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Just a simple but kinda cool project?

CrossBow

Entry posted by CrossBow in Ivory Tower Technical Info & Notes

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The 'Tower' was without power most of last week due to powerful storms on Father's day. As a result it put me behind a bit on console services and projects. Well last night as I've been working kinda constantly on console stuff to try and get caught up, I took a break and decided to do something I'd been meaning to try and implement for a while now.

I'm sure many of you here are aware of the Atari Vox? In summary it is a small device that plugs into controller port 2 on the 2600 or 7800 systems to allow you to save game scores and can also provide a means for speech to be played back in games that support it. Very cool device but it has one annoying thing about it. That is the fact that the audio from the Avox is separate from the rest of the system so you either have to plug in a set of external speakers or as I had been doing, I would use a 1/8" to RCA cable and plug one of the RCA jacks into one channel (usually the right) on my AV receiver audio input and the 7800 audio out in the other channel. Or, you have to use an external audio mixer to combine the two into one. None of that is really elegant so I thought of a simpler way to go about it. I'm sure you can see where this might be going?

So the 7800 especially is a little unique in that it was designed to make sure of an external audio input from the cartridge port. Typically POKEY enhanced games use this for audio. The basic mixing for this in the console is to tie the TIA audio coming in internally from the console's TIA chip and the POKEY audio from the external cartridge audio input line with different resistors for each to balance their signal so that one doesn't overpower the other. Well, why not simply add in a third audio line into that mix with a resistor to also bring it down in level?

That is exactly what I did as is demonstrated in this video...

 

I have some pics I can provide for those interested but in a nutshell I installed a separate 3.5mm audio jack along the back of this test 7800 I have in the ITC lab and instead of if providing audio output, it is used as an audio input and is part of the mix along with the external audio and internal TIA audio. This allows for all three to be used at once and have all the audio could out through my normal audio output RCAs I have installed on the console. 

No separate speakers...not Atari audio from just the Left with the AVox speed only on the right. It is all properly mixed together in dual mono as I would prefer. I will next do the same on my actual daily driver 7800 where this would be used most, but I'm glad to have it on my lab 7800 as well. The way this was done, should also be possible on a 2600 and I might very well explore that on a 2600jr I also have in the lab. 

I know this isn't the first time something like this has been done as I've seen other projects where owners have embedded the AVox completely into their consoles and then with a lot of wiring, use a switch to enable/disable the Avox as needed. But I was looking for a more simpler solution that would still allow the AVox to be used with multiple consoles and not be gutted and dedicated inside a single system and yet still easy to use without a lot of extra wire and mess. One small headphone to headphone patch cable is all that is needed now for this when I want to use my Avox.

For those that might want to try this on their own, know that a limiting resistor is needed as running the audio output straight in from the AVox is likely to sound messed up/distorted and would cause audio cut off on other audio sources trying to play at the same time. I used an 8k resistor in my test here but I think anything between 6.8k - 10k would suffice. I would also start with your volume pot on the AVox set to about the 1/3 volume level and then play a game that uses both speech and other audio at once to dial in the volume on the Avox until you are happy with it all.

 

Edited by CrossBow

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CrossBow
15 hours ago, RickR said:

That custom 7800 case though.  👌

 

4 hours ago, - Ω - said:

Yeah, no kidding... super primo excellent.

Bob printed that case for me as a thank you for services I've provided to him a few years back. He has one he made for himself of course and also made a custom case shell for Albert for use with one of his 7800s during PRGE and other convention events.

Bob released the STLs for this case I believe yesterday for those that might want to do check it out. There are a few caveats on getting everything to fit and I don't know if his STL includes the holes already done for the RCA and s-video jacks as he did when he printed mine.

 

 

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RickR

I haven't 3D printed anything all year.  I need to...I've got a VIC-20 multi-cart that needs a shell.  I find it to be such a PITA to remember how to do it.  I think I may just give my 3D printer away to a local kid or something. 

Your video has an important piece of info about the AtariVox I didn't know...that it has a separate audio out.  That's kind of like the O2 "The Voice" module, except no built in speaker.  Given that thought, I wonder how well a small speaker built into a new bigger casing for the AtariVox would work?

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CrossBow
2 hours ago, RickR said:

Your video has an important piece of info about the AtariVox I didn't know...that it has a separate audio out.  That's kind of like the O2 "The Voice" module, except no built in speaker.  Given that thought, I wonder how well a small speaker built into a new bigger casing for the AtariVox would work?

That would work quite well provided it is loud enough and or close enough to the player to be heard clearly over the rest of the audio. Likely pretty simple to do and there might even be one of those premade project boxes that could be used for that. I've not tested this yet, but I don't see why it couldn't be done... but...

I should plug my Sony digital walkman into it LOL! I mean, I don't see a reason why it wouldn't work provided I adjust the volume?

 

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CrossBow

I also just remembered that my Vectrex Audio Tap or V.A.T. for short I have installed in my Vectrex, actually has a 3.5mm jack on it for audio input for use with the Avox+ in Veccy mode! So really this has been done in this fashion several different ways in the past. I wish I had thought of this before working on all of Al's consoles last year as I'm sure this would make his PRGE setups much easier. He actually uses a separate small audio mixer for each of the consoles to mix the Avox speed with the console audio through a new audio output from the mixer box that he then plugs into his commodore monitors.

 

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CrossBow

Last night I did the same thing to my daily driver 7800. As I have the RF modulator removed from that 7800 completely, I used one of my studio grade quality 3.5mm jacks for this and epoxied it to the 7800 main board in place of where the RF was since that was empty and the hole was already there in the case shell. 

ITC78_A1DD_AudIn.jpg.4f5499b4399d6f8c3527ee604abc20fb.jpg

ITC78_A1DD_AudIn_wire_detail.jpg.74cf7e77da15c1f1b93ffe91c8f2a492.jpg

ITC78_A1DD_AudIn_rear_detail.jpg.e4749d15489eb4ccdcaf4f5bc33af697.jpg

 

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CrossBow

I was able to do the same to a 2600jr console over the weekend. It required having to first breadboard up the wiring so I could try different value resistors before dialing it in, but finally settled on 2k being the magic number. Bu this will depend on where you tap the audio from and might still have some variation from console to console. But anything more than 2k, and the AVox gets lots in the TIA audio. It is still heard just way lower and kinda hard to make out. Less than 2K and it seems to start to kill the TIA audio instead. Anyway, here are a few pics of my 2600jr in the lab where I did this.

Here is the internal shot. You can see the wiring that runs along the back. This is to provide the audio input. The 3.5mm on the left rear of the console in this pic is the new audio input, and the original RCA for the RF and small 3.5mm next to it is my composite video output and audio out I had in place already.

itc_26jr_oview.jpg.ae38282f94fe801e19f413353296acc2.jpg

 

And here is what that looks like from the rear of the console. In this pic, you see the RF output and small 3.5mm next to it that is again the audio out. The singular and slightly larger 3.5mm on the right rear side, is the audio input.

itc_26jr_rear_oview.jpg.3dfa43763536be9b3baef597e4d18499.jpg

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