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" I am not convinced that this fancy iMac of the OP is not the source of trouble here. "
There's no guarantee I've ruled out my devices, but I did not limit myself to my 2019 iMac, but also tried my current iPHONE 15 Pro and an old iPAD 3 using MAX volume then one unit at a time decreasing volume until Apple II+ stops responding. I've tried 5 different cables - 2 of them brand new.
CVT, your cable effort is useless, but anyway here are my 4 provoking but hinting questions:
1. Where do you measure these 50 0hms on your super-puper cable?
2. Why do you connect a 50 Ohm cable to a roughly 24 000 Ohm apple2 cassette input?
3. Is the coaxial cable better than the twisted pair?
4. Have you heard about signal to noise ratio?
I wouldn't call the cable useless, since it works and it took a lot less time (and tape) to make than your transformer contraption. (LOL)
The useless stuff here are your questions, since you are not paying attention to what I have written. This coaxial cable happens to have 50 Ohms impedance, but this is something that is irrelevant in this case. As I said, I am simply using it because it has good shielding. Its 50 Ohm impedance has no positive or negative effect on the quality of the audio signal which I am transmitting over its length.
The questions pushed you to the limits of your knowledge and should have motivated you to educate yourself. But, alas, they seem indeed useless. The impedance is dependent on frequency. The cable you used is UHF cable. It has no benefit for audio low frequencies over any other coax cable. Instead of focusing on the cable that is nearly irrelevant for a couple of kHz signal there are different weak points in this setup that can be improved if you are afraid of noise.
This is exactly what I said. I am simply using it because it has good shielding. But once again you are not paying attention and your argument falls flat on its face.
If you really know something about transmission lines (hopefully more than "impedance is dependent on frequency"), then you should use that knowledge to help the author of this thread instead of bickering with me, which is useless. And what you are doing is petty bickering and you know that very well, since coaxial cables are often referred by their impedance.
If I told you that the outside diameter of this cable is 2.54 mm, are you going to ask me how this matters for the signal quality?? LOL
"You might also want to eliminate the connection to the monitor as a possible source of the noise. Just carefully unplug the RCA video connector right after you type LOAD. Then hit RETURN, do the playback and connect it once the playback is complete to see if the result is the same."
Just tried twice with HIFI and once with 8K FI. No luck.
Of course, there will be no luck. It is just where the knowledge ends and religion starts, especially for those who evaluate coax cables by cutting them :)
I can send them to you, so you can tape them back together and post pictures. LOL
Eliminating the monitor as a possible cause has nothing to do with religion or luck and you wouldn’t claim that if you weren't only interested in bickering. Sad.
I don't wish to interrupt this fascinating exchange (really), but with respect to coaxial cable used for audio, is the shielding really a benefit? Any signal from a player to the Apple II must involve a current flow, and this current must flow in a loop, isn't that right? So the EMI blocked (and absorbed) by the shield is still coupled into the signal, since it is superimposed on the return current path.
Cables are categorized as shielded and unshielded, but also as balanced or unbalanced. Balanced cables have current flowing in opposite directions in equally sized and spaced wires, which is supposed to improve CMRR. A coaxial cable such as the one shown is shielded and unbalanced, so CMRR will be worse, if that matters for the case in question.
Professional audio connections are both shielded and balanced, which requires 3 pins for a single audio channel. That's the application of XLR connectors, where pin 1 connects to the shield, and pin 2,3 are the balanced twisted pair. This allows for EMI absorbed by the cable shield to be coupled to a node separate from the signal current loop.
The AUX cable between the "cassette player" and the Apple II+ needs to be unbalanced and shielded. The shield is connected to the chassis:
CassetteDataIn.png
An unshielded or "fake shielded" cable (one that only pretends to be shielded) will cause higher EMI. And just to make it clear for some people in this thread, it doesn't need to be 50 Ohm coaxial, 75 Ohm coaxial or even coaxial. It just needs to be shielded.
@CVT Wrong. The cable is good to be shielded but it is not necessary at all in this case, neither the UHF feeder coax cable is. What interference do you expect from the monitor and how significant it could be? Robespierre tried to explain you something but it seems too much for "на всяко гърне мерудия".
