Software Parametric Equalizer Affect on Bit Perfect Transfer Question.

[bhall11]

Hi All

 

I just purchased a DAC1 HDR and have it connected to a PC via USB. My question is, if I apply software parametric equalization (Winamp plugin) will this affect bit perfect transfer to the DAC. I believe it's suggested to turn off any DSP and graphic equalization apps. within the software player as this could or will affect BPT. I'm guessing the parametric equalizer would have similar results.

 

If this is the case, could anyone suggest a method of using parametric equalization at some point in the system without affecting the signal quality. I'm considering using an external digital parametric equalizer between the DAC and power amp, but I'm concerned the DSP processor in the equalizer will degrade the output of the DAC.

 

Any ideas or suggestions appreciated.

 

[Audio_ELF]

Any plugin designed to alter the sound will stop the output being "bit-perfect" as the bits that are output by the player will no longer be the same as the bits on the drive - any form of digital manipulation will be result in the same effect whether done in software (Winamp plugin) or hardware. This isn't necessarily bad though - the whole "we need bit perfect" is a starting point and is about the User being able to control what is going on. If you (with eyes open as to the result) use a DSP / Plugin then there is no issue.

 

If you use a hardware DSP parametric EQ between the DAC and the pre-amp, you have the added potential for degrading the signal by the path adding an additional AD then DA stage. If you wish to use a digital Parametric EQ best if you can go digital into the EQ and forgo your existing DAC.

 

Eloise

 

[bhall11]

Thanks for the reply Eloise.

 

I'll try the software PEQ and do an A/B comparison (with and without PEQ) and listen to the results.

 

[tmfidelis]

Btw, please note software eqs. are not equal. Most may have a tendency to raise the floor noise level substantially.

 

I ran across the phenomena, through the time consuming work of others, when researching the possibilities using digital RIAA to format convert vinyl into digital.

 

Regards,

 

Tim Marutani

 

 

 

 

 

[Nyal Mellor]

The question I would ask is what are you trying to achieve with the parametric EQ?

 

And Tim I guess you are talking about how different software EQs deal with the quantization error and how this may impact the noise floor through dithering?

 

[bhall11]

I would like to improve the room acoustics while using the DAC1. I'm currently using a Denon AVR with Audyssey MultiEQ for my 7.1 system. The DAC1 is connected to the AVR using the EXT IN input, which is a direct mode and bypasses the Audyssey processing.

 

Any suggestions which software PEQ I should try.

 

[cfmsp]

 

"Any suggestions which software PEQ I should try."

 

Amarra is a good choice. A recent release includes a third setting.

 

For doing this on the cheap - software wise - consider any of the software-based DAWs which accept VST / AU plug-ins and find a Parametric EQ plug-in you like. High quality ones may cost a bit of money. The cheapest tool I'm aware of for easily inserting plug-ins on a Mac is Audio Hijack Pro, which is inexpensive. Not sure about PC.

 

clay

 

[cfmsp]

"If you wish to use a digital Parametric EQ best if you can go digital into the EQ and forgo your existing DAC."

 

The best approach would seem to be a high quality DAC that provides high quality DSP / software EQ as an integrated function, e.g. the Sonic Studio/Metric Halo boxes with Sonic/MIO Console software. Amarra's EQ can also function standalone (purely software-based, and therefore works with any DAC) or in conjunction with their boxes. Not sure as I don't use any EQ, and the details on benefits of integration are non-obvious.

 

clay

 

EDIT: Apologies, I didn't notice the winamp reference earlier. i'll leave the post here for others, in the same situation.

 

 

[aljordan]

Hi,

 

I've been playing with some software based PEQs lately (all in the VST format). I've tried a number of them, and the one I think has the best sound quality is unfortunately ridiculously expensive; the Flux Epure II. The Flux Epure II has amazingly pristine high frequencies, but unfortunately the cost is too high for me to justify.

 

While I've tried about 8 or 10 different PEQs lately, others that I think stand out obove the bunch are the Electri-Q (posihfopit edition) by AIXcoustic which is free software, and the Apulsoft APeq (not free).

 

If you try the Electri-Q, be sure to use Digital mode with a quality setting of Normal. It is the most transparent sounding of its various modes.

 

The APeq also has a number of different quality parameters. I like to have the FFT resolution set to 32k, Oversample set to 1x, and my various EQ node stacks set to 4x.

