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PetarLD 30th March 2005 07:20 AM

Pictures of my almost complete P68-500W version
Hello, I am very excited since I have build a working P68 and I thought I'd share back with the community that I have learned so much from. Well it is complete as far as the circutry goes, it produces sound, very deep bass might I add. Still working on the enclosure since I can't find anything that this will fit into. Well I was on a limited budget so I didn't buy the PCB but instead I designed my own, and I needed more hours for my senior project too, which this took about 3, plus 9 for the fabrication. Maybe for my senior project in college I will design the amp myself but for now, I used Rod's design.

Well I still have some problems that I have to solve, the 3.3 Kohm resistors R10 and R11 get really hot, even after I changed them to 1 Watt, started out with 1/2 Watt but they got even hotter, so I decided to change them.

The second problem is when I plug the amplifier in the outlet, it makes a THUMP sound when the volume is turned up, is this in any way damaging the output transistors or anything at all, the speaker maybe?

The last problem for now is, when I have the fan working, because Q7 and Q8 heat up the heat sink to a relatively warm temperature, have yet to measure it, there is a hum that is thrown back into the amp, I am pretty sure it is at 60 Hz, and I know it comes from the fan because when I hold it, it has an auto shut off circuit inside and it turns off for a couple of seconds, during which the hum disapears. The fan is 24 VDC, and I didn't use a regulator, only a rectifier and a capacitor which is 2200uF, I just need to know how I can get rid of that hum? Other than that it's pretty noiseless, when it's idiling.

Well here are the pictures enjoy and don't hesitate to ask for more:

Picture of the Subwoofer Controler PCB by Rod

In the construction phase

The Amp's driving circuitry

The bottom side of the driving circuitry

The complete setup bottom of output stage

The complete setup top of the heat sink

Thanks, Petar.

Tazzy 30th March 2005 08:57 AM

I would never have guessed that this amp needs an even bigger heatsink than yours :hot:

Luckily I have allready upscaled my sinks last week. Plans are to finish my P68 before summer.

Optical 30th March 2005 09:18 PM

sorry i dont have an answer too your questions, but id be interested to hear about what you find in the future..

amp is looking good! im planning on doing a similar effort on one myself in the near future..

PetarLD 2nd April 2005 01:44 AM

Yeah, the only reason I need fan cooling is because of the two transistors heating up too much and I am scared of them blowing :hot: .

Giaime 2nd April 2005 12:56 PM

Maybe it's a stupid thing... like wiring the fan too close to input circuitry, or wiring something wrong, or taking power from the preamp power supply...

When I go on fans, I prefer usually to add a separate transformer for that. Or just stick a 110V/220VAC fan...

PetarLD 3rd April 2005 03:51 AM

haha, thanks for proving my stupidity, would a regulator fix the noise? I don't have another transformer.

Giaime 3rd April 2005 01:57 PM


Originally posted by PetarLD
haha, thanks for proving my stupidity
No, I wasn't saying you're stupid, I intended that most of us make many big, beautiful things, but also little stupid things. And the devil is in the details... I was referring to a little wiring mistake that most of us sometimes do.

Sorry if I didn't express me well, English is not my native language.


PetarLD 4th April 2005 10:56 PM

I didn't take it literally, I understand what you are saying and English is not my native language either. I just didn't know how much noise a fan could throw back into the system.


PetarLD 3rd December 2005 11:38 PM

Ok, guys sorry about the pictures not showing up anymore, I had that domain for free but it was only a trial period, I'll try to get them hosted somewhere else, in the meanwhile please feel free to ask me any questions.

Update: I have put this amplifier in an old computer case and I am using the computer ps for powering the cooling fan and it's working pretty good, I'll post pictures of the final product as soon as I go home for christmas break.

TonyTecson 3rd December 2005 11:52 PM

hi petar,

you links seems to be broken from my end..

:smash: :smash:

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