PC Engine audio amp help?

[Drakon]

I tapped stereo sound from my original white pc engine but man...it's so quiet and weak sounding.  Has anyone come up with an amp design for it?

[gtsamour]

Indeed the sound signal tapped from the expansion port on the PCE or TG16 is weak. There's also a low buzzing probably because of that (even with all the caps replaced).

[Drakon]

Uhm...my system has no buzzing in the audio.

[SignOfZeta]

Isn't the signal coming from the expansion bus the same one that eventually makes it out of the IFU? I have no issues with my IFU setup sound-wise. I mean, PCE sound is always pretty thin and noisy, but a) you're never going to get rid of the noise short of playing the game in an emulator because its the sound chip that produces it and b) if you want to fatten it up, that's what AV receivers are for.

[Drakon]

I've never heard any noise out of mine.  I built a simple low pass filter to make the bass stand out more and it worked great.  The audio is quiet there's probably an audio amp in the rf box.  Anyway I've got some opamps that already showed up so I'll look into building an audio amp when I find the time.

[SignOfZeta]

Have you ever just thought about adjusting the bass/treble on the TV? I ask because...its the same thing and a lot less soldering.

[gtsamour]

Isn't the signal coming from the expansion bus the same one that eventually makes it out of the IFU? I have no issues with my IFU setup sound-wise. I mean, PCE sound is always pretty thin and noisy, but a) you're never going to get rid of the noise short of playing the game in an emulator because its the sound chip that produces it and b) if you want to fatten it up, that's what AV receivers are for.

Τhe sound coming out of the Core II (out jack) is loud and clear without noise though....

From both TG-16 I have the sound tapped from the expansion port is a bit noisy, not much but since you turn the volume up to bring sound to a decent level, you can hear it.

[Drakon]

Have you ever just thought about adjusting the bass/treble on the TV? I ask because...its the same thing and a lot less soldering.

Yes of course but the idea is to get the audio coming out of the system sounding the same as all my other consoles.  I don't want to adjust back and forth everytime I go from using my pc engine to something else.  I can build a small amp I think it'll be a fun project.  Getting more bass out of the system was a fun experiment and it works perfectly with all games.

[NightWolve]

Has the unit had a full capacitor replacement yet ? Weak sound is an indicator that the sound-related caps are dying possibly. When I did my full cap replacement on my Express, I used the chart from here:

http://www.pcenginefx.com/forums/index.php?topic=5303.0

On the first image you see a suggestion that if you replace the 2 sound-related capacitors (colored yellow which are 33uF 6V) with 47uF 6V ones, you'll get slightly louder audio. I would think you could try this on your PC Engine board - find the sound-related caps and replace them with higher values.

Here are the preamp sound caps on a Duo:

http://www.multimods.com/images/Sales/R9x600.jpg

Can't find something on a basic PC Engine here it seems.

There's also a low buzzing probably because of that (even with all the caps replaced). From both TG-16 I have the sound tapped from the expansion port is a bit noisy, not much but since you turn the volume up to bring sound to a decent level, you can hear it.

From what I learned from thesteve, if one uses good, expensive tantalum or ceramic caps related to the power supply and for the sound, you can eliminate the hum! I can hear the hum pretty bad in my Express after full cap replacement with cheap aluminum SMDs, but I didn't know at the time, otherwise I would've bought the good ones.

[HercTNT]

Steve recapped my Gt and the sound is very loud and perfectly clear. I get no hum at all.

[Drakon]

This isn't a GT, Express, or a duo.  My system is the original white pc engine.  I'm having fun building a small amp so all is good.

[NightWolve]

Right, we knew that, and that's why I tried to find an image of the board, but couldn't and instead showed you an Express and a Duo - it's possible somebody posted an image of the PCB of the PC Engine around here, but I couldn't find it... Anyhow, the concept of replacing the sound caps with slightly higher values is still applicable regardless to all NEC hardware - you just need to identify the right ones and replace them...

[Drakon]

Yeah I'm not trying to fix my pc engine I want to go through the fun of learning how to build a good audio amp for the system.

[turbokon]

I noticed this too when I added an earphone jack on my pce and tg16. Sound output is really low compared to when docked or using rf. I found this some where but haven't tried it yet.

[turbokon]

Looks like there is no need to built the amp circuit as the pce/tg16 already has an opt amp, C358C that is only used by the rf box for sound output. The input pins of the opt amp are connected to pin 20 of hu6280 for the mono sound. I think all you have to do is cut the traces from pin 20 and instead jump them to pin 18 & 17 instead for the amplified stereo output.