First Power Up!
 
It Works!
 

 
A few things to note:
 
1.  Note wires on left side.  It is currently powered from +5VDC from my bench supply. The battery is not installed, and as you can see, the battery meter board is not in the circuit.
2.  Film is still on, knobs not installed.
3.  It basically works/sounds pretty good, but it does have a few issues.
4.  The sound effects board was not working at all.  After hours of troubleshooting, I finally discovered that the problem was due to my bench power supply.  I was very conservative in setting the PS current limit -- Just in case.  With each of the tone/op amp boards having lots of filtering, it was presenting a large initial load on the PS.  The current limiting was apparently causing the voltage to come up in a way that hung the sound effects board.  Nominal (steady state) current is almost exactly 0.25A, but in rush is over 0.5A.  With the PS current limit set higher, everything powers up OK, and it does play the sound effects.
5.  There was an issue with the Cue/Live switches due to a short resulting from the close soldering on the tiny toggle switch contacts.  This was fixed, but I'm still not sure if something is wrong with the Cue switches/cue bus wiring or not.  More testing will be done to determine if there is still a wiring problem or not.
6.  Generally, control ranges are pretty good.  One significant problem is that the fader does not fully fade out the opposite player when fully faded to the other side.  I don't have a solution for this at the moment.  It is fundamental to the way the fader pot is made, and a relatively high impedance downstream of the fader.  It's more of a problem because the player modules do not stop at the end of a track -- they go on to the next track, so unless the gain for that side is turned down, or the player is stopped, the next track will be heard faintly in the background.  More thought is necessary on this issue.
7.  I will experiment with different options for power/battery/battery board configurations.  Hopefully I'll make a decision on the configuration today.
8.  It seems at least acceptable from a noise/interference point of view.  I may line the bottom panel with grounded aluminum tape just for shielding "best practices".
9.  The effects keyboards are not sticking to the chassis.  I will remove them, add 3M outdoor permanent double sided tape, and re-attach them.
 
Once I get the power system configured as it will be, and I have installed knobs and removed the protective film, I plan to do a video showing how it works.

I used my Poor Man's GO DJ for an actual gig last night.
 
I was hired to DJ for a small car show in my local area, so I decided to take my PM GO DJ along as a back up.  The Stanton SCS.4DJ was my primary Player/Mixer.  Early in the evening, I got a request from the wife of the venue owner for Thriller by Michael Jackson.  I was certain I had loaded up Thriller, as well as a hand full of other Halloween classics on both the thumb drive I use with the Stanton, and the SD cards in the PM GO DJ .  However, I was unable to find Thriller on the USB drive I had in the Stanton.  I verified that Thriller was on the SD cards in the PM GO DJ.  Since the Stanton does not have an SD card slot (add that to my list of complaints), I couldn't simply swap or add media.
 
I figured this was a good enough excuse to actually try live DJ'ing on the PM GO DJ in front of a real audience.  It took a moment of down time to switch over, but the PM GO DJ connected to the amp I was using, and Played the request flawlessly.  I stayed with the PM GO DJ for several tracks before switching back to the Stanton SCS.4DJ.
 
Despite the previously mentioned limitations in the Media Players used in my PM GO DJ, it was actually quite usable.  Here are some more observations.
 

• The font on the PM GO DJ Media players is much larger than the tiny font on the small Stanton display.
  
• The Stanton Browse list does not retain the directory structure of the media, so you cannot use the media's directory structure to organize your tracks.  The media players in the PM GO DJ do retain the directory structure.  While I generally just have folders for artists, one could also use folders basically as crates, or any other structure you would like (such as a directory for "Halloween Songs").  Of course you can create playlists on the Stanton, but that would be tedious using the Stanton interface itself, or would require using other software on a PC.  Simply using the directory structure for crates or playlists may not be sophisticated, but it is simple and easy.
  
• Quickly moving through large numbers of tracks is actually just as easy or easier than on the Stanton. Quickly browsing the browse list on the Stanton using the jog wheel is not smooth, and suffers from lag.  You either have to scroll slowly enough for it to keep up, or risk significant overshoot.  As mentioned, the Media Players used for the PM GO DJ are fast and direct if you just keep mashing the >> or << buttons.
  
