Best possible Audio-Output-Stage

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Best possible Audio-Output-Stage

Postby nada-san » Sun Jan 12, 2014 10:01 pm

Hello together,
as i have struggled a while to get a nice audio-output on the C64, i have started the same project on the STE. I hope to get nice and clean sound through an OPA-Stage. So i drilled some holes into the backside and fit some nice cinch-sockets into it. Through it i get an alternative stage. I fiddled out where the normal audio can be taken from, right before the 1k-Resistor near by the YM2149, but i do not understand where i can taken the DMA-Sound from the board!?

I really wonder if i can get a better combined audio-stage through an OPA. On the C64 it works wonders! But on the good ol' 8-bit i don not need ampflification like in the ste. After doing a first run, i noticed that the normal volume-output of the chip is far to low. i searched for the amplification-stage on a ste-schematic but could not find it. Don't understand me wrong, i' not an engineer, but i like to learn more about it. Anyone? Has anyone ever done something similar on the ST or STE and could tell me his experinence?

I just want the best possible audio-quality, because i like to use the ste as an music-/demo-player via a hifi-system. :D

Your help is appreciated,
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Re: Best possible Audio-Output-Stage

Postby Hippy Dave » Sun Jan 12, 2014 10:25 pm

STe sound at the Left/Right stereo outputs (theoretically judging from schenatic) should be the best.
What is wrong with the sound at these outputs (I don't have a STe) ?

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Re: Best possible Audio-Output-Stage

Postby nativ » Sun Jan 12, 2014 10:50 pm

Hippy Dave wrote:STe sound at the Left/Right stereo outputs (theoretically judging from schenatic) should be the best.
What is wrong with the sound at these outputs (I don't have a STe) ?


Correct me if I am wrong but I think he wants the 3 channels of the YM each on their own out put! There is some information around about doing this I believe. Otherwise as HippDave says the STe's phono outs wire microwire are a more than adequate solution providing a mix of all YM and the STe DMA sample output.

You could in theory use a Playback cartridge and write a driver that puts the YM out through that or Just the audio and leave the STe phonos to take the YM (vice versa)

good luck
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Re: Best possible Audio-Output-Stage

Postby nada-san » Sun Jan 12, 2014 10:59 pm

Not bad at all! But as i found out, that the C64-output-stage was really bad, i thought why not trying to beat the ste's output. :D
As i have searched through the web furthermore, i found the LMC1992-Audio Mixer. Seems to be the right thing to take the assembled audio from, as it is connected with the cinch-output. I try to put an OP-Amp-Stage behind it and we'll see...

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Re: Best possible Audio-Output-Stage

Postby nada-san » Sun Jan 12, 2014 11:02 pm

nativ wrote:
Hippy Dave wrote:STe sound at the Left/Right stereo outputs (theoretically judging from schenatic) should be the best.
What is wrong with the sound at these outputs (I don't have a STe) ?


Correct me if I am wrong but I think he wants the 3 channels of the YM each on their own out put! There is some information around about doing this I believe. Otherwise as HippDave says the STe's phono outs wire microwire are a more than adequate solution providing a mix of all YM and the STe DMA sample output.

You could in theory use a Playback cartridge and write a driver that puts the YM out through that or Just the audio and leave the STe phonos to take the YM (vice versa)

good luck


Hello,
no i won't do some pseudo-stereo-things. I only want to try to get a cleaner and more powerful audio-signal, if possible. If i take the audio after the LMC1992-Mixer-Outputs am I also going to get the YM-Sound if chosen by the software-player? Or do i have to grap the YM-Audio elsewhere from the board?
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Re: Best possible Audio-Output-Stage

Postby MiggyMog » Mon Jan 20, 2014 7:28 am

You can either have dma only, dma + ym or dma + ym-12db. This is set in software though. The ym is not configured for stereo though in STE, the ym has pins for it's three channels and there has been previous discussion on modifications to get stereo sound from it (like amstrad cpc has). It may be worth modifying it to get cleaner sound as you suggest as there has been awful line noise on most STE's I have used. That said easy option is to use as is.

