Thanks blmn, but I think I will continue with my AB design as long as I think it's reasonable enough (believe me, that doesn't have to be very reasonable). 🙂
I'm a little worried about getting all my output transistors to cool evenly. If you saw my plans for mounting and heatsinking, you'd know why. I might have to use liquid cooling.
Audiofreak, not to be impatient, but when are you going to post on multiple outputs? You said you would.
I'm a little worried about getting all my output transistors to cool evenly. If you saw my plans for mounting and heatsinking, you'd know why. I might have to use liquid cooling.
Audiofreak, not to be impatient, but when are you going to post on multiple outputs? You said you would.
Sorry Kilowatt been rather busy the last few days.....
here goes....
To use multiple output stages from one front end there are a few ways you can go about it.
1. This is the obvious solution ... make a driver stage capable of twice the current then use resistors to ensure that each output gets approximately equal current .... problem with this in a hi power amp is that the current sharing between the output stages is exactly that APPROXIMATE! kinda like a lick and a promise. Not what your after
2. Make the front end fairly normal and put a buffer (unity gain) at the input of the output stage .... this ensures that each output stage gets equal current because the current is being drawn from the buffer not the front end and the front end is never taxed to supply current beyond its means. this of course means extra devices 🙂 there's always a trade off.
also remember this .... you dont necessarily need a driver stage .... you could run the outputs direct from the Voltage Amp.
If you go this route connect only one output stage at a time and make sure it works well and is stable (start off at very low power!) then do the same for the other before connecting both.
+/-150VDC will get you 1875W RMS into 6ohms.... hope those rails are stable 🙂
You will need a current sink in the input stage to ensure that the turn-on/turn-off thumps dont hurt some of your speakers.... i am not kidding.
Use a cascoded input stage to keep dissipation to a minimum and bootstrapping for the driver stage (Class AB) to minimise distortion.
You might also like to look up the info available about the H-bridge circuit .... there is a patent for the circuit and it is used in some commercial Class AB / B amps to minimise the zero-crossing distortion.
here goes....
To use multiple output stages from one front end there are a few ways you can go about it.
1. This is the obvious solution ... make a driver stage capable of twice the current then use resistors to ensure that each output gets approximately equal current .... problem with this in a hi power amp is that the current sharing between the output stages is exactly that APPROXIMATE! kinda like a lick and a promise. Not what your after
2. Make the front end fairly normal and put a buffer (unity gain) at the input of the output stage .... this ensures that each output stage gets equal current because the current is being drawn from the buffer not the front end and the front end is never taxed to supply current beyond its means. this of course means extra devices 🙂 there's always a trade off.
also remember this .... you dont necessarily need a driver stage .... you could run the outputs direct from the Voltage Amp.
If you go this route connect only one output stage at a time and make sure it works well and is stable (start off at very low power!) then do the same for the other before connecting both.
+/-150VDC will get you 1875W RMS into 6ohms.... hope those rails are stable 🙂
You will need a current sink in the input stage to ensure that the turn-on/turn-off thumps dont hurt some of your speakers.... i am not kidding.
Use a cascoded input stage to keep dissipation to a minimum and bootstrapping for the driver stage (Class AB) to minimise distortion.
You might also like to look up the info available about the H-bridge circuit .... there is a patent for the circuit and it is used in some commercial Class AB / B amps to minimise the zero-crossing distortion.
Ok, thanks, the buffer idea sound good.
I know I've got to supress the on/off thump. I bet it could easily damage my speakers, despite their huge power handling capability. Not to mention scaring the neighbors.
I know I've got to supress the on/off thump. I bet it could easily damage my speakers, despite their huge power handling capability. Not to mention scaring the neighbors.
That's interesting.
Anyway, for outdoor use, what does R51 on the Leach SuperAmp do? It's not even on the parts list, it just shows it on the schematic seperate from everything else with a ground symbol on each end.
Now, a question. Please forgive me for not knowing one of the basic audio principles, a few pages back, everyone was going crazy about that. It seems to have chased a few people away from the thread. Not to mention names, but Geoff, where you been man? And the question is: how can I increase an amp's slew rate? There was some talk about it earlier.
[Edited by Kilowatt on 12-07-2001 at 02:28 AM]
Anyway, for outdoor use, what does R51 on the Leach SuperAmp do? It's not even on the parts list, it just shows it on the schematic seperate from everything else with a ground symbol on each end.
Now, a question. Please forgive me for not knowing one of the basic audio principles, a few pages back, everyone was going crazy about that. It seems to have chased a few people away from the thread. Not to mention names, but Geoff, where you been man? And the question is: how can I increase an amp's slew rate? There was some talk about it earlier.
[Edited by Kilowatt on 12-07-2001 at 02:28 AM]
I know this isn't what you want to hear, but people that given up on the thread because you were ignoring most of thier advice.
