Best Way to Add Audio-In to an Amstrad CPC 464?

[@no1leader135]

What a great video. I love how you explain your work using schematics, scopes captures, and other tools. Keep up the good work. ¡Muchas gracias!

[@NoelsRetroLab]

Much appreciated! Glad you enjoyed it!

[@doktor6495]

Very nice that you digged deeper and found the solution why you hear the data sound at the speaker! Great teamwork! That's the mindset of an engineer! 😃 Best regards, Doc64!

[@NoelsRetroLab]

Thank you! Glad you liked it 👍😃

[@LongyFromCork]

Fantastic video Noel. Your in-depth knowledge is always inspiring. Your videos are very well put together, and I love that you don't edit out your mistakes, it makes for a far more engaging experience. Love the look of the CPC464 computer, with its multicoloured keys. Thanks for putting out such quality videos.

[@johnsonlam]

Mystery solved, community power!

[@deanconnolly1065]

Excellent was looking forward to this one. Glad you didn't have to remove the epoxy I applied😊😊. I bought that Amstrad from a local seller in Belfast and applied a Bluetooth mod which is why I added the power socket. I've just managed to bag another 464 locally for £25, and intend on modifying for a standard audio in (not Bluetooth this time). I might even feed the cable through the expansion slot so no drilling. I'm pleased you worked out the best input points in the PCB, very informative Noel👍

[@NoelsRetroLab]

Yes, me too. That epoxy was really well applied, so that was perfect being able to reuse that. Cheers! 😃

[@sirtinley-knot2944]

wow this must have taken an incredible amount of work. Thank you so much for doing this and sharing it with the retro community 👍🏻

[@andrewdaly5797]

Thanks Noel, another great video. You're helping to inspire my 6 year old to learn computing and electronics. You will not be surprised that the Spectrum +2 (grey) has the audio input mod in the exact same place - it's even called C317 there too!

[@NoelsRetroLab]

Oh that's fantastic. It's one thing the people who lived through those computers enjoy the videos, but to inspire the next generation... that's awesome! 😃 Thanks for confirming the Spectrum +2 is very similar. I wouldn't be surprised if Amstrad used the same off-the-shelf tape deck and just changed the buttons and the cosmetic elements.

[@philipwittamore]

Many years ago I wired a tape head to the audio output of a home made shortwave receiver, and glued it in a casette so that it was positioned in front or the CPC's tape head. Crude solution, but with a home made morse decoder written in locomotive basic, I intercepted messages in clear from the French navy in Toulon. Those were the days...

[@Thebasicmaker]

How did you got the data from the tape Dec head? The sound chip registers?

[@philipwittamore]

​@@Thebasicmaker sorry, but it was so long ago I don't remember

[@stefanocrespi5424]

Since both Output and Remote jacks seem to be actually electrically mono, I wonder if the TXDuino design could be reworked to accommodate a single 3.5mm stereo jack for both output and remote connection, so you can have a single cable and most important punch a single hole in the computer plastic. Very entertaining and informative video. Thanks Noel.

[@lovemadeinjapan]

Had the same idea. It should be possible. It will even allow a good designed file player on a computer/tablet to react to the control signal, if it has a 4th ring for the microphone. But I need a no-drill solution.

[@richardohare7708]

I love the speeded up soldering bits. Keep up the good work 👍

[@Thebasicmaker]

Great answer to my question about how the tape signal was going to the audio amplyfier!

[@voneschenbachmusic]

I've really enjoyed the Amstrad series on this channel - this was a computer completely off my radar growing up in the land of Commodores, Apple ][s and TRS-80s but what a versatile machine!

[@NoelsRetroLab]

Glad to hear that!! 😃

[@TheStuffMade]

Interesting video, thanks. Capacitive coupling between traces can be a pain, especially with square waves that have a lot of high frequency content. It would've been a lot better if whoever did the board layout had tried to make a ground fill running between small signal traces instead of the somewhat peculiar isolation layout method they used for this board.

[@Xoferif]

I really love that Sony Bit-Corder that Noel keeps showing in his videos! I never saw one back in the day, but I can imagine it'd be a lot more comfortable to use in a typical home micro setup than a traditional cassette recorder - no need to half stand up every time you need to peer at the tape counter, for one thing.

