swampman Posted September 7, 2009 Share Posted September 7, 2009 After some hairy moments at the end of the last season and a very long time in the nearest workshop due to failures with some aged Peavey & Crown amps I am looking to structure an orderly replacement plan:Economic times are not wonderful so priorites must be set:0. Start with the Bass (now critical) and head upwards...1. Reasonable price 2. Weight not so important3. Rack size ideally 2U per amp to squeeze it all in ! Current Structure each side:Bass bins 2*18" 600w 8R =1200W at 4R Three 600w Mids use 2*300w at 4R at present. They could be series rewired to provide a 600w at 16R load each which would then give 1800w at 5.6R A fourth Mid is to be added which would then give 2*1200w 8R loads Hi Horns: the PV260s do a good job with limiters incorporated: 80-130w at 8R/4R I have looked around for beast to work at these power levels and H-class amps seem ideal since the problems with Hi frequencies (above 2.5kHz) will not be a worry.We have been offered Yamaha P7000S, at a reasonably price/power ratio but my ears are itching for any sugestions or comments. Link to comment Share on other sites More sharing options...
Jivemaster Posted September 7, 2009 Share Posted September 7, 2009 http://www.bkelec.com/Pro/Amplifiers/MXF1200D.htm ---they are only 1U May meet some of your criteria. However given your forum location "south of spain" possibly a brand with local support would be a good choice. Link to comment Share on other sites More sharing options...
Simon Lewis Posted September 7, 2009 Share Posted September 7, 2009 H-class amps seem ideal since the problems with Hi frequencies (above 2.5kHz) will not be a worry. Might you expand on that comment? It's not a characteristic I've come across... With regards to your amp dilemma, I have a rack of Yamaha P7000s amps, and whilst not as "punchy" as (say) Crest CA series (and their ridiculously heavy "linear" power supplies!) I have found them to be versatile, easy to transport and (when purchased) cost effective. The price has gone up since then, so I'd be tempted to look at the Behringer offerings and check Rob Beech's posts on their effectiveness. Simon Link to comment Share on other sites More sharing options...
swampman Posted September 7, 2009 Author Share Posted September 7, 2009 Thanks for thoughts so far:Jivemaster: I looked up Bkelectronics since I have used their "plain simple reliable" modules in the past, a toolbox (literally) 2*110W fan cooled mosfet is regularly used as a replacement when sending something to repair - now 15years old and only two fuses blown on a shorted cable!Their web page does NOT lead to the amp you mentioned. However with no bridge mode it is still too light powered or did I miss something? The 400w modules also caught my eye but are not so "rackable" . Smon Lewis:After checking on the workings of the P7000S I looked up EEEngine and G & H class amps. They either modulate, switch, or provide four or more voltage rails+ ground to the final output stage or.... This explains the cost and why Crown (Amcron) QSC LabGruppen et al. high performance amps are brilliant for voltage/power and a complete mistery to understand without a diagram...The forums I studied expressed concerns about the transfer of the switching transients of the voltage on the rails to the outputs with the consequent effect on the sound and the possiblity of instability with the higher frequencies in audio and the need to switch the bus voltages for high loads to serve them.We also have to work with some pretty unpredictable power supplies. I read up on the BR about Nexo speakers not responding to well to the model quoted and wondered if the reason was the load: speakers are not resistive devices: the do produce heat & movement (resistance !) but also inductive loads (mainly the coil) and an assortment of artifacts related to the box, suspension, porting etc. U.P.S. and voltage inverters for caravaning TV, lights, fridges etc work well for a fixed frequency and possibly odd loads but a PA amp goes from 20 to 16000Hz+. I prefere the simple for servicing and will check out Crest locally. Behringer ceased to be traded by one ot my suppliers because of the difficulties with the tight "return to destroy and replace" policy they have and since manufacturing in China feel a bit thinner than their German origin equipement though I use a variety of good reliable bits of theirs.... but somehow amplifiers, I do not know - would a BMW made in China feel/drive the same as one made in Gemany !?! Link to comment Share on other sites More sharing options...
