diyAudio Forums Archive > Top > Amplifiers > Solid State Pages: 1 2 [3]  Leach clone, pretty good looking - Click HERE for Original Thread JensRasmussen I updated and moved the manual. It's now found at the amplifier page. There is a chapter about different output transistors. Comparing TO-264 vs. TO-3. No final conclusion yet, but I find the new flat devises better. Please comment, Thanks \Jens JensRasmussen Today I got some of the parts needed, so I started putting together two boards. JensRasmussen Close up \Jens jacco vermeulen Jens, mind telling the viewers what parts you are using ? Especially the emitter resistors i am curious about. (i am using 0.22 btw, Mox, unless someone can advice me how to get MPC's or Isabellenhute PBH's in a 1150 mil spacing) After regular J time, of course. JensRasmussen Hi Jacco, Sorry for the delay, Ill send you a component list from the local shop. Here is a pic while you wait :) EJ Hi Jans, That looks really professional. I've been working on my own layout, from the schematics of Jans. Here's my result. In order to reduce the board size, I have removed the 10000uF caps from the board. JensRasmussen To all builders: Change of value for R28 and R30, both must be 330 ohm. This is only important if you run the amp above +-60V rails The change is in the componentlist on the website now. I am making a table with values for different rail voltages, it will be included in the manual that I'm working on. Sorry for any trouble this may cause, I know that removing components from the PCB is hard work, so please be carefull when you perform the operation \Jens jacco vermeulen Attention all builders : Jens blew up his first Leach output on +-75V. :clown: JensRasmussen Hi Jacco, Nope, my prototype is running at +-75V as we speak, but on a test supply. I just made a calc that suggested that 330 ohm was better for higher voltages ;) I'm waiting for my 1000 VA 2x55V AC trafor, when it arrives I will make a short circuit test at see what happens :eek: EDIT: Did you have a look at the new graphs I mailed you Jacco? \Jens jacco vermeulen BUMMER, Oh well, maybe next time :clown: I have read the manual revision, Jens. I figured weekend is J&J time. And i am not the other J !!!!!!!!!! The load line for the MJ15003/15004 on the 3 device version does point out how little the powerhandling of a device is worth. I chose 0.22 Ohm emitter resistors instead of the 0.47 Ohm, or the original 0.33. So i have to change R28/R30 anyway to activate the protection gear. Setting it around 25 amps per device. I am going to use an intelligent protection circuit that will activate the output relays depending on the product of Vce value and output current, with a delay of 10 mS. Within the 10 mS its up to the Leach driver protection btw: did you get my skype messages ? first time i tried it, maybe you could give a hint for a convenient skype talk time schedule JensRasmussen The reason for using 0.47 ohm in stead of the original 0.33 is to get better current sharing between the output devises (and I could get the 0.47 ohm devises) Jacco: I'm online now \Jens Villaw Jens, You dont seem to suggest the use of two traffos and two discrete PSUs for the modules. Is using two traffos a waste of time and money? JensRasmussen I plan to use only one trafo and one railvoltage. You can improve effeciency by using lower rails for the output . I have not tested this, so if you try it please tell us the result, as it might improve performance with a more "silent" supply for the input part of the amp. At the moment I'm waiting for my trafo. I will post results when it arrives. This will test the amp at 75V rails. I was hoping on some more response on the manual - there are some things that might make the TO-3 vs. TO-264 debate come to life again. \Jens jacco vermeulen quote: Originally posted by Villaw Is using two traffos a waste of time and money? Using 1 transformer is a waste of money. Do as Jeff Rowland does, use no transformer, stick 12 LM3886 in a box and charge +$ 10.000 for it. Oh, why does no one post a couple of those nice Leach manual soa graphs on this thread ! Villaw quote: Originally posted by jacco vermeulen Using 1 transformer is a waste of money. Do as Jeff Rowland does, use no transformer, stick 12 LM3886 in a box and charge +$ 10.000 for it. ... and when the LM3886 shorts, whoever touches the speaker cable will get a nice electrocution and die... Upupa Epops To jacco : " Take it or leave it " and don't touch this glory name :cool: . jacco vermeulen To Pavel : Remember the days of Rowland Research Model 7. Upupa Epops It was glory name :cool: , today I don't understand. Maybe money ... ;) Upupa Epops P.S. : Sometimes I was talking with