[@NoelsRetroLab]

Right. That thing is da bomb! Looks great, works great, and the ergonomics are very good. I got it a couple of years ago because a good friend of mine had it back in the 80s and it was really good.

[@Spyd77]

I have one of those. It's one of my cherished treasures.

[@Spyd77]

A suggestion to avoid having two plugs for the audio in + control. Use a four pole minijack plug, and then make a Y cable with the four pole on one end and audio + control jacks on the other end. Use the microphone pole for control, ground for both grounds, and left and right for the sound. It may be done with a three pole stereo jack, but then there may be problems if someone tries to use a standard stereo cable for the audio-in.

[@siskodata]

Yes good idea that's exactly what I thought by using a stereo jack with 3 poles one being a common ground and then have a cable split to the headphone jack and remote of the duino.

[@NoelsRetroLab]

Yes, that's a good idea. Someone on Discord suggested that just with the stereo cable. The only trick is figuring out all the possibilities and making sure it's not wired in a way that will damage something if it's connected to a different device. I do like the 4 pole solution.

[@mrblc882]

There are two potential issues: 1.) If someone connects three poles jack in Amstrad, play on signal is grounded. Since it's driven by open collector transistor, that will not cause damage, but will keep relay on. Minor issue. 2.) If someone uses 4 pin cable to connect phone, he is bringing 5V, trough relay, to mic input, which is way too high for that poor input. Possible solution is to isolate system using open collector or just diode, but I think that wouldn't work because Arduino is somehow detecting if there is remote control signal. Could be by sense contacts on jack, but more probable method is pausing when input is pulled high via relay coil. Modification on Arduino side could solve that issu, but would make it incompatible with other Amstrads, unless there is disable switch.

[@Plan-C]

Nice work! Thanks for tracing it all out. I just soldered to the backside of the read head. Guess I should revisit that 🤣

[@minombredepila1580]

Such a masterclass Noel. I'll save the video link to do the mod when I return home "por navidad" and could reach out to my CPC464. Thank you so much for this.

[@electronash]

One thing to add to this - I agree it's best not to hook up the input to the output of either opamp, so the place you used is a good one. But, I've seen mods where people hook up the input directly across the Play head. That can "work" OK, but beware that if you leave a tape in the drive and the tape is still touching the heads, the external audio input could "write" a gap into the tape and create a loading error if you try the tape later on. So yeah, the input to the first opamp looks OK, as it has the fairly high-value 470K feedback resistor (and the cap), plus it has the cap on the opamp input, which will help block any DC bias from damaging the transistor.

[@NoelsRetroLab]

Good point about the possibility of affecting the tape if connected there! That was indeed one of the (many) places I've seen recommended for that mod. Thanks for the tip.

[@saddiqkhan5821]

thank you so much - you are awesome to explain the technicals with scope waves etc. So many YT vids show the audio inputs connected to the R/P head points on the PCB of the tape deck. Now you have provided a much better solution through proper technical analysis! keep up the great vids. Gracias!

[@Davidprograma]

Great job Noel! I'm more like a Spectrum guy, but your videos are making me get interested in Amstrad too (first thru emulation). BTW, I have watched your Spectrum videos and they are also great. I have started repairing spectrums myself, thanks to your strategies and advice. You are such a great inspiration!

[@TRONMAGNUM2099]

Excellent work! Unraveled a mystery and showed the best way to add an audio jack. Lots of great content this episode. I can't wait to get my hands on it and really dive in.

[@lindoran]

Another amazing engineering video well done to everyone involved!!

[@NoelsRetroLab]

Thank you so much!

[@misterkite]

I needed 16 audio converter boards for my extron video switch, so I designed the boards and used pcbway to print them.. I ordered 15 and they were nice enough to actually ship me 19 boards.

[@NoelsRetroLab]

Nice! I've never had extra boards shipped to me, but maybe you hit some odd dimensions or something that caused them to print extras. Nice though though.

[@edgeeffect]

Admiration for your hand-soldering SMD skills!

[@luisdardis5223]

you did a looot here in just one move, and ultra didactic, great.

[@deanconnolly1065]

Did the audio mod today, seems to work better on the final input point you selected, compared to the common input used on other videos. Weird thing though I couldn't get my kindle tablet to work with the mono jack socket I fitted for some reason - sound kept going on and off? Changed to a stereo jack socket using tip only and working perfectly, thanks again

[@AClockWorkKelly1]

Wow .. what a fantastic piece of detective work

[@NoelsRetroLab]

Thank you! Glad you enjoyed it.

[@RobR386]

You lucked out with that audio jack 😀 Nicely done 🙂

[@NoelsRetroLab]

Seriously! I couldn't believe my luck because I was starting to be concerned about removing the connector there since it was so well glued in.

[@gertsy2000]

Once again superb troubleshooting video, with some help. Luv it. "A day may come when the courage of Men fails, when we forsake our friends and break all bonds of fellowship,,,, but it is not this day"

[@bricerive]

Great work figuring out the tape to speaker path!

[@NoelsRetroLab]

Thanks, although CPCRetro is the one that figured it out. I bet you don't have that path emulated exactly that way in your emulator 😃

[@RudysRetroIntel]

Excellent investigation!!

[@8BitRetroJournal]

Pretty neat. I'm learning more and more the value of capacitors :-) Along the lines of what David Swann below posted but keeping it simpler...you could use a stereo jack and connect both the audio and remote control signal on one jack and not cut another hole in the case. Then just create a cable that plugs into the stereo jack and gives you audio and remote control to go to the arduino.

[@NoelsRetroLab]

Don't feel bad. Capacitors are hard to grasp, especially when they're not taught well. I got a degree in computer systems engineering and only in the last few years I'm finally getting a feel for what a capacitor REALLY does and how to use it as part of a design. Agreed on piggybacking the remote control signal on the other channel. The thing I need to be careful with is someone plugging in a regular device with a normal stereo jack.

[@TotoGuy-Original]

Great vide I really like watching these investigation video's and solutions to problems. Keep them coming thank you 😁

[@respergu13]

Great video Mr Noel!

[@NoelsRetroLab]

Glad you liked it!

[@mogwaay]

Great video, I'd tried adding a audio in to my Amstrad build ZX Spectrum +2A and I got stuck with what point I should insert the audio, thought it would be easy but yeah there were many points that it could go, so nice to have your take on it too when I get back to that computer. Another very enjoyable video and I really really like your deep dives!

[@NoelsRetroLab]

Glad you liked it. Does the +2A not have an audio in either?? I had forgotten about it since all previous Speccies had it. Weird. I suspect it's pretty similar, although they may have a different configuration of amplifiers. Let me know if you end up doing it.

[@mogwaay]

@@NoelsRetroLab might be specific to the later +2B revision I've got but no audio in. I think at the time I was just going to insert into the tape deck connector to avoid any soldering and it didn't work very well coming from a phone. But as you've shown the audio from a phone isn't just like the tape deck or the TZXduino. Anyway, it's on the long list of retro jobs, will give a little update if I do get back to it.

[@markretro3612]

+2A is a breeze to mod .. you can use the signal off negative side of C200 (bottom right of board) .. and mod the audio output jack to work the same as the +3 .. the audio output jack on the +2A has left and right channels linked together so you can break the link and connect the input signal wire to the right hand channel .. thus using left channel for output and right for input * the link is under the jack so it would have to removed

[@RetroWK]

Great video! Thanks man!

[@NoelsRetroLab]

Glad you liked it!

[@gregborders8713]

Great sleuthing! Now everyone has an easy way to update their CPCs!

[@NoelsRetroLab]

Thanks!

[@PJBonoVox]

Hey dude. Great video as always. I had a thought regarding the remote; could you not replace the jack with a TRRS jack and then have both the audio and remote come in there? Then you could have a neat little splitter cable to split back out to the TZXduino. If you wired it in a certain way that a regular mono jack would still connect to the audio in pins, it would be a nice tight solution.

