Korg Forums

Hi, I have already posted on Pa3X section about my last Pa500 audio improvement (with audio demos)

http://www.korgforums.com/forum/phpBB2/ ... hp?t=75836

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

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

I´m very happy after this stunning quality achieved, no more complaints about the Pa500. Thnks!

He Alfredo,
when I saw schematic of Pa500 audio-flow first time I believed layout was made by Korg to reduce audio-quality and it seems that was true.

Congratulation to your Pa500MaxAudio. I think MaxxAudio are using gyrators as active filters like Korg do with its 4-band-Equalizer.

And now what did you do? Changing components round the gyrator (simulated inductors IC5, IC6 – NJM2060M)? Is it possible to get detailled infos about the parts you changed to get such a good quality of sound?

Hi Siebenhirter,

Check alfredo's BLOG. Link is the last line of his Posting.
Pictured Details - WOW ! in my opinion he delivered a "doctoral dissertation" - - Congrats, Alfredo !


best Wishes from
TBLECK

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Hallo Thomas,
i could not found informations how to upgrade built-in-equalizer of Pa500.

Alfredos blog contains his doctoral dissertations and pictures how to upgrade Pa500 for better dynamic range.

He did it some months ago, but what he did again and that is new, he upgraded the internal 4-band-equalizer to get better sound. In german forum we had a discussion resulting in calculations about that gyrator-schematic, but no one get optimizing them in diy as Alfredo did.

If our calculations are useful, with the built-in components, the individual bands should have the following operating frequencies:
IC-6A: 57 Hz, Q = 39> ratio R75/R70 is substantial increase in bass
IC-6B: 231 Hz, Q = 18> R80/R84> significant reduction (maybe cabinet resonance)
IC-5A: 3660 Hz, Q = 41> R51/R46> narrow-cut (natural resonance, softer sound)
IC-5B: 14 kHz, Q = 13> R57/R63> compensation of treble

A: for small speakers to be crammed bass, also often made in small stereo ...
B: filtering cabinet resonances, probably a resonance of the speakers ?...
C: speakers probably has a natural resonance to be filtered out - also sounds's soft when you remove the upper mids ...

I have realized many thing to improve the quality, for example a new schema of +Vcc for the op amp stages, improvements on the decoupling capacitors for better frequency response and a re design of the filter stage.
The model Pa500 was not properly designed and this affected the overall audio quality. My recommendations on my blog are the most important steps to do that will fix the Korg Pa500 "low dynamic range issue".

I want to share an easy solution that works for all and that's the idea of my bog. All the information to reach a good audio quality is available online on my blog.
Because the other circuit changes involves power supply handling this operation can lead to short circuits and other delicate parts such the filter due the manipulation of SMD devices, so the fix is very difficult to do. Again the most important and at the same time easy to do is exposed on my blog.

The idea is to share a solution for all avoiding to enter on complicated aspects

Regards.

Hallo Alfredo,
thanks for your excellent work performed and for the provided information.

I think audio section of Pa500 was probably deliberately designed to a sound quality what remains somewhat worse like less dynamic compared with more expensive models.

Now is publishing that a limiter and final 4-band parametric EQ have been added to the sound output of the Pa600. And everything could be processed by a powerful and musically refined EQ, easily adapting the sound to a musical taste or adjusting sound in a problematic live environment.
But that is the same as built-in in Pa500, only intentionally adjustet to a lower sound quality.
In my opinion just changing resistance-values near IC5 and IC6 could be significantly better for sound like published for Pa600. But my lack of technical knowledge is too risky for an amateurs trial.

if you have an idea how to to improve equalizer in a simple DIY procedure, I'd be very grateful for related information.

What makes me angry is the keybed notes drop on Pa500. The keybed scan events is performed by a secondary microcontroller that run a keys notes on/off detection program and maybe the code is not well developed. Of course many user noticed this main failure, we can´t say that this is intentionally developed despite the Pa500 is the cheapest arranger on the Korg line. It cost 1100 US dolars..., not so cheap when a Casio plays the keys without issues on the "note on/off events".

That's the reality about the failures that I found on the Pa500, some issues are minor for example bugs on the OS when playing the backing sequences out of sync, but audio quality and notes events can´t fail.

We are talking about a professional arranger not a cheap Casio line.

This is amazing Alfred. Wish you had the before and after version side by side for us to hear the difference.

Assyrianpianist wrote:This is amazing Alfred. Wish you had the before and after version side by side for us to hear the difference.

You can check the available Pa500 demos on internet to have an idea about the factory sound. On some of them a normalization process was performed after recording, despite this procedure increase the volume level it don´t recover dynamic range and nuances of the samples ROM.

The Pa500 overall quality is average and the samples bank are not so superb. In other words I think that for backing sequences/accomp works OK but solo instruments are a bit weak. At factory the sound quality was muddy without details and low dynamic range.

Please check my blog at www.alfredoblogspage.blogspot.com.ar because I put some links about Pa500 demos to compare the factory sound quality (Demo1 to Demo5 youtube videos links).