My new R3 shines in sound quality (audio demos + video)

[alfredokiwi]

Hi all, yesterday I was performing some changes on my R3 synth. I added a LPF antialiasing filter after DAC converter to remove all type of high frequencies noises and unwanted signals that are out of ear audible spectrum.
Also I have compensated the line out stage after filtering with more output level and with an active equalization to follow Fletcher-Munson human ear response theory. This circuit design is much better as in Pa500 circuit changes that I have developed because it has a double EQ compensation network to compensate not only low freq also highs. At the same time the DAC antialisang filter is much better as in Pa500 because Pa500 original filter freq cut off is set a 40Khz and on my bended Korg R3 I have set it to 12,5 Khz approximately. Has not sense to set a filter at so high band pass response because high freq components are not audible, consumes amplification power wasting efficency and produce ear fatigue and severe damage at very high levels. Also the response on lows freq is improved to because I have increases the DAC overall stages decoupling capacitors values for better bass impulse.

Korg R3 original design don´t use an active DAC antialiasing image filter stage after DAC, sounds strange and the reasons why this is removed from other designs I don´t know. A detailed explanation of this topic on my blog

http://www.alfredoblogspage.blogspot.co ... ality.html

Here some pictures about the circuit changes





I have check the quality before and after, what I can say is that audio quality is superb after changes, with more details. Also I have improved the dynamic range due the low audio output.

I will see to add some audio samples.

[alfredokiwi]

Here some audio demos, the final part of "R3 Medley demo"

The R3 factory sound quality without changes
<iframe width="100%" height="166" scrolling="no" frameborder="no" src="http://w.soundcloud.com/player/?url=htt ... "></iframe>

The first circuit bend after month ago, only output increase without antialiasing filter and active EQ compensation, remains the same as factory but with more volume to drive a mixer
<iframe width="100%" height="166" scrolling="no" frameborder="no" src="http://w.soundcloud.com/player/?url=htt ... "></iframe>

After final changes, with a DAC antialiasing 12,5Khz cut off filter (4 poles aprox -36dB attenuation at 48Khz) and Fletcher-Munson active EQ compensation
<iframe width="100%" height="166" scrolling="no" frameborder="no" src="http://w.soundcloud.com/player/?url=htt ... "></iframe>

[alfredokiwi]

Hi again, I have recorded a short demo about the final quality on R3 after circuit bend.

<iframe width="100%" height="166" scrolling="no" frameborder="no" src="http://w.soundcloud.com/player/?url=htt ... "></iframe>

The vocoder is one of the best things in R3, maybe for analog sounds recreation is a bit limited and can't compete with soft synths, but regarding user reviews vocoder works very well !

[djcactus]

that is some awesome modding. Between the clean work and audio quality im blown away. I checked out your blog but didnt see this project in there but im certainly happy to see it here.

[alfredokiwi]

that is some awesome modding. Between the clean work and audio quality im blown away. I checked out your blog but didnt see this project in there but im certainly happy to see it here.

I have included an article about this topic on my blog

http://www.alfredoblogspage.blogspot.co ... ality.html

I buy the R3 on Dec 2011 and was a bit disappointed about the outputs levels and overall sound quality. At first only I have increases the outputs levels, but sounds remains stuck at low quality.

On last Tuesday I added the active DAC filter stage and after this R3 sound quality is amazing

I'm a happy owner of a R3 !

[Akos Janca]

Dear Alfredo,

Thanks for sharing this great idea. I have read all your posts on your blog about the Pa500 and R3.

Your result is excellent. The quality improvement is sensational!

I would try it on my R3 - so I am looking forward to reading the details or step-by-step explanations, when you will have time to share.

My best regards,
Akos

[jondis]

this is awesome man. i would love to have this done to my radias im not very tech savvy tho, are the parts u installed readily available ? It'd be great if there was something i could just plug my radias into to achieve the same/ similar result. great work very interesting I've been on a search for something to get for my radias to improve its sound , was thinking of getting a tube buffer amp or headphone amp for the output . I dont really know what i can do to achieve better sound out of it. Thanks for sharing this

[alfredokiwi]

Reaching the best quality is very important on recordings. People spends a lot of money on rack units to have a better audio, I was one of them. But I learned that on analog stages if quality is affected on the audio chain the degradation of sound is permanent due the lost of audio information. And the solution is a good circuit stage design from beginning, this is the most important aspect on recordings setups.
When I have a chance I will put all the information of the last circuit changes on my blog at http://www.alfredoblogspage.blogspot.com.ar/

I want to share the last R3 uploaded track after circuit bend to show the importance of a "good audio quality".

