NV

I would be interested in a case, particularly if you can arrange for silk screening as well. Do you have a photo of your entire case pieced together?

I would certainly be interested in the possibility of a bulk order for the control surface PCB. Seeing as how you've mentioned that the PCB was originally designed with a 3U rack in mind (and similar to TK's control surface design), is it safe to assume that a design using the PCB in a rack mount enclosure could utilize the same Schaeffer files as TK provides (aside from the additional button row of course) or would other less obvious modifications need to be made to accomodate the PCB?

My PCB arrived today in great shape. Thank you for organizing and providing this service ultra, it's very much appreciated!

If you decide to organize a second batch in the future I would certainly be interested in participating. Hopefully there will eventually be enough interest to do so.

300mA should be plenty to supply the OPL3 board alone; the OPL3 really only needs less than 100mA on average, as you've seen from Thorsten's schematic. The rest of the MBFM is powered by the 5V supply in the CORE board, so as long as you're supplying enough power for the 5V then the bipolar PAiA supply should integrate well enough for most everyone's uses. The only reason you may need more is if you chose to utilize an additional bipolar AOUT, but even then the extra 200mA should very well prove sufficient to drive it. One concern would be that the kit utilizes a wallwart transformer, which is only really an issue if you want to keep things a bit neater from the outside and avoid having two separate plugs for the MBFM. However I imagine that most people utilizing this kit won't be interested in AOUT options, fiddling with transformers, or concerned about additional plugs, so for those purposes it should certainly get the job done in one clean shot.

My knobs arrived today with everything in great shape. Thanks again for organizing all of this Goblinz, it's very much appreciated!

Hi Doug, You may want to add the Curious Inventor store to your list for their small quantity solder offerings. When purchasing something like .031" solder it's great to buy a pound and be done with it, but I've never felt justified in spending ~$40 for .015" or .02" solder when such a small amount goes a long way. The Curious Inventor store (from the video at uCApps and on your Wiki) has .02" solder in 1oz. quantites for about $2.50, and 1oz. of .02" solder will last through pretty much all the SMD chips most Midibox builders will ever use. Here's the link if you're interested: http://www.curiousinventor.com/store/category/15 It's not 63/37 eutectic, but if you're only doing a few SMD chips then it should be exactly what you need at a fraction the price.

Thank you very much for your input Seppoman and Shum. I apologize if I stepped on anyone's toes here, my intention was just to make sure everything would work together before making any investments. As I mentioned earlier I have a solid amount of experience with DIY projects in general, but the concept of building bipolar power supplies is a new topic for me and one which I figured warranted more of a sense of perfection when dealing with potentially dangerous voltages. Shum's admirably detailed schematic has provided me with exactly the information I need to complete the puzzle. My original intent in this thread was to find accessible distributors for MBFM/SEQ capable transformers in North America, which after some scouring I have been able to locate. Once I've established more of a sense of what is actually in stock as opposed to carrying large hidden minimum orders I will post a list to assist those who may be struggling with similar issues. Judging from the many bipolar PSU postings in the MBFM forum, I feel this topic is often the primary roadblock for potential builders. As such I hope that much of the information in this thread will prove fruitful to others in bypassing that point. I hope my many questions did not prove too aggravating. I do feel quite comfortable with the topic at this point which is considerably further along than I was a week ago, so your efforts in assisting me were most certainly not in vain. Once I have nailed everything down definitively I will try to make something which may help others in a similar situation as I have found myself. Thank you all again for your considerable time and trouble and know that it is enormously appreciated!

Hi Shum, Thank you for your recommendation. Fortunately I have been able to find a significant stock of the transformer you mentioned, so that makes things much easier. Your schematic is especially appreciated since I can integrate it into the existing schematic I was planning with different capacitor values and minor layout changes to accomodate the parallel transformer and bridge rectifier. Is there a specific value you recommend for the bridge rectifier? While I have spent some time looking into voltage ripple and understand what it is, I am having trouble discerning what the effect would be on circuits such as those in the MBFM. I imagine reducing the voltage ripple would simply reduce noise and extend the longevity of the circuits, although I am unsure if this is entirely correct or if there is much more to it. Also, the transformer you suggested has a parallel output of 18VAC @ 1.64A. Using the schematic you provided, would it be possible or even advisable to use a transformer with a lower parallel amperage (such as 18VAC @ 1.1A or 700mA)? I am attempting to keep the total amperage of my MBFM and SEQ under 3A, although I can certainly go above that if it would lead to better overall performance. Given that the OPL3 and AOUT_NG boards have such a small amp draw of ~100mA each, do you think a lower amp output on the transformer would present any issues? Or does the swing from 18V to +/-12V affect the amperage enough for it to be a concern? Thank you for your advice!

Depending on the size of your design you will most likely not need nearly as many as 50, particularly with light as noticeable as purple/UV and the 20mA LEDs you specified (water clear, ultra brights). LEDs are cheap, and while you may not need to be sparing with the 200 pack you've purchased you certainly don't need to utilize any more than is necessary. Provided that you use all 50 LEDs without any resistive elements you'll be drawing 1A from your power supply, which is more than an entire Midibox in many cases. Using resistors you will be able to lower the current draw and thus the brightness of the LEDs, although the wiring of 50 LEDs and resistors is nothing to scoff at, particularly if you are trying to outline a display rather than simply grid them in a uniform pattern. I would experiment with a few LEDs at first and see how you like the appearance. Assuming your design isn't enormous (I'm thinking around 6" x 6" as a guess? Using 5mm LEDs?) you could probably use 12 LEDs with resistors and achieve basically the same result as 50, only with less wiring nightmares, less current draw, and less of a headache when it blasts on and illuminates your neighborhood through the window. Positioning the LEDs to accomodate their relatively small viewing angles and providing them with appropriate power and space should be plenty to illuminate your display uniformly without any dead patches. Just to give you an idea of how bright these LEDs can get, I have a flashlight with six 20mA 5mm white LEDs in it, and it can light up an entire room from 20 feet away.

Thank you all for your enormously helpful replies! To begin, thank you Shum for your transformer recommendation. I will certainly keep it in mind for future projects, although at this stage with my MBFM I have chosen to utilize a different transformer set. Regardless, I think it will prove very helpful to others who choose to utilize NLX's schematic for their projects and I will look forward to finding my own uses for it as well. Thank you for your help! To Stryd, thank you for your advice. I will certainly keep the possible power supply complications you have mentioned in mind. Should the schematic I am utilizing prove to be troublesome I will do my best to figure out where the problem lies for future builders. As for the 24V swing, I am intending on utilizing a transformer which will provide solid headroom amperage with that possibility in mind, so hopefully it shouldn't become an issue. To Seppoman, thank you for your recommendations. It's been very helpful to be provided with your suggestions so as to give me a general idea of what to be shooting for. Using the advice you have both given me, I have found the following two transformers: For Core Module: Type - Standard, 115V 50/60Hz Windings - Single primary/single secondary, no center tap Series Output Voltage - 9VAC @ 1.77A Parallel Output Voltage - N/A Maximum Power - 16VA Data Sheet For Bipolar Supply: Type - Standard, 115/230V 50/60Hz Windings - Dual primary/dual secondary, no center tap Series Output Voltage - 16VAC @ 1.25A Parallel Output Voltage - 8VAC @ 2.5A Maximum Power - 20VA Data Sheet I'm operating under the assumption that the combination of these two transformers and the bipolar schematic I provided earlier would provide adequately for the MBFM synthesizer and the SEQ, both with additional power requirements (AOUT_NG module for both, LED matrix breakout box for SEQ). Of course, if I am wrong feel free to let me know. Would 1.25A be a bit much for the bipolar supply? Would it be possible to go for something like 700mA, or would it be best to stick with something closer to 1.25A in case there is an issue with the stepdown from 16V to +/-12V affecting the amperage? From what I have learned, I feel quite confident in these two choices and am excited to finally move away from the power supply stage and back into the work of preparing and ultimately assembling my FM synthesizer, as well as plotting out the rest of my SEQ. Thank you all so much for your help, you have made this entire process so much more inspiring and informative!