[@KittyFae-]

What I was thinking as well

[@WacKEDmaN]

very comprehensive Noel!.. great stuff what about audio out? the output jack never seemed to work for me, with powered or unpowered speakers.... i eventually just hooked up 2 wires to the speaker, through an audio transformer (to isolate the systems and provide some impedance).. and out to an RCA jack to drive hifi system.. i used that to make my "music" video..with B&W "composite" out from the monitor connector to a VCR (Beta!)...swapped 2 screens in and out of video ram space.. and added the sound over the top..(there was a write up in AA about it!)

[@JWSmithy]

Great video! I might have to try this myself.

[@tainusm5805]

Impressive. Thanks Noel!

[@jaycee1980]

I have a small board, originally designed for the ZX Spectrum, which accomplishes this fairly painlessly :) It uses surface mount parts though which might put a lot of people off.

[@GrantMeStrength]

Fantastic investigation!

[@mrblc882]

I think I have safest way of using TRRS jack for both audio and remote. Connect optocoupler with photodiode parallel to relay and exit from optocoupler connect to jack. On Amstrad's side, only one resistor and one optocoupler is added. On Arduino side, pull up resistor is needed, and it can be added via jumper to disable it when using with unmodified Amstrad. Activating optocoupler when phone is connected will trigger headphones button, which is not an issue. Additionally, by adding capacitor on both audio lines (audio and audio ground), complete DC decoupling is possible if needed.

[@mrblc882]

I would still add additional capacitor. For iPad is probably not an issue, but Arduino, outputting DC offset, could overload transistor because only collector resistor is limiting current. Even if it's not an issue in normal conditions, accidentally turning on the tape while using Arduino still can cause overload if Arduino is outputting high and head is feeding current to base.

[@NoelsRetroLab]

I agree. I even did it that way originally but then convinced myself it was the same as using the capacitor on the board, without thinking of the voltage offset there. I'll just add it near the audio jack connector.

[@Joko_things]

Lo cierto es que me ha servido para responder mis problemas con el mod de audio. Yo lo tenía conectado en positivo directamente al pin 6 del IC302...

[@AnotherUser1000]

Nice work again, computers' doctor! And a note for all of the Firefox fans: I had my beloved Firefox browser updated a couple of days ago and I realized that it can' t open the KZbin' s pages any more! So, I just use Chrome for the time being. If you see any weird security alarms in Firefox, now you know...

[@NoelsRetroLab]

Thanks! Yes, I've been hearing horror stories about Firefox in the last day or so. I won't be upgrading any time soon!

[@AnotherUser1000]

@@NoelsRetroLab And it seems that KZbin fixed something, because Firefox is still in the version where the problem has been introduced, but now it' s OK.

[@juanantonio4955]

Absolutely great, Noel!!. Thanks.

[@NoelsRetroLab]

Glad you enjoyed it!

[@CyclingSteve]

Loved this video, so did you try speeding up the loading time?

[@CyclingSteve]

Ignore that, I found you did.

[@KolliRail]

Great and very useful!

[@NoelsRetroLab]

Glad to hear that! 😃

[@kobe3576]

An alternative to using two separate jacks for data and for remote, you can also use a din connector similar to the MSXs cassette connector. If you make it with the same pin out than the MSX you could use the same cable for the MSX, for the CPC, as well as spectravideo that use the same pinout.

[@dlfrsilver]

Hi Noel, thanks a lot for playing Batman 1 CDT in your video (i guess you picked it on CPC power right ?) It shows that CDTs loads very well, thanks to CSW2CDT ! :D

[@cliffroesli5246]

Always perfect

[@NoelsRetroLab]

Thank you!

[@cjmillsnun]

A potential solution for the remote feature on the audio in for the TZXDuino in future. Use a stereo jack on the CPC and make up a lead that includes the remote function on the right channel with the audio on the left. As they share a ground that shouldn't be an issue.

[@ALcreationvideo]

Bonjour, merci pour cette super vidéo! Cependant Il manque des infos sur les composants, par exemple le voltage pour les condensateurs (C1 100nf C0805)? Hello, thank you for this great video! However, information is missing on the components, for example the voltage for the capacitors (C1 100nf C0805)?

