hi my name is martin and i live near montreal canada, im used to build tube amplifiers but i found the nice dx amplifier on greg website and decide to build the base one ...on the website it is specified that a power supply of plus -minus 35v would be ideal but will it work the same with 33v psu (less power of course) thank for your answers and sorry for the bad english
If the VA rating of your transformer is adequate - say 300 VA for both channels, you won't notice any difference. Smaller rated transformers will work too but the supply voltage and thus output power will then drop further as the signal drives the output closer to full power. This is not so good for audio either.
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Something I overlooked: You did refer to AC voltage from the transformer, I hope. as this is specified at 35V and converts to +/-50V DC rails - not 35 or 33V DC which would amount to much less power, even if the amplifier functions normally.
However, it may still be an acceptable amplifier driving 4 ohm loads, I think.
However, it may still be an acceptable amplifier driving 4 ohm loads, I think.
thanks for your answer , this amplifier specified a +/-35v dc on the rails but my power supply is only 33v+/- dc , (with 25v ac transformer) the amp is this one :Greg's Web Site it was made by a skilled person on this forum i do know he tested it with many voltage but i dont know if i have to modify something from the bias circuit or the offset... will it be out range for adjustement ??
tanks a lot to you ...i realise suddenly that i have a long way (may be painfull)to go from tube to solid state !!!
Obviously you must read all of Greg's site.
But, add PASS, ESP & Decibel Dungeon to your reading list.
But, add PASS, ESP & Decibel Dungeon to your reading list.
i do all they say on the site , i check all ...maybe three or four times .....i look for shorts on pcb there no shorts ...
Firstly, are you sure your power supply is a symmetric one ? This is a common mistake made by tube guys who are used to only one very high +B voltage (and heater supply).
Solid state amplifier circuits typically require a symmetric supply - this means there are two voltages, in the case of the DX amp it means 35V above ground, and 35V below ground, often written as +/-35V. This typically requires a transformer with a centre tapped winding, or two identical windings connected to form a centre tap.
Solid state amplifier circuits typically require a symmetric supply - this means there are two voltages, in the case of the DX amp it means 35V above ground, and 35V below ground, often written as +/-35V. This typically requires a transformer with a centre tapped winding, or two identical windings connected to form a centre tap.
it is a symetrical power supply but i make a mistake when i wire the vbe multiplier board ..so the amp draw 100w on both rail for a second (the time i realise something is wrong) so i fix that first mistake and test all transistors , they seems to be fine (lucky or impossible i dont know) so i do another test , this time i be able to adjust the bias properly ...the amp draw 3.5w total in idle mode (input shorted) but 2sc5200 get hot,2sa1943 stay very cold (i mount them on separate heatsink for the test) and i have a plus 20v on speaker wire .the amp did not oscillate , there is no shorts on the board i tested it .the voltage seem to came from tip41 but i remove it for test and it test good ...im confused ....maybe i destroy the bd139 (vbe multiplier) but it test good and i be able to adjust the bias...twice more confused !!! maybe there is something wrong with the negative power and driver ...they also test good .it remind me the tube amp i did ....i destroy a nice pair of 50's 6l6gc rca blackplate (150$ a piece) they popped like fire crackers with a wooping 750v on screens....almost beautyfull....but this time nothing smoke nothing pop and all seems to test fine it is possible to have transistors test fine but be not good and what with the positive power output getting hot and negative be cold ???it is somewhat confusing to me ...
if you can feel that the heatsink output device is getting hot then you are pulling a lot more than 3.5W !!!
Power up through a bulb tester. You can now measure voltages without anything getting warm and certainly not hot.
It seems from your description that you have made no protection for the amplifier when first powering up. As AndrewT suggests, you need to power the circuit with a light bulb in series with the input AC. Obviously, this is dangerous without safe, insulated mounting and the proper socket and wiring but unless you restrict the current like this when first powering up, you run a high risk of burning everything and leaving no clues as to what went wrong.
Surely you have read the cautions and advice to this effect on the other websites. These are not simple-safe battery circuits - one critical error or misreading of instructions and it is a silent farewell to your expensive semis too. So, if you need the opportunity to measure what is going wrong (and it sure looks like you do) make up one of these bulb arrangements so that destructive currents can't flow and you have an indication how bad the circuit is adjusted or built by the brightness of the bulb.
When you have realised that something like a transistor is reversed , or a substitute has a different pinout or it has shorted but your meter can't check power transistors or other common errors, you can systematically search for the real fault and correct it. You haven't told us, but I assume you have built it from a kit but used instructions written for the original project. This may be problem as I have seen 2 Ebay kits, one with reversed pin TO92 transistors and marginal types, too.
You say the amplifier draws only 3.5 watts but one power transistor gets very hot. What do you mean by "draw 3.5W total", Do you mean volts or amps or have you calculated this as power for both +&- rails?. This suggests enough current to get the transistor warm but if you say hot, then 3.5W total is not right - what are you measuring here?
Last. there is a very long thread here for the DX with many rediscoveries as new people try it out. Read as much as you can about setting it up to test after building.
http://www.diyaudio.com/forums/solid-state/96237-destroyer-x-amplifier-dx-amp-my-amplifier.html
That is the thread for specific DX amp problems.
Surely you have read the cautions and advice to this effect on the other websites. These are not simple-safe battery circuits - one critical error or misreading of instructions and it is a silent farewell to your expensive semis too. So, if you need the opportunity to measure what is going wrong (and it sure looks like you do) make up one of these bulb arrangements so that destructive currents can't flow and you have an indication how bad the circuit is adjusted or built by the brightness of the bulb.
When you have realised that something like a transistor is reversed , or a substitute has a different pinout or it has shorted but your meter can't check power transistors or other common errors, you can systematically search for the real fault and correct it. You haven't told us, but I assume you have built it from a kit but used instructions written for the original project. This may be problem as I have seen 2 Ebay kits, one with reversed pin TO92 transistors and marginal types, too.
You say the amplifier draws only 3.5 watts but one power transistor gets very hot. What do you mean by "draw 3.5W total", Do you mean volts or amps or have you calculated this as power for both +&- rails?. This suggests enough current to get the transistor warm but if you say hot, then 3.5W total is not right - what are you measuring here?
Last. there is a very long thread here for the DX with many rediscoveries as new people try it out. Read as much as you can about setting it up to test after building.
http://www.diyaudio.com/forums/solid-state/96237-destroyer-x-amplifier-dx-amp-my-amplifier.html
That is the thread for specific DX amp problems.
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tanks a lot to you all , i did not buy it in a kit , i do the board myself with a lazer printer ..it works very well. i dont trust kits ...but the idea of having a light bulb for safety is great i will try to post pics of the board i made ..im still learning so i expect to make mistakes i think its a great desing to start with and you all are a great help thank you all .i will buy other transistors and try again there is no learning without troubles or mistakes .i will give you news when i got thoses.
after i fixed somes mistakes i made the first time , the amp work quite fine ,i was able to perform all adjustements and it work just as it was supposed to.powerfull and bassy. it was a good learning project ...the main trouble is that i dont have printed the good pcb...when i resize the image two lines had joined together because i don't use the right definition :less detailled image ...it is something i had to be more carefull about for the next one.
hi martin766,
Congratulations on getting your DX Amp up and going. It sounds like there was enough info on the DX Amp site to get you nearly there and a few experts here helped you over the line. Many thanks to those guys. 😛
Regarding your problem, which pcb image did you use, the gif or the PDF? Is there a note I should put on the DX Amp site to help others? I don't make my own PCBs so
If you would like to try a couple of the DX Amp PCBs to compare to your home made ones, drop me a line.
regards
Congratulations on getting your DX Amp up and going. It sounds like there was enough info on the DX Amp site to get you nearly there and a few experts here helped you over the line. Many thanks to those guys. 😛
Regarding your problem, which pcb image did you use, the gif or the PDF? Is there a note I should put on the DX Amp site to help others? I don't make my own PCBs so
If you would like to try a couple of the DX Amp PCBs to compare to your home made ones, drop me a line.
regards
thank to you , there is no errors on your site .i use the gif image but i resize it without setting the definition to a higher level.people should use photoshop or jasc paint shop pro , as these programs allow you to increase or keep the original (mostly high) definition and save the resized image in jpg or bmp,as thoses have less compression and higher definition, the fine lines will not merge together or be cut .etching pcb ourselves is somewhat messy with iron chlorine but it works quite well, the main difference are on the silscreen side as the lazer printer (mine) print in black only, so you have the components names an values written in black.this is the poor man solution as it goes for diy ...many thank to ian finch and andrew t who help me with that one and to you to provide such a great site.
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