The Parasound and krell have enuff outputs to build you 10 Centurion's , so i beg to differ and yes i can prove it will hurt dynamics, easy to compare with and without, i have done the comparision enuff to be confident of the results..
I would prefer to use a slightly undersized transformer to protect outputs, amplifiers done this way, have better performance when asked to stretch themselves as oppose to output watchdogs ..
On my 3rd Suspension airbag my range rover days were Over, yep over deh
Rover , dem say ....
Ohh , Nige, I want to upgrade my LP12, so I'm going to give your LP12 posts a look over, any additional info would be appreciated ..... !!!
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The Parasound and krell have enuff outputs to build you 10 Centurion's , so i beg to differ and yes i can prove it will hurt dynamics, easy to compare with and without, i have done the comparision enuff to be confident of the results..
I would prefer to use a slightly undersized transformer to protect outputs, amplifiers done this way, have better performance when asked to stretch themselves as oppose to output watchdogs ..
Well then, use one of them by all means.
As for the difference between with and without protection circuits, I have to say I have been honing that particular circuit for some 30 years or so. The things I have done to it would probably qualify me for a long stretch behind bars for unnatural fornication. In return, I think it's fair to say that I have a complete grip on it and can make it do exactly what I want, just as I want it done. It is, in fact, a classic dual slope circuit with activation time delay, but with virtually immediate cutoff once the danger has passed. Not perfect, of course, but heading there. It's simple, clean and clear.
That said, I repeat - it can be left out completely with absolutely no effect on the amp, however, by leaving it out you assume all responsability in case of a short circuit or some such, in which case your speakers might well become history.
I should also warn you that I have seen quite a few speaker drivers rated at say 100W continuous and say 200W peak programme material fry at just 40 or 50 Watts of solid power. People are frivolous with specs these days, and that's the lurking danger you assume when you throw out the protection circuits. My job is to provide them, and it's up to the user to decide whether he'll use them.
To that end, I also privided the optional visual indication of the output voltage. Far too many people have no idea what it means to the amp when they switch the loudness on and then turn the bass control to the max. They have no idea that they are asking the amo for an extra 20-22 dB of power in the energy hungry low range, because they want to "rock". That indication is there to tell them what they are doing and to back off before permanent damage is done. As I say, optional - if you don't want it, don't fill in the parts, you can do that later on if you change your mind, it's just a few resistors, diodes and LEDs, plus one IC.
Lastly, the matter of transformers. Again, you are free to do as you please, right or wrong, and what I think of it is of no consequence. In my view, the transformers and the subsequent power supplies are the last place to save money. I believe in big transformers, which will hold their ground even under the most stressful conditions; while I lack most of what you people have in USA, thankfully I have four manufacturers of toroidal transformers locally, and they will all do as told. The quality of the toroids is best seen by their rather small regulation, the 500 VA models have just 3% of the nominal voltage difference between load off and full nominal load on. Tried and tested many times.
But again, you do as you think it should be done. That's the fun of DIY, much is left for you to decide.
My rule of thumb is class AB is 50 % efficient . 2 x 100 watts 8 R needs a minimum 500 VA . That allows any load to be driven . Forget 6 to 1 crest factors as Tecno music ( Carlsbro style ) is 3 to 1 . Transient 1 R stereo load as a possibility . If one 300 VA transformer per side that is better still . I still think these ratings a bit on the mean side if driving complex loads . The Quad 405 used 300 VA stereo for 2 x 100 W . That's a bit mean and says 4R and above .
D,
So you prefer to have the v12 with a governor at 150 , while I'm saying more fun is to be had from that turbo 4 which tops out at 155 ....
Personally i have never lost an amp or speaker in 40 yrs at this, including when i did PA systems many moons ago, so feel free to name names of these fakes speakers. Over the years i have had all sort of and type of speakers and amps, Amps with nanny on board never ever worked for me, its says toy and since this is DIY , why not go for a sonic treat, whats the big deal D ...
Anyway dont get this wrong D, I'm playing devils advocate, hurry up with this so i can give this a try , of course a little more outputs would help , i think i would roll mine with 5 prs, would be nice , you know SOA and thing ...
So you prefer to have the v12 with a governor at 150 , while I'm saying more fun is to be had from that turbo 4 which tops out at 155 ....
Personally i have never lost an amp or speaker in 40 yrs at this, including when i did PA systems many moons ago, so feel free to name names of these fakes speakers. Over the years i have had all sort of and type of speakers and amps, Amps with nanny on board never ever worked for me, its says toy and since this is DIY , why not go for a sonic treat, whats the big deal D ...
Anyway dont get this wrong D, I'm playing devils advocate, hurry up with this so i can give this a try , of course a little more outputs would help , i think i would roll mine with 5 prs, would be nice , you know SOA and thing ...
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D,
So you prefer to have the v12 with a governor at 150 , while I'm saying more fun is to be had from that turbo 4 which tops out at 155 ....
Personally i have never lost an amp or speaker in 40 yrs at this, including when i did PA systems many moons ago, so feel free to name names of these fakes speakers. Over the years i have had all sort of and type of speakers and amps, Amps with nanny on board never ever worked for me, its says toy and since this is DIY , why not go for a sonic treat, whats the big deal D ...
Anyway hurry up , so i can give this a try , of course a little more outputs would help , i think i would roll mine with 5 prs would be nice , you know SOA and thing ...
