Dx Blame MKIII-Hx - Builder's thread

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I was thinking about you Juan .... you can use the wire you have

the enameled wire you find.... 1 millimeter of bigger diameter ... you can have this wire from a dismantled power transformer... also you can buy in shops... at least in my country we can buy these reels with wire in all diameter..we buy by weight.

Also you can use plastic insulated wires from telephone line .... also you can use ADSL dismantled cables... these ones are low resistance...this is what matters..to keep the resistance at 1 ohm or even lower than that...the bigger the diameter the smaller will be your resistance.

Reel internal diameter can be 20 to 40 milimeters, i have used 30 milimeters reel from a medicine adhesive white tape... a cloth with adhesive, white colour, used in wounds.

The coil does not need to be pretty, as you have not the winding machine to help you...put the turns you want trying to reach 250 turns.... this will be in series with your woofer, and will be good to a 6 to 8 ohms woofer.... at the woofer terminals use something around 100uf/100 volts...or two 220 volts capacitor with 50 volts insulation...you will love the result as this will filter the mids you have in your woofer... only nice bass will be reproduce there....then you pick the audio from the power amplifier terminal, using other pair of wires and in series with the positive install a 22uf bipolar or build a bipolar yourself, installing two 47uf capacitors back to back...connect negatives together and use the two positive sides to connection...this will be in series with the positive (live) audio wire....then mids and highs will go to your tiny speaker that has two drivers (the movie you made).

If you want to perceive more your bass, then install resistors in series with your mid/high speaker...you can try low resistance in series or install a 50 ohms potentiometer or 100 ohms potentiometer... of course in series in order to attenuate mids and highs at same time....then the bass will be more present to your ears.

You should use a speaker enclosure..speaker this way is not good.... you gonna have phase cancellation because the speaker is not assembled into a cabinet (enclosure or box). ... the way you are using you will have almost no bass compared to this same speaker attached to an enclosure.... have not?...use a card box...or a front panel (dipole) and put the front panel in the corner or your room.

Cardbox must be glued not to vibrate too much...it will of course vibrate..but layer of material cannot be clapping.

regards,

Carlos
 
coil next stuff to do...

I will my friend I just got get some materials for that purpose, wow! you just game a recipe for best tasty sound lol, you right I can not feel the bass with out the box is just drawing with to much air, needs to be inside a sealed or vented box, I like the idea of the coil to block mid tones, I use to play with that a long time ago, when I don't even know how they work but now that my mind is more open to ideas, so far this board sounded really good with out box, and no passive crossovers is just that sound is clear with all that, but hey, I gonna get it little by little, thank you again, I'm going to play some pc games, I got to rest my mind a bit, take care.

regards
vargasmongo3435
 
Hello Mr.Carlos Sir, I,m sorry to bother you with this little problem, But about a year ago I send you 3 groups of Transistors. 2 of these groups you acknowledeged you,ve recieved the 3rd group you never said you recieved them. However I ran a trace on that package and it was in a customs office waiting to be picked up. So in my mind you were to busy to picked them up. Thats ok But I got this package back 1 week ago and I remember the package said something to the effect REFUSED,,I Believe I may have send them to the wrong address. Could you please send me your correct address again by my private email address. Thank You Evette
 
Oh!... sorry dear Evette... strange this refused.

I am really needing 2N5551 and 2N5401 or any high voltage audio transistors... these small ones for small signal.

Thank you dear Evette...send them once again...i hope they will not charge you once again for that.

Carlos Eugênio Mergulhão
Rua Dona Balbina Menelau 56 - 1601
Candeias - Jaboatão dos Guararapes
Pernambuco - Brasil
South America
Zip code: 54440-615

It is a good idea to write outside the envelope to avoid customs to bother... reading that they will give their ok to delivery to my home.

"Gift for a friend, transistors for audio, not a business, value below 50 USD"

If shipment is heavy and clear above 50 USD (more than 10 power transistors) then put in more than one package..... if possible, as this increases mail cost.

I am feeling you strong here dear Jack...how are you doing?

I use my ex wife adress for mailing purposes, dear Jack, because there are more employees there to receive the postman...it is 300 meters distant from my place....it is near the beach and employees knows me very well as i have lived there for 15 years long.... since the building was constructed.

regards,

Carlos
 

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I am glad you like Juan Vargas

Use air core to your coil, do not try transformers because the core may saturate, avoid ferrite core...air core is the best option.

The biggest the wire diameter the lower will be your resistance.... also the cost of that copper will increase, also size and weight and troubles to wind using your hands ...heheheheh.

Enjoy and be happy...these things are nice...produce good results, fast, in a simple way.

regards,

Carlos
 
Music still nice!

Hey man music still lovely! no matter what I do is really hard to mess it up lol, I just change the transformer for the larges toroidal I have that supply more or less 54V good.........:up: ok ok now I'm going to have some fun with a bunch of enameled wire hell yeah!..

regards
vargasmongo3435
 

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I can't fit all the parts in my chassis

I bought what I thought was a pretty large chassis but, as you can see from the photos, I doubt that I will be able to fit all the parts inside of it. The stuff sitting outside the chassis are the bridge rectifiers, the soft start, and two fans.

You can see from the photos that much of the space is taken up by the boards, and all that space above and below the boards is wasted. I'm considering bending the transistors and putting the board parallel to the heatsinks, but that would put the transistors at the very top of the heatsinks, which is not as efficient for heat dissipation as is putting them in the center of the heatsinks. Do people think that this will work?