A reoccuring point being made in this thread is possible signal volume not being high enough. I found yet another piece of gear lying around that was worth a test. An FIIO OLYMPUS 2 is a gadget I bought to boost music volume for my headphones, and it works quite well for that purpose. To my ear it sounds like at least 20% louder than simply iMAC headphone jack alone, AND it sounds very clean. I'm no audio pro but it sounds louder without distortion. This is the unit:
https://www.amazon.com/FiiO-E10K-Headphone-Amplifier-Black/dp/B00LP3AMC2/?_encoding=UTF8&pd_rd_w=ejRTq&content-id=amzn1.sym.e92d427b-6681-44e4-9201-8463289b9c75%3Aamzn1.symc.f3a6ae52-fb92-4bbd-ba18-628777ebc1c0&pf_rd_p=e92d427b-6681-44e4-9201-8463289b9c75&pf_rd_r=TEBAMNRF6VFR74SRSK7T&pd_rd_wg=j4E6G&pd_rd_r=85992026-70fa-45a4-9204-26a84bdb93ee&ref_=pd_hp_d_atf_ci_mcx_mr_ca_hp_atf_d&th=1
I just tried yet another battery of tests from both website direct, to downloading the WAV and playing it back boosted through Audacity, or playing back as loud as it goes in Quicktime. I tried again both HIFI and 8KFI and started with MAX volume, then steadily backing off until Apple II+ no longer responds.
I feel the important detail in ALL of these tests is the consistency of results. Changing cables, software players, hardware devices, 2 different audio boosting devices allowing me to bypass the iMAC headphone jack, wide variety of volume amplitutde settings - EVERYTHING yields a binary response from the Apple II+. It either attempts to work that leads to an error, or the volume is finally too low and doesn't work at all. That's not 100% true. Sometimes just before the volume becomes too low to be usable the screen will scramble full of miscellaneos characters and Disk Drive 2 will engage. It's pretty to look at, but just another version of failure.
Bottom line - days of testing all seem to point to my specific Apple II+ just not liking Cassette In as a data input unless it's LOFI. I've heard good things about Monster cables, so I ordered one as a last attempt. Unless someone comes up with another viable testing idea, it sounds like my computer may simply have a problem I can't overcome with this input option. Again, i'm hoping if someone downstream has this identical problem - maybe this thread will prove helpful without the need for tons of gear and testing like I'm putting myself through.
If the goal is to reduce EMI (and it is) then it needs to be shielded, simply because it is good to be shield, as you put it.
The goal was also to eliminate the monitor as a possible cause just like we did with the cards, not to estimate how significant it can possibly be, which can be anywhere from 0 to 100% significant for a 40+ year old monitor. You should know that if you are still pretending to be an expert.
Also are you saying that you agree with what robespierre wrote in post #60?
The age of the monitor is hardly relevant apart from the fact it has no switching PSU which further lowers its EM emissions. The possibility up to 100% you are referring to would even be doubtful for a non-expert casino gambler, not to mention an engineer. Just think of the SNR. Try to evaluate how much energy could be transferred from the monitor to the cable by mutual inductance and how much signal amplitude will it generate across the output impedance of the sound player alone compared to the sound signal. The lesser you know the more the logic is simpler and such logic dictates you to use a more expensive and mechanically "better" UHF cable just because it looks mechanically well made, "just in case". The simple logic is indeed needed when adapting and using open source code from many open source emulators, and compiling them for a very cheap Chinese ESP processors.
LOL! That is a personal attack, but pretty weak to even be offensive.
But if I were to reply to it, I would simply ask: and what have you made exactly?
I would much rather address the Bulgarian expression you dropped in your previous post. I don’t think you know what it means, because if you did, you would see how it perfectly applies to you. I joined this discussion to simply help a client with a specific use case of the ESP32 SoftCard. After I did that by providing him with two separate working solutions, I tried to help him with the general case of being able to format a floppy using the cassette port. And since I have the exact configuration as him I simply shared all the details of my setup.
You on the other hand entered the discussion with a 3 sentence post. The first sentence was super weird, the second was a fallacy and the third was a repeat of something that was mentioned already. Do you see my point now?