• The combination of the Media Players not stopping at the end of the track, and the Fader not totally silencing the opposite (faded away from) player leads to the next track playing in the background if you forget to stop it.  I think I did this for over half the tracks I played using the PM GO DJ.  I should state that the level of the undesired track is very low, and I don't know if it was noticeable to the audience or not when it happened.
  
• While the PM GO DJ has 2 mic inputs (as opposed the the Stanton's single mic input), they do not pass through, so they can only be used for recording.  A live mic input is really needed, and it would be nice if it had equalization.
  

 
I'm still planning on doing a video demonstration. Check back for a link soon.

The folks that run the local True Value Hardware Car Shows continue to hire me to DJ, and I continue to bring my PM GO DJ as a "Back UP".
 
I am also bringing a Samson L1200 Professional Mixing Console.  Yeah, that's overkill for a neighborhood Car Show, but in addition to being able to use more than one microphone, I can also have the PM GO DJ and the Stanton SCS.4DJ connected simultaneously. This gives me 4 player decks, as well as the other features (such as Bluetooth) of the PM GO DJ without switching or downtime.
 
In fact I find myself using my PM GO DJ more than the Stanton SCS.4DJ.  This isn't a conscious decision just so I can use the device I designed and built.  I really find myself naturally or subconsciously gravitating back to the PM GO DJ.  There are a few reasons for this:
 
-- The larger text on the player modules that comprise the PM GO DJ.  I'm not a young DJ.  I can read the small text on the Stanton, but having the larger text on 2 separate screens is much easier for me.
-- I don't have to continuously switch between the "Waveform" display and the "Browse" screen like I do on the Stanton.  I actually think it is about the same number of button presses to cue up the next track, but on the PM GO DJ it's all on the same screen.  That makes it ergonomically easier.
-- As previously mentioned, the Chinese media players are very quick at moving through the tracks.  The Stanton skips, and does not scroll smoothly.
 
Lastly, I'm beginning to think that my PM GO DJ actually sounds better than the Stanton SCS.4DJ.  Yeah, OK -- I know the response to that.  I'm not an un-biased, or objective observer here.  It could be totally opposite.  Also, I generally connect the the PM GO DJ to 2 channels of the Samson mixer, and the Stanton to the "CD/Tape" input.  All of the EQ controls for the 2 channels are set to null, and the pans are set so that each channel is properly mixed by the Samson, but it's possible that the Samson just does not have as good a quality components on the CD/Tape input as it does on the actual mixer channels.  Obviously more objective testing (and a far more objective tester) would be needed to determine if there really is a perceptible difference one way or the other.
 
A few more notes on this:  The PM GO DJ players will play FLAC files, which the Stanton will not.  Using High quality FLAC files *will* make a
difference in the sound as compared to an MP3.  Objective or otherwise that is an objective fact.  However, very few of the files loaded onto the PM GO DJ's SD cards are FLAC.  90+ percent of them are the identical MP3 files loaded onto the Stanton.
Actually none of them are FLAC.  I attempted to load some FLAC files, and they would not show up in the Media Players.  As of right now, I don't think this actually will play FLAC files.  It may still play other lossless formats such as WAV.
Another Edit:  Sorry to keep changing the story on this, but here is the issue:  The Chinese Media Players will play FLAC files.  However, the players are limited to 24 bit samples.  The FLAC files I was attempting to play were 32 bits/sample. They would probably work fine if I used ffmpeg to reduce the depth to 24 bits/sample, but of course that would probably "hurt" the file (reduce fidelity) almost as much as just re-encoding it as a high bit rate MP3.
 
It's also an objective fact that there is a *lot* more digital circuitry on the Stanton between the digital source files, and the output jacks.  I'm not sure if the Stanton implements it's tone control in a DSP environment, or with analog components.  I can tell you that I don't remember seeing groups on OP amps and analog circuitry.  I also know that the Stanton is very slow at scrolling, scanning media, etc.  It seems very limited on computing power for the job at hand.  If the Stanton is trying to do a lot of real time signal processing on a system that seems to be somewhat limited, then it is very likely that my PM GO DJ really does sound better.
 