product manager of Revox and he said to me, that they need " junge blut ". Young blood was coming and spirit of WS gone away ;) . By RR is it probably the same :D , " young blood " is offten quite cynical ;) and is looking only for money. Villaw Jens, what is the theoretical max power output of your version of the amp? (irrespective of output impedance) Can one expect a doubling of power at least down to 2 ohms? JensRasmussen No I don't think so - reason follows The output power is related to the output voltage and current, and the current is related to the voltage and load. No powersupply is going to be big enough to sustain the current into 2 ohms. But testing have shown 300W + into 8 ohm and 450W+ into 4 ohm (both resistive), but this will depend heavily on the supply capabilities. I have not yet tested into 2 ohms, and prefer to wait until I have a proper heatsink, the rail voltage must be lowered below 60V (again not tested) if the amp is going to be used into 2 ohms continues operation. The ability to double the power will depend on the size of power supply, and the protection circuit of the amp. I don’t recommend anyone to use 2 ohm loads unless they really know that the amp is up to it. I will post the result of the 2 ohm test when I have it. \Jens Villaw Well if this can do a 450 w on 4 ohms who needs the super leach amp? How can you use such high voltages for the gain and driver stages anyway when the small leach amp is working on a lot less than the ones you mention (70 or 75 rail v)? Have you made any changes there and can the driver section sustain output of such wattage? JensRasmussen quote: Originally posted by Villaw How can you use such high voltages for the gain and driver stages anyway when the small leach amp is working on a lot less than the ones you mention (70 or 75 rail v)? Have you made any changes there and can the driver section sustain output of such wattage? I have chosen transistors that have high enough Vce ratings. I have had no problems with the driver stage running out of current, but then again 4 ohms is not a really hard load to drive. I change some resistor values a bit, to closest standard value 300 ohm => 330 ohm etc. I also changed the short circuit protection to fit 5 parallel devises and a higher railvoltage. \Jens rajeev luthra Jens, at po max say 450w what is the max dissipation in each output device , also at this time what is the voltage across its collector emitter and what is the current passing through it ? JensRasmussen rajeev, It depends on if you ask for maximum power out (peak) or the avarage power during one cycle. Or maybe the maximum power dissapated in the output transistors. Peak power out is easy: Rails = 70V Output_peak = 60V Vce_peak = Rails-Output_peak = 10V Ic= Output_peak/(RL*5) (5 parallel devises) = 60/(4*5) = 60/20 = 3A @ Vce = 10V well inside the SOA curve. The other ones I will have to look into tonight when I return home. \Jens rajeev luthra Hi Jens, Please send me those figures , as I need them for calculation of the extreme limits I can take the devices safely in my amp . JensRasmussen Regarding the numbers.... Please be patient, I'm very busy with my "non-diyaudio" life at the moment. I have started a transistor analyses to compare some of the most used ONSEMI transistors. I will be part of the manual I make for the Leach amp pcb, and will include calculations for 5 parallel and 3 parallel transistors. All calculations are show in the manual, so other DIY folks can use them to find out how many transistors to use in a new amp design. I will update the manual this weekend I hope, and then there will probably be very little news the next couple of months, as I’m in the process of moving. \Jens rajeev luthra Thanks Jens , I am waiting , Rajeev jacco vermeulen I just cut a 10 mm Aluminum plate to size for the Leach chassis bottom plate and vented heat tunnel. Not sure if i will drill and tap the strips on the baseplate or weld the things. JensRasmussen Jacco you are a :wiz: Rajeev, I have updated the manual on the homepage.... I think you will find something usefull if you look through it. As always please comment Thanks \Jens rajeev luthra Hello Jens, I went through your mannual , very interesting and informative , learnt much on SOA , power loss in output stage & heatsinking , good work . Regarding the use of MJ21193/94, MJ21195/96 your comment is that thay are too slow and you would not use these devices though they are very rugged . You suggest MJL3281A/1302A & MJL4281A/4302A for medium power fullrange amplifiers between 200w - 450w . But you do not recomend them for subwoofer or other applications where high - long term power is needed . Now like this there