I can understand your hesitation here, but I think the amount of time you have spent preparing samples and debating digital topics which you do not seem to fully understand is perhaps similar to the amount of time it would take to research and prepare the means to construct a streamlined MBFM synthesizer. DIY projects can be expensive of course, but one appeal of the Midibox projects is that they are quite modular so you can easily mold them to your needs. It doesn't actually take much time or money to construct a working FM synth - the price and time constraints don't really shoot up until you start building elaborate control surfaces and customizing them to your own desires. Since you have mentioned that you have spent time synthesizing within your computer using the OPL3 Soundblaster cards, I don't imagine you having any difficulty adapting to the JSynthLib SysEx editor. Using that you won't need a control surface and could fit the entire MBFM synth into a small box or corner. There are many people here who are willing to help out as long as you demonstrate that you are both willing to listen and willing to work. Perhaps you aren't intending to, but the topic of frequency-shift keying certainly concerns the matter. "Frequency-shift keying (FSK) is a frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier wave." Taken straight from the Wikipedia link you posted.

Alright...whew. So after analyzing the things you have both said and doing further research on my own into transformers and PSUs, I've decided that in the interest of preventing possible future problems and making my MBFM as efficient as possible I'm going to attempt to build a supply myself rather than utilize NorthernLightX's supply. My intention is to create two separate but identical supplies for both the MBFM and the SEQ. In order to do this, I will purchase a 7.5V transformer to power the 5V core, and then a 15V transformer and a schematic I have discovered from a few searches through the forum for the +/-12V AOUT_NG and OPL3. When I first discovered this supply I was a little overwhelmed by all of it and focused on NLX's instead, but now after learning quite a bit from you two and my own further research I think I am prepared to tackle it. At the very least it will be a growth experience. The bipolar supply is linked as follows: http://www.generalguitargadgets.com/pdf/ggg_bipolar_ps.pdf (Hopefully they will forgive me for posting it extraneously...) From what I have read this supply will more than adequately provide for my needs in both the MBFM and the SEQ, as well as being compact, efficient, and providing just what I need without unnecessary extras. Everything is quite clearly laid out in the documents, so if anyone would be so kind as to entertain just a few more questions to make sure I am on the right track then I would once more be in your debt: When powering the core module, I am under the impression that providing more than the recommended 500mA in order to provide some headroom does not present any problems with the circuit (such as providing 1A with a 7.5V transformer). Is this correct? I am under the impression that the MBFM and AOUT_NG require less than 100mA each to function properly (as seen here: http://www.ucapps.de/mbhp/mbhp_opl3_psu.pdf). Given that this is the case, I am assuming that a 15V transformer supplying more than 200mA should be fine with the above linked single-transformer schematic to power both modules. Since the supply is turning a 15V transformer input into a bipolar 12V output, will this affect the mA rating of the transformer at all? Is there a VA/mA range that may be recommended? When utilizing two separate transformers (in my case a 7.5V and 15V), how do you wire them up to a single AC line? Thank you both so much for all of your assistance. At this point I am beginning to feel quite comfortable with the entire subject, although I am well aware I still have much to learn. Regardless, it is fantastic having a resource such as this with patient and knowledgeable people willing to provide assistance to newcomers. Thank you!

