Dx Blame MKIII - Builder's thread

efragnani

New member
Yes Lira. One per channel. I'll make this a powerful amplifier unit, even i'm sure that I'll never get him to play at full power, because I'll always use it at home. I think that with this configuration, I can use it smoothly in adverse situations.
Greetings!

Eu vou fazer uma unidade mais potente desse amplificador, mesmo tendo certeza que nunca vou colocar ele pra tocar a toda potencia, pois so usarei em casa. Penso que com essa configuracao, posso usar ele tranquilamente em situaços um pouco mais adversas sem forçar seu funcionamento, a 40-60% de sua potencia.

Abraços.
 

Lira

Member
Finally my boards has arrived!

Can't wait to assemble them!


Thanks to Carlos and Thanks to meanman64 and everybody that made this possible!

 

destroyer x

Compulsive builder
I am following the thread, thank you all as you're publishing

pictures when receiving your boards and saying thanks.... i ensure you i am reading and feeling good with your gratitude, and happy that you have received your boards.

regards,

Carlos
 

mj777

New member
DX Blame MKIII HX on test

Greetings to you Sir Carlos, I have finished 2 channels of the MKIII and now I'm testing it, my voltage reading on some testing point are as follows:
Dc offset: -4 millivolt
Bias adjustment: reading on the 100 ohms resistor in series with the positive and negative rail is 4.7 volts
Voltage across 0.47 ohms 5 watts Resistors 0.9 millivolt
output transistors used are: mjl4281A and mjl4302A
drivers used: mje15034 and mje15035
pre drivers used: mje15030 and mje15031
bias transistor used: mje15032.
All the transistors came from a good friend Evette(Joseph) and are really very good.
I have tested the amplifier and played some instrumental music, and really the sound is so clear, crisp
crystal clear with a punchy clear bass. I just played it on a 1/3 volume at the meantime and is really working fine.
Except for one thing I noticed the pre driver transistors reaching a temperature of 50 to 52 degrees celsius im talking about the two transistors in the seperate small heatsinks, Are this normal Sir Carlos? But the output transistors are not heating it is only around 30 degrees celsius.
I'm using a rail voltage of plus/minus 68 volts dc from a 50-0-50 volts ac transformer rated 10 amperes.
thanks in advance for any comment or input u can share, especially Sir Carlos.

Regards,
mj777
 

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destroyer x

Compulsive builder
52 degrées celsius is not that bad...but you can replace heatsinks by larger ones or

introduce added "L" shape aluminium strip together your heatsink to help it to lower your temperature to 45 to 48 degrées celsius....of course the better solution is to replace by taller heatsinks, bigger ones.

Depending the supply voltage you can have more or less heat there, as power is the current multiplied bu the voltage present from colector to emitter.... watts of heat will appear there.... the ones are using 70 volts or even more voltage will have higher temperature.

I dislike this temperature, i do not think this may burn, but for sure i would like these transistors operating less hot.

In my home testings, these transistors where attached to the main heatsink, reason why i could not notice these small heatsinks could be a problem...i do think the substitution for bigger ones can be a very good idea.

regards,

Carlos
 

meanman64

Member
How much space is there between the board and heatsink are you sure nothing touches the sinks beneed the board?
 

destroyer x

Compulsive builder
About that heat our friend have measured..if not a assemble trouble, then we can fix

producing a resistor replacement as explained below:

People that feel these 2 small vertical heatsinks too much hot can reduce VAS current in order to reduce heat there.... i have simulated and i found the original schematic fine... with the modification you will have changes in performance, but not that huge.

The 22 ohms resistor that sets the CCS current can be increased to 47ohms in order to reduce current...then you will have these transistors mounted into vertical heatsinks (CCS to VAS and VAS transistor) less hot.

I found power there not that big...the left one is the CCS transistor, CCS to feed VAS (Voltage Amplifier Stage) and it is dissipating 1.65 watt.... the rigth side one is the VAS transistor, the second stage, the most active unit, following the buffer and the power there, dinamic power, will be around 1 watt....not that huge power and the small heatsinks should fit in most of the cases... exception is when people is using higher supply voltage... say... really higher voltage.

You can replace the 22 ohms resistor by a 27 ohms, 33 ohms, 39 ohms or 47 ohms.... i suggest you to go to 47 ohms because will really cool down in order to work fine with tiny vertical heatsinks... with this resistor replaced, the performance when using low impedance output loads will clip earlier.... some loss in power...not that huge, not that important.

Some high current, high voltage and high speed diodes installed into the output, in the power transistors, from colector to emitter, can be used too as we gonna face some back EMF there.... so, if you intend to push the amplifier hard, then search for high speed, high current diodes used to fly back purposes there...what model to use i cannot suggest you as i do not use them, so they are not familiar to me... search for high power amplifiers and copy the diode model to apply to yours....this is to play heavy metal, full power, distorted sound and connected to 2 ohms loads... an extra protection if you intend to operate your amplifier above the limits, entering distortion and draining huge ammounts of current and generating enormous output having a lot of back EMF in your output line.... normal civilized use will not need these diodes.

If you intend to use your amplifier under the dB competition of bass...then for sure you gonna need these diodes as you will operate in clipping mode and speaker will generate back EMF high voltage spikes that may destroy your output...diodes will "eat" these spikes helping you a lot.

These diodes usually are in the output, nearby the power transistors..from positive line to output line and another one to the negative line to the output line..... or from power transistor colector to emitter, one to each rail, one up and other down...both with arrows pointing up when schematic is draw standard, input at left, output at right side, positive is up and negative is down..this is standard position to draw and show and read schematics.

Enjoy your amplifier boys...sound is awesome and you will perceive that instantaneously.

regards,

Carlos
 

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mj777

New member
Some more pictures in the testing

nothing touches between the board and the heat sink, the gap is around 5mm, also i think i will use a bigger heat sink on the VAS transistors, over all it is really very strong and refined amplifier from DX corporation, thank you Sir Carlos for sharing this amplifier.
 

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mj777

New member
DX Blame MKIII HX on test

Sir Carlos I have made two things to decrease the temperature for the VAS transistors first I increase the size of the heat sink and the temperature came down to about 43 to 45 degree Celsius but I don't like how it looks, so what i did to another board is i put the transistors under the board and it works fine no more heating up so i think i will do the same on the other board. I attached some pictures for you to see.

regards,
mj777
 

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Lira

Member
producing a resistor replacement as explained below:

People that feel these 2 small vertical heatsinks too much hot can reduce VAS current in order to reduce heat there.... i have simulated and i found the original schematic fine... with the modification you will have changes in performance, but not that huge.

The 22 ohms resistor that sets the CCS current can be increased to 47ohms in order to reduce current...then you will have these transistors mounted into vertical heatsinks (CCS to VAS and VAS transistor) less hot.

I found power there not that big...the left one is the CCS transistor, CCS to feed VAS (Voltage Amplifier Stage) and it is dissipating 1.65 watt.... the rigth side one is the VAS transistor, the second stage, the most active unit, following the buffer and the power there, dinamic power, will be around 1 watt....not that huge power and the small heatsinks should fit in most of the cases... exception is when people is using higher supply voltage... say... really higher voltage.

You can replace the 22 ohms resistor by a 27 ohms, 33 ohms, 39 ohms or 47 ohms.... i suggest you to go to 47 ohms because will really cool down in order to work fine with tiny vertical heatsinks... with this resistor replaced, the performance when using low impedance output loads will clip earlier.... some loss in power...not that huge, not that important.

Some high current, high voltage and high speed diodes installed into the output, in the power transistors, from colector to emitter, can be used too as we gonna face some back EMF there.... so, if you intend to push the amplifier hard, then search for high speed, high current diodes used to fly back purposes there...what model to use i cannot suggest you as i do not use them, so they are not familiar to me... search for high power amplifiers and copy the diode model to apply to yours....this is to play heavy metal, full power, distorted sound and connected to 2 ohms loads... an extra protection if you intend to operate your amplifier above the limits, entering distortion and draining huge ammounts of current and generating enormous output having a lot of back EMF in your output line.... normal civilized use will not need these diodes.

If you intend to use your amplifier under the dB competition of bass...then for sure you gonna need these diodes as you will operate in clipping mode and speaker will generate back EMF high voltage spikes that may destroy your output...diodes will "eat" these spikes helping you a lot.

These diodes usually are in the output, nearby the power transistors..from positive line to output line and another one to the negative line to the output line..... or from power transistor colector to emitter, one to each rail, one up and other down...both with arrows pointing up when schematic is draw standard, input at left, output at right side, positive is up and negative is down..this is standard position to draw and show and read schematics.

Enjoy your amplifier boys...sound is awesome and you will perceive that instantaneously.

regards,

Carlos

Try using MUR860 Diodes, they are shotkey, and for 8 amps; I always use them for other proposes, and i can say they are good!
http://www.datasheetcatalog.org/datasheet/fairchild/MUR860.pdf

Best Regards

Lira
 

destroyer x

Compulsive builder
Thank you Lira and also thanks to MJ777

Was nice you to inform your tests MJ777, i will inform people about your results.

regards,

Carlos
 

destroyer x

Compulsive builder
Uncle Charlie!....my amplifier is not working!

Here you have something about.

regards,

Carlos[video=youtube;FXeWVbIwgwI]http://www.youtube.com/watch?v=FXeWVbIwgwI[/video]
 

destroyer x

Compulsive builder
Meu amplificador não funcionou!....my Blame amplifier is not working

Algumas possiveis razões estão descritas nesse video.... some possible reasons are described in this video.[video=youtube;vt5e7pITIdc]http://www.youtube.com/watch?v=vt5e7pITIdc[/video]

regards,

Carlos
 

mj777

New member
my DX MKIII HX near to finish

some update pics......
 

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mj777

New member
Finally my DX Blame MKIII HX is finish

A finish amplifier from Sir Carlos hard work, i'm very happy with the outcome. The sound of music from this amp is really loud, but clear and defined, you will not regret building this amp. Thank you Sir Carlos for a very well designed amp. I love it. I have attached some pictures for all DIYers like me to see. cheers...

regards,
mj777
 

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mj777

New member
Well done. Nice assembly.
How did you build the box enclosure?

Thanks for appreciating my work Sir giololucas, the box enclosure was a recycled case from a big damping resistor for a solar power panel. It was given to me as a gift by my good friend Junie, and it was a really good fit for the MKIII project.

Regards,
mj777
 

giololucas

New member
Thanks for appreciating my work Sir giololucas, the box enclosure was a recycled case from a big damping resistor for a solar power panel. It was given to me as a gift by my good friend Junie, and it was a really good fit for the MKIII project.

Regards,
mj777

Ok mj. Thanks for your reply. I´m building an amplifier too.
First I did the smps with help of diysmps to power it, and now I´m searching for a way to do a nice box to assembly it.
Good luck.
 

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