Poor Man's version of the Monster GO DJ

[admin]

Originally Posted: Thu Jul 08 2021 21:35:24 GMT-0400 (Eastern Daylight Time)


New Player Modules Installed.



I have installed the new player modules in the "Poor Man's Go DJ".

Here are a few notes on other functions of these players:

• Bluetooth does not work at all.  Both Players have the same Bluetooth Name (CD-028), and they respond to a Bluetooth Pairing request even when not in Bluetooth mode, and even when not powered on.  There is no way to disable Bluetooth, and no way to change the name.  So if there are 2 of these players any where near each other (not just in the same box) they continuously attempt to pair and then disconnect.  See below for possible work arounds.
• The Microphone jacks on the PM Go DJ are no longer functional.  These modules do not support recording or an external microphone.  The internal mics (seen at the top of each player) are for a Bluetooth phone call only.
• Line-In does not seem to work either.  I connected the RCA Input jacks to the line input of player 1, but all I get is that same Bluetooth connecting sound.  More research into this issue is needed, but the result of this is that I currently have no way to play my phone through the PM Go DJ.  Connecting the phone to a separate mixer is the only option.
• As mentioned, the high power consumption of these modules is a significant problem.  In addition to the problem of reducing battery life, this causes two other issues:  1.) The 5VDC power supply (Boost module) currently installed in the PM Go DJ is only rated for 1A continuous, 2A surge.  2 modules, plus the other hardware in the PM Go DJ now add up to nearly an amp @5VDC, and thus well over 1A draw from the battery.  In addition, the built-in charger only charges at 1A, in other words, I am am likely discharging the battery even when powered from external USB power -- no matter the rating of the USB power source.  With both modules "off",  draw is still over 600mA, so I am charging the battery only very slowly.

A Little Good News:

• As long as the batteries and the boost module hold out, it works very well as a basic, improvised DJ player/mixer.  As I mention in both the YouTube video and post #20, Having at least some indication of time remaining, as well as stopping at the end of the track improve the usability of the PM Go DJ enormously.
• The Color Screens make the PM Go DJ look more like a contemporary product.
• Battery life should still be somewhere around 4 hours (assuming the battery can be fully charged).  Battery life would be significantly extended beyond that by using an external USB power source.
• It's even more fun to use and play music on, although due to the issues mentioned above, I would not rely on it to actually DJ an event right now.
• It still sounds great, and seems to have a little stronger output level if the media player volumes are turned up.

Solutions:

• The obvious solution to the additional load on the 5VDC boost module is to use a boost module rated for the observed current.  This is not a problem from a cost or space point of view.  I will order a 4A/5A rated module in the next few days and install it when it arrives.
• The charging problem can be solved by simply rearranging the power as it is in "normal" devices.  In other words connecting the power switch downstream of the charger circuit.  I like having a true battery disconnect from the point of view of both safety and shelf life.
• Another solution would be to install a separate power switch for one or both of the modules.  This would have several benefits:
    1.) It would likely solve the Bluetooth issue since one module could be completely shut down during Bluetooth pairing and/or operation.
    2.) It would allow faster charging by eliminating draw during charging.
    3.) A single player could be used when not actively mixing tracks, allowing much longer battery life.
• It may be possible to change the Bluetooth name of one (or both) of the player modules. Note that the Bluetooth chip is made by JieLi -- the same company that makes the main chip in the previous (monochrome) players. While it seems this is at least plausible, it is unlikely it is worth the effort.
• Another solution to the Bluetooth issue would be to disable Bluetooth on one module by simply destroying the JieLi Bluetooth chip.  Of course if this affects other functionality, it would probably be necessary to replace the entire player module.

Sadly, this is a classic case of an engineering trade off -- trading improved functionality in one area for less in another.

The "Poor Man's Go DJ" is still a very cool and nice looking (IMHO) project.  It is now more usable as a fun personal media player with analog controls, and a useable backup media player/mixer for casual events.

The ultimate project would be to combine 2 Raspberry Pi's with quality DAC's, and quality touchscreens with the analog hardware from this project. It would also need some good artwork, and lots of programming.  This would result in a consumer -- or possibly even professional -- grade product that could represent not just a replacement for the Monster Go DJ, but a significant improvement over it.

