Genesis 1 & Mega Drive 1 stereo mod no headphones volume control

[CrossBow]

Finished a preliminary board layout design. All components are surface mount, meaning the board will lay flat wherever you mount it. Still a work in progress, but it's getting very close!

That is an excellent design! Too bad I'm not young enough in my eyes or hands these days to do any SMD work. What are the actual dimensions of this PCB. It looks to be about the same size as some Intellivision composite video mod boards I install for clients?

[Firebrandx]

Current board size is 3 centimeters by 4.3 centimeters. I'm thinking of squeezing it into an exact 3x4 cm board size on the next revision. Right now I'm just waiting to hear back from an EE on my layout to make sure it passes scrutiny.

And for the record, SMD soldering is easy with the right tools and flux (my preferred is Kester 959T no-clean). There's also the paste-&-bake method, but I prefer hand-soldering for DYI kits. I'm 44 years old, and I have to often break out the magnifying glass to check my work, so I know how you feel!

[Firebrandx]

Revision #3. I've squeezed in everything to a perfect 4x3 centimeters total board size, and managed to clean up some trace work in the process:



Unless I'm informed of changes I need to make from my EE friends, this 'should' be the final design going forward.

[Xaranar]

Looks sexual, I can't wait to give it a whirl.

[Firebrandx]

Heard back from my EE friend. He felt I needed to increase the clearance on the pads so as to avoid shorting to ground during soldering (for beginners that might mess the up). Also he directed me to change the location of the inverting resistors much closer to the pins that I currently had them. Basically the closer you get these resistors to the pins the much more effective they become in doing their job. So here's revision #5 with the changes. It may look less sexy than before, but it's a superior design:



Soon as I hear back from him on the new arrangement and he gives it the thumbs up, I'll send it off to OSH Park for prototype board production.

[CrossBow]

You planning to offer these boards pre-populated at all in the future? I'd be interested in getting one to put into my my va6 that exhibits lower volume as compared to my other Genesis and MD consoles in my collection.

And you and I are the same age, but I assure you, I bet I shake a lot more than you do using an iron. I have to steady my hand against something when soldering. Just how it is for me and I've dealt with it for about the past 5 years now. I do use a jewels magnification helmet when working on smaller stuff and sometimes just to read the damn values on the caps.

[Firebrandx]

You planning to offer these boards pre-populated at all in the future? I'd be interested in getting one to put into my my va6 that exhibits lower volume as compared to my other Genesis and MD consoles in my collection.

Yes, I'll be making a batch for sale in addition to offering the board for free on OSH Park for people that want to make their own.

Sorry it's taking so long, but the more input I get in making this right is going to make it the best mod that it can be out of the gate.

By the way, I need some suggestions for 5 audio tracks to do test recordings from. Basically a good selection of various music that test both low and high frequency ranges.

[CrossBow]

I'm sure there will be many with better choices, but these are some of what I use to test audio on my Genesis systems:

Vapor Trail - all of it! LOL
Thunderforce 2 - I test this for audible clicks and noise in the audio line as for some reason this cart seems to magnify them
Wiz N Liz - Just a great soundtrack in general, but really pushes the Genesis quite a bit as well
Streets of Rage 2

And then I also have and use my YM2017 and Future 2612 carts going forward for audio testing hehe. But not everyone has those or access to them.

[Firebrandx]

Board finalized and sent off to OSH Park for prototype production. Here are the previews from Eagle and OSH Park:





I've already ordered the parts to do both line level and boosted variants in order to do music test recordings of both. Should take about two weeks for everything to arrive, then I'll post the files once testing makes sure the board is kosher. Thanks to everyone that gave me help and tips!

[Xaranar]

No way, I get a credit? I'm truly touched

[CkRtech]

Oh man. I am subbed to this thread but haven't received anything (or I missed the bus), and HOLY SNAPPLE! Look at the evolution!

Interested in hearing the results of the line level edition. That circuit I did evolved from having the TL072 on-hand already, and I wouldn't mind hearing output using something else.

Happy to see progress is still being made, thanks for the time spent on this, and... hard to believe it has been a year since that TL072 circuit.

[Firebrandx]

Oh man. I am subbed to this thread but haven't received anything (or I missed the bus), and HOLY SNAPPLE! Look at the evolution!

Interested in hearing the results of the line level edition. That circuit I did evolved from having the TL072 on-hand already, and I wouldn't mind hearing output using something else.

Happy to see progress is still being made, thanks for the time spent on this, and... hard to believe it has been a year since that TL072 circuit.

Thanks for the initial schematic! Ace and Ste really helped me a lot, and I was able to sponge a lot of knowledge from the both of them. The board are already in fabrication, and OSH Park expects to have them back to me in 10 days max. I've already got the parts to do both board variants, so the plan is to record tracks in the following manner:

1. Straight tapped CXA1034P.
2. Line Level board output.
3. Boosted output.

I'll be using my Sony ADC deck that was top of the line in its day (paid $500 for it 20 year ago). To demonstrate the ADC quality, here's a track I ripped from my own AES Neo Geo console directly into the deck:

https://filetrip.net/dl?NUkFZJKp0H

Also here's a pic of the finalized schematic for posterity:



Note that ALL of the 47uf caps are bi-polar for maximum reliability and compatibility. The output side doesn't technically need to be bi-polar, but it doesn't hurt and it makes the BOM simpler.

[Firebrandx]

Boards are on their way back from fabrication! I already have the parts ready to solder onto them, so in just a few days we'll have recordings to listen from both my VA3 and the VA2 just for posterity's sake.

[Xaranar]

Awesome I await with bated breath.

[CrossBow]

Boards are on their way back from fabrication! I already have the parts ready to solder onto them, so in just a few days we'll have recordings to listen from both my VA3 and the VA2 just for posterity's sake.

That is excellent! But need to a comparison against the later revisions as well. Like I said, I'm quite happy with the volume output from my va2 and va3 units. It is my va6 units that are of lower volume. It would be interesting to compare raw audio capture between them without any normalization being done to balance them out.