Hi Rudy
As I noted there were stability problems with the original build that made it impossible to put a real load on the amp without provoking oscillation. I had originally intended to do just the comparison that you asked about gain. I have no idea what caused the original to oscillate and it might very well have been an error in construction. But after checking everything out several times without locating the problem I decided to move on with the modifications. I did run simulations on both versions and the one with reduced gained had significantly lower THD. I assume this was because of the increased global feedback. In any case I don't know that I would trust the results of an unblinded listening test comparison enough to offer it up as evidence as to the relative merit of the two versions. I can say that I like the sound of the modified Blame very much. Since the mods are relatively simple you might want to try them and see what you think. So far I have built one channel. I will attempt the original design again on channel two. That will allow me to do side by side listening tests assuming I don't build another oscillator.
Hi Steve,
Thanks for your response.
I am building the amplifier again with its own power supply and I have 2 torroids 1000VA 2x42 volt 2nd hand purchased.
Easier to make a compare with other type amplifiers the amplifier is then easier to transport, and I will certainly apply the yours modifications.
I asked in a previous post or another had done this modification because I don't have the necessary knowledge and measuring equipment at home.
It would be a sin if the amplifier would go broke because I don't have the necessary measurement equipment.
Hence my question.
Regards,
Rudy
Thanks for your response.
I am building the amplifier again with its own power supply and I have 2 torroids 1000VA 2x42 volt 2nd hand purchased.
Easier to make a compare with other type amplifiers the amplifier is then easier to transport, and I will certainly apply the yours modifications.
I asked in a previous post or another had done this modification because I don't have the necessary knowledge and measuring equipment at home.
It would be a sin if the amplifier would go broke because I don't have the necessary measurement equipment.
Hence my question.
Regards,
Rudy
Hi Rudy-
I do have a scope and was able to see the oscillation, but you can't miss it anyway. The zobel network resistor began to smoke and then the rail fuse blew!!.
Good luck with the new build. I will post my measurements for my 2nd channel (original design) here.
Happy building,
Steve
I do have a scope and was able to see the oscillation, but you can't miss it anyway. The zobel network resistor began to smoke and then the rail fuse blew!!.
Good luck with the new build. I will post my measurements for my 2nd channel (original design) here.
Happy building,
Steve
Have your unit oscillated Meanman?
Mine was rock stable....are there more guys facing troubles?
CDom should be increased! ....the value posted is the smallest possible value...i have tried 82pf, 100pf, 120pf and 150pf .... checking mine i found the value you may see.
56pf is a big risk..... i cannot understand why i have not mentioned that....haven't i mentioned this before in this thread?
regards,
Carlos
Mine was rock stable....are there more guys facing troubles?
CDom should be increased! ....the value posted is the smallest possible value...i have tried 82pf, 100pf, 120pf and 150pf .... checking mine i found the value you may see.
56pf is a big risk..... i cannot understand why i have not mentioned that....haven't i mentioned this before in this thread?
regards,
Carlos
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Carlos,
Could you maybe go over this and other Improvements necessary to the Mk3, a lot may have been lost in this thread ...
Regards,
Dx Blame MKIII Hx was built and tested
Here a video about the stuff:
Dx Blame MKIII Hx was built and was checked! - YouTube
regards,
Carlos
Here a video about the stuff:
Dx Blame MKIII Hx was built and was checked! - YouTube
regards,
Carlos
Video made by Juan Vargas, our forum friend.
The man is a Iraq war veteran and lives now a days in Puerto Rico.
An amplifier made by a real man.... tested under fire!
Dx Blame MKIII Hx Carlos Mergulhão circuit designer - YouTube
regards,
Carlos
The man is a Iraq war veteran and lives now a days in Puerto Rico.
An amplifier made by a real man.... tested under fire!
Dx Blame MKIII Hx Carlos Mergulhão circuit designer - YouTube
regards,
Carlos
I'm just happy to be part of the forum of MKIII
I just happy to be part of MKIII Hx build, and my babies still waiting for the right moment to get the chassis and toroidal transformer, I haven' post anything because I think the way I have is just perfect for me, and settings according to Carlos were just right, so there is no need to change anything, and about the video is just an appreciation to mister Carlos and all the persons involve on the projects and also the guys on this forum that also give me lot of help too, thank you guys for let me be part of this awesome experience that still going and going.