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Re: Best possible Audio-Output-Stage

Postby nada-san » Sun Jan 26, 2014 10:20 pm

Hello guys,
so i have started with some decoupling capacitors and searching for a better ground...i also drilled some holes and put some fresh rca jackets into it, to be able to compare it to the original output. Therefore I soldered some wires at the outputs of the LMC1992 an lead them to my new jackets. It was not very hard. As far as i know the LMC contains the whole output-stage, but decoupling is afterwards. My first impression was: 8O ...because even with only the wire and without any capacitor the STe delivered far more dynamic, clarity and power. To be honest, that is not difficult, cause the original output sounds very muffled and dirty in my opinion. I then tried a simple decoupling stage and it's crackin' my wildest dreams now, because the STe is going to sound real great now. And this modification is just so easy.

I will go on testing. may you are interested. as i have told before my STe runs via my hifi-system and i want to get the best sound out of it. No pseudo-stereo-tweaks or sort of! Just the real thing. stereo and mono, as it is used to be...

:cheers:

bye,
nada
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Re: Best possible Audio-Output-Stage

Postby ausl8 » Sun Jan 26, 2014 11:56 pm

Thanks for sharing! My main issue with every STE and TT I've heard is the high level of audible line noise from the RCA outputs. Is this being addressed with your modifications or are you not experiencing this?


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Re: Best possible Audio-Output-Stage

Postby Guest » Mon Jan 27, 2014 1:23 am

mostly with the ste its noise from the psu
replace the bridge rectifier
with the TT the audible noise comes from poor coupling capacitors now some 20 years old and more
and daft opamp GP type ic choices based on cost
simply replace the parts with better opamps and rework the audio stages caps for new ones {small value electro caps dry fast}
not sure about the TT psu
ive found all sorts of ripple on both the 12 v and -12 rails
replaced all the caps and changed some 1000uf for 1500 2200 for 4700
the 12v rail supplies all the audio stages with 9v via a regulator in both machines there is an inverter for -9
and usually inverters and charge pumps are noisy
i think you need to replace the opamps with better ones they are dual rails
so use something like an analog devices opamps
you can just ask there site for some dil samples
you need to hunt

but a tip or three is to
1} use an email ad from a domain not a public
2} dont be greedy and just ask for 2
you get three every 6 months
3} describe a common application as they ask questions so invent an answer

i would look for something better than LM386/324 4458 LF347 etc etc crap noisy old design fets and jfet
that supplies the pathetic audio to the falcon jack and even the dma sound and st ste tt etc

or !!! just add two coupling 10 or 47uf eleccaps to the output of FM and DMA{pin2 on both d-a
and FM use a dual channel parametric EQ and a mix FM to DMA to audio to EQ
to mix back the dma into the main audio to the EQ then use a mixer
as above post the problem is the digital VCA chip gets in the way as its a volume control chip etc
this is the main issue old style vca etc mixer ic's are VERY noisy
but no probs if you use raw audio from the d-a's or FM
its a no brainer
its far better to balance its spectrum using a decent PC like Maudio or even an audigy 2 and something like cool edit or
some spectrum analyzer
and write a simple program to perform as a sweep frequency oscillator to ramp up and down tone /pitch and amplitude
then you only need to add two capacitors and forget the whole back end audio sections and let them chrun out the noise

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Best possible Audio-Output-Stage

Postby nada-san » Mon Jan 27, 2014 11:20 am

Thank you for tipps and comment, simbo2! I think i will change the bridge rectifier first...

@ausl8: at the moment i only try to get a proper decoupling stage, but i' am hunting for tipps related to this topic. Reminds me of the c64 with it's noisy vic-chip coming through the ext-in-port of the sid. The solution there was to cut the pin. Easy. Even easier cause the sid has it's socket.

The ST seems to be more complicated. I have heard of a "schwingkreis" near by an IC. Don't know the english word. At the moment i have to turn the volume of my amp to nearly 50 percent to get audible noise via my output. But i use to hear with 30 percent at maximum. Nevertheless the noise is really disgusting, even contains a long beep. But I can only hear it when nothing plays... that's a bit irritating. Does anyone know if the noise is always there and still running via the lmc1992 with playing music?



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Re: Best possible Audio-Output-Stage

Postby nada-san » Sun Aug 17, 2014 7:06 pm

Ok, finally i gained some motivation back to search for a better STE-audiostage. Just for reference I first made a connection to the YM-2149 and fumbled a little decoupling-stage together. And what a surprise it was! Such a clear and refined sound I haven't heard from the STE till now. As we know the overall problem is the far to loud and noisy sound from the original phono-jackets. So I drilled my own and laid a second line from the LM1992 to it. For decoupling I tried some things, everything has made a difference. It was not easy to decide. When it comes to verification I had to compare the waveforms I recorded in Audacity, as I have no oscillator of my own.

I used "Arkanoid" as a reference at first and some other MAD MAX and TAO-Tunes for verification. It came out, that the decoupling for the YM2149 had to be different compared to the LM1992 summarized audio. As you may have experienced and read her in the forum the STE-Output is too loud. And when I say loud, I mean LOOOUUD!!! It' s so noisy that every amplifier gets voltage overload. Some have experienced distortion, especially if you want to record something you cannot adjust it to a normal level - it's just too LOUD!

So if you want to get a normal level, you have to reduce the sound level with a voltage divider. I arranged something and compared it to the Chip-output. I looked into the original schematics, but that didn't helped me, because there is an complicated OPA-stage combined with the decoupling. I' am honest: I didn't understand it. After a while I got a clue: "Arkanoid" sounded more and more the same via my two stages. But something was still missing: The big bassy (a bit boomy) sound in the beginning was kind of thin with the original YM2149-Output, while the LM1992 really blasted some bass out. I first thought the YM-sound is the way to go. But as I compared the sndh-file I realized that I was wrong. 8O 8O

Things are goin' better and sound was becoming better. I added some resistors and capacitors, far less than the wild original LM1992-Output, and made some more tests. Now I think I have got it. Both outputs are singing now and this is the important thing: without any annoying sounds. May you experienced that the high notes on the STE are really annoying and nearly distorted? That is not how the YM sounds, it have to be nice and smooth, also with a deep bass and punchy dynamics.

I also use another external PSU for less noise on the 5V-rails. With the original psu you get a darker and less refined sound.

I will show some waveforms in comparison, so you can imagine the difference.

Anyway, hope you are interested!??

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Re: Best possible Audio-Output-Stage

Postby dma » Sun Aug 17, 2014 7:18 pm

This is definitely interesting, please don't hesitate to post more on this subject.

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Re: Best possible Audio-Output-Stage

Postby nada-san » Sun Aug 17, 2014 7:21 pm

Here is an example of the different gain-levels of the LM1992 (mixed YM2149,DMA) and the direct YM2149-output. As you can see the LM-Signal is really overdriven on the phono-jackets. So there is no way to record it without compression and distortion.
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Re: Best possible Audio-Output-Stage

Postby dma » Sun Aug 17, 2014 7:28 pm

Audio samples would be interesting to compare the sound. :)

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Re: Best possible Audio-Output-Stage

Postby FedePede04 » Sun Aug 17, 2014 8:22 pm

dma wrote:Audio samples would be interesting to compare the sound. :)


+1
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Re: Best possible Audio-Output-Stage

Postby nada-san » Sun Aug 17, 2014 8:30 pm

I will upload some test-samples next week. Everything comes through my pinboard till now, nothing has been soldered so far. But you will hear the important differences...
ImageUploadedByTapatalk1408307399.905526.jpg



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Re: Best possible Audio-Output-Stage

Postby !cube » Mon Aug 18, 2014 8:20 pm

Anxiously waiting to hear the results. I hate my STE audio output currently, full of noise and distorted as hell.
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Re: Best possible Audio-Output-Stage

Postby nada-san » Tue Aug 19, 2014 9:21 pm

Good evening,
i just uploaded some files onto my Soundcloud. There is still a server-processing going on, hope it will be finished soon!
https://soundcloud.com/rockabit/tracks

It's pretty self-explainable. You can also download the files to compare each other. I have chosen Arkanoid by Jochen Hippel in different versions.