This post continues a mini-review of the "CD-028 Wireless Bluetooth 5.0 Decoder Board Stereo Audio HD Video Player MP3 FLAC WAV APE Decoding FM Radio USB TF Music player" and it's applicability to the "Poor Man's Go DJ" project, and other uses.
 
Other features and improvements over the more primitive player modules:

• They support Cryllic characters in filenames.  (Yes, I’m publicly admitting that I listen to Soviet Wave, and maybe even a little Russian Hardbass). Interestingly, they do not seem to support European accented characters (Like Ü, for example).
  

The CD-028 Media players support Cryllic characters in filenames.
NOTE: The light color of the right side of the screen is an artifact of the camera only.
This is not a deficiency of the screen.

• One of the repeat options is “random”, although it is random throughout the entire media. There does not seem to be a way to play the tracks in a single folder, for example.
  
• They display the track playing in a list on the left, and the full file name at the bottom right. (See bugs later.)  You can go to the next or previous track without leaving the “Music” function.  In other words, the same functionality of the JL players, however, navigating via the “Folder” function is also available.
  
• Quality -- They play 32 bit/sample FLAC files that the JL medial players would not recognize. Over all, the sound quality of both  players is very good.  I have not noticed any pauses or stuttering.
  
• The display is crisp and clear. The top-to-bottom viewing angle is good, but if the unit is observed from the side, the user quickly gets out of the optimal viewing angle.  I have not tried it in bright sunlight, but user expectations should be low in this regard.  Having color displays also improves the appearance of the "Poor Man's Go DJ".
  

In general, the “CD-028” Media Player modules are stable, and navigation speed and robustness is adequate, but like all devices in this class, they have their bugs and issues.
 
Bugs and issues:

• They feature a front panel power button, but it continues to draw almost 250mA while “off”. Current when on is about 350mA. With 2 players, and the analog circuitry, total current draw of the “Poor Man’s Go DJ will rise to nearly an amp, (almost 4 times what it is now.) External control of the power will be necessary for any battery powered or mobile application.
  
• There is an attempt at a spectrum display on the “Music” page.  It may look cool to the casual observer, but it is so slow that it serves no function. The spectrum feature cannot be turned off.
  

The Music display features an attempt at a spectrum display. This is so slow as to be meaningless.
It would have been better to use available processing power to improve the overall user interface.
NOTE: The light color of the right side of the screen is an artifact of the camera only.
This is not a deficiency of the screen.

• Like the JL players, the CD-028 board features software (DSP) equalizer presets.  While the better processor in the CD-028 allows for a little better equalizer effect, I still recommend leaving this feature off (“standard”), and using external analog tone control/equalization if desired.  There is no “custom” equalizer setting.
  
• They do not seem to recognize ID3 tags; only the filename and directory (folder) names.  While I did not specifically try including a playlist file, I am pretty sure that there is no playlist functionality.  The player does not seem to use album art, but if cover art is included as a separate file, it can be displayed by opening it separately.  Music continues to play while a picture is selected and displayed in the “Folder” function.
  
• There are display/graphical bugs including filenames displayed partially off the screen, and areas of the screen not being drawn, resulting in black rectangles (or as black as the display is capable of).
  
• The CD-028 will display picture files if selected from the “Folders” display. Doing so enables several possible slide show  functions, but if this menu is opened, it seems to get “stuck” to the bottom of the display, and overlays other functions.  The only way I could get rid of it was via a hard power cycle.
  
• The user interface is inconsistent. For example, the functionality of the >>, <<, and >| buttons are not consistent between navigating files and folders, and navigating the settings page.
  

 
The CD-028 modules are slightly larger than the monochrome JL based players, but they should fit in the Poor Man’s Go DJ with minimal physical and electrical modifications.  Of course since the cut-outs must be enlarged, there’s no going back. Once I do a little work to ensure that the increased current draw will not cause any problems, I will probably modify my project with these players in the coming days. Check back for updates and pictures.

