dsp/digital volume control directly to a power amp. Tidy setup and I don’t notice any degradation from the digital volume. I thought about adding a passive pre on the path, just for the pleasure of turning a knob, but the potential channel imbalance made me dump the idea

I bet.

 

[Kal Rubinson]

I thought about adding a passive pre on the path, just for the pleasure of turning a knob, but the potential channel imbalance made me dump the idea

Then put the knob where it doesn't have the ability to affect channel imbalance. https://www.audiosciencereview.com/forum/index.php?threads/are-pre-amps-necessary.9327/post-244469

 

[flaviowolff]

Then put the knob where it doesn't have the ability to affect channel imbalance. https://www.audiosciencereview.com/forum/index.php?threads/are-pre-amps-necessary.9327/post-244469

My minidsp setup does not involve a computer. The transport is a smart tv playing Spotify and YouTube via optical to the minidsp.
Nonetheless, this usb pot would be nice for my headphone PC setup, which has a usb dongle dac/amp.

 

[Rastanearian]

Right, OK...

Now consider every D/A converter Amir tests, he loads its line outputs with a 200K ohm analyzer input. How is that remotely representative of typical power amplifier input impedances? Hint: it's not. Most power amplifier input impedances range between 10K and 50K, and with amplifiers incorporating input level pots, the impedance will be likely at the low end of those numbers.

D/A converters (line output) will have output impedances ranging from a few ohms (the good ones maybe) to many hundreds (or thousands) of ohms for the average ones. All of that combines to make the otherwise flat FR and low THD numbers less likely (if at all) to occur in a real system. Take the industry darling NC-500 (or equiv) with its unbuffered 1.8K ohm per input and tell me a typical D/A converter is going to perform well into such an impedance. And yet people are plugging sources into these modules without using an outboard buffer in some cases.

Good preamplifiers have output impedances below most of the headphone amplifiers tested on ASR. They can swing large voltages at very low impedances and happily drive long cables and multiple amplifiers with little or no modification of the ruler flat FR and low THD.

People obsess over headphone output impedances but rarely even consider the line output impedance of their D/A converter before eschewing a proper preamplifier and plugging in their power amps.

Nailed it!!

 

[dualazmak]

Let me join only on the topic on "Master Volume" and "Individual Volume and Balance" in crossover+multi-channel + multi-amplifier system.

Nowadays, almost all of the Hi-Fi power amps do not feature volume/gain/balance controllers, and I always feel a little bit uncomfortable about that. As discussed here, it would always give us possibilities of accidental damage to our speaker units, and give the issue of "where to control master volume?, and, where to control L-R balance?"

I fully agree with RichB's policy of; "I do not trust using a PC as a preamp". Just for example, I hate and should never to touch the gain control of input channels of my software crossover EKIO while listening to music; I only adjust the input gains after muting all the output channels, or the DAC's and/or amp's volume/gain being set in sound-off position, like all of you are always doing so...

I believe the software (or hardware) digital crossover should be processed in high gain (of course just under clipping level) in order to minimize the bit-loss in digital processing. The Master Volume (and L-R balance also?), therefore, should be controlled after the crossover process, preferably by multichannel-DAC's "Master and Individual Volume" controller(s); this should be also nice to protect your speakers. This would be nice as well to avoid/minimize any possible "phase complication" given by L-R unbalance within our software crossover.

Since currently available several nice Hi-Fi integrated amps, however, have advanced and sophisticated, sometimes fully digital, volume and balance controllers which would have no or almost negligible deterioration to the total sound, I believe we should not exclude the possibilities of using high quality Hi-Fi integrated amps in multi-amplifier system.

And I also think that the digital crossover, and any of other digital processing, within PC should be as simple as possible, and as minimum as possible, in terms of the "total sound quality".

In my current project of "Multi-Channel, Multi-Amplifier Audio System Using Software Crossover and Multichannel-DAC", I carefully integrate the above considerations in total system design, including the possible utilization of Hi-Fi integrated amps.
If you may have interests, please visit;
https://www.audiosciencereview.com/...oftware-crossover-and-multichannel-dac.12489/

 

[Willem]

I use an RME ADI-2 as a preamplifier and I see no downsides. It has a knob for a volume control, just like any pre amplifier. When I turn it on it comes up at the last volume setting, so unless I did somethng daft last time, I am fine next time. And it has balance, tone and dynamic loudness controls. Output level can be set automatically for best S/N. What more can I want?