Now if you are pretending to be this amazing engineer and in the process of showcasing your knowledge you manage to help Skipper fix his problem, I would be really happy with that. However your posts have been nothing but petty bickering with pretty much everyone who is trying to help him and as a result your posts have achieved absolutly nothing constructive.
I don’t know what you get out of it other than getting long time members like softwarejanitor to permanently leave this forum.
"I joined this discussion to simply help a client with a specific use case of the ESP32 SoftCard. After I did that by providing him with two separate working solutions, I tried to help him with the general case of being able to format a floppy using the cassette port. And since I have the exact configuration as him I simply shared all the details of my setup."
Just a quick shout out thanks. The card you sold me was really only part of the transaction. I love the card and all it can do. It takes my Apple II+ to a new place I never imagined. I'm sure purists can quibble, but as someone who grew up having my very first computer experiences with the plus, it's a blast watching the old dog doing new tricks. But your customer service has really been the most impressive aspect. You shipped quickly, I feel I got value for my purchases. You've also gone out of your way to find solutions to my problems, including your help on this forum. In the end It's been fun trying to figure out this puzzle. Why CAN an imput intended for a mini-jack from a consumer cassette player not use the data from high quality sources? For the moment it remains a mystery. But thanks to everyone for trying.
As for retro_devices, I've stayed out of the shenanigans. Why anyone would find pleasure being a sarcastic wannabe know-it-all lobbing cheap attacks to people trying to help one another says everything I need or want to know about such a person. You offered little in tangible solutions / suggestions, but plenty of wasted time being obnoxious and childish. I hereby end with my very favorite insult.
I hate people like you with the burning fire of a thousand urinary infections.
Interesting...because that is contrary to all of Apple IIx Reference Manual recommendations and my own personal experience using audio-data input/output signals with a II Rev 0 and IIe. There is an optimal audio signal level, too low...no joy, too high...no joy, too much distortion...no joy.
No debate required...that's just been my experience since 1977.
"No debate required...that's just been my experience since 1977."
This is the kind of insight I find EXTREMELY helpful. An original user's POV. Thanks for the insight so far. Considering all the ways I've tried to make this work, got any possible solution ideas?
Forgive me if this is a long-shot, but just in case...
You probably ruled out this problem when you tested external audio boosting devices, but make sure that you tested with a cable that has a 3.5mm connector with no more than 3 connections at the plugs.
The Apple II only connects to the tip and sleeve of the cable. That works fine with a 2-wire (TS) mono cable or 3-wire (TRS) stereo cable because the source socket shorts the ground and microphone together, which attaches the ground to the sleeve. But if you attach them with a 4-wire (TRRS) cable, then the sleeve will be connected to the source's microphone input instead of the ground. The source's ground will be connected to one of the rings, where the Apple won't connect to it.
To make it clearer, here's an excellent illustration from Audio Jacks Explained, which illustrates why a TRRS jack ought to work with an ordinary 2-wire or 3-wire headphone/line cable but not with a 4-wire TRRS extension/headset cable.
TRS and TRRS diagram.png
TRRS cables used to be rare, but they've become common enough that it seems sensible to check. If you custom order a cable for this, don't order a 4-wire TRRS cable for an Apple cassette port -- it won't perform well.
Wikipedia lists common pinouts at https://en.wikipedia.org/wiki/Phone_connector_(audio)#TRRS_standards
" Forgive me if this is a long-shot, but just in case... "
EXCELLENT INFO! I'll dig into this later tonight and really inspect the cables I've tried.
Thanks!
The Apple II/II Plus/IIe cassette/audio input jack is a monoral socket, not stereo, so there is the potential for poor or less than optimal connection when using a mini-stereo jack to insert into the Apple II mini-jack port. A stereo mini jack commonly works fine...but just bear this in mind.
Mind you, my personal experience is based on actual cassette tape input levels adjusted accordingly OR cassette tape signals digitally recorded as WAV files and played back through monoral channel audio mixer signals with input levels adjusted accordingly.
What Apple Disk Server is doing is similar yet different, to mine mind's eye, and could well be more senistive to variation.
I'm gone for a week and looks like I missed all the fun!