is some or other problem in all your tested devices , what device do you recommend for PRO SOUND applications . A friend has commented as follows , : "SOA at high voltages is not all that important in audio amp design. That is because when a transistor is exposed to the highest voltages, it is not conducting at all. For example, consider the device connected between the load and the positive rail. When the output signal swings negative, this device is turned off and conducts nothing. Al long as the device can handle the voltage, you are fine. It is only when the signal goes positive does the transistor conduct. And in this case, as the output voltage rises and the current rises, the voltage across the transistor falls. Thus, the SOA requirements are not as stringent as many believe. We have used the Toshiba devices with great success with rails as high at +/-100V. " what do you have to say above , Please also post a SOA chart of Toshiba 5200/1943's , as you know I was going to use 11 pairs 5200/1943's at +/- 87v for an speaker load upto 2 ohms and the same was turned down by K-Amps also it is not possible as per Quasi,s graph , will these 11pairs 5200/1943's be 0k at +/- 87v and load 4ohms pro sound use . You reccomend the 10 ms SOA curve for audio use , if I see this curve of the 5200/1943's at 10ms without derating it is not bad , it is 2A at 100v , 4A at 80v the devices should be safe at +/-87v and 4 ohm loads with enough margin for the protection circuit to come into acton , also the supply would fall to 70v or lower on load , thus increasing the SOA . Your Comments please!! amplifierguru You seem to be on track rajeev with your pulse assessment. The SOAR's at high voltage are very necessary consideration for reactive loads as only resistive loads switch the output half off at zero crossing and the amp need deliver NO current at zero volts but real reactive loads are more demanding. My rule of thumb is to deliver full 8 ohm load current at zero volts satisfies medium duty needs eloquently. jacco vermeulen I think it depends on where you put the emphasis on. If sound quality is the supreme goal, linearity of the output signal is of great importance, which legislates the use of extreme high bandwidth output devices. If very high power output is the primary goal, linearity at 20 KHz should not be that vital. A subwoofer puts even lower demands on frequency behavior of output stages. Many who build amplifiers want the best out of the first couple of watts. Only some desire the most of the last watts, as you, Rajeev. If you wish the most power you can get i would not be concerned with bandwidth specs of 4 or 30 MHz for different devices but go for the ones most affordable and most sturdy. For a hefty subwoofer amplifier or a stage amplifier that delivers the most reliable, i'd opt for high power TO3 Motorola's instead of sota very high bandwidth Japanese devices. "Nothing beats cubic inches" applies to Pro amplifier gear too. Seems to me that K-amps recommended some good ones. Why you need all that excessive power is still a puzzle. rajeev luthra Jacco you write "Why you need all that excessive power is still a puzzle." the answer to your puzzle is that I am a small touring pro sound operator , and high power amps are the requirement of my sound system . You will find this interesting , I just did a survey and found out that most of the branded pro amps of today like Crest , Crown , QSE , Yamaha , Pavey , Behringer etc are nowadays only using TO-264 case devices in the output stages. WorkingAtHome I think what makes it "easier" in pro amps like those, is that you can liberally add fans to control temps. Home amps typically cannot afford the fan noise, so require a much more meticulous design. jacco vermeulen Look who is talking, Mr BlowerFan Brian ! hienrich most commercial pro amps are usually using those plastic packages because of thier convinience since they only require a single mounting screw and perhaps when designing the PCB lay outs these packages are even very easy to include in, thus hardwiring is practically deminished, one more thing, designing amps with plastic packages looks more elegant to look at.....:dead: jacco vermeulen I was interested in the facts of Pro amplifiers for a few years and subscribed to a "professional sound" magazine. A common thing with pro gear seemed to be that they all had very tight protection circuitry, and below 4 Ohms the max output was restricted by the protection limit. Most of the PA amplifiers i saw pictures of had plastics, and that fase of mine was 10 years ago. JensRasmussen quote: A friend has commented as follows , : "SOA at high voltages is not all that important in audio amp design. That is because when a transistor is exposed to the highest voltages, it is not conducting at all. For example, consider the device connected between the load and the positive rail. When the output signal swings negative, this device is turned off and conducts nothing. Al long as the device can handle the voltage, you are fine. It is only when the signal goes positive does the transistor conduct. And in this case, as the output Voltage rises and the current rises, the voltage across the transistor falls. Thus, the SOA requirements are not as stringent as many believe. We have used the Toshiba devices with great success with rails as high at +/-100V. " what do you have to say above , Reactive loads changes this. I plan these transistors: I will use 5 parallel MJL21195/96 or MJL21193/94 for my subs. I will use 5 parallel MJL4281A/4302A for my upper bass or in a full range system. I will use 3 parallel MJL4281A/4302A for my midrange. I will use 2 parallel MJL4281A/4302A for my tweeter. \Jens jacco vermeulen As far as i got the story right Vce level is of major importance in the high frequency range, where very fast transients occur. At lower frequencies the output changes much slower from positive to negative, theoretically at zero crossing there is no output current. Which implies that in most cases voltage level over an output device's collector and emitter is no higher than the PS voltage. Vce at 50v or 100v makes quite a difference on the soa sheet. A tweeter has to battle for every 1/10th of a dB, because there is very little energy in high frequencies. In return the power handling of tweeters is not high, when Vce reaches the maximum there will be very little current going to the tweeters. imo, at low frequencies the 1st thermal breakdown of the soa line is important, that is where high voltage levels and high currents are needed constantly. Calculating the integral[1/2*Rho(air)*square(Sin (Vair))] for a 20Hz tone is nice to get a grip on the energy that goes into these low frequencies. For the higher frequencies its the 2nd thermal breakdown part of the soa that applies. if you look at half cycle: Everything above 500Hz is in the 1mS and shorter range. Signals above 50 Hz are inbetween 1mS and 10mS. Signals above 20 Hz from 25mS to 10mS. If electrostats are skipped the highest phase shift generally occurs in the upper frequency zone too. Ribbon tweeters have both high phase shifting and require relatively high currents, for those i'd think setting up an output stage for enough current at high Vce is sensible. If not, then i tend to agree with Rajeev's friend. JensRasmussen I think that is is important to look at both active and passive speakers as they will be different loads to the amp. Passive speakers have som sort of a filter that will contribute to the overall impedanse that the amp sees. This can create a more reactive load compared to the active system. The Active speaker will be more easy to cope with from an amp point of view. There is no passive filter to mess things up. I think the two different sceneraios need to be evaluated seperetly, but since I'm building active speakers, I have not looked much into the actual numbers of a passive system. I have simply looked at the worst case where the load is reactive, and the output devises can "See" 2 x VCC while at the same time having a high current load. The peak dissapation is huge (about 150W pr devise in my 5 parallel setup) when you look at reactive loads. but for a short time every cycle. \Jens jacco vermeulen The only loudspeakers i know of that can actually produce an almost perfect square wave are the ESL63's.(and their successors). For the amplifier that is only relavent if a square wave is placed on the input. example: the Quad ESL63 has a 2.4 Ohms minimum impedance. At 86 dBW sensitivity anything of 50 watts continuous and above is enough, the ESL has a built-in voltage protection to prevent the foil to sparkle. Maximum phase difference is like 60 degrees or a bit above, at the impedance minimum. Suppose you have a Leach amplifier with 70Vdc PS voltage, 140 Vpp. 20 Volts continuous is enough for 17 db in relation with 2.828Volts( 1 watt at 8 Ohms) Peak SPL would be at 103 dB. Suppose output voltage is at 20 Volts, output current would be like 8 Amps. Thats at 90 degrees from the Sine zero crossing. At 60 degrees phase shift the 8 amps would be needed when output voltage is at 30 degrees on the Sine curve, around 10 volts output. Vce would be 60volts, dissipation in the output: 60*8 = 480 watts. With the output stage phase at zero crossing it would be even higher, a bit over 500 watts dissipation. In this example the protection circuit of the ESL's would not be triggered. Now if you look on the soa curve you made, even with the 10-device output stage of the Leach the output stage would be experiencing 2nd thermal breakdown. Burn baby, Burn ! Now, at 50% temperature derating 10 Toshiba devices are good for 750 watts dissipation. As half Sine waves are very short the dissipation is shared, the 10 devices are able to handle the 480 watts dissipation. I am using 70Vdc on your 10-device Leach boards, and placing a higher voltage on the front end of the Leach that enables the output to reach almost the max PS voltage on the output. I am hooking up the 10-device Leach on ESL's. I am certain that the amplifiers will drive the Quads and not die. Depending on the performance of the heat ducts i am using i am making it even harder for the devices, making sure they are at 87.5C by pumping 300 to 350 watts in them continuous.(25C ambient) With 350 at 70Vdc PS voltage good for 2.5 amps bias, 100 watts class A in 8. JensRasmussen I would not recommend rails 0f 70V into 2.4 ohms!! I have assumed worst case impedances of 4 and 8 ohm in the calculations I have made so far. Any way, the temp derating is only good if you know you actual case temperature of the output devises. Since the worst case calculation shows below 87 degrees in the exampel I have made in the manual, the temp derating does not have to be as high. This also means that the allowed peak power will be higher. Besides, the priotection circuit is designed to kick in if the load goes below 3 ohms anyway, so hopefully nothing will burn ;) \Jens jacco vermeulen Can you put me up for a day or two if they do ?:clown: JensRasmussen Sure, and I will even get you a beer to cool you down while you sweat over the hard work of changing all those transistors :) In fact you can have you own room ones we move into our new home . \Jens AndrewT Hi Jacco, Re post 242; "Vce would be 60volts, dissipation in the output: 60*8 = 480 watts. With the output stage phase at zero crossing it would be even higher, a bit over 500 watts dissipation. In this example the protection circuit of the ESL's would not be triggered. Now if you look on the soa curve you made, even with the 10-device output stage of the Leach the output stage would be experiencing 2nd thermal breakdown. Burn baby, Burn !" You state here that at case temp of 25degC the transistors have exceeded SOA curve. But in the next para you say; "Now, at 50% temperature derating 10 Toshiba devices are good for 750 watts dissipation. As half Sine waves are very short the dissipation is shared, the 10 devices are able to handle the 480 watts dissipation." Surely if you derate the SOA curve by 50% then the transistors will be even further outside the curve? Are you offering the derating by 50% as an alternative to the SOA curve? AndrewT Hi Jens, re post 239 The philosophy you show for pairs of output devices seems very logical. Can you confirm these are for 4R and 8R loads or for 4Z & 8Z reactive loads? And at what Vrail voltage? JensRasmussen My test transformer for my subwoofer arrived today:) :) :) 2x55VAC 9.1A \Jens jacco vermeulen Evening Andrew, i am building the extended Leach with 10 output transistors, operating in class A to a level where the transistor Die's are at 87.5C degrees for an ambient temperature of 25C. At that temperature level the soa line is halved, as (almost) any datasheet will have added. I am making an aluminium cooling tunnel to reach a very low heatsink thermal resistance, monoblock setup. Consisting of a 0.4" thick aluminium bottom plate, measuring about 24" * 12", aluminium plates of the same thickness mounted vertically on top of the bottom plate to hold heatsinks. One of the heatsinks will hold the Leach pcb Jens made., making the amplifiers modular. In front of the duct 2 sets of 2 Papst ventilators, 2 rotating clockwise, the other 2 counterclockwise, for higher efficiency. I posted pics of the stuff. At 87.5C degrees the maximum dissipation of the 10 devices is half of 1500 watts, 750. For the devices not to reach primal thermal breakdown dissipation is not allowed to exceed that 750 watts for 1 second. The Die's would heat up to fast and have a melt-down. The same happens if at any output voltage the maximum current is exceeded as the soa also shows. For the 1302/3281 Toshiba's i am using, the current of a single device can not exceed 16 amps during long term signals. Each device can deliver 30 amps of current during a single 1mS pulse. Important is that pulses to test devices are single square signals, the worst load. At 87.5C Die temperature these peak currents reduce to 8 and 15 amps, per device. Jens mentioned many times he assumes the absolute worst case situation for the soa load line graphs he made. Assuming that Vce level reaches anything between 0 and 2 times PS voltage for 4 and 8 ohm loads for the load lines he placed in the soa graphs. The way i see it is to derate the soa curve first, my preference is 50%. Next is to see, for different impedances with max phase shift, if soa current is exceeded for the given PS voltage for those impedances, be it 8, 4 or any other desired load. The third is to check soa again for those frequencies where transients can be so fast that Vce is between PS voltage and twice that value, when the positive rail device opens and output is still at something near -Vps. This happens only with really fast signals, high audio frequencies or above that. The 1mS line applies to any frequency of 500Hz or higher. At 500Hz transients are far to slow to reach a high Vce level, below 500Hz only 1st thermal breakdown limit should not be exceeded. Vce level will never be twice PS voltage: - voltage at the emitters will never reach PS voltage level. - emitter resistors dampen the output voltage - voltage at very high level for such high frequencies will result in huge distortion and the tweeters will be destroyed. - PS voltage will drop under load. - while output current increases the reversed voltage on the output drops. The actual situation is far less dramatic: the curve area of a sinus is less than 2/3d of that of a square pulse. Area of a square pulse from 0 to Pi is 1*Pi. Area of half of a sine is : Integral(SineX) from 0 to Pi= 2 So the actual load can be 57 % higher. By placing a filter before the amplifier input the amplifier not only has protection from oscillation, and local signal slewing resulting in distortion, but also reduces the risk of 2nd thermal breakdown due to fast transients dramatically. For the ones i am building the thermal load decreases with a signal on the output, an advantage of class A amplifiers. I am using a protection circuit that disconnects the output when there is a risk of 1st thermal breakdown, a current level too high for more than 10mS opens a couple of very fast output relays. That protects for lengthy transients too, for 2nd thermal breakdown. Long before that my Quads will have shut down, any regular loudspeaker given up and you'd better have DC protection. Very hefty nice looking tranny, Jens. JensRasmussen Jacco, I might have missed it, but what SOA curve do you start with? 1) 10 ms 2) 100 ms 3) 1 s I have used the 10 ms and derated that to 50%. This roughly gives the 1 s curve, and indeed this curve is what I have used in all my graphs. Agreed, I could use the 100 ms to start with, but sine signals have full power for of a short time only. And I use the absolute worst case load line where the Vce voltage can reach 2xVcc. So I think our conclusion is more or less the same. 5 parallel transistors is enough for almost any domestic amp. I will use the amps in an active system, so any experience with hard passive speaker loads will be much appreciated. \Jens jacco vermeulen Jens, you should be busy moving house ! Your derated soa curve is fine, stated before. And you mentioned from the start taking the worst possible as criteria. For known loads without any form of current limiting that is the way to go, imo. I am saying that efficiency with such a setup is low, it is a choice. The worst possible only happens on very few ocassions, with the slack the soa testing gives more can be taken from an output of such size. example: i constructed the LFA50 Elektor amplifier long time ago. With 4 output devices and a large heatsink it was good for 50 watts class A in 8 Ohms, aided by a responsive protection circuit. The class A Forte Audio amplifier with a little lower output power i had used an output stage twice that size and no current limiting or protection circuitry at all. Both used similar MT200-package ringemitter output devices. It is a choice, yours is the old Threshold way. Supported by your output power testing of the Leach i hope to get something between 200 and 250 watts in 8 Ohms out of your Leach boards, by using higher voltage separated regulated power rails for the voltage gain of the Leach, and 1200watts of toroid for the output stage. With the extreme heatsink setup i am constructing hopefully i'll get 100 watts of class A power at a modest Die temperature of 87.50C degrees, usual is around 100C for a class A amplifier. The current limiting would allow output power levels of say 350 watts in 4 Ohms and +500 in 2 Ohms. Peak output current would still be 75 amps by the assumption that simultaneous reactive loads and extreme Vce level will not happen, aided by nearly 60% margin on the soa curve and a lower Die temperature under load. You did load lines for 4 and 8 Ohms, what about 3 Ohms ? Your amplifiers will live without current limiting on 3 Ohms loads when it is not a worst case situation. i see this as the difference between a computer controlled fuel injection engine compared to a big engine with a large carburator. One is not better than the other, one uses more hardware, the other more silicon. JensRasmussen Hi Jacco, I just love the way you always come up with some sort of explanation that involves cars :) I just tested the amp in my “lab” with the new transformer Rails idle = +-81V Rails fully loaded with 8 ohms = 72V Peak output into 8 ohm = 66V => 270W into 8 ohms, should be plenty Have not tested into 4 ohm yes, I’m afraid to burn the load :hot: :hot: \Jens jacco vermeulen I should hope so ! Times 10 is enough to need re-decorating your new nest again shortly, i see the plaster already falling down from the ceiling. That should put my hot ladies over the 200 line on 50vac transformers and some gained volts from 75 Vdc regulation. Actually i am a flunked car mechanic. I do not know any transistor sizes but i know bore and stroke of every Chevrolet engine, be it road, race or baja, by heart. The 1000VA-er is a Plitron? i seem to see a rainbow on the label. JensRasmussen The Transformer is from www.el-supply.dk they import the transformers them selves. Im unsure of the brand, but the tracking of the two windings is ok (within 0.5V) and there is no hum from it. I can however hear it when I play a sinewave at full power, it sings along, but so does the resistor load that I use. I guess that is difficult to get rid of mechanical noice when the transformer is pumping 500W. \Jens jacco vermeulen Thanks for the chat, Jens. Forgot to ask you if you ever saw the site from a company in one of the former easterblock countries that sells toroids for very low prices, even huge ones ? I'd have to look on my explorer fav. list for the name. mikeks quote: Originally posted by JensRasmussen Hi Per, Thanks for the nice words :) I have plans for a PCB order soon, but right now my financial situation doesn’t allow it (Det er jo jul). I have uploaded the gerber data for the small version also \Jens Hi Jens.. Most excellent work!! Where do you get your pcbs done...which package(s) do you use..? Cheers! JensRasmussen I use Elprint (www.elprint.com) they have a great software sulution called macaos where prices are calculated based on the gerber data of a design. \Jens mikeks Yes...but what package do you use to lay out your circuits in the first place? JensRasmussen I used an older version of Eagle, V4.11. for the Leach. A friend from work imports it. I also use PADS power PCB and PROTEL. It all depends on who I'm laying the PCB out for. \Jens mikeks ..not sure your choosen SOA protection permits efficient use of available SOA from your bank of output devices... :scratch2: 5 pairs can be persuaded to drive 4ohms<60deg. to nominal 55V rails.... With a triple slope SOA protection locus derated to roughly Tc~70deg., (or ~140W;adequate heatsink assumed), you could drive 4ohms<60deg., or even a 1ohm load to the supply rails without invoking protection.....no sweat... ..and..yes..i've examined your manual... AndrewT Hi Jens, re post 254; could that mechanical hum be due to DC passing through the primary? Have you tried a DC block yet? Pumping 500w? 2 channels @ 260w divided by efficiency, indicates about 800va (getting close to your 1kva) Go on, find a way to do 4R and 3R testing - please. Could you submerge the power resistors in a bath of cooking oil? While your at it you could volunteer to use the power to make dinner tonight. Earn a few points, it may help later! JensRasmussen quote: Originally posted by mikeks ..not sure your choosen SOA protection permits efficient use of available SOA from your bank of output devices... :scratch2: 5 pairs can be persuaded to drive 4ohms<60deg. to nominal 55V rails.... With a triple slope SOA protection locus derated to roughly Tc~70deg., (or ~140W;adequate heatsink assumed), you could drive 4ohms<60deg., or even a 1ohm load to the supply rails without invoking protection.....no sweat... ..and..yes..i've examined your manual... Hi, The load lines in the manual are absolute worst case. They allow 2xVcc Vce on the output. There is no protection curcuit in the manual.......yet ;) \Jens mikeks quote: Originally posted by JensRasmussen Hi, The load lines in the manual are absolute worst case. They allow 2xVcc Vce on the output. There is no protection curcuit in the manual.......yet ;) \Jens Actually, your loadlines (e.g fig4-11) do not represent the worst-case 4ohm reactive load....This is an error i believe originated sometime in 1970-72WW. Easy to prove: Just plot a 4ohm<60deg load line (an ellipse actually) and superimpose it on your fig 4-11.... You'll find it falls way beyond your 'worst-case' 4ohm projection...Try 4ohm<45deg as well... see below: JensRasmussen mikeks, Nice graph, what does it show? Peak values, RMS values and what is the graph based on square waves or sine waves? I have been looking for literature that describes how to make the graph at different impedance loads, but so far I have been unable to find anything else than the DC load lines I have already presented. There are plenty of application notes that mention the 45-degree load line as worst case, but none of the papers I have found actually explain how they arrive at a given graph. If you have information, please post it…. I want to offer the best documentation that I can find. SO far I have used info found in Self’s and Sloan’s books. \Jens mikeks send me mail...shall respond by 22:00GMT mikeks check your mail... Villaw Jens I was just having a look at the qsc 2450 schematic where they are using 4 pairs of PNP NPNs per channel (2SA1943 2SC5200 toshibas). They run them at 100v per rail with no problems. The amp delivers a massive 1200w at 2 ohms. If this can run at such high voltages I dont see why the extended leach cannot, which uses exactly the same drivers and similar power transistors with an added pair of transitors. It appears that using forced cooling an amp can deliver easily 400w at 8ohms. I guess the only difference is that the qsc is a class H amp with modulated PSU voltage. rajeev luthra wow only 4 pairs of 2SA1943 2SC5200 can deliver 1200w , Class H looks very interesting . K-amps While talking about modulated PSU's the Sunfire power amp (used the older and less rated c3281/a1302) was rated at 300w into 8 ohms, 1200 into 2 ohms and 2400 into 1 ohm. I am not sure how many pairs it had but I think it was not more than 4-6 pairs. However the issue is on that amplifier, the supply rails kept only 6v above the voltage needed to output the waveform, so the trannies were virtually working on +/-6vdc rails. At that voltage, those trannies can output the full 15amps each device. As the signal strength rose, the rails would rise as well still leaving only 6 volts to dissipate the amps. The worst case scenario was 15amps at 6 volts = 90 watts per transistor. Bob also has a Signature version with the exact same design and output section but this one was rated 600 watts into 8 ohms, and 2400watts into 2 ohms (not rated for 1 ohm like the other). This thing used NO heatsinks. The trannies were mounted on to the body of the amp. Unfortunately the same does not hold true for class-A-AB amps. Class-H is in the middle somewhere and so is class-G when it comes to efficiency. In the order of efficiency (from worst to best as far as I know) A AB B C G H Sunfire (switching power supply) D K-amps quote: Originally posted by jacco vermeulen Thanks for the chat, Jens. Forgot to ask you if you ever saw the site from a company in one of the former easterblock countries that sells toroids for very low prices, even huge ones ? I'd have to look on my explorer fav. list for the name. Jacco, are you referring to Rockna electronics? they quoted me nice prices but I was suspect of sending my money to a Romanian manufacturer that no one had tried before.... K- jacco vermeulen Yep, this one: http://www.rockna-line.com/toroids.htm I'd like a couple of them biggies. I was thinking now that we have a Romanian stiff on one of the threads he might be able to check Rockna's MO. If you count class C radio amplifiers you might as well include class F microwaves as well.:fim: What is the max power rating of a ribbon tweeter ? Villaw class H does sound v good though, in comparison with a number of other amps when used with a good pre. AndrewT What's all this ClassC and ClassH stuff on a Leach thread? Let's get back on topic. rajeev luthra Hi, That was compairing , A class H amp with 4pairs of OP devices can deliver more power than a class AB amp with 10pairs of OP devices duekfx Can anyone tell me a recommend power supply for a 3 pair version? Like 2x40/45/50VAC and the R26, R34, R68, R69 and R41, R42, R43, R60, R61, R62, R28, R30 values? Im driving 8 Ohm loudspeakers (but might replace them later) Thanks in advance AndrewT 3pair on 40Vac+40Vac. My 40+40Vac gives +-58Vdc and 170W into 8r0 just before visible clipping. duekfx Thanks for the reply. And what about the "missing" resistors, those marked as "TO BE DEFINED"? jacco vermeulen You'll have to calculate those yourself for the setup you've chosen. Jan Didden's SOA calculator: www.linearaudio.nl/SOA-2.htm

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