[@guffaw1711]

If you don't want to drill another hole you could replace the mono socket with a stereo socket, for both audio in and remote control out. Then use a Y-splitter cable.

[@ronnyverminck2741]

Fantastic explanation !!

[@NoelsRetroLab]

Thank you!

[@MrRidged]

so noel have you tryed about changing the Gerber file to change the 3.5 mm jack and the 2.5 mm jack to a single 3.5 4 pole so you can put it all in one cable for sound and remote or even a 6 pin din and tap 5v from the cpc to power the entire board ,carry data and the remote signal ?

[@abaudrand]

Just discovered your channel and loved it. Maybe someone suggested it or you already know about it but the loading sequence of Birdy from French company Ere informatique on tape (not disk version) had a beautiful music played while charging blocks into memory. This Stephan Pic masterpiece was synched with blocks data: if you pause the tape, the music also stopped playing. I ever wonder how they made it. If you have a clue…

[@NoelsRetroLab]

Thanks! I didn't know about Birdy! I think I played the disk version, but that sounds very interesting about the loading with music. Off the top of my head, I imagine that one byte out of X bytes had sound information for the AY. So if you stopped the tape, it stopped feeding data to the AY and the music stopped. I wonder how much slower it was because of that (probably not a lot and probably it was worth it). I'll have to check it out now.

[@mattcole6230]

Brilliant video. One question I have is, can the mod speed up loading?

[@jtsiomb]

The ripples in your square wave is just ringing, most probably caused by your probing, not actually present in the signal. I expect you used the long ground lead of your oscilloscope probe for this. If you instead try to use the little coil with a sharp tip that goes around the shield of the probe tip, I expect most of that ringing will disappear. It's less convenient as you'll need to find a ground point very close to what you're probing for it to reach, but that's the only way to probe high-frequency signals without ringing (the high-frequency part is this case are the sharp square wave transitions, which contain infinitely high frequencies of super-imposed sine waves). The TZXduino signal probably had somewhat slower transitions, which is why you didn't see ringing.

[@NoelsRetroLab]

Are you talking about the ripples in the audio output of the iPad? I doubt that. Those are actually really slow signals compared to clock signals I often look at. Those are definitely artifacts of the audio hardware of modern sound devices running a 48KHz sampling rate (and probably some additional filtering on top of that).

[@jtsiomb]

​@@NoelsRetroLab Yes, the decaying ripple after every rising and falling edge of the ipad square wave. That's what it looks like to me at least. It's not the frequency of the square wave you're measuring which causes it, but rather the sharp transition of the rising and falling edges. The fourier of an instantaneous transition (a perfect square wave) contains infinitely high frequency components. In reality of course no square wave is perfect, but the sharper the edge, the higher the frequency.

[@atomicmole6820]

Hi Noel; excellent video, thanks. I’ve managed to install the audio mod but how and where can I purchase one of these devices? 👍🏻

[@lasticppc529]

A question on the audio in connection towards the TZXduino . Am I correct that you are using a mono female jack on the Audio-in signal ? What kind of cable are you using between the Audio-in and the TZXDuino output ? Stereo or mono ? Thanks for your very detailed video , it made it super easy for me to follow the required steps and perform the mod myself.

[@herbmyers805]

I have seen wires tacked on PCB of Commodore tape decks as well. I have a deck will do this accordingly. I have a Tape Cart SD as well. Smiles!

[@NoelsRetroLab]

That's a great idea. I'm probably going to do that with an SVI-328 tape deck as well.

[@swarmadd]

Now I know why I couldn't load anything but the "header stage" on most external playback devices. I know a wire that will be soldered elsewhere very soon :'D Thank you very much !!

[@atec9228]

Great job!!! Fantastic

[@fred-9929]

Excellent! I was not aware of this mystery (I didn't have a 464, but a 6128), but it is very fun to see you dig into it. BTW, is there a TZXduino-like DIY device able to also *record* programs? I would like to use it with my ZX81 and TI99/4A...

[@CoolDudeClem]

I would have to get these pre-made, as there's no way I could possibly solder SMD parts, my hands are just not steady enough.

[@saddiqkhan5821]

You can buy TZXduinos made already on ebay.

