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Old 20th August 2011, 08:29 AM   #21
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Default About heatsink size, output power and transformer selection

This was published in the group buy thread, as people is subscribed there too... so, i use to publish something there.

Here is the copy:


The big heatsinks i am suggesting is to face heavy duty work

--------------------------------------------------------------------------------

Full power, distorted power of 10 percent.... continuous distorted power...playing already distorted masters, modern electronic music or Heavy metal distorted music.... two channels driven and using two huge transformers of 2 kilowatts each one of them....so.... the available power, when distorting, will be huge, will go to 1 kilowatt each channel (2 ohms)

And believe me or not, there are guys that does not perceive that as bad sound...they understand that sittuation as "loud sound"...some guys feels distortions as "crisp" sound because introduces harmonics and sound starts to have more "body".... seems more solid...i do think it is awfull, but i see that many guys does not mind... the ones loves distorted, already clipped guitar tones (already present in the audio source recording) do not mind...for them this is much more an effect than a defect.

For "normal", standard use... to average listeners.... the ones does not accept distortion, these 15 by 30 centimeters heatsinks (2 pieces of 15 by 15 attached together in the picture), to one channel, will be good enougth to operate at 8 ohms with continuous undistorted tones (250 watts RMS) and will be good also for musical 500 watts... seems the average is 250 watts and you have peaks that will reach 500 watts or more.... listening normal music, not modern electronic music.... a jazz music, a classical music for instance.

My suggestion to use 7 times this heatsink shown is to heavy duty.... two channels as i said...pumping horrible continuous distorted sound at 10 percent THD levels...two channels playing.... so... power transistor will survive to such kind of torture.

You do not need to do this way if your transformer is smaller....your power to each channel will be, let's say limited, by 50 percent (aprox.) of your transformer power....so, if you select two 600 to 700 watts transformers, then your avaiable power may be around 350 - 450 watts RMS to each channel and this heatsinks shown in the 3D picture will be good for 8 and for 4 ohms...and i do think this is the most rational use.... instead to push the unit to produce 2 kilowatts in stereo with 10 percent distortion (chip amplifiers uses 10 percent specification because people really goes to this level... average people... no audiophile people...less demanding people)

Please, watch the power specifications to 8 ohms and 4 ohms.... this gonna be the most used condition i suppose... watch the demand of transformer power, the continuous power and distortion levels.... your transformer power will be what will decide the power you will be able to put out from your amplifier...so.... take care about this decision and select heatsinks, rectifiers, electrolitic condenser bank.... all this in order to face your custom use...not to waste money buying giant transformers that will never be needed to your particular application.

So, select your power transformer in order to match your power needs...if you need 150 undistorted watts to each channel, if you do not tollerate distortion, then you will be running at this maximum power level...maybe to match your expensive speaker power ration, then select two 300 watts transformers or a single 600 watts transformer.... this will limit your power if you do not increase further entering distortion.... will protect and match your speaker and will save your money in heatsinks, rectifiers, electrolitic condensers, size of your case and transformer...will avoid to waste money and will save your speaker coil to be melted by a crazy kilowatt. sustained power.

Observe that your selection will save money a lot.... to 200 watts you will need 10 thousand plus 10 thousand microfarads to each channel.... two 5A bridge rectifiers will be good...heatsinks will not be that huge...transformer will not be that big too.

Adjust your power amplifier iddle current in order to read 1 milivolt Dc developed across your power emitter resistors, the ones are installed at the power transistor emitters, you have one resistor in each emitter, they may read not that different voltage if they are matched...this will guarantee cool operation.

regards,

Carlos
Attached Images
File Type: jpg 15 by 30 centimeters heatsink to one channel.jpg (58.7 KB, 1617 views)
File Type: png Power specifications 1.png (35.1 KB, 1589 views)
File Type: jpg Warning.jpg (45.8 KB, 1522 views)

Last edited by destroyer X; 20th August 2011 at 08:43 AM.
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Old 20th August 2011, 07:29 PM   #22
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Post Ideas to implement recent changes

I have some ideas about the correction Carlos posted in post#10 and also post#127 In the group buy forum.

The boards were already ordered, and were being made when Carlos posted the change. I’ve been trying to figure out how the change can be made with the existing boards (currently on a FedEx truck). First, I’ll replace the previous numbered schematic and board layout with these new ones. If you look at the new schematic, you see that the changes 1) add a 10ohm resistor (named R31 and written in red) between signal ground and R01, R17, C04, C06 and C07, and 2) redirect R17 from ground to R01, C04, C06 and C07.

Now, if you look at the right side of the board layout, you see that C04, C06 and C07 (in red) are all connected to the same track, which winds its way around to signal ground on the left/middle/bottom of the board. It would seem that this track must be cut somewhere left of C07, then the cut bridged with our new resistor (R31). Because R30 is optional, and will probably not be used by most builders, its upper hole seems a convenient place to put one end of the new resistor. I guess we’ll just have to scrape away soldermask to mount the other end of R31.

It would seem that R17 (also in red) can be flipped around so the end which used to go to signal ground now attaches somewhere to that track which connects C04, C06 and C07.

That leaves R01. The only effect of the change that I can see is to put R31 between it and ground. Because R01 is already 47K, it doesn’t seem that an additional 10ohms will do much. I assume, then, that we can leave R01 alone. This would mean the schematic would actually have R31 in between R01 and C04, with R01 going straight to signal ground.

I’d appreciate people’s thoughts, especially Carlos’ input.

