my 1st ever D-amp, WORKING!!!

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#165
I just thought it's not much money to try it since I already have a stock of 300+ NPN switching transistors sitting here doing nothing. 😉

since each can only take about 15A each, I'm starting small, for a car amp doing around 400W total. and even that would take at least 10 pairs of transistors for the primary side.
 
#166
2nd build

!!! WARNING!!! LARGE GRAPHICS!!!!



Hello again guys,


side view:

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another view: man!! bad looking solder!!!

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THe board, UNetched.....🙂

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Board etched, coated with clear gloss lacquer, to keep it clean...(but hard to solder 🙁 )

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Top view/ no MOSFETS yet

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Another view... see the deadtime adjustment trimmer???

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Underside, ugly SOLDERING tsk tsk

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separate modulator board (daughterboard)

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now I had to clean up the board, I hate solder BLOBS/bad solder joints?? perhaps.....
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top view

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underside.. see my home made 50milliOHM?? its a brass shim, measuring 7.5mm x 3mm x .001mmthick... i get aroud .055ohms with that....nice n clean solder..

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modulator TOP

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modulator copper side... nicer solder.. believe me, it would have been MUCH easy if SMD was used in THESE board....

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The 2 boards, side by side....

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boards COMBINED:

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now the amp, happily playing..can you see the switch?? to enable/disable current source??
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about the AMP:

I used 18/18V @2-3A, +/-25V unloaded with 2,200uF filter caps per rail( i know its small).. but its only for testing porpuses...

>>DC offset(with current source ON) = -8.00mV
>>DC offset(with current source OFF) = -120.00mV

i have no clue as to WHY I ALWAYS GET negative values.. 😀 maybe negative side mosfet driver is "sucking" more power from the Hi side? hahaha

>>RMS output?? with current PS, maybe 50Wrms..for the fact im just using (+/-18V@2A).. just playing around with it...

basically its my -MORE REFINED- diy UCD... runs much cooler too(the series pass transistor regulator powering-up the hi/lo side mosfet drivers).... as you can see in the pictures, I just put small heatsink and NO heatsink for IRFZ40.. YAH! you read it right.. IRFZ40.. heheheh just want to play around...just for kicks... but it works 😀 but the real reason is I HAVE NO IRF540 in my junk(YET)..still need to buy some..but at those supply voltages, MOSFETS are barely warm to the touch(even at full volume settings).. btw, that board has NO op-amp buffer YET..Im just driving it with a low impedance source(like the HEADPHONE out of my CD-player).. that is where I control the volume since it has level-out control....

the WO03090343A2 patent && UM10155_1(Philips) patent DID help me a lot in understanding and refining my diy ucd.... I suggest you read them too...

what I have gained from those patent/s was optimized modulator/oscillator || better filtering in&out of circuit || less powersupply shoot through(less heating of POWER component/s) || and of course nicer looking board hehehe no seriously, its a more compact layout.. less EMI/RFI(my main goal) as you can see, its much tighter....switching and modulator as close as possible to one another.... and perhaps SOME ground plane,I know , its just single sided...2 sided would be complicated, but I can do.. just lack of time...

I believe this 2nd make would be a big difference in sound quality and overall layout and also EMI/RFI emmisions....

-whew-


@Gertjan,


Im going to do your suggested mods regarding power supply RC filtering for op-amp buffer... that would be cool! thats my next project, the other board with over-voltage/overcurrent/op-ampbuffer/and its regulated supply...

@Chris,

how are you?



well, thats all for now.....

Regards,
Raff
 
#169
SDF,

thanks...😀 hard work really pays off



Chris,

well, I had to DO something... only lowest value I could get is 220milliOHM 2W... paralleling 4 of them would come close to 55milliOHM... BUT is physically large...

I searched the net for a software that could calculate PCB track resistance... found TRC100.. quit nice app.. and free too... 😀

now Im off to making the other circuit (op-amp buffer && the UCD protections)

wish I HAD a scope 😀



Regards,
Raff
 
#170
You're going to end up with a highish dc offset if you use the 5532 op amp, might look at something like an opa2134 instead. Also I'd encourage you to further investigate discrete solutions... For the sake of fun and learning etc.

I just got a scope btw..... no probes yet. 😡

Can't help but think you'd appreciate it alot more if you just made a second channel before worrying about the input stage. Stereo is a blast.
 
#172
classd4sure said:
You're going to end up with a highish dc offset if you use the 5532 op amp, might look at something like an opa2134 instead. Also I'd encourage you to further investigate discrete solutions... For the sake of fun and learning etc.

I just got a scope btw..... no probes yet. 😡

Can't help but think you'd appreciate it alot more if you just made a second channel before worrying about the input stage. Stereo is a blast.
Click to expand...

i GOT 2 diy ucd already.. remember my 1st build??
😀

its still up and running fine... 🙂 i did NOT canibalize it for parts... I just need 2 IRF540 for my new diy..and make another board with buffer/ucd protection.... 🙂
 
#173
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Chris,

see?? stereo.... 2 channels 😛


the leftmost one, my 1st build....it STILL needs
some minor tweaks(compared to my new one), but is a performer already...I
plan to make another new board and transfer some
parts to it....

the middle circuit is the amp newly built, but needs
buffer and protection...

rightmost, is my SMPS.... +/-55VDC @4A...


btw,

been playing around again with the regulator section(hi/lo mosfet driver)..had to get more current OUT of it.... final result: -0.8mV(current source ON) // 355mV(current source OFF)... so I guess I could go DC coupled with it now, right???

Regards,
Raff



🙂
 
#177
Re: Convert PC power supply to amp supply

Bent said:
Raff,

Since you are such a clever guy using up used parts to create an audio masterpiece (if not visual ;-) ), why not try this?

I am not sure if it is even possible actually, however it seems to me even most of the PCB could be used.

Cheers, Graeme
Click to expand...


never tried them... but I know its possible... but i think limited voltage/current output due to smaller transformer.....

and I have NEVER ever built an SMPS from mains-> DC... 🙂
 
#178
my 2nd build completed

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direct link:
http://i6.photobucket.com/albums/y209/beamrx5/IMG_0034.jpg



the op-amp buffer + protection board, finally
connected....


ALL I can say IS : ONE HECK of an AMP... 😀
even with supplies of only +/-19 (+/-25V unloaded) ,
IT DELIVERS!!! so superb!!

DC offset(at speaker output, speaker disconnected) is
6mV, still with coupling caps... wanna GO DC coupled
some other time.... op-amp (NE5532) offset is around
15mV with input grounded....

all I need is another channel to make it stereo..

as you can see, I used another larger coil at the
output....its a PQ core.. with about 1.2mm airgap in
the middle.... 9Turns and measures about 22uH..

AND some additional filtering for the op-amp buffer..

well, nothing else more to say ...

Bruno, I salute you!!! for such a POWERFUL yet
simple(discrete) amp!! 😀
Chris, Kartino, and others.. thanks!



cheers,
Raff
 
#179
@ chris,

is this just normal for DC offset to VARY from 50mV down to 20mV at speaker output? I Have gone DC coupled....

seems like I need to HEAT up the amp 1st before offset becomes stable...


btw, I have just finished another board for stereo... IM still stuffing IT with parts.. canibalized some parts from my OLDER diy UCD...

Regards,
Raff
 
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