1. LM1992 - directly from the chip with the very high gain output. Everything distorted ;-)
2. LM1992 - original STE phono jackets: this is the sound which comes normally out of the jackets. "poo in poo out". I lowered the level of my sound card as far as i can. There is no headroom. Also distorted.
3. LM1992 - my simple decoupling stage. Not leveled perfectly...
4. YM2149 - my simple decoupling stage - directly from the YM-chip...

Please judge for yourself! :coffe:
Maybe it can be bettered? What do you think of it? Does it sound the right way?

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Re: Best possible Audio-Output-Stage

Postby nada-san » Wed Aug 20, 2014 10:28 am

Ah, by the way, and in the case someone doesn't know: the LM1992 is the Chip which sums the Signal from the YM2149 and the DMA-Samplesound. After it there is an original outputstage which leads to the STE phono jackets...

Please let me know if you want to hear a special tune. I will record it then and upload to the Soundcloud. Is anyone ok with that and especially with access to my soundcloud?

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Re: Best possible Audio-Output-Stage

Postby spiny » Wed Aug 20, 2014 10:57 am

this link works to access your soundcloud page:

https://soundcloud.com/rockabit/

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Re: Best possible Audio-Output-Stage

Postby spiny » Wed Aug 20, 2014 10:59 am

your 'fix' definitely sounds better :)

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Re: Best possible Audio-Output-Stage

Postby nada-san » Thu Aug 21, 2014 8:45 pm

Thanks for your reply spiny!
I have just added some more tracks to my soundcloud for comparison. I even managed to improve my output-stage for the LM1992. The voltage divider was not exactly right, there was a little high-frequency-distortion left. Furthermore I uploaded two classic tunes of Jochen Hippel from the cuddly demos. That seem to be the best way to judge about the quality, at least for me... :lol: Honestly the rough quality of the chip tunes is the best way to identify strange behaviors and illegal distortion :wink:.

https://soundcloud.com/rockabit/

Have fun,
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P.S.: in the picture you see the latest Waveform of Arkanoid with my updated and improved decoupling-stage.
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Re: Best possible Audio-Output-Stage

Postby FedePede04 » Thu Aug 21, 2014 10:08 pm

spiny wrote:your 'fix' definitely sounds better :)


100% what spiny says :)
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Re: Best possible Audio-Output-Stage

Postby FedePede04 » Thu Aug 21, 2014 10:13 pm

btw i hope you will release you schematics, so we other also can make them, my STE sound like crap
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Re: Best possible Audio-Output-Stage

Postby dma » Fri Aug 22, 2014 7:40 am

nada-san,

Really interesting sound, quite great it seems, but it's indeed hard to judge how faithful it is to the "true" sound with only one tune.

Could you, by any chance, record some some extracts of the following tunes from the SNDH archive, which use STe DMA sound along YM?
- 505\DMA\Hushrush.sndh
- Excellence_In_Art\DMA\Brit.sndh
- gwEm\DMA\Sillyventure_2014_Invite.sndh
- 505\DMA\Cyborg_Clubbing.sndh
- Dma-Sc\DMA\Antiques-Physics_Part.sndh
- Dma-Sc\DMA\ATARI-su-ba-ra-shii.sndh
- Dma-Sc\DMA\YMetal.sndh

Also some YM only tunes but quite complex (sound-wise and composition-wise) tracks would also be interesting :

- Big_Alec\Reality.sndh
- Cube\Blipblop_Memories.sndh
- Jess\Sharpness_Buzztone.sndh
- Mad_Max\Buzzer.sndh


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