Regards
vargasmongo3435
I just happy to be part of MKIII Hx build, and my babies still waiting for the right moment to get the chassis and toroidal transformer, I haven' post anything because I think the way I have is just perfect for me, and settings according to Carlos were just right, so there is no need to change anything, and about the video is just an appreciation to mister Carlos and all the persons involve on the projects and also the guys on this forum that also give me lot of help too, thank you guys for let me be part of this awesome experience that still going and going.Regards
vargasmongo3435
I have just tested the Dx Super A module together the Dx Blame MKIII Hx (Home Edition
and was approved for this small powered version only (guaranteed only using 40 plus 40 power supplies and iddle current of 300 miliamps each rail.... dissipation 24 watts)
It worked fine and reproduced clear Class A sound for the first watts....maybe 2 watts at 8 ohms of clear class A sonics... then the circuit goes back to original bias of class AB amplifiers..injecting only 5 miliamps each power transistor...so.... goes biased in accordance to class AB amplifiers... dinamically the bootstrap makes some difference, of course.
I have dismounted and returned to the original Home Edition because all i want was to collect values needed to match the Dx Blame MKIII Hx currents.
Now i will try it into the Dx Blame ST and then i will do the same with the original Dx Amplifier.
This is an effort to provide the Class A lovers (I am not class A lover) a good class A sound into the power levels we usually listen our amplifiers.
Here you have the video about the return to Class AB (original):
Dx Blame MKIII Hx going original again - YouTube
Here you have two videos showing first test made with the Dx Blame MKIII Hx...sadly my tweeter was damaged and this have fooled me:
Dx Super A installed and first test done - YouTube
Super A was mufled because tweeter was damaged - YouTube
Dx Super A - 300mA in class A - Supply 40 + 40V - YouTube
Audio recording made using Digital Cameras does not register high frequencies and saturates into low frequencies...has noises and distortions too..so...hard to evaluate quality while listening these recordings..but, at least i am providing you something to see and listen.
regards,
Carlos
and was approved for this small powered version only (guaranteed only using 40 plus 40 power supplies and iddle current of 300 miliamps each rail.... dissipation 24 watts)
It worked fine and reproduced clear Class A sound for the first watts....maybe 2 watts at 8 ohms of clear class A sonics... then the circuit goes back to original bias of class AB amplifiers..injecting only 5 miliamps each power transistor...so.... goes biased in accordance to class AB amplifiers... dinamically the bootstrap makes some difference, of course.
I have dismounted and returned to the original Home Edition because all i want was to collect values needed to match the Dx Blame MKIII Hx currents.
Now i will try it into the Dx Blame ST and then i will do the same with the original Dx Amplifier.
This is an effort to provide the Class A lovers (I am not class A lover) a good class A sound into the power levels we usually listen our amplifiers.
Here you have the video about the return to Class AB (original):
Dx Blame MKIII Hx going original again - YouTube
Here you have two videos showing first test made with the Dx Blame MKIII Hx...sadly my tweeter was damaged and this have fooled me:
Dx Super A installed and first test done - YouTube
Super A was mufled because tweeter was damaged - YouTube
Dx Super A - 300mA in class A - Supply 40 + 40V - YouTube
Audio recording made using Digital Cameras does not register high frequencies and saturates into low frequencies...has noises and distortions too..so...hard to evaluate quality while listening these recordings..but, at least i am providing you something to see and listen.
regards,
Carlos
A. Wayne..... this amplifier was deeply tested...i have several boards operating
one guy or two said had troubles related the gain.... this way i do think these ones should reduce the gain by themselves to face their personal troubles.
I do not think i should change the entire project because one or two... say... to change officially and to ask everybody to change the gain... the ones that believe this is a need they can do by themselves as this was published by you or by another guy (i do not know exactly the one did).
You have your special demands.... are recognized by uncle charlie as being someone that wants power over low impedance loads....so, a very personal case..someone that have special application in mind...i cannot fix the north of my designs into one particular special sittuation...if this worked great for you, them try your gain modification and be happy.....for a while i will be waiting more complains about.... then i will change.
The class A circuit was not recommended or suggested to be applied together the Dx Blame MKIII Hx....say..the full power unit..with the officially suggested supply voltage....i have just used the assembled board i had at hand in the moment (and it was a Dx Blame MKIII Hx - Home Edition, powered with 40 plus 40 volts) i had the need for a board to test the circuit...i do not think the full power MKIII Hx needs that, and also i have huge fear that this may become a tragedy while using the Dx Super A together the MKIII Hx because it is already too much hot and people is already using too much tiny heatsinks and i am smelling fire and troubles on that....i was clear when i said "home edition".... it is operating with 40 volts symetrical, not 44 volts symetrical...and this already make a difference.
