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kipman725

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Everything posted by kipman725

  1. It would be easier to design a new amp to be honest using the principles, the patents must be expired by now. Here is an explanation of the grounded bridge: http://aetechron.com/pdf/grbgpapr.pdf Class-H doesn't have to be heavy if a SMPS is used to supply the power rails: https://www.abeltronics.co.uk/amptesting.php?z=crest_audio_PRO-9200
  2. Void used to have their own amp designs up to and including the X series (X6/X8) but now rebrand Powersoft. QSC amps have the capability of combining amp channels in parallel:, series and series parallel: https://www.qsc.com/systems/products/q-sys-ecosystem/products-peripherals-accessories/network-amplifiers/cx-q-series/cx-q-8k4/?L= The MA5002VZ is kind of the ultimate class AB (ish) amplifier (just check its specs, very Hi-Fi). It has a circuit topology called grounded bridge which doubles the effective voltage swing of the power stage and also a circuit that series stacks the power rails. The end result is efficiency like a class-G amp (switched rail) but with the performance of a lower voltage class AB amplifier (no rail switching events, lower voltage faster output transistors). It also includes extensive monitoring that models the thermal reserve of the output transistors and keeps the amp in safe operating area. That means if its working right you can just load it up with parallel sub drivers until the Ilimit lights start to flicker or the amp starts to thermal limit. However to do this lots of the circuits are floating and there is a lot of complexity (no microcontroller) so when the amplifier goes wrong its hard to fix at a component level. Fixing the amp at the module level is very easy though due to extensive diagnostic indicators and easy disassembly. It would have been very interesting is Crown had made a SMPS version of the MA5002VZ as almost all the weight and bulk is due to the transformers, it would have been very competitive with class-D amps (although perhaps not in cost due to the large number of transistors required).
  3. Do you have a MA5002VZ? I have a couple in very bad shape that I'm trying to fix and as they have previously been fiddled with and there are discrepancies between the service manual wiring diagram and the silk screen I'm unsure if the cables P500 and P501are in the correct positions (there are another set of cables underneath them) (this is how it came to me). I did some basic checks against the MA5000VZ schematic on the pin outs and I think this is correct... As for parallel mode like lots of the design of this amp it doesn't make sense to me as at least at the time it was launched the available drivers had 8 ohm voice coils so for it to be useful the amp would have to be loaded with a ludicrous number of drivers. The very large number of parallel transistors approach was used with amps like the Void Infinite 8: https://www.abeltronics.co.uk/amptesting.php?z=Void_Infinite_8_mk2 *on a side note the forum upload limit seems to have been reduced to 0.08MB!?!? (my picture didn't seem to work as well - try https://drive.google.com/file/d/1iQ59CYpxIum91ivtv0ULTfLJV3aFF2jt/view?usp=sharing )
  4. I understand where your coming from, when you hear a well set up PA system at decent volume there is no going back to home Hi-Fi and even if you have the speakers at home the space is too small and the neighbors too close. My situation is actuality pretty similar to you, having spent my whole life not going out much and when I did hearing pretty crap PA systems (line arrays etc) I went to party with a big stack of relfex subs and orbit 4 tops which sounded like an infinitely powerful Hi-Fi and was instantly hooked. Since then I have heard quite a few good systems but never at the larger more commercial gigs. I think I started building up my system a few months after that first time and also started with sealed subs but have recently rebuilt them as reflex due to box heating issues and optimisng for more output in the >30Hz range. For me the reflex is a big improvement but I'm running them pretty hard for 12+hrs. I have only really started building up some contacts in the past year, not been an especially outgoing person. A good way to meet people is to attend local music events and talk to the people running the system (although not possible at this time). A possible issue you might encounter is where I am (North West UK) is a lot of venues have license clauses preventing the use of external sound systems due to historical noise complaints, may not be an issue but its worth looking up your local licensing situation.
  5. I don't have any stuffing in my ported subs as I figured it was pointless with one driver operating magnet out. I only get noise out of them if pushed beyond xmax or if they are pushed at the tune frequency with sine waves (air noise).
  6. https://bonsaihifi.co.uk/ is a similar idea and pretty fun but I don't know how it would be possible to make money from such a thing unless you have a lot of existing contacts (Rich people house parties?) it also won't work if you have to space people out, no one is going to start spending 4x as much in a recession. I can confirm though that people are in general very keen on the oiled wood aesthetic compared to the normal PA black paint so this is a good idea (although less durable). Up to the point you run out of power, money or weight allowance sealed boxes will give the most output per unit volume but in PA use the lack of air exchange can be a problem as the air inside the box gets hot.
  7. these are very solid numbers, if it could avoid blowing up it would probably be OK with 2ohm load. What kind of instrumentation are you using on the supply side?
  8. Pro gear like Behringer DCX2496, Symetrix 8x8 DSP, QSC QSys are often better value for money especially second hand. I run an 8x8 DSP which I have modified for silent operation by replacing the top of the box with mesh and replacing the fan (by using a 12V fan and a 24->12V buck converter).
  9. It sounds like you don't have much space in which case the most compact solution would be equalized sealed boxes. Multiple subs are one of the best sound quality improvements so for home use I would prioritize more smaller subs over a single large sub. Outboard DSP/DSP amps are quite easy to use, you can just enter the coefficients from REW into the parametric EQ. Berhinger Inuke/NX are powerful and cheap but have noisy fans so you would want to locate them in another room. There are also plate amplifiers with DSP available which could be an option if you don't want any large/nosiy equipment.
  10. Flat frequency response is not the most important characteristic considering that room modes have far greater effect. Most people here are running room equalization and house curves so beyond giving an indication of the minimum frequency where sufficient output can be coaxed from the sub the frequency response isn't very important. A flat measured in room response will sound thin and overly bright on electronic music, a typical house curve would be -1dB/octave for general purpose playback but I would add significantly more bass boost for playback at 'party levels' (~95dB A weighted average) of electronic music.
  11. Looking at the VBSS thread it looks like the xmax specified for the PA460 is geometric and so the usable excursion is a bit greater than specified: https://www.avsforum.com/forum/155-diy-speakers-subs/2226642-v-b-s-s-diy-subwoofer-design-thread.html
  12. This may be a concern or not but the SAN214.50 will have more resale value than the many PA460 option and if your needs change IMO is the more flexible option. This is assuming that you only have two locations to place subs, if you have lots of locations for subs making many PA460 subs would be the best option for even bass throughout the room. I would recommend Hornresp for simulating sub performance, its quite easy to use once you are used to the weird interface.
  13. So I wouldn't go as extreme in some ways as that pdf suggests, the bass boosts are way too much and will make a system sound like mud if you actually follow an equal loudness contour. However the tip "110 - 120dB 2.6kHz -5dB BW= 0.34 Q= 4.233" is totally spot on if your playing dance music and system sounds a bit harsh. My procedure for dance music is: 1) system has existing PEQs that make it flat on axis 2pi 2) play pink noise and adjust aiming of speakers to maximize stereo image area (you could get a distinctive whooshing noise in this area) 3) perform spacial averaged measurements in room 4) fit system response to overall room trend (usually about -10dB at 20 kHz) using PEQs 5) start playing tracks and tweaking, normally all that's required is the above and a some bass boost depending on the room perhaps a PEQ at around 50Hz to apply a small amount of boost 6) configure input compressor with 10:1 ratio and slow attack and release times with pink noise at the point the limiters are starting to be occasionally triggered.
  14. the 93Hz (actually 91Hz sorry) is a bit of an in joke, hit someone with 120 dB of 500 Hz and you still get TR: https://forum.speakerplans.com/uploads/8883/Void_System_Tips_EQ.pdf my sub section is 4*15" reflex (soon hopefully 6*15") and my tops (in total) are 2*15" reflex (with a way smaller amp) so it makes sense to keep the crossover high. Another type of user who keeps the crossover high is someone using fully horn loaded tops as usually the horns are too small to have good efficiency at a low sub crossover point.
  15. I use a 120Hz crossover to my subs in my PA system LR4 slopes, I match the sensitivity of the subs and the tops so this is also the acoustic crossover frequency. My tops do play down to 80Hz but I want to keep the thermal load off them and reduce the chance of clipping their smaller amp. A lot of PA's (essentially everyone I know personaly who isn't running a large touring sound company) will use an 80Hz electrical crossover but then tune the sub amp sensitivity by just turning it up until it sounds right. This adds an effective bass boost and puts the acoustic crossover typically around 150 Hz. Another reason I like to cross at 120Hz is I actually want a mono source for 93Hz which is the frequency that rattles the chest, subs can be arranged for best coverage but top locations are more fixed for stereo image . The kick drum in Bicep - Glue is at 53Hz If your interested in tests that might be applicable for higher frequency speakers I find knowing the residual noise with no signal interesting as some amps hiss too much to be used on compression drivers in quiet environments.