The new incarnation of the "Poor Man's version of the Monster GO DJ" had it's first real job today -- again, a local Saturday morning car show.
 
It was a pretty good stress test.  It was a very hot Summer day here in central Florida.  There was no breeze for the first hour or so of the event, and the sun was low enough to come in under my canopy tent.  Between still having the Boost converter rated for 1A max, and the direct sun on a black case, the unit got very warm.  
 
The sunlight coming under the canopy also provided a test for the displays that are part of the CD-028 Media Player Modules.  They actually performed better than expected.  Using the high-contrast white-on-blue really helps.  It was definitely easier to see the displays on the PM GO DJ than the display on the Stanton SCS.4DJ.
 
So it didn't burst into flames, and I could see the displays, but did it actually play any music?
 
It did.  While the Stanton was there as a back up, I never even cued up a single track on it.
 
With the track progress indication, my mixes (simple fades) were much better, and there was only once -- for a few seconds -- that I inadvertently had an incorrect track playing in the background.
 
Pictures always make a post more interesting, so I'll finish this off with a simple graphic I made for this unit:
 

Who saw this one coming?:
 

 
Given the Stanton SCS.4DJ "Purchasing Incident", and the fact that I am obviously more than a little "Go DJ obsessed", perceptive readers may have foreseen a photo like the above eventually popping up here.
 
I regularly search eBay for a number of things, and after passing up a very reasonably priced Go DJ plus, I got the "Should've's".  So when this Original Go DJ came along at well under half what they normally sell for, I went for it.
 
...and I have to say that it is incredible.  Completely open, public admission:
 
                   It puts my "Poor Man's Go DJ" absolutely to shame!
 
Going all the way back to my Gemini Dual CD player with remote control head, I wish I had just bought a brand new, full price Go DJ, and never bought any other DJ player/mixer.  The elegance and functionality of the Go DJ is amazing.
 
So... With all that said, I still also stand by everything I previously said about the Go DJ and Go DJ Plus.
 
In the first post of this thread, I wrote: "The Monster Go DJ, cool as it may be, is also totally useless."  Maybe a bit harsh for such a cool product, but I stand by that statement for the reasons I gave at the time.
 
I also agree with the statement under "Reception" on the relevant Wikipedia page: "It has been criticized for its small size, which belies its feature set and likens it to a toy or game, and for its lack of dedicated hardware equalization knobs."
 
Lastly, I'll point out that even though I paid less than 1/4 of what it costs new, paying that much for a 2G MP3 player in 2022 -- no mater how cool looking -- is also complete lunacy.  (Although apparently people are paying far more ludicrous amounts for original iPods)
 
With all of the above said, I still like the "Poor Man's Go DJ", and here again are some points:

• I'd like to note that the PM GO DJ addresses both of the points of the Wikipedia criticism.  My PM Go DJ is a very good size for actual DJ'ing.  The analog controls are better for professional use due to their size, single functions, and layout.
  
• In addition to physical (and analog) tone controls, it has a dedicated physical master volume at the top right corner. Master volume should not be 7th function of an encoder wheel.
  
• Ability to play FLAC and other high quality file formats.
  
• Storage capability -- The internal 2G storage of the Go DJ is wholly inadequate by modern standards.  I do not know the size limitation of the SD card slot. My PM Go DJ has (2) 64G drives in it right now -- I use them redundantly since the players can't share storage, but it could be used as 128G total.  I'll also note that the PM Go DJ players can take larger drives, and can use USB drives and SD cards simultaneously.
  
• Physical Pads for effects instead of on a separate screen. (Yes, the Go DJ Plus has this)
  
• The VU meters on my version are far better.
  

The Poor Man's Go DJ project was certainly not a waste of time.  Despite lacking features like beat detection/matching and scratching (does anybody even do that anymore?) it is still a very functional digital music player.  I will be DJ'ing a car show tomorrow evening, and I still plan to use my "Poor Man's" version.  I'll take the real Go DJ as a back up.