 

[A800]

I think a good tube preamp IS necessary.

 

[Willem]

Can you provide evidence, or are you joking?

 

[dualazmak]

Let me add just one more point, please.

I think, or rather believe, that the DA processing in USB DAC (or in USB multichannel-DAC) should be done also in as high gain as possible (of course just below clipping level) in order to minimize the bit loss, again in terms of "total sound quality".

Even though I understand Willem's current satisfaction with "RME ADI-2 (software) as a preamplifier", I do not fully understand, however, whether the volume/gain/balance control by RME AD1-2 would be applied to the signal before the DA conversion, or after the DA conversion. (Sorry, but I still did not have closer look at RME ADI-2 yet.) In case we would hear our sound/music in rather small volume/gain (e.g. when enjoying nice sound of music in midnight while our kids are sleeping upstairs), it should be more critical to apply volume/gain/balance control(s) after the DA conversion, I believe.

Consequently, my idea or policy is that all of the digital processing including the final DA conversion should be done in as high gain as possible in terms of "total sound quality". I am much excited about, therefore, the "volume/gain" controller of DAC8PRO, as a preamp, which enables "Master and Individual volume/gain control" for all of, as well as each of, the crossovered (divided) 8 channels.

In this line of consideration, high quality pre-amp+ Hi-Fi power amp or high quality Hi-Fi integrated amp, are still worthwhile to be used in multi-channel + multi-amplifier audio system, even though we would intensively utilize digital processing with PC.

I stop here since I am afraid that my post would be somewhat becoming out-of-scope from the main discussion of this thread. Thank you for your kind attention....

Edited to add...
Hello Willem,
I could look at info and spec of RME ADI-2, and fully understood your points. In my project of stereo 5-way 10-channel multi-channel + multi-amp system, however, I do need volume/gain control of each of the 10 channels as well as the Master Volume. As for Master Volume control, I agree RME-ADI-2 can do it, if I would introduce RME-ADI-2 (as DD converter?) in front of EKIO crossover processing...

Even though EKIO can control gain of each of the crossovered (divided) channels, I would like to try no gain control with EKIO to have almost flat line level Fq response in high gain (avoiding possible phase complication by gain control or L-R unbalance), then final "attenuations and L-R balancing for each of the channels" would be done after the DA conversion in multichannel-DAC like DAC8PRO as a preamp.

 

[watchnerd]

Step up transformers are what you really need.

 

[Burning Sounds]

I haven't used a preamp for years. I can't see the point of putting another box and cables in a primarily digital system.

I use a fanless PC with JRiver, multi-channel DACs (mostly pro DACs with no volume control) and multi-channel amplifiers feeding active speakers and never had any issues. Although I don't do it as matter of course (I was taught turn off the power amp first and work back to the source) I'm quite happy to turn off the PC with the power amp on. There is never so much as a click from the system. On the rare occasion that JRiver freezes I can reboot the PC with the power amp on and everything is perfectly silent. JRiver will re-load automatically and volume is set at -40db. It has the potential to be a real speaker saver.

Interestingly, Roon doesn't have this functionality and one of the reasons I rejected it when I had a long trial.

I use the volume control in JRiver controlled by a USB connected knob -- better than any up/down button on a remote for me.

I wouldn't contemplate turning most pre-amps off with the power amp on. Maybe the newer, better ones have soft turn-off circuitry.

 

[dualazmak]

Hello Burning Sounds,

Very nice to see you here again. I highly appreciate your above post since your system design is quite similar to my current project;
https://www.audiosciencereview.com/...oftware-crossover-and-multichannel-dac.12489/

It is very nice of you giving us info of "Roon doesn't have this functionality and one of the reasons I rejected it when I had a long trial". As I informed you several days ago, I use mainly JRiver and Roon, and after hearing your comment here, I should be much careful when I would use Roon in my trials.

You would please let me ask your thoughts regarding possible "bit loss" in digital processing, especially in case of "low gain" situation.