Why that?
A big lie the transistors can dissipate 100 or 150 watts....all lie.... they cannot!....if you try at home, for instance, to apply 10 volts and 4 amperes...then you gonna see the hell thing becomes hot atop of the transistor... in the place you have the component identification number..when we have heat there, this means the transistor is not dissipating...means it is not transfering heat to the heatsink...and this is happening with 40 watts!.... so, these transistors can hole 40 watts or even less...that 100 or 200 watts of specification is not reality because they keep the unit, using huge refrigeration machines and heavy huge metalic block behaving as heatsink (real infinite heatsink) to FORCE the component to be operating at 25 degrées centigrades maximum...this way it can dissipate more power....but never while using the heatsinks people use and submited to the environment temperature.... so.... i do think (observing pictures) that almost everybody is using too much skiny heatsinks....very small area and several are using internal heatsinks.... inside a case they work very badly.... i strong believe if people include the Dx Super A into the Dx Blame MKIII Hx they will have damaged output.
40 volts and lets say 300 miliamperes each rail means 24 watts.... a huge stand by current...this generates a lot of heat.... 44 volts will be even more....will be 26.4 watts..... more trouble if use 45 volts...i hope this is an unloaded voltage.
The other problem is that people will increase current to 0.5 amperes or even more....because this is the current we usually see in several class A power amplifiers....so...people will try because if a lot of factories are using this level of current, then they will try.
Now imagine the trouble with someone that is using 75 volts into the Dx Blame MKIII Hx..... this will represent 75 watts of heat to each channel.... 150 watts of heat...man!... inside the enclosure people is using.... disspated by the small heatsinks people is using (half the size i do think will be good)... this gonna be a tragedy.
Because these worries i said that i do not suggest this circuit to be used together the Dx Blame MKIII Hx that is powered by the standard supply voltage.... i did the testing with mine small unit because was more safe..but even this way i had worries...with reasonable size heatsink to 24 watts of power dissipation, with fan blower...and even this way i have perceived the power transistors as a hot spot.... they where much more hot than the heatsink..this means these ones are not transfering heat...only 12 watts to each one and i found them overheated while compared to the heatsinks...and that difference use to be small when things are operating correctly.... atop of the transistor cannot be too much hot...if we feel hot there and it is not radio frequency units, then it is because heat transference is not fine.
This way, dear A Wayne.... as you will try with 44 volts, take care of ventilation, heatsink size, thermal grease, quantity of output transistors and keep current low.
I have made because people like...i do hate these heaters.... they are good to put a coffee pot atop the enclosure to keep coffee hot...but to Brazilian environment this is a suicide.... despite we have towns that reaches -6 degrees centigrades with snow and ice...usually our environment temperature is around 30 degrées celsius....here, in my place, class A is a madness.
Today i will test with this one...the Dx Blame ST...image attached.
regards,
Carlos
one guy or two said had troubles related the gain.... this way i do think these ones should reduce the gain by themselves to face their personal troubles.
I do not think i should change the entire project because one or two... say... to change officially and to ask everybody to change the gain... the ones that believe this is a need they can do by themselves as this was published by you or by another guy (i do not know exactly the one did).
You have your special demands.... are recognized by uncle charlie as being someone that wants power over low impedance loads....so, a very personal case..someone that have special application in mind...i cannot fix the north of my designs into one particular special sittuation...if this worked great for you, them try your gain modification and be happy.....for a while i will be waiting more complains about.... then i will change.
The class A circuit was not recommended or suggested to be applied together the Dx Blame MKIII Hx....say..the full power unit..with the officially suggested supply voltage....i have just used the assembled board i had at hand in the moment (and it was a Dx Blame MKIII Hx - Home Edition, powered with 40 plus 40 volts) i had the need for a board to test the circuit...i do not think the full power MKIII Hx needs that, and also i have huge fear that this may become a tragedy while using the Dx Super A together the MKIII Hx because it is already too much hot and people is already using too much tiny heatsinks and i am smelling fire and troubles on that....i was clear when i said "home edition".... it is operating with 40 volts symetrical, not 44 volts symetrical...and this already make a difference.
Why that?