  16. The leads can be preformed but this is an additional manufacturing step so would add cost. In this image of a real LG amp I found they are also soldered on top but the pads are more surface mount style. This image is actually quite surprising to me as lots of the components look very 'retro' (blue axial leaded capacitors!).
  17. thats odd, it looks like the leads are meant to be bent through the holes but have been cut too short. Also where is Q50?
  18. Have you checked the relay is open when the amps switched off? the contacts may be welded shut Also what amps do you have to test?
  19. Two minutes of full output it too long in my opinion, sure the amp should survive but it doesn't reflect real world operating conditions and as such the 'thermal reserve' (to use the MA5002VZ terminology) is typically insufficent. When testing the Crown CTS4200 which is an SMPS class AB the amp started to thermally limit at 1:30 of full output on a single channel. "The longest duration of more or less uninterrupted bass was 28 seconds with a pretty low crest factor." I feel this is towards the upper end of what is asked of amps. Contrast is needed in the music so going on much longer than 10s has diminishing returns. Yeah my amp looks quite close to what Powersoft is dong, much less sophisticated and not full range but similar results. I would love a couple of X8 but I don't think that's happening any time soon.
  20. I'm in the UK where the most common power is 240V, 13A so that's my initial target*, but if I can complete the project I will try and do universal PFC. Basic topology is: 240VAC -> 3.5 kW boost PFC (390VDC output) -> three phase buck converter operating in average current mode control (this is where the maximum current regulation occurs which in turn will regulate the line current) (300VDC bus, that drops under load) -> Full bridge IGBT based, low switching frequency class D amp Input is digitized and a look ahead limiter with trajectory estimation on the rail voltage is used to avoid clipping. The buck converter is using microprocessor control so the maximum current can be set based on the available AC power and there is the possibility of lowering the 300VDC bus for IPAL compatibility. Another feature is no mains isolation to increase efficiency. Its early days at the moment I am working getting the buck converter stage test boards produced. One issue is actually testing this properly is going to require a really big electronic load! *I have made power converters before up to 90kW continuous output so I'm OK with going to higher currents but I don't have the facilities or test equipment at the moment and things get very expensive fast.
  21. My commiserations on blowing the amp I have also had an amp blow during testing (DAP Audio Qi-4600), nothing aggressive just sustained 4ohm load on one channel. I then proceeded to totaly blow it trying to fix it. Forgetting that it had a bipolar supply I hooked the scope probe up to the negative lead of a decoupling capacitor, shorting the power supply and unleashing a spectacular fireworks show. My view is that if an amp fails like this its better than failing in a more critical situation and/or taking out speakers (the DC protect did not work on the Qi-4600, relay jamed shut). My main lock down activity has been working on a new subwoofer amp that addresses the stout AC line issue by using a current limited supply and large capacitors. The idea is that it never pulls a line current over a preset maximum but has huge transient energy reserves. The attached PDF shows the basic idea. Bass_hit_analysis.pdf
  22. with the +19dBu issue quite a few amps are designed to give their maximum output at 18dBu input. So the input of something connected to your interface output could have some input voltage protection circuit that's causing distortion
  23. Ah great I have added them to the list, I started the thread after getting a load of Cloud VTXs home and finding they where so loud that I could hear them clearly several rooms away from where they where on with a closed door! subsequently I fixed a few of the amps and found they had failed because the airflow over the circuit board in one particular location was so strong it had worn away the track that switched the output relay.
  24. This is the best design I have seen so far. Especially for the compact size and ability to have such a wide selection of loads. I attach an image of my load bank which sits at the other end of the quality spectrum and is just a fixed 4ohms. I tested a couple of amps with this load here: https://www.diyaudio.com/forums/pa-systems/339848-quiet-pa-amps-5.html
  25. Performance looks great, more output than my subs in half the size. You also don't have any deep cancellation notches from the port pipe mode.
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