You wan't to build an extremely high power amplifier, but want it to be simple, cheap, and of decent quality, well as many people have tried to tell you, it doesn't work that way. Amplifiers at this power level will be complicated and they won't be cheap, its the nature of the beast.
With the way you are currently headed you are going to end up with a lot of toasted transistors, a bunch of blown speakers, and, god forbid, risking serious personal injury.
I really think that you are biting off a lot more than you can chew. You tell us that you don't have a lot of experience in amplifier design, yet are considering significant modifications of existing designs, to the point where they have little resembelance to the original amplifier. Its not as simple as taking an existing schematic and throwing in some more transistors with higher ratings. There are concerns with slew rate, oscilation, thermal problems, component drift, variation in part specs, safe operating ranges, fault handling, just to name a few and these are only general problems that people can think up of off the top of thier head, never mind the specific issues that will be seen with the final schematic.
You're basically telling us, "I just bought a new table saw, and don't really have much wood working skills, but can any one tell me how I can cheaply and easily build a solid oak Queen Anne Dining Room set for 12 people with hutch and buffet.", maybe you should try building a bookshelf first.
If you really need this kind of power (and remember that virtually all drivers will reach exursion limits at low frequencies long before they reach thermal limits), I would go with Anthony Holton's 1000 Watt Amp, build 4 of them to each drive a pair of your Audiobahn's. Its not going to be cheap.
You wan't to build an extremely high power amplifier, but want it to be simple, cheap, and of decent quality, well as many people have tried to tell you, it doesn't work that way. Amplifiers at this power level will be complicated and they won't be cheap, its the nature of the beast.
With the way you are currently headed you are going to end up with a lot of toasted transistors, a bunch of blown speakers, and, god forbid, risking serious personal injury.
I really think that you are biting off a lot more than you can chew. You tell us that you don't have a lot of experience in amplifier design, yet are considering significant modifications of existing designs, to the point where they have little resembelance to the original amplifier. Its not as simple as taking an existing schematic and throwing in some more transistors with higher ratings. There are concerns with slew rate, oscilation, thermal problems, component drift, variation in part specs, safe operating ranges, fault handling, just to name a few and these are only general problems that people can think up of off the top of thier head, never mind the specific issues that will be seen with the final schematic.
You're basically telling us, "I just bought a new table saw, and don't really have much wood working skills, but can any one tell me how I can cheaply and easily build a solid oak Queen Anne Dining Room set for 12 people with hutch and buffet.", maybe you should try building a bookshelf first.
If you really need this kind of power (and remember that virtually all drivers will reach exursion limits at low frequencies long before they reach thermal limits), I would go with Anthony Holton's 1000 Watt Amp, build 4 of them to each drive a pair of your Audiobahn's. Its not going to be cheap.
This thread reminds me of the "Never Ending Srory",and the
listener is not listening to some very knowledgeable people.
listener is not listening to some very knowledgeable people.
Kelly
You've hit the nail on the head in your first paragraph. Thanks for saving me another lengthy post.
Geoff
You've hit the nail on the head in your first paragraph. Thanks for saving me another lengthy post.
Geoff
Oh, I know, I've learned not to care how expensive or complicated it is, as long as I get it done. It doesn't matter if it costs $2000 or more for the amp. However, I still want to use bipolar transistors and a direct line supply, ok? Any other changes are fine as long as I get 1800W into 6 ohms for each amp. The Audiobahns have a 31mm Xmax, so I wouldn't worry about excursion. It's clear that I don't have the experience to start building tomorrow, but maybe I'll get it done eventually. I can't just do everything everyone suggests, I'd end up with something that's nothing like my original plan, but I'll take some advice, I already have. Sorry for discouraging people.
Ok here's an idea. Since I can't build an 1800W amp (any more than I can build a solid oak Queen Anne Dining Room set for 12 people with hutch and buffet), maybe I can build a 100W amp From ESP project03, except it would have a +/-150V supply, and it would drive 108 ohms. I bet you know what I'm getting to. There'd be 18 per amp. Now my only problem would be slew rate. So, now, as a complete and total novice to the audio world, how do I increase the slew rate so it will swing the full 300V at 20kHz? I know I'll just be using it as a bass amp, but I want it to be able to do the full range anyway. If I build it this way, the channels will cost nearly $1000, but I'd sure have experience at building PC boards after I finish the 72nd amp! And it would be almost invincible as each one would have it's own output protection and volume controll so I can match them exactly with an oscilliscope, and If one blew, the other's input would be limited (and therefore output) and would not overload the rest. How's that? Or can I just put multiple (high gain) output stages on one project03 driver? It's just like paralleling many little amps, just like everyone agrees I should do.