KevinE Posted September 7, 2009 Share Posted September 7, 2009 The forums I studied expressed concerns about the transfer of the switching transients of the voltage on the rails to the outputs with the consequent effect on the sound and the possiblity of instability with the higher frequencies in audio and the need to switch the bus voltages for high loads to serve them. Sounds like they dont know what they're talking about! Class G and H are well-proven designs and are adopted by most manufacturers from the budget to the high-end. Were these audiophile forums or Pro/PA websites? Link to comment Share on other sites More sharing options...
swampman Posted September 8, 2009 Author Share Posted September 8, 2009 KevinE: please have a look (at the 28 pages !) and comment. Some is coherent, some parts doubtful, others clarifying and some others r*bb**h. http://www.diyaudio.com/forums/showthread....ighlight=classs Just one of the things I dug up recently - though an audience with 3 pints beer /3 glasses of sangria is not really concerned with A B D G H J Klass matters anyway !! Link to comment Share on other sites More sharing options...
Jivemaster Posted September 8, 2009 Share Posted September 8, 2009 The link I gave does lead to the amp I expected. Look also at the http://www.chevin-research.com/ range of amps I had an A300 which is too small for your needs but the whole range is good on features and very light on weight also so well protected that it's hard to need a spare fuse. Go to their site and choose "A range" and look at the A1500. There are also some four channel amps there suited to some bins and tops applications, also some asymetric amps suited to running one amp at each speaker stack. Class H amps do fall down performance wise but at more like 300+KHz and the bats are not paying for tickets so they don't count! Link to comment Share on other sites More sharing options...
Simon Lewis Posted September 8, 2009 Share Posted September 8, 2009 KevinE: please have a look (at the 28 pages !) and comment. Some is coherent, some parts doubtful, others clarifying and some others r*bb**h. Indeed.... Quite a few comments point out flaws with earlier, superseded designs. Although there are differences in different supply and output topologies, the reputable manufacturer's designs represent good quality audio with high output capability in a dependable package. At the moment, I'm more concerned with the power sources you want to want / need to use. What's the story there? Simon Link to comment Share on other sites More sharing options...
swampman Posted September 8, 2009 Author Share Posted September 8, 2009 Jivemaster: Clarification with BK-electronics: their home page is click-on-graphic and the amp you sugeested is not linked in, it would not be found without knowing "it is there."About Chevin-research: interesting models, food for thought and the name seems familiar but the site is unfinished and there is no company info or supplier links... Simon Lewis: the thread mentioned brings to light the engineering challenges of designing non linear power supplies for audio, worthy manufacturers should have taken these factors into account in their designs.The power supplies are usually from mobile generators between 30kVA and 120kVA which have improved in stability in recent years but are usually supplying the lighting rig as well (the horror of doing some budget events); to avoid load instability we usually ballast load with 500-1000w halogen floods on each phase all the time. Othertimes we must make do with stadium power supplies on long lines.For example: one amp fizzled out (power transistor part) on either undervoltage when being pushed during a sound check or caused by an intermittent shorting speaker cable found when doing the post mortem checks. I have not done the voltage drop calculations but on that event it was a distributed speaker system about 2.4kW + 2 monitors + mixer + racks and a bass+guitar amp backline through a single phase 6mm of about 130mts (Edit: missed out the tennis court !). The rest of the afternoon went without a problem. Link to comment Share on other sites More sharing options...
KevinE Posted September 8, 2009 Share Posted September 8, 2009 Mm, the DIYAUDIO forum (of which I'm a member) does generate lots of audiophile consternation over 'our' side of things. I once argued that YES the Crown Macrotech MA5002VZ did have sufficient DC Bus capacitors, NO it would not be improved by increasing the DC bus voltages and YES it did have sufficient heatsink surface area. But it was a hard-fought argument! These are the people modifying PA amps for their home-cinemas so they sound more 'natural'. I think you can safely disregard anything said on the 'G/H is bad' topic. The PV2600 is class G. :) Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.