-Byron
 

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Depending on your power needs, I would suggest you remove the external caps and replace the onboards ones with 10KuF and only use those. That's what I'm doing, no extra caps outside the boards.

Why the fans? your outside-directed main heat sinks are good without fans... But your CCS and VAS heatsinks are small, increase them and put the 47 ohms CCS resistor, still no needs for fan.

You should then be good.
 
Yep! caps out, and 22 ohms to 47 ohms

Yep, canonnica is right, take the caps out, plus your heat sink are good enough you want to see what I'm using? is just a plain piece of aluminum bar. lol and is good for now before I order the amplifier chassis, good luck my friend Byron. but you do what ever is the best for you bro.

regards
vargasmongo
 

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rule of thumb is to put the heat (mosfets in this case ) 1/3 up from the bottom .

Is that because hot air travels up? I never thought about it. I guess that makes sense.

The fans are to blow air across the surface of the board, including the on-board heatsinks. I am also planning on replacing the heatsinks with taller (50mm) ones. The aluminum dividers channel the air across the board, and shield the board and signal wires from RFI from the power supply. The problem with the fans is that they are 8cm X 8cm, so if I kept them and the dividers, I can only move the dividers about 1cm each. But even without the fans, the tall capacitors and on-board heatsinks will limit how far I can move the dividers. Also, note that there are no vents in this case at all. With the fans, I would only need to cut a few vents near the front of the chassis. Without the fans, I would need to cut a lot more vents to keep cool air coming into the chassis.

Now, if I got rid of the dividers, that would free up a lot of space (with board parallel to heatsinks) and I could keep my fans.

I'm loathe to remove my filter caps, largely because I paid so much for them! They're super low ESR, low ripple, low inductance etc . . . On the other hand, they are overkill, and I just bought 12 LM3886 chips and some monster torroids from the swap meet. Help! I'm out of control!!

I think I'll put the board parallel to the heatsinks, with transistors on the bottom and play around and see what I can do. I can always bend those dividers if I need to. And I can probably get away with 1/2 the filter capacitors.

Thank everyone for their input,

-Byron
 
I bought what I thought was a pretty large chassis but, as you can see from the photos, I doubt that I will be able to fit all the parts inside of it. The stuff sitting outside the chassis are the bridge rectifiers, the soft start, and two fans.

You can see from the photos that much of the space is taken up by the boards, and all that space above and below the boards is wasted. I'm considering bending the transistors and putting the board parallel to the heatsinks, but that would put the transistors at the very top of the heatsinks, which is not as efficient for heat dissipation as is putting them in the center of the heatsinks. Do people think that this will work?

-Byron

Byron flip the boards upside down and keep the caps, you will appreciate the difference. Myself had to go to monoblocs, due to space issues and heat sink requirements..
 
Myself had to go to monoblocs, due to space issues and heat sink requirements..

Please post pictures! Monoblocks sounds really cool, and I don't think we have anyone building monoblocks!

My concern is the cost. I already bought this chassis with heatsinks on both sides. I have considered an external power supply - or maybe part of the PS, like the transformers and soft start external.

So many options! But none are obviously best. I don't do well with too many options. I can't juggle them all in my head at once.

I'm glad someone thinks I should keep as least some of my filter capacitors. I think I have bonded, emotionally, with my filter caps.:hbeat:

-Byron
 
Oh!... a lot of nice messages.... nice

About bias adjustment:


- When you cannot decrease the current you should increase the resistor value you have in series with the bias adjustment trimpot

- When you cannot increase the current you should decrease the resistor value you have in series with the bias adjustment trimpot

- Depending the transistor gain and also the supply voltage, you may need to adjust the resistor you have in series with the bias adjustment trimpot.... values suggested worked into the simulator and also worked real life...but replacing transistor model, or replacing transistor by other with different gain, we have to tweak the adjustment once again.... usually the trimpot has range enough to "cover" or compensate these variations...but if you face troubles and cannot adjust....if current is too much high even increasing the trimpot resistance...or if the current is too much low and you cannot increase the current decreasing the bias trimpot resistance adjustment..them proceed to replace the resistor that is in series with the trimpot in order to make it work to your special case.

regards,

Carlos
 
I can't fit all the parts in my chassis

I bought what I thought was a pretty large chassis
it looks like you developed and built the amplifier while of after you were procuring your chassis.

I suggest you build up an amplifier on a piece of board. Add on all the nice to have options. Look at how it can be packaged. Mimic that package and particularly the way the inter wiring will end up and test again for hum and noise and oscillation. Then decide what size chassis is required.

The fans should not be needed.
DX PCB near but not touching the heatsinks and vertical will save a lot of space. Throw away the internal aluminium panels. They are not achieving anything useful. You can measure their effect before you discard them.

High quality PSU comes before anything else in a power amp. Keep the good caps, all of them. Keep the PSU very compact. Transformer to rectifiers to smoothing cap wiring should be very short. Before you cut the transformer wires. Experiment with rotating the transformers to minimise hum in the two channels. Then cut to final length.
 
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Back in july while waiting for the boards to arrive, I made a paper model to see how everything could fit inside a given box... Yes, I took an evening "rolling" paper caps and transformers :p... But it gave me this (see pic), and now everything is going as planned. Within a week I should be done and I will posts the end result. It's gonna look mucho like the paper model... a tad heavier though.
 

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