This ain't smorgasboard, Wayne old buddy. We don't do special orders and one-off amps without some serious cash exchanging hands. This one I did as I did it, it's simply take it or leave it. A special one would have to go practically from the start, new filming, new artwork, new samples, testing from scratch all over again - that's serious work.
As for hurryuing up, remember, the Centurion is FUN, not work, so it takes a back seat to my regular duties. But yes, I will work on it as fast as I can, and yes, you can have the gerber files so you can make the boards locally. In the end, there will also be a Bill Of Materials (BOM) for it, with some notes and pointers for asembly.
Nige, just making sure we all got it right here - I plan on using 500 VA toroids as one per channel. So, a stereo amp would contain two such transformers.
The only amp I ever lost without protection was a C&M labs unit that had stability issues. It seems the B+ fuse was weaker than the JBL's I had back then, so only the amp failed. I do some basic risk abatement; bananas that have a separator prevents them from touching. Things like that. I think all of my current amps have protection except my Creek, and I have a board I am putting in that. Protection is hard. Getting rid of the cap charge fast enough without it going through the outputs is a trick. Fuses and relays are too slow. With really big expensive triacs, one could crowbar the power supply. Not cheap but that is the best idea I have come up with. I think I would rather put in so many outputs that they could take a dead short and drain the PS without damage. Then a crowbar across the output could save the speakers.
Me tinks you getting the wrong Idea D, its a discussion, not a hop to it ....
I might have taken you too seriously
, er, literally. Sorry!In principle, I would do it for a friend if I had more time; as is, telling someone they have to wait for it a year or so isn't too reasonable, is it?
If you remember that German made LAS amp I keep harling about, way back from 1977 or so, did use TRIAC protection to cut off the power supply.
But this is a much bigger deal we are really talking about here. Every solution has its own issues. Yes, at current prices of output devices, I could add a few pairs for the hell of it, but remember, parallelling many devices solves some problems, but is not without its own issues. You also parallel their capacitances, and there is the issue of matching them, they require still bigger (and more expensive) heat sinks, and so on.
Also, I think the key issue here is one's initial standpoint. You guys are assuming full power levele output over protracted periods; I assume a typical home use, which allows for transients of at least 6 dB, which means this amp will normally dissipate no more than 25W on any continuous basis, only occasionally dissipating more. Given that I use nominally 200W devices, which gives me a theoretical power capacity of 1,200W, I would think that's sufficient for actual 25W dissipation. Even assuming the heat sinks get to say 65 degrees, that would be 85 degrees inside the trannies, and using Motorola's derating curve of 1.43W per degree above 25 C, the effective power capability is still 6x114W, or 680W in total. I feel that's more than enough for just about everybody using any setup - begging your pardon Wayne, but your 1 Ohm speakers are all but common.
Lastly, you gents are talking about what you would do for yourself. But a project like this one has to consider far more variables, some of which you can't even imagine. Much like safety regulations - take a long look at any of them an you might be surprised at gthings you see there and may wonder do the lawmakers think you an idiot to even write that. Actually, they don't think you an idiot, but they damn well know there are such idiots out there, and that was written for them, not you.
Same here - I have to cater for all sorts of people who might want to make it. I have to assume I'll have a typical distribution of possible users ranging from you guys on one side to absolute morons on the opposite extreme, so I have to cater for all.
Just as an example, if I was doing it just for myself, given that my speakers are an exceptionally easy load to drive, I'd make some changes. I'd take the higher PSU supplies because my speakers do not go below 6.5 Ohms, so I don't need terrific current capability. I seriously wonder whether I even need a triple at the output, I think two pairs would be just fine, especially so as my speakers are also relatively efficient at 92 dB/2.83V/1m.
Heck, my H/K Citation 24 amp has just 2 pairs per side, and it has all the current capability I would ever dare throw at a speaker. And still manages to be a supremely neutra amp, definitely one of the most neutral amps I have ever heard - that's what made me buy it in the first place.
Bigger is not always better by default.
That is what practicality says . As you are saying 100 watts 8 R it looks that your amp will sustain 1 R with ease ( music ) . As you say 2 R it will genuinely drive . 500 VA is the point where transformers do not return much for the money spent going larger . 2 x 500 VA better than 1 x 1200 VA for example . I could write on this for pages . Better for everyone I don't as it won't say more than this.
I might have taken you too seriously
In principle, I would do it for a friend if I had more time; as is, telling someone they have to wait for it a year or so isn't too reasonable, is it?
It would be easy to add extra outputs to your current gig, your driver stage will handle 5 prs , I was surprised you never went with 4 pr originally , seeing you are Mr load tolerant .....
PS: I do have other speakers chap , some even as benign as 8 ohm 89db/w/m , guess which type of amps sounds best with those...
It is highly debatable . I did mean 2 x 500 VA better if using commercial off the shelf designs .
Cross talk I suspect never happens . Undersized is the only question ( cross theft I would call it ) . I am assuming separate windings if so . In fact 3 winding sets would be best . Left , Right , Both drivers . 1000 VA .The problem is that becomes a specialist winding . No one know knows how to do it will be cheap . I suspect 2 x 500VA and 1 x >100 VA driver would be optimum use of money . The 100 VA can also run pre amp functions .
Cross talk I suspect never happens . Undersized is the only question ( cross theft I would call it ) . I am assuming separate windings if so . In fact 3 winding sets would be best . Left , Right , Both drivers . 1000 VA .The problem is that becomes a specialist winding . No one know knows how to do it will be cheap . I suspect 2 x 500VA and 1 x >100 VA driver would be optimum use of money . The 100 VA can also run pre amp functions .
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