A big lie the transistors can dissipate 100 or 150 watts....all lie.... they cannot!....if you try at home, for instance, to apply 10 volts and 4 amperes...then you gonna see the hell thing becomes hot atop of the transistor... in the place you have the component identification number..when we have heat there, this means the transistor is not dissipating...means it is not transfering heat to the heatsink...and this is happening with 40 watts!.... so, these transistors can hole 40 watts or even less...that 100 or 200 watts of specification is not reality because they keep the unit, using huge refrigeration machines and heavy huge metalic block behaving as heatsink (real infinite heatsink) to FORCE the component to be operating at 25 degrées centigrades maximum...this way it can dissipate more power....but never while using the heatsinks people use and submited to the environment temperature.... so.... i do think (observing pictures) that almost everybody is using too much skiny heatsinks....very small area and several are using internal heatsinks.... inside a case they work very badly.... i strong believe if people include the Dx Super A into the Dx Blame MKIII Hx they will have damaged output.
40 volts and lets say 300 miliamperes each rail means 24 watts.... a huge stand by current...this generates a lot of heat.... 44 volts will be even more....will be 26.4 watts..... more trouble if use 45 volts...i hope this is an unloaded voltage.
The other problem is that people will increase current to 0.5 amperes or even more....because this is the current we usually see in several class A power amplifiers....so...people will try because if a lot of factories are using this level of current, then they will try.
Now imagine the trouble with someone that is using 75 volts into the Dx Blame MKIII Hx..... this will represent 75 watts of heat to each channel.... 150 watts of heat...man!... inside the enclosure people is using.... disspated by the small heatsinks people is using (half the size i do think will be good)... this gonna be a tragedy.
Because these worries i said that i do not suggest this circuit to be used together the Dx Blame MKIII Hx that is powered by the standard supply voltage.... i did the testing with mine small unit because was more safe..but even this way i had worries...with reasonable size heatsink to 24 watts of power dissipation, with fan blower...and even this way i have perceived the power transistors as a hot spot.... they where much more hot than the heatsink..this means these ones are not transfering heat...only 12 watts to each one and i found them overheated while compared to the heatsinks...and that difference use to be small when things are operating correctly.... atop of the transistor cannot be too much hot...if we feel hot there and it is not radio frequency units, then it is because heat transference is not fine.
This way, dear A Wayne.... as you will try with 44 volts, take care of ventilation, heatsink size, thermal grease, quantity of output transistors and keep current low.
I have made because people like...i do hate these heaters.... they are good to put a coffee pot atop the enclosure to keep coffee hot...but to Brazilian environment this is a suicide.... despite we have towns that reaches -6 degrees centigrades with snow and ice...usually our environment temperature is around 30 degrées celsius....here, in my place, class A is a madness.
Today i will test with this one...the Dx Blame ST...image attached.
regards,
Carlos
Attachments
Last edited:
Please, do not assemble the Dx Super A module for a while
I have made a huge mistake!.... i forgot important connections that make the circuit to operate dinamically.
Here you have a video explaining the problem:
Do not assemble Dx Super A for a while - YouTube
regards,
Carlos
I have made a huge mistake!.... i forgot important connections that make the circuit to operate dinamically.
Here you have a video explaining the problem:
Do not assemble Dx Super A for a while - YouTube
regards,
Carlos
Uncle Charlie ,
I love Brazilian coffee , promise I will use amp to warm coffee while listening, no temperature would go wasted ..
Uncle the gain is too high for those of us with pre-amplifiers and or CD PLAYERS,
For home edition uncle Charlie needs lower gain, better for sonics , higher bias , of course for those responsible enuff to make the necessary changes and correct voltages...
Regards ..
I love Brazilian coffee , promise I will use amp to warm coffee while listening, no temperature would go wasted ..
Uncle the gain is too high for those of us with pre-amplifiers and or CD PLAYERS,
For home edition uncle Charlie needs lower gain, better for sonics , higher bias , of course for those responsible enuff to make the necessary changes and correct voltages...
Regards ..
Just increase the gain resistor value in order to reduce gain
The one is in the second transistor base.... the resistor in series with the electrolitic condenser...well..you know...adjust it the way you want.
Be happy!
Dx Blame ST was approved together the Dx Super A.
Video being uploaded.
regards,
Carlos
The one is in the second transistor base.... the resistor in series with the electrolitic condenser...well..you know...adjust it the way you want.
Be happy!
Dx Blame ST was approved together the Dx Super A.
Video being uploaded.
regards,
Carlos
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