@CVT, I'm with you... seems some folks think coax mean RG-59 or RG-60 used for tv signal transmission... we know a cable structure. I'm also with you, to avoid most RF interference the foil and braid sheidling do a really good job at removing a large percent of noise when properly grounded. Frequency isn't really a factor other than if it can be received by the conductor it can be received by the shield and diverted to ground before impacting the signal. @skipper_martin, I think I or others asked about this before, but if not.... what condition is you power supply in? Does it have a working RIFA (C1 on a AA11040B supply; still C1 on AA11040 but not a RIFA). It may or may not be a factor but something that could affect signal quality more than the noise from the unshielded monitor. The comparitor needs both +5V and -5V and the -5V line is fairly low power and also part of the video output circuit so that should be checked, but like others have said with examining the signals we're talking about require a scope to get accurate level readings.
Did you try cleaning the casette port to remove any oxidation? De-Ox D5 is good for that, but alcohol can do a good job too. Just let whaver have enough time to dry before using.
I also took a look at my 2019 imac to see if there were any special settings that would be important (like ear protection which I found out it does not have), but I did not find anything. While it was up I tried playing a disk writer wave file at full volume while wearing my headphones and word of caution: DO NOT DO THIS!! Holy crap that's loud!!! I walked 3 rooms down the hall (like 50' and could still hear everything coming out of the headphones!) I suspect the signal is amplified for external speaker or similar it is not meant for headphones! My imac is not in the same room with my bench, but after hearing that I really would like to see what that signal looks like coming in to the cassette port. I also have my II+ so I could try but every time I touch my imac I break the screen so I'm not looking forward to that. lol
I'm glad Scott shared an example of the different construction with the cable ends, I had made reference to that in my first post but in addition to what Scott shared of the extra 4th contac (mic) there are also stereo cables which have slightly different construction so some signal could be shorting to ground while it's possible (but maybe not likely) that you've got contact which is fine for lower frequencies (wider pulses) but because of the contact may attenuate the signal enough at the high speed timings that the comparitor misses bits.... the checksum error would suggest you're getting data that's either too low or saturated. After hearing the headphone level, my money is on it's too loud at max output! I would try two things if I were in your shoes.... first if you have a multimeter I'd tone out the input jack contacts to all three (stereo) or two (mono) contacts at the end of the cable that will be in your mac. The ground and singal shold each only be found on one contacts on the end at the mac end. If you check out my post where I show the loader not being received on a scope the contact points for the input and you'd need to find the same side of the c10 capacitor. Ground can be checked with the metal structure around the video jack.
If it's not a contact oxidation problem, or power supply issue, I'd bet a signal level issue. Your II+ can receive the loader application correctly and when it runs to receive the disk writer it fails (crash or checksum error), this is exactly what I saw with a low volume level. But in your case with the imac output at 11, I'd go to maybe 2 squares and see what happens, I'd bump up output by 1 each time until the loader can load after that I would not increase volume more than another 2 squares. After typing all that I just realized... have we had you test your RAM? The cassette loader works out of the lower memory but I'm not sure about disk writer. Since it appears like data is getting through (checksum error, and the * rather than just spinning on the "loading" message) you can easily test RAM from the monitor (CALL -151 (return)
*C050 C053 C054 C057 N 265:0 N 266<265.BFFEM 266<265.BFFEV 265:FF N 266<265.BFFEM 266<265.BFFEV 34:14<space><Return>make sure you don't forget the space before the return, it's important. This only tests the lower 48K and I haven't yet figured out where Instawriter is loaded but if it goes outside 48K taht memory should be checked too. The MEC Computer Inspect or Memroy Test v1.4 which are available on asciiexperess can check RAM but you gotta be able to write a disk first.
I think I know what's happening....
@skipper_martin, can you try to dial you imac's volume to 11-13 block (I hate that interface), basically -4 from max and see what happens? As I was typing up my reply I relized I thought I saw a iie in your video, I just tested the II+.... I hope this still helps. There are longer delays transferring data with tout the format so be patient.
I know you've said you've tried every volume level, but I can confirm I see the same no work disk server images (tried ADT and RAM tester) at volume block levels of 0-11 and 14-16, the 12-13 seems to be the magic spot.
Low speed data is fine at >9 vol blocks, but high speed needs 12-13 at least for me. Too low input signal and the opamp can't switch states correctly. level 14-16 the opamp holds highs too long.
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