-Byron
Attached Images
File Type: jpg Dx Blame MHIII Hx 2011-07-31_schematic.jpg (108.5 KB, 1570 views)
File Type: jpg Dx Blame MHIII Hx 2011-07-31_board left.jpg (128.2 KB, 1573 views)
File Type: jpg Dx Blame MHIII Hx 2011-07-31_board right.jpg (123.7 KB, 819 views)
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Old 20th August 2011, 08:15 PM   #23
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Default Oh!... all these numbers drives me confused dear Byron

The 10 ohms was already there.... in the original layout from Alex mm.... i do think there is anything to fix...the input ground in alex schematic is already floating (lifted ground)...he made that way...not problems to keep the way he made.

I do not know if i am too much stupid but i could not understand.... modifications?... why?.... is your board different while compared to the schematic?.

Well...today i am not feeling very well....tomorrow i will try to understand your post.

You know... the last schematic has the ground lifted the way Alex mm have made.... so...anything to fix..... ME....uncle charlie is the one HAD to do something...and what i did?...i have included the 10 ohms resistor in the schematic on order not to be different if people compare the schematic and board...board was checked...no error...the only one was that 330/390 ohms resistor...anything more to be fixed.

You know dear Byron.... i have made a new schematic to include the resistor...it was not placed in the previous schematics published...then Alex mm included...he thought i forgot (was not really this way..was my decision to remove) that lifting 10 ohms resistor, the lifted ground..the low noise ground to the input circuit....i have made the schematic to match board...in order NOT TO BE NEEDED to change anything in the board or to provide instructions to forum guys...i am confused.... and result the opposite?..... i made the schematic in order to match the board... to avoid to instruct guys about new parts...the 10 ohms was already there...was only a bureaucratic decision to fix the schematic to avoid confusion.... there's anything that needs to be changed... the board, unless the one i revised, is the same Alex mm board design.

All these numbers confuses me....my brain does not accept these numbers and it blocks the entrance in my neuroniums....i do not use these numbers.....i use values in the board....so, to follow these numbers to understand what you mean is the ultimate torture to uncle charlie...i do think these numbers are terrible...the identification numbers is something i have avoided ...was a big figth to be rid of them man... and now you bring them back to life.

Please, watch the image Byron....resistor is in place.... even the board that had mistake from the Advance Circuits had the resistor in the correct position..what is going on?

regards,

Carlos
Attached Images
File Type: jpg The lift resistor is in place...jpg (183.7 KB, 844 views)

Last edited by destroyer X; 20th August 2011 at 08:31 PM.
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Old 20th August 2011, 09:26 PM   #24
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Default I finally could understand.... was not that easy

as i am not feeling very well today.... vision is confused (i do not drink or use drugs...not even a beer..i do not like alcohol)..... i am strange today.

I see the resistor is not provided into the board...the 10 ohms lifting resistor is not there....maybe is that you intend to say... no problems...it is all right, amplifier works fine without it and also works fine with it.

You have concerns how to wire the 1K to the lifted ground too....no problems, it can be out from the lifted ground.... can keep it the way it is...it is direct to the ground and will work fine this way too.

I hope this is what you meant.....so... it is all rigth.

This 10 ohms resistors is such a long story that i feel lazy to comment...i suppose i have explained that in audio to you, or videos published or posted in the forum...for sure i have explained.... let it be....too much long to repeat.

These ID numbers produces a short circuit inside my mind...i hate that stuff.

regards,

Carlos

Last edited by destroyer X; 20th August 2011 at 09:29 PM.
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Old 20th August 2011, 10:22 PM   #25
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Default ...... pcb in the mirror ?

Sorry but I dont understand what hepend with my designed PCB for MK III HX ?! All components will be soldered on bottom side ????? and silk screen on pads???? I'm totally disappointed he could get out PCB's of the factory To many comments regarding 10 ohm resistor , what big deal , make an link with wire (shortcut) .
Alex.
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File Type: jpg MKIII.jpg (148.0 KB, 751 views)
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Old 20th August 2011, 10:30 PM   #26
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Default Was a mistake from Advance Circuits...but they have accepted

to manufacture boards once again...these ones (picture) gone to the trash box.

People will have new boards with all that stuff fixed....boards are on the way to Byron home.

regards,

Carlos

Last edited by destroyer X; 20th August 2011 at 10:33 PM.
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Old 20th August 2011, 11:27 PM   #27
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Default About lift ground.... comments here

About lifted ground to MKIII-Hx input. - YouTube

regards,

Carlos
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Old 21st August 2011, 11:52 AM   #28
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Default The input connector, the RCA type connector to MKIII-Hx input

Image attached and a video link down here:

RCA connector input for MKIII Hx - YouTube

regards,

Carlos
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File Type: jpg RCA connector.jpg (320.1 KB, 427 views)
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Old 23rd August 2011, 03:17 AM   #29
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Lightbulb Now I understand

I didn't realize that the 10ohm resistor you added to the schematic is the same optional 10ohm resistor Alex added. I though is was a new component which was not in the board. So we can all just forget everything I wrote about cutting tracks and scraping off soldermask.
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Old 23rd August 2011, 01:25 PM   #30
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Default It is all right Byron...both ways are fine

Last videos made about Dx amplifiers...the input connector, the lifted ground is here:

RCA input connector for MKIII Hx - YouTube

And here you have the Star ground, and noise pickup that sometimes happens when using some potentiometer brands:

Star ground and potentiometer noise pickup in Dx amplifiers - YouTube

regards,

Carlos
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