Hi camelator,
after all the trouble shooting and advises, we (Mr. Mile and his fans ) deserve some pics here...
reg
prasi
Beautiful PCB, what's the size ?
see post 7089 ; http://www.diyaudio.com/forums/solid-state/164093-100w-ultimate-fidelity-amplifier-709.html
Thanks,
Eric
please excuse, I was very busy this week end but I will post full pics of my system this evening.
Everything is up and running fine. Sound is really good. But I am facing two issues:
1/ Finally I understood how bias works and how to better use my multimeter (yes I am a typical noob) and was able to adjust bias.
Unfortunately, I can not reach the 130ma expected as temperature look high.
At around 70ma it is 68°C
Here is my heatsink system: the mosfets are fixed on a big aluminim heatsink with adhesive thermal pad. It looks like dissipation is working as the heatsink is hot.... Not hotter than the mofsets but very hot. I have to say I have 2 FX8 on this heatsink.
2/ I tried to put a 100K ALPS on the signal path between my DAC and the amp to balance between analog volume and digital volume, because sound is too lound for my speakers (I have to set max 15% volume on my DAC to fill the room). But I am facing a humm.... I think it is related to ground loop and star grounding... But after several tests like link the signal ground from the input of ALPS to the star ground, I was not able to correct it. Without ALPS no hum.
well... I will post pics this evening.
please excuse, I was very busy this week end but I will post full pics of my system this evening.
Everything is up and running fine. Sound is really good. But I am facing two issues:
1/ Finally I understood how bias works and how to better use my multimeter (yes I am a typical noob) and was able to adjust bias.
Unfortunately, I can not reach the 130ma expected as temperature look high.
At around 70ma it is 68°C
Here is my heatsink system: the mosfets are fixed on a big aluminim heatsink with adhesive thermal pad. It looks like dissipation is working as the heatsink is hot.... Not hotter than the mofsets but very hot. I have to say I have 2 FX8 on this heatsink.
2/ I tried to put a 100K ALPS on the signal path between my DAC and the amp to balance between analog volume and digital volume, because sound is too lound for my speakers (I have to set max 15% volume on my DAC to fill the room). But I am facing a humm.... I think it is related to ground loop and star grounding... But after several tests like link the signal ground from the input of ALPS to the star ground, I was not able to correct it. Without ALPS no hum.
well... I will post pics this evening.
Your heatsink is to small for 70mA bias... set bias to 30mA.
You must use preamp to isolate 100k pot, you can find nice and simple line preamps with OP in this thread.
Regards
this is what I have been doing last few weeks-universal chassis for most of discreet amplifiers supplied with 10-58vdc per rail,all with 11A of current,40000 uF per rail, with apex zack protection, clipping indication,with raised voltage for 10Vdc 1A per rail(related to output stage voltage) to supply VAStage with 1000uF per rail,all decoupled with about 30 smd 100nF per rail. it has regular soft-start but instead ceramic resistor I plan to use small 40W 230V light bulb. using a switch in series to soft-start relay I can use test mode (something gets wrong and �� light turns on) or regular soft-start mode.
transformer is toroidal 1000VA and it has 2x7.5,2x11 and 2x25Vac all 11A,2x12Vac 1A to supply apex zack protection, and 2x9Vac 1A for raising VAS voltage for 10V higher than main rails are.
combining secondary voltages I can get many symmetrical voltages from 2x7.5 to 2x43.5Vac:
7.5Vac
11Vac
17,5Vac (25-7.5)
18.5Vac(11+7.5)
21.5Vac(25+7.5-11)
25Vac
28.5Vac(25+11-7.5)
32,5Vac(25+7.5)
36Vac(25+11)
43,5Vac(25+11+7.5)
all of them rated at 10A.