[admin]

Originally Posted: Sat Jul 17 2021 21:30:19 GMT-0400 (Eastern Daylight Time)


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:

[admin]

Originally Posted: Thu Dec 02 2021 14:58:31 GMT-0500 (Eastern Standard Time)


Previously in this thread, I have mentioned other products similar to the "Poor Man's Go DJ".

I have since come across 2 additional products that are even more similar -- Both bearing the "Technical Pro" brand name.  These units are particularly pertinent to this thread, because these units seem to share the idea of using simple, generic music player modules.


Technical Pro DJ2USB.  Photo from Manufacture's website



An even more basic unit seems to exist, or have existed:


Technical Pro DJ4PB.  Photo from eBay vendor

Given how basic the players look in both of these units, I'm going to say that they probably have similar or more limitations than either the original players used in the "Poor Man's Go DJ", or the new, color screen media players currently installed.

I want to be clear that I have never seen either of these Technical Pro units in person, and of course never used them, but I am confident that as with the project described in this thread, the Technical Pro offerings also lack features such as:

• Beat detection
• Speed Control, or Pitch Bend, Brake, etc.
• Scratching
• A-B looping
• Waveform Display

Note also that they do not seem to share the USB or SD card slots.  Like the "Poor Man's Go DJ", separate media for each player appears to be required.

I would hope that at the vary least, the media players display time remaining, but unless Technical Pro developed or modified the players, these decks (and it's quite a compliment to call them "Decks") may suffer from the same awkwardness as the players originally used in the "Poor Man's Go DJ".

I'd like to point out the fact that the DJ4PB has 2 microphone inputs with separate level controls, and Bluetooth on one of the players.  The DJ2USB has analog tone controls (although "High" and "Low" only, no Mid Range).

They appear to support only MP3 and WAV file formats.

There is no indication that either of these units will run from Batteries.

Am I publicly bragging or dissing Technical Pro here?  Well -- Yeah -- Maybe a little.  The "Poor Man's Go DJ" has been a very successful project.  It has more features, and likely better sound (when playing a better quality FLAC file) than the Technical Pro offerings.  It also has the 8 sound effect/beat/sample player.

The Technical Pro units win in terms of a mountable metal chassis, and microphone inputs.  I should also mention that Technical Pro also make players other than the ones shown here, and some of those do have more elaborate player mixers, and some support scratching/etc.

However, while Technical Pro has some very compelling and desirable Karaoke mixers/amplifiers, for casual events, they are not really known for living up to the "Pro" in their name.

[admin]

Originally Posted: Wed Feb 09 2022 11:49:57 GMT-0500 (Eastern Standard Time)


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.

[admin]

Originally Posted: Sat May 21 2022 14:59:50 GMT-0400 (Eastern Daylight Time)


So this project is finished (or is it?), but I still have a few updates:

1. I continue to use the Poor Man's GO DJ to DJ local car shows and other events. I prefer it over the Real Go DJ for the reasons mentioned. Most importantly it stays on the table. The Real Go DJ has no rubber feet, and very little weight. It tends to move around on the table when used, or pulled by the cables.
2. I use the Real Go DJ as a bedroom audio player, and a compact back up for events.
3. I have made a simple modification to the power system in my Poor Man's GO DJ so that the batteries remain connected to the charger module. The main power switch isolates the rest of the circuit. Some may say this is how it should have been in the first place -- and I'll take that. The load of the 2 media players was never allowing the battery to charge. I ran the unit on batteries last evening for almost an hour. I have a major event coming up in a few hours, (supposedly televised on 3 local TV stations), so perhaps making a change like this wasn't smart either, but we'll l see how it works. It sure wasn't working acceptably the other way.

More updates if/as needed.

[admin]

Originally Posted: Tue Oct 11 2022 15:34:58 GMT-0400 (Eastern Daylight Time)


Power System Upgrade

As mentioned in previous posts, the power system if the Poor Man's GO DJ was never really designed correctly.

The charger module (salvaged from a portable "power bank") was not connected as intended.  This was mainly for 2 reasons:
1. The module only supplied around 4.5VDC to a connected load, while it was charging the batteries.
2. I wanted to implement a full battery disconnect switch.

5VDC was produced by a separate Boost converter.  I later re-arranged the power so that the unit could be charged while powered off, but I was still having issues.

The Boost supply wasn't designed for powering a device from a Lithium Polymer battery.  It did not feature (for example) low voltage cut-off.  It would stall at low voltage, but still present a load to the batteries. Most significantly, It was only rated for 1A max, and with the new color media players, I was pulling much more than 1A on the 3.7 (Batter) side of the Boost module.  The boost module was also running (even with a charged battery) very close to it's minimum input voltage.  It was operating in a region well below it's best efficiency.  This made it get hot enough to warm up that entire end of the unit.  Even the USB drive in the left media player was getting quite warm.  I'm quite surprised that the Boost Module withstood the abuse.

While the Poor Man's GO DJ always got me through an event, and I never had to resort to the real Monster Go DJ or any other player/mixer, I knew I did not have a proper power supply or proper battery management.

I finally ordered one of these from a US eBay vendor:



This module is rated for 2A load, and 2A charging.  It produces 5.1V out during charging [s]or discharging[/s].  CORRECTION: See Next Post. It also features automatic power on and off, so the large power switch at the top left of the PM GO DJ retains it's functionality as master power.  The batteries can be charged with the unit (load) on or off.

I have been running the PM GO DJ for over 2 hours, and nothing is getting hot or even warm.

The original charger board remains in place. but the incoming USB power traces have been cut so that the only thing it is doing is acting as a mount for the USB connector.

The pictured module is currently installed inside the unit, and the 4 LED's are not visible.  I have ordered a small Digital Panel Meter (DPM) that I will connect to show battery voltage.  This will give me more insight into the condition of the battery than the 4 LED's or a 0-100% indication.  I will mount it in place of the 0-100% indication on the original battery board -- again using that original board only as a mounting support.

[admin]

Originally Posted: Tue Nov 22 2022 14:03:21 GMT-0500 (Eastern Standard Time)


The Poor Man's GO DJ let me down during an all - day Car Show earlier this month.  For part of the show, I had to switch over to the real Monster GO DJ, which also presented a problem -- I was set up in direct sunlight, and I couldn't see the displays of the real GO DJ.

I finally had to go sound off, unplug the real GO DJ, take it over to some shade, find the backlight brightness setting burried in the various settings tabs and pages, and turn it all of the way up.  I'll note that there is no contrast setting. Even with this done, I still struggled to see the screen of the real GO DJ.  I was not having any problem seeing the screens of the Poor Man's GO DJ under the same conditions.

As it turned out, once the Poor Man's GO DJ charged for a while, I was able to go back to using it to finish out the day.  It ended up only being 2 breif periods without music.  I still got paid, and I got several compliments on the song choices and sound quality.

So why did my Poor Man's GO DJ let me down?  As mentioned previously, the new, color LCD player modules draw a lot more power than the B&W screeen modules used in the original design.

While the charge/discharge module mentioned in the pevious post seems to power the PM GO DJ fine from the internal battery, it does not -- unfortunately -- maintain 5VDC output during charging.

When charging, the output voltage (to the load, not to the battery) drops to several tenths of a volt lower than the input voltage.

Given the length of wire from a 5 V USB charger, and the load of both charging the batteries and running the device, I end up with about 4.7 V at the USB connector, and less than 4.6V for what is suppose to be a 5V supply.

Typically, devices designed to run from a regulated 5 VDC power source have a tolerance of 5VDC +/- .25V.  So a voltage down around 4.6 won't cut it.  The player modules glitch or spontaneously re-boot.

I should also mention that the +/- boost converter that supplies the dual rail voltage for the analog sections seemed perfectly happy with this input voltage.  The failure is silent -- the music simply stops -- there are no pops, clicks, etc. when this happens.

So I still have the original problem -- I need a steady source of +5VDC at about 1 amp under all conditions.  This should be easy, but I have not found a module that will do this reliably.

Solution space:

1.  Forgo battery power --- After all, I am never going to do a DJ job on battery power.  All of the other equipment (except wireless mics) need external power available, so why shouldn't the player have the same requirement?  I designed the player to run from a battery only because the real Monster GO DJ has a built-in battery.

1a.  Power the PM GO DJ from an internal 5VDC SMPS.  SMPS's with more than enough current capability are redily available, inexpensive, and would easily fit in the current player.

1b.  Simply remove the battery, and rely on the power directly from an external USB source.  A quality USB charger and cable should provide the needed voltage without a problem.

2.  Down - then up again solution -- use a buck converter to drop the output of the charger module to about 4 V then boost it again to a stable 5.1 V.  The chager module would always provide enough voltage to operate the buck, and I have bucks on hand that are rated for the full load current even at 4V.

3. Up - then down again solution -- take the output of the charger module and boost it to ~8 V, then use a buck to make a regulated 5V.  Again, the charger module should provide sufficient voltage for the boost converter under all circumstances.  With a minimum of 4.6 V input, and ~8V output, the boost converter is working at lower currents than it was in the original design (when it was boosting the battery voltage), so it should be running in a more efficient range, and thus it should remain cool.

4.  One additonal Conversion -- Find a buck/boost converter that will reliably provide 5VDC output from inputs very close to that same value.  So far, I have not found this.  Most boost converters want the output to be at least 1V more than the input, and similarly, most buck converters need  the imput to be at least 1V more than the desired output.

5.  By using a very short USB cable, the charger module may provide enough voltage as-is.  I would then power the GO DJ from a USB power source very close to the unit.  If I can eliminate voltage drop in a long USB cable, I may be able to tolerate the drop through the charger chip.  As long as I can reliably stay over 4.8V, I should be good.

[admin]

Originally Posted: Wed Nov 30 2022 14:22:20 GMT-0500 (Eastern Standard Time)


I am basically applying the Infinite Monkeys Theroem to power supply design.

I agree that providing +/9 Volts and + 5 Volts from a Lithium Ion battery source is not complex these days;  However, I have a few constraints:

1.  I am not using a microprocessor to do the battery management, as is done in most devices such as the Real Monster GO DJ, a mobile phone,  or this tablet I am using right now.
2.  I am not making custom PC boards, or purchasing individual components.  I am limited to available modules/circuit boards.
3. The high power requirements of the 2 player modules.

I have basically returned to the original design with the following changes:

1.  I am using the 2A battery management board instead of the original Portable Battery Pack board.
2.  I am using a Digital Panel Meter (DPM) for battery monitoring instead of a 0-100% meter, or the LED's on the battery management board.
3.  I have added a small heat sink to the same adjustable boost module that I was using before.

Here is a current schematic of the Poor Man's GO DJ power system:



Note that +5 VDC for the DPM is provided by the Battery Management Board.  This allows me to check the battery voltage while the rest of the unit is fully off -- In other words, I can check both the no-load voltage and the loaded voltage of the battery pack.  I can also monitor the voltage during charging with the unit off.

Another big improvement was basically to make a low-resistance USB A - to - micro charge cable.  I cut a 10' cable, which used slightly heavier guage wire, down to about 4 ft.  With this cable, the PM GO DJ will now charge at 1.2A (up from 900mA using a regular USB cable.)

This arrangement seems to work adequately.  I have run the PM GO DJ for several hours without drain on the batteries.  The boost board still gets warm, but the heat sink is definitely helping.

Why not run the +/-9 VDC Boost either directly from the Battery Management board, or from the battery -- thus reducing load on the 5V board?  As mentioned in a previous post, when the Battery Management board is simultaneously charging and supplying power, the output drops below 4.75VDC, but it also seems unstable.  To prevent any noise, I did not want to chance running anything from this output.  Also, the +/-9 VDC Boost will not function when the input drops much below 5V.

Remaining problems -- There is still no real under volt protection.  If the unit is left on, the boost converter will stall someplace around 3.3V.   At first that sounds good, but when it stalls, it does not present an open or high resistance.  Boost modules of this design present a straight-through path when they stall.  This could continue to discharge the battery to a level where damage will occur.  The mitigation is the user's ability to monitor the battery voltage, and turn the unit off when the battery voltage is too low, or the players start to behave erratically.

I'm confident the PM GO DJ will make it through my next DJ Job, which is important, as I have a full-paying gig on December 3rd.

[admin]

Originally Posted: Sun Dec 04 2022 08:24:54 GMT-0500 (Eastern Standard Time)



QUICK UPDATE:

I DJ'ed for a 5 hour gig yesterday (Saturday).  The Poor Man's GO DJ worked almost perfectly for the whole gig, and using the new digital voltmeter, I could tell that the batteries were actually charging throughout the day.  This was the first time I was confident that power would not be an issue.

I should also mention that I was using a normal, unmodified USB mini cable, although it was a qood quality one.

I did have a problem with several MP3 files ending abruptly, but this is not the fault of the player.  There is a known issue with lame that causes wrong header information to be written to Variable Bit Rate (VBR) MP3 files, so if I miss running ripped music through vbrfix, this issue can result.  FLAC files are not effected.

Other than that, the day was pretty much flawless.  Nice weather, lots of very nice cars, and -- Food Trucks !!, One of which donated a fried shrimp meal to me.

The real GO DJ?  It stayed in the truck.

[admin]

Originally Posted: Mon Apr 10 2023 16:01:52 GMT-0400 (Eastern Daylight Time)


So I keep learning about other similar products.

In addition to the 2 Technical Pro Products described here, I have discovered a number of others.

What I will describe here are all similar in at least the basic form factor.  They are rack mountable Dual MP3 players/mixers.  As far as I know of this writing, they all fit in a 3U rack space, but are also designed to be operated just laying flat on a table.  They are likely intended as a "drop-in replacement" for the control head of older Dual CD Players, but of course not needing the separate (also rack mount) Dual CD Player (Drives).

It's not my intention to single out a particular product, but I am going to use the PYLE-PRO PDJ480UM as most typical of these products.  It is pictured here:


                                                              PYLE-PRO PDJ480UM  Photo from Pyle Website

PYLE-PRO PDJ480UM
The same product (although unbranded) seems to be available from Chinese manufactures/vendors listed simply as "DJ Controller, Supports USB and SD Card Player".  I have also seen what appears to be the same product branded as the "UC3".

Numark DDS
This one appears slightly more elegant than the other products mentioned here.  It has a single Color display in the center.

Pyle-Pro PDJ450U Pro DJ Media Player Controller
Another Pyle branded product, and like the Numark DDS, it has a single screen in the center.
The same product seems to be sold as the T&W International Audio Co.,Ltd SDJ-1000US  as well as possibly other identities via  various Chinese Vendors.

The next several products seem to be the same device with different cosmetics and branding:

American Audio SDJ2
JB USB 900  (JBSystems)
Citronic MPSD-2
OMNITRONIC MMP-1 SD/USB
UD999 (Unbranded)

The UD966 (Also Unbranded) seems similar.

Another one is the American Audio SDJ1 / SKP Pro Audio USD-2010 /  DJ Tech S1.  The same device may also appear with additional names/branding.
Note that these devices are just dual players with separate outputs.  They do not have mixers, faders, tone controls or Mic inputs.  I am leaving them on this list because they are similar devices.

Note that this list only contains self-contained units that do not include or attach to CD players.  Many Dual CD players/controllers will play MP3 files burned on to a CD.  This list would be much longer if I added those.  (Note reference to my Numark Mix Deck Express referenced earlier in this thread.  I also have a Gemini Dual CD player with remote head.)

It is very possible that all of the devices listed on this page are obsolete, although some seem to be available.

Note that none of these devices seem to have nearly the sophistication of the Go DJ / Go DJ Plus, such as the spinning record animation or waveform displays.

None of these devices are portable/battery powered.

Note also that newer, high end devices, such as the Denon DJ Prime Go are not on this list.  I consider them to be in "Their own class" (and I'm sure Denon would not want the DJ Prime Go on a list with $150 obsolete products). The Denon DJ Prime Go was mentioned early in the thread.

If you have any additional information about the devices mentioned here, or other similar Dual USB/SD players, please register. If Registration is not working please try back in a few days.