[@TheLemminkainen]

With MSX cable and MSX2cas worked 100% CPC and cable and WAV Files 1 /50 games worked. I bought DDi3 for CPC tape loading is pain in ARSE with it :)

[@DouglasFish]

Annoying commenter nitpicking time! The "LCD" at 4:40ish is a OLED Regardless, love the content Noel. Thanks as always!

[@NoelsRetroLab]

Haha, no worries. You're completely right, of course. Glad you enjoyed it 😃👍

[@lovemadeinjapan]

an OLEDD? ;) I miss the N and the extra D.

[@markretro3612]

* OTLA turbo loaders can be loaded from audio input on the cpc as well .. can be tricky to get the volume just right though ..

[@markretro3612]

another great video,, i had an issue getting sound files to work going from my pc to AV receiver.. whatever settings i used on the pc or the amp and they would fail.. then i tried streaming the same files into my apple tv and into the amp and they work fine .. think last time i did a audio input on a cpc i used the read head i will defiantly be trying C317 next time

[@KevinFields777]

Here's an idea - could you modify an audio cassette adapter using Audrino to load files from a MicroSD card directly into the head of the cassette deck? And either include a small LiPo battery for power or use the capstan to drive a small power generator? That way you can preserve the original use of the deck and not have to solder or drill holes into the case?

[@NoelsRetroLab]

That sounds almost like this (minus the power issue): kzbin.info/www/bejne/mn7TeHqcYr6IsLc

[@KevinFields777]

@@NoelsRetroLab That's almost it! But it looks like it's not passing through the tape head, but still routing an audio signal out from the cassette through a wire that then connects into the sound jack on the side.

[@andycraig7734]

I once heard of a person who would place a handheld AM radio receiver near their computer to listen as programs would load. I think it was one of the TRS80 models, which had notoriously noisy RF.

[@timealias9697]

Great project. Although you do not recommend to use a car cassette adapter I use one... Unfortunately my Windows out is not recognized on the CPC correctly. I think the driver does some funky optimizations. So I always boot Linux from stick to play the WAV files. I never found out how to force Windows to use a vanilla sound driver... BTW I use cpc2tape to create WAV files.

[@rubirubiales3534]

Buen video, gracias por compartir. Hace tiempo le hice una modificación parecida a una zx spectrum +2. Lo que hice fué conectarle una entrada de jack 3.5 a la entrada de audio del cassette y a través de una app en el movil, con un cable auxiliar de audio, cargo los juegos. No será ni de lejos la mejor forma y deja la entrada de audio en un taladro hecho en un lateral de la carcasa, pero a mi me funciona. :)

[@kriswillems5661]

You need an AC coupling to that opamp input, not a DC-coupling. Couple it with a 22nF cap to the input of the first opamp. It's not good to have a DC coupling at this stage, because the system should work independently of the average DC level of your external board. This opamp can handle high DC offsets at the input, but they can't all do this. Your second solution isn't great either. The output of that transistor also has a DC offset. It's just not done to couple 2 signals with different DC offsets together. You could blow up your transistor. If the transistor is driven (your play a tape), it shorts out the DC level coming from your external board.

[@NoelsRetroLab]

I'm not concerned about the tape being activated at the same time as the audio input, but that's a good observation about there being a voltage at that input point, which is not ideal. I agree that the best solution would be to connect it to the input of opamp 1 with a small capacitor. I even had it like that at one point but went with the exiting capacitor when I saw it right there. Doh! I'll do a mini-update in the next video about this and a couple other things. Thanks!

[@jasonhowe1697]

I'd likely use the card connector and a sd card as the preferred tape/disk/cart medium for gaming ..

[@richardtherrien4696]

Hi, Sorry for being a noob here but what type of wire did you use? Is there a specific size or type I would need to do this mod. Cheers.

[@stephenwhite506]

I wonder if the same audio in mod could be done to a zx spectrum 3? I will have to find the schematics.

[@NoelsRetroLab]

Well, the Spectrum +3 already has an audio in, doesn't it? You shouldn't need to do anything 😃 I'm sure a similar thing can be done with the +2 though.

[@m5sib]

It looks like you used a little hand held vacuum part placer it's not included in your list of tools.... Could you give me more info on it, it looks very helpful...

[@arminsauter]

Hope you can help... Where world be a good spot to connect a back to create a audio output signal to record a wav file? Thinking about saving directly to record the audio to PC or tablet.

[@nickolasgaspar9660]

Do you get those PCBs from Europe or they are shipped from Hong Kong?

[@battmann7089]

Hi, can the volume of an Tzxduino be adjusted- I still get a few load errors (not too many) and I’m going in via a direct audio connection.

[@MisterAML]

What is the brand and model of your external speaker ?

[@sysghost]

Now I'm going to try something similar on my C64. Will of course try to avoid any permanent mods as much as possible.

[@dfkcfk4701]

no se mucho inglés Noel pero lo que e entendido es que escuchamos la carga de la cinta por el altavoz no porque le salida del AY lo vuelve a sacar y lo pasa por el amplificador como el sonido de los juegos sino que por culpa de un mal diseño se acopla el sonido en el amplificador del altavoz ?? otra pregunta quiero hacer ese MOD a mí CPC 464 para cargar los juegos por el móvil , lo conecto entre el transistor y el condensador C317 antes del ampli ?? aunque yo creo que sería mejor en rl pin 9 del operacional la verdad me lío con el ingles bueno Maxudino la salida son señal TTL de 5v se podría poner directamente en la entrada del 8523 ?

[@siamsurf]

0:26 So... Leo sent it to you from the UK, and then he traveled to the US to get it back? I am not sure what surprised me more... that, or you being credited on the PCB and having activated the community to solve a mystery. :-)

[@NoelsRetroLab]

Fair enough, I wasn't very clear: Leo is from the US. I bought that Amstrad through Ebay on the UK and had it sent to me to make some videos, fix up some things, and them mail it to him in the US. Now it all makes sense 😃

[@siamsurf]

@@NoelsRetroLab Ahh, ok, yes that makes sense. :-) I actually thought you said US by accident the 2nd time. ;)

[@EgoChip]

I love your t-shirt

[@galier2]

Noel Columbo !!!

[@NoelsRetroLab]

🤣🤣🤣

[@mattmyers9351]

Where did you get your Amsoft t-shirt?

[@NoelsRetroLab]

I got it from here (along with most of my other shirts 😃) www.latostadora.com/retrocomputers/

[@mattmyers9351]

@@NoelsRetroLab thanks!

[@chuck2501]

I remember that you used to be able to buy mp3 players that were cassette shaped, I wonder if they'd work in an 8 bit computer?

[@Sheevlord]

The "feature" where the audio amplifier picks up and plays parasitic signals due to poor PCB layout is an example of a digital electronics engineer designing an analog circuit. When making digital circuits crosstalk isn't much of a concern - there usually isn't enough noise to be a problem. This is also why early PC sound cards were for the most part awful - lots of hum, hiss and high-frequency noise - all because the boards were poorly laid out (and also because they powered analog audio chips from the main 5V line that was extremely noisy)

[@disposablebasterd]

Did you install the remote control jack?

[@NoelsRetroLab]

Not yet. I'm exploring other options using the same jack so I don't have to drill any holes.

[@aussie_retro_dude9253]

Can the SVI-CAS be used with the 464 ?

[@AngDavies]

19:50 - that doesn't look like a sampling issue, that looks like an impedance mismatch/inductive ringing issue. truncating the fourier series will give you oscillations, but they'll be after and *before* the transition in a way that looks unphysical ( how does the system know the transistion is about to come up?) that waveforem looks more like something is oscillating in the system in response to the sharp transitions. moving it evidently fixed the oscillation, and that's why you don't see those oscillations in the output of the ipad when you move it

[@computerman200]

Set the data output pin of the arduino to pinMode(data pin, INPUT); when not sending data to make it high z. Set it back to pinMode(data pin, OUTPUT); to send data

[@OTuit]

That's CRAZY!!! :)

[@MrAlan1828]

Can't we use old car cassette to line in adaptors?

[@craiggilchrist4223]

I always wanted to play my music tapes in it lol.