I'm not trying to discourage you, but an 1800Watt amp is NOT a begginner level project, even if a kit were available. I suggest either going with a known design (such as the Holton, which is the only DIY design I've seen with this kind of power rating), or else start working with much smaller designs and work your way up. If you want to design your own high powered amp, pick up some books and start off small. Design a 50 watt amp and see how that goes, then work up to 200, then more. Either that or be prepared to see hundreds of dollars in transistors and drivers go up in smoke, and I'm not kidding.
I can't emphasise enough how amazingly bad an idea a direct line supply is, especially for a beginner project, or someone with a lack of experience. It's something that most experienced designers stay away from, and even when it is done, an isolation transformer is almost always used. If you're going to the expense of buying a high power isolation transformer then all you've really done is just build a power supply using a 1:1 transformer. One mistake and we're not talking about dead components, we're talking dead hobbiest. To extend my woodworking metaphor, you're suggesting operating your tablesaw without a guard, push sticks or safety goggles. Sure if you know what you're doing you might be able to get away with it safely, but even Norm Abrams uses saftey glasses and push sticks.
On one hand you're telling us that you're not that experienced and want to learn, but on the other hand keep saying I want an 1800 Watt amp, line supply, using bi-polars. You really have to ask your self, why are you insisting on these requirements? What about your project is driving these decisions? Cost? Cool Factor?
Are you sure the about the 31mm Xmax? The Audiobahn site only lists it at 16mm, which is decent, but not overwhelming. Still, at low frequencies you'll find that a driver, even a large excursion one, will bottom out with amazingly little power (like 100-150 watts or less). It all depends what you're planning on using this for? Deep bass?? Max SPL over 50Hz?? Sonic Weaponry??
I can't emphasise enough how amazingly bad an idea a direct line supply is, especially for a beginner project, or someone with a lack of experience. It's something that most experienced designers stay away from, and even when it is done, an isolation transformer is almost always used. If you're going to the expense of buying a high power isolation transformer then all you've really done is just build a power supply using a 1:1 transformer. One mistake and we're not talking about dead components, we're talking dead hobbiest. To extend my woodworking metaphor, you're suggesting operating your tablesaw without a guard, push sticks or safety goggles. Sure if you know what you're doing you might be able to get away with it safely, but even Norm Abrams uses saftey glasses and push sticks.
On one hand you're telling us that you're not that experienced and want to learn, but on the other hand keep saying I want an 1800 Watt amp, line supply, using bi-polars. You really have to ask your self, why are you insisting on these requirements? What about your project is driving these decisions? Cost? Cool Factor?
Are you sure the about the 31mm Xmax? The Audiobahn site only lists it at 16mm, which is decent, but not overwhelming. Still, at low frequencies you'll find that a driver, even a large excursion one, will bottom out with amazingly little power (like 100-150 watts or less). It all depends what you're planning on using this for? Deep bass?? Max SPL over 50Hz?? Sonic Weaponry??
Kilowatt:
If cost is no longer an issue just buy a PA amp that is capable of what you're looking for.
It is becoming more and more clear that this is beyond your reach and as Kelly pointed out, why are you still insisting on these two criteria?
If cost is no longer an issue just buy a PA amp that is capable of what you're looking for.
It is becoming more and more clear that this is beyond your reach and as Kelly pointed out, why are you still insisting on these two criteria?
That would be nice if I didn't have to do much designing, with my low experience level and all, so where can I find plans for the Holton amp? The only site I've seen on it has nothing but pictures. That's a MOSFET amp too, isn't it. Can I somehow make it use bipolars? I'm thinking not, but I'm not sure.
As far as my supposedly man-killing power supply, what is it that worries everyone? If it's supply voltage coming out the input in a failure scenario and electrocuting a guitarist, or something, that's been discussed on this thread, and I'll have isolation transformers at the inputs. If it's plain old HV danger, don't worry, I'm fine with that, trust me. I've done many projects that deal with line voltages, and even microwave oven transformer stacks (4kV, 1A or more). I have far more experience with lethal voltages than with audio. If it's the danger of electrocution from touching a speaker hookup or worn cable, that's been discussed too, and I believe that would be no more dangerous than an ordinary power cord.
Here's why I want 4 x 1800W (2 x 3600W bridged): The amp is mainly for cool factor. One day I just decided I should do it, and it would suck if I wasn't able to for years. Back then, I knew practically nothing about audio, but I thought I did and assumed close to 100% efficiency for the amp. And so since 7200W is available from a 240V 30A outlet, I figured that's what I'd do for the amp's power output. And the math is easy when you use values like 1800, 3600, 7200, etc. I later learned that It would draw at leat 50A (probably much more) at full volume, but I kept the specs the same, just changed where I'd plug it in. These are fairly convenient values for my power supply and speakers too.