 

Alan

 

[tmfidelis]

When one tries eqs. does anyone go through a layer of due diligence by testing for artifacts?

 

Regards,

 

Tim Marutani

Emeryville, CA

 

[aljordan]

I don't see how any EQ can be applied without artefacts of some sort. Minimum phase software EQ will change phase just like hardware EQ, as well as add post ringing, and linear phase EQ will add both pre and post ringing. There is a VST plugin analyser available at http://www.savioursofsoul.de/Christian/programs/measurement-programs/ that can be used for some objective testing.

 

However, since these things are made to listen through, I generally use my ears to test. There is a VST router called Console that makes it very simple to switch different plugins in and out when listening, and the Foobar VST host allows bypassing very easily as well. I've noticed that some EQ plugins can have negative effects in the low frequencies, and others add problems to the higher frequencies. Some, however, sound very transparent.

 

Alan

 

 

 

[tmfidelis]

the degree of artifacts from digital eq. to digital eq. This is the world mastering and software engineers have experienced for decades. The playback sector of the industry is implementing new playback methods and may be unaware, at this time, the challenges to assemble a truly quite and resolving playback system.

 

Best regards,

 

Tim Marutani

Emeryville, CA

 

[bhall11]

Thanks for all the great feedback guys. I'm a hobbyist in the world of audio playback and it's apparent I've come to the right forum for info on this subject. It seems some of you design and build this equipment. While some of the discussion is beyond my understanding, I like to read and learn from the people that do this for a living.

 

I'll try some of the software PEQs mentioned above and check the results.

 

This is off from the original subject post, but I'll ask anyway. Has anyone (company) considered building a multi channel DAC, say a 5.1 or 7.1 with HDMI inputs? The stereo purist will likely cringe at the thought, and it's likely a limited market, but I would be interested in such a unit if offered at the right price point.

 

[RayW]

Here's what works for me: I do Parametric EQ for room correction. (I won't go into how I got the parameters here, nor argue with the purists who don't believe in room correction. That would be beyond the scope of this thread.)

 

The EQ is not done in real time, but rather as part of the process of transferring audio from CD to hard drive. I use Adobe Audition on a PC, although other Digital Audio Workstation software could be used. The steps are:

1) Read in CD.

2) Convert 16-bit integer to 32-bit floating point.

3) Do EQ processing in 32-bit floating point, so additional quantization distortion is negligible.

4) Convert floating point to 24-bit integer and save as .wav files.

5) Transfer 44.1 kHz, 24-bit .wav files to iTunes on MAC and play through Weiss DAC2.

 

There is actually another step between Steps 3 and 4:

 

3a) Check for peaks above full scale that would clip in Step 4. Note maximum over CD and attenuate all tracks by that amount while still in floating point.

 

The weakest link in the whole chain from recording to playback remains the 16-bit quantization used in producing the CD.

 

(I am also experimenting with apodization filtering, as championed by Meridian, as part of this process. I've found that it does improve soundstage depth on some older classical CDs, i.e., from the 1980s & 1990s. Oops, I'm off topic again, so I'll quit.)

 

Ray W.

 

--------

 

iMac -> Weiss DAC2 -> McIntosh C46 -> McIntosh Mc402 -> Dynaudio Evidence Temptations

 

 

[aljordan]

What happens if you want to listen to the rip in a different room, or if you move? What a pain it would be to re-rip everything. At least with real-time EQ, you can change the parameters if you decide they might be improved upon.

 

[Nyal Mellor]

Well I also tested a few and the best (but most expensive) was the Flux Epure. Having said that compared to the money we spend on stupid power cords its really not that expensive! Even compared to a cheap external parametric EQ they aren't that much more.

 

I verified that when no EQ was on the route iTunes->AU Lab->Epure was bit perfect, using the 'invert the phase compare the samples' technique.

 

Plus the benefit of using these EQs is a) you can do linear phase and b) you can put in filters with a Q of 50, which is what you need to do in order to kill those modal resonances.

 

I would be very happy though if someone developed put an AU host in iTunes. One of the problems I've found is that the audio routing applications on OSX have limitations - Jack is 44.1 only and SoundFlower (also used by AudioHijack) doesn't do 88.2 or 176.4. Therefore I have to switch off the EQ when playing 88.2 or 176.4 material, like the HRx releases.