<iframe width="100%" height="166" scrolling="no" frameborder="no" src="http://w.soundcloud.com/player/?url=htt ... "></iframe>

And here the vocoder test with an introduction about me.
<iframe width="100%" height="166" scrolling="no" frameborder="no" src="http://w.soundcloud.com/player/?url=htt ... "></iframe>

I´m very happy with the improved R3 sound !!!

[javaj]

Wow- I think you just gave Korg a reason to come out with an R3 XL.

[alfredokiwi]

Hi again, I have uploaded the last demo on Mixcloud because it streams the mp3 data without interruptions. On the demos played by me I have used octave arpeggio chords for the bass part/ left hand and a random melody on right. I have connected my Pa500 as MIDI keyboard to the R3 to have more octaves on playing, that´s all.
<div><object><param name="movie" value="//www.mixcloud.com/media/swf/player/mixcl ... ram><param name="allowFullScreen" value="true"></param><param name="wmode" value="opaque"></param><param name="allowscriptaccess" value="always"></param><embed src="//www.mixcloud.com/media/swf/player/mixcl ... t_standard" type="application/x-shockwave-flash" wmode="opaque" allowscriptaccess="always" allowfullscreen="true" width="720" height="160"></embed></object><div></div><p><a href="http://www.mixcloud.com/AlfredoAlejandr ... ource_link" target="_blank">Korg R3 demos (HQ antialiasing DAC filter + Fletcher-Munson EQ)</a><span> by </span><a href="http://www.mixcloud.com/AlfredoAlejandr ... ofile_link" target="_blank">Alfredoalejandro</a><span> on </span><a href="http://www.mixcloud.com/?utm_source=wid ... epage_link" target="_blank"> Mixcloud</a></p><div></div></div>

Also I made a video about the improvements (Please set before the video quality to 480p !!!)
<iframe width="780" height="480" src="http://www.youtube.com/embed/69hDBcJ5ShE" frameborder="0"></iframe>

Again I´m very happy with the sound quality and thanks for the replies !!! Cheers !!!

[Timo]

One wonders why Korg, with all their expertise spanning decades, don't incorporate such equalisation and gain management as a matter of course and quality control? It seems the added components are inexpensive, and the positives are numerous.

[alfredokiwi]

Hi again, I have good news about the DAC improvement. I decided to eliminate the factory passive filter after DAC due the addition of the active LPF on my circuit bend. Before removing it I have performed some on board measurements. On the factory passive filter the used values are a 680 Ohm series resistor with a 18 nf capacitor to ground. This gives an attenuation filtering factor of 12db at 48 kHz (the common DAC sampling frequency). OK but at 10 Khz the high part of the audible spectrum the passive overall filter resistance is 680 ohms series + 885 ohms capacitive reactance in parallel which gives an overall DAC load impedance of 1585 ohms at 10Khz. This impedance overloads the DAC internal output stage affecting the voltage swing aka "dynamic range" on highs frequencies spectrum. But this situation goes worse due the internal DAC output impedance (approx 500 ohms) and weak signal output when DAC is overloaded. Manufacturer datasheets recommends to use always an active operational amplifier LPF stage for high DAC performance designs with a minimal resistance of 5000 ohms load on the DAC output to avoid overloading and voltage swing drop of the audio signal. The active filter stage that I added not only filters the DAC sampling images frequencies, also it acts as an audio buffer stage due the high input and low output impedance of operational amplifiers.

Here a small audio demo from last night, always I make the improvements without sleeping

<iframe width="100%" height="166" scrolling="no" frameborder="no" src="http://w.soundcloud.com/player/?url=htt ... "></iframe>

After removal of the passive stage using only the active board (the small PCB circuit) the sound quality is amassing, I will add more audio demos with patches from MS2000 and Korg bonus banks.

[alfredokiwi]

Another demo with MS2000 patches converted to R3 from Korg website.

<iframe width="100%" height="166" scrolling="no" frameborder="no" src="http://w.soundcloud.com/player/?url=htt ... "></iframe>

Here my last post on my blog -> http://alfredoblogspage.blogspot.com.ar ... ality.html

Again what can I say about the R3 after circuit bend... is an amazing instrument

[laikenf]

Can you mod my R3?