Yes, I'm sure about 31mm. Check it out at http://www.audiobahninc.com/parameters/2000_parm.htm . It's the ALUM12, scroll down to "12" PARAMETERS & ENCLOSURE VOLUMES" and you'll find it. Think about it, these things have 1.75" surrounds.
jduncan, cost isn't as much of an issue now, but it's enough of one that I don't want to buy a PA system. Also, I'd just like to build it myself.
Can't I test my amps with a current limited power supply to make sure they work before I put full power to them?
[Edited by Kilowatt on 12-07-2001 at 07:40 PM]
As far as my supposedly man-killing power supply, what is it that worries everyone? If it's supply voltage coming out the input in a failure scenario and electrocuting a guitarist, or something, that's been discussed on this thread, and I'll have isolation transformers at the inputs. If it's plain old HV danger, don't worry, I'm fine with that, trust me. I've done many projects that deal with line voltages, and even microwave oven transformer stacks (4kV, 1A or more). I have far more experience with lethal voltages than with audio. If it's the danger of electrocution from touching a speaker hookup or worn cable, that's been discussed too, and I believe that would be no more dangerous than an ordinary power cord.
Here's why I want 4 x 1800W (2 x 3600W bridged): The amp is mainly for cool factor. One day I just decided I should do it, and it would suck if I wasn't able to for years. Back then, I knew practically nothing about audio, but I thought I did and assumed close to 100% efficiency for the amp. And so since 7200W is available from a 240V 30A outlet, I figured that's what I'd do for the amp's power output. And the math is easy when you use values like 1800, 3600, 7200, etc. I later learned that It would draw at leat 50A (probably much more) at full volume, but I kept the specs the same, just changed where I'd plug it in. These are fairly convenient values for my power supply and speakers too.
Yes, I'm sure about 31mm. Check it out at http://www.audiobahninc.com/parameters/2000_parm.htm . It's the ALUM12, scroll down to "12" PARAMETERS & ENCLOSURE VOLUMES" and you'll find it. Think about it, these things have 1.75" surrounds.
jduncan, cost isn't as much of an issue now, but it's enough of one that I don't want to buy a PA system. Also, I'd just like to build it myself.
Can't I test my amps with a current limited power supply to make sure they work before I put full power to them?
[Edited by Kilowatt on 12-07-2001 at 07:40 PM]
Kilowatt
It is becoming clear that your intention is not to build a working amplifier but is just to create the longest thread on this forum (and to wind up the readers/respondents in the process). I therefore suggest to all other (sensible) members that this be the last post in this thread.
Your comments regarding the use of 18 ESP 100W amps is asinine. Your total disregard of any constructive advice is a waste of everyone's time. If your comment that "I have far more experience with lethal voltages than with audio." is true then I am surprised that you have lived to tell the tale in view of your apparent total lack of any basic knowledge of electrical/electronic theory and practice.
I am usually very mild mannered and like to help those with less knowledge than myself, so I would not normally have posted a reply such as this, but you have tried our patience too far.
Geoff
[Edited by Geoff on 12-08-2001 at 06:49 AM]
It is becoming clear that your intention is not to build a working amplifier but is just to create the longest thread on this forum (and to wind up the readers/respondents in the process). I therefore suggest to all other (sensible) members that this be the last post in this thread.
Your comments regarding the use of 18 ESP 100W amps is asinine. Your total disregard of any constructive advice is a waste of everyone's time. If your comment that "I have far more experience with lethal voltages than with audio." is true then I am surprised that you have lived to tell the tale in view of your apparent total lack of any basic knowledge of electrical/electronic theory and practice.
I am usually very mild mannered and like to help those with less knowledge than myself, so I would not normally have posted a reply such as this, but you have tried our patience too far.
Geoff
[Edited by Geoff on 12-08-2001 at 06:49 AM]
Fine, sorry If I come across that way, I didn't think I was a total jerk about it! I thought I was just trying to get help with my amp. This thread has been going downhill for pages. It just happens to be the 2nd longest thread on the site because there was a lot to say (mostly negative). If that's how you guys feel, fine, forget the whole damn thing! Obviously, I can't build the amp, at least I apparently shouldn't try. Let this be the last post in the thread. Unless someone has something else to say, this thread is closed!
Apparently I know less about posting on a forum without ******* people off than I do about audio.
Hopefully, I'll find complete plans for something, but for now, the amp is done. I've had it!
[Edited by Kilowatt on 12-07-2001 at 11:41 PM]
Apparently I know less about posting on a forum without ******* people off than I do about audio.
Hopefully, I'll find complete plans for something, but for now, the amp is done. I've had it!
[Edited by Kilowatt on 12-07-2001 at 11:41 PM]
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