The OPL3 is a digital synthesizer. It doesn't matter if you are playing it real-time, recording it, or running it through a karaoke machine - the OPL3 is a digital synthesizer. All digital audio is based upon sample rates and bit rates. 44.1kHz, 16-bit is CD standard. 96kHz, 24-bit is DVD standard. There are ranges below, above, and in between. If the audio was ever at any point in the digital domain (on your hard drive, on a CD, generated by a digital synthesizer such as the OPL3), then it was at one point digital audio with an accompanying sample and bit rate. In order for you to hear digital audio, it must be converted to analogue. This does not mean that it was never digital - if audio is generated by a digital synthesizer (like the OPL3), then it is a digital signal that must be converted to analogue in order for you to physically hear it. In the case of the OPL3, the digital OPL3 chip generates a digital waveform, which is then converted into an analogue sound by the YAC512 digital/audio converter chip. Therefore, if you hear any sound from an OPL3 synthesizer, regardless of what you ran it through, then it was at one point a digital signal with a sample and bit rate. After an audio signal has existed as a digital signal, whether it originated as a digital signal or if it was converted even if for a split second, any artifacts from that digital existence (a low sample rate, a low bit rate, an error in the sampling process) will remain with the audio even once it has been converted into analogue. These sonic artifacts (such as clipping, noise, or slight digital errors) are permanently a part of that audio unless you can find a way to carefully remove them. It may not be digital anymore, but the audible effects of its digital past are still there. When you created the samples you have shown us, there was a very slight difference between the left and right channels of the stereo file, which can be seen by viewing the 44,100 individual samples of the file itself. This could have been created by many things, one of which could very well have been the OPL3 chip itself. Regardless, this audio discrepancy became part of the signal and remains with the audio even once it has been converted into analogue. It's there when you record it, it's there when you play it in real time, and it's apparently there every time you have used the OPL3 digital synthesizer. This discrepancy appears to manifests itself in the same way every time, and that is the way that Stryd demonstrated in his earlier post. This discrepancy is the reason you hear the effects you are hearing when you invert the phase of the sound file you included. Please, try out his experiment for yourself and see what happens. It may make more sense to you after witnessing it first hand. I think that your difficulty in understanding what we are trying to say results from a confusion about how digital audio works. That's fine - digital audio is a dense topic, and it functions in a manner completely different from analogue audio. You can very easily understand one and not the other. However, it is a topic that can sometimes be difficult to fully grasp without diagrams and elaboration upon miniscule details. I sincerely hope that Stryd is able to piece together some sort of pictoral demonstration as I am unsure what else to say short of an extended discussion on the fundamentals of digital audio, which I believe may not be the best solution and would be better achieved through a book rather than an internet forum regardless.

Because the OPL3 is a digital synthesizer. It creates the waveforms using digital technology and then the DAC chip (YAC512) converts it into analogue so that you may hear it. Exactly, that was my earlier point - your karaoke device has nothing to do with the sample or bit rate, and therefore has nothing to do with aliasing, which in turn has nothing to do with phasing. Your karaoke device does not affect the sample rate of the original file at all and therefore has nothing to do with the effect described here; if you can hear it on your computer speakers, you'll hear it through the karaoke device just the same. As soon as you can hear it the audio is analogue, no matter where it is coming from. It is impossible to hear digital audio without it first being converted into analogue. The phase shift inherent to the file is something which exists whether it is in the digital realm OR the analogue realm. The stereo file you provided was a digital file and is therefore segmented into a sample rate. The individual samples of the left channel of the file in question are ever so slightly ahead of the right channel. The sound you are hearing when you invert the phase is a direct effect of this sample differential. The phase shift occurs in the digital realm, yes, but the fact that you can even hear it shows that the digital effects are manifesting themselves in the analogue realm where you can physically listen to it. You cannot hear digital audio since it is only binary code. You can hear it only once it has been converted to analogue audio. However, any digital artifacts that may affect the audio while it is still in the digital stage are still present once it has been converted to an analogue signal. I think much of your difficulty in grasping this concept is related to a misunderstanding of how digital audio works. I think Stryd has proven his point somewhat definitively. As Seppoman stated earlier, if you like the effect of inverting the phase of one channel then that is perfectly fine, but he and Stryd are both very much correct with their comments regarding the filtering of frequencies in the signal achieving a similar if not identical effect, sans the additional noise. If you do not believe them for whatever reason, then try Stryd's earlier suggested upsampling experiment. All the information you need to do so should be in the Audition manual.