I still have to buy heatsinks, it will be two of them with main plate thick 10mm,and the ribs will be 30mm high at every 10mm distance,each heatsinks 20cm wide and 15cm high.
transformer is toroidal 1000VA and it has 2x7.5,2x11 and 2x25Vac all 11A,2x12Vac 1A to supply apex zack protection, and 2x9Vac 1A for raising VAS voltage for 10V higher than main rails are.
combining secondary voltages I can get many symmetrical voltages from 2x7.5 to 2x43.5Vac:
7.5Vac
11Vac
17,5Vac (25-7.5)
18.5Vac(11+7.5)
21.5Vac(25+7.5-11)
25Vac
28.5Vac(25+11-7.5)
32,5Vac(25+7.5)
36Vac(25+11)
43,5Vac(25+11+7.5)
all of them rated at 10A.
I still have to buy heatsinks, it will be two of them with main plate thick 10mm,and the ribs will be 30mm high at every 10mm distance,each heatsinks 20cm wide and 15cm high.
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Hi Mr Mile,
Many thanks for your answer,
As promised here are the pics of my prototype.
At the center is a raspberry pi 2 with DAC powered by a meanwell smps.
I know I have to do better with the power supply, but hey...step by step. I am learning.
What I can say about the sound....
Bass... Well... Excellent. Better than my previous class d amplifier in term of quality...It is a surprise for me as my power has a little riple current. I can not say bass have more power... Not bass are just perfect in a quality way. precise and strong.
I also notice benefits in vocals: on high frequencies I always had little noise with my previous class D amps.
With FX8, it is a clear improvement. No Noise, and the vocals are perfect (if it is possible).
The issues I am facing:
Improve power supply
Preamp for volume control :I have px6 in mind because I think the FX8 boards can be used with little changes... I hope it is a good choice.
adjust bias -> It is a surprise for me, the heatsink is not small..So i don't know if I have low bias what can be the impact on the sound quality...
Sometime, I have pop while changing songs... Don't know why.
Sometime I don't know why, When I power on my system I have no sound. I suspect a kind of rejection current as I don't have diodes in serie in my power supply, but I don't know to be honest. I am noob.
Again, many thx all the writers here for help and advices.
Regards,
Christian
Attachments
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since I can not upload pictures from my mobile,here is a link to a fb album,i hope you could see it...
https://mobile.facebook.com/aleksandar.mikulic/albums/1490914354267343/?_rdr
I have same heatsink on my stereo FX8 and use a small 60mm 12v graphics CPU cooler fan (speed reduced to inaudible with 100R resistor) and it stays perfectly cool. These fans are $1 ea and can use a 7812 voltage regulator from main supply if <35v. Or wind some wire around your toroidal trafo to pull off maybe 8v and rectify and smooth. I am running 120mA to 150mA bias current and it stays around 30 to 35C.
Pops from changing songs is your DAC. Some of them do that when they don't have auto-mute function on song change or bit rate change. Mine does it too CS4398. Not all the time but sometimes really bad and have to unplug DAC and replug it in or even reboot PC.
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Hi xrk971,
many thx for the tip, but I hate fan as it is very audible for me... so... If I have no choice... Well... maybe I'll do it.
for the pop, I am not sure it is only a DAC issue: in my previous system, I have the TPA3116 and a tube pre, and I had no pop (with the pre or without). But I have to say I just changed the player, and it maybe a software isue.
I got a lot of tips from you by building this amp... So many thanks for the sound I have in my room.... Far far better than my DENON class D amplifier, and far better than the other amps I had. and I am learning a lot.
regards,
Christian
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Adding a resistor is a good way to prevent the motor starting as it gets older.
It is far safer to generate a lower voltage for a more reliable starting.
Pass gave us a very simple low voltage drive for a fan motor that gave a short term higher voltage to ensure the motor did start when required.
It is far safer to generate a lower voltage for a more reliable starting.
Pass gave us a very simple low voltage drive for a fan motor that gave a short term higher voltage to ensure the motor did start when required.
Do you have a Schematic for this Mr. Miles? Is this based on FX-100 PSU?http://www.diyaudio.com/forums/solid-state/162081-dc-servo-mosfet-amplifier-61.html#post4624521
reg
Prasi
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Yes it is based on FX100 PSU but can be use for any other amp and I rename it to PSU100
Regards