Hi. I measured the 100p caps that i found and 1 of them has a resistance that doesn't change and it is 7k. The other one if in switch polarity of the multimeter the resistance varies until infinity.
I presume that the one with 7k is damaged, right???
I presume that the one with 7k is damaged, right???
the resistance across all the capacitors is shifting when i measure them but this is just 7k. now i have to search again for 100p.
If i use ceramic, the amplifier will work??? or i risk burn it again?
If i use ceramic, the amplifier will work??? or i risk burn it again?
Dont use the broken one... throw it in the bin now.
You could put 2 220p caps in series to get 110pf
You could put 2 220p caps in series to get 110pf
AndrewT said:
what about this ceramic-cap? Are this one good for audio?
http://www.farnell.com/datasheets/76082.pdf
They are not as linear as say polyester or polypropylene... which means there is a greater variance between its capacitance at say 20 hZ and 20Khz... if you will hear it straight away is debateable... but it will work. and you can always swap it out later....
The only ceramic caps that are good enough for audio and are not so quickly frowned on is np0 or sometiles also called c0g caps... they are almost as linear as polyproylene.
The only ceramic caps that are good enough for audio and are not so quickly frowned on is np0 or sometiles also called c0g caps... they are almost as linear as polyproylene.
Hi,svemir said:
rubbish for coupling audio.
Ceramic are excellent at VHF. They cannot be beaten. But don't pass audio through either of the HiK versions.
The C0G = NP0 are a little better but never as good as plastic film in the audio frequency range. They change capacitance with applied voltage.
I keep ceramic for supply rail decoupling/deglitching and some builders won't even use them for that duty either.
Your choices for audio coupling are PP, PS, PES, MICA (teflon is too expensive). In small values only the last two give any reasonable choice of values. Here in the UK mica are ten times dearer than PP so I only buy what I actually need after measuring the built amplifier.
I have powerd the amp and its sounds better then my LM4766 🙂 .
When I will have the acc charged for the camera i will make photos of it.
So I wish to thank you very much for your help and patience (sometimes i do ask stupid questions).
When I will have the acc charged for the camera i will make photos of it.
So I wish to thank you very much for your help and patience (sometimes i do ask stupid questions).
Hi
I just made some photos of the amplifier. Here they are, and a small question regarding the speakers at the end of the post:
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It sound well to. A little strange at very low volumes, but powerful bass at high level.
Until I build the other amp's for my speakers I have another question: if I have 2 speakers in my enclosure and they are 8 ohm each, I want to connect them in parallel and use only a capacitor on the tweeter. Can I do this at 35V dual supply (theoretically I will end up with a 4 ohm speaker enclosure). The reason why I want to do this is the filter that I have in my enclosures are not the same and one speaker sound very different from the other. So by using just a capacitor for the tweeter I presume that I can make them sound the same. Can some one help me with this to?
I just made some photos of the amplifier. Here they are, and a small question regarding the speakers at the end of the post:
.
.
It sound well to. A little strange at very low volumes, but powerful bass at high level.
Until I build the other amp's for my speakers I have another question: if I have 2 speakers in my enclosure and they are 8 ohm each, I want to connect them in parallel and use only a capacitor on the tweeter. Can I do this at 35V dual supply (theoretically I will end up with a 4 ohm speaker enclosure). The reason why I want to do this is the filter that I have in my enclosures are not the same and one speaker sound very different from the other. So by using just a capacitor for the tweeter I presume that I can make them sound the same. Can some one help me with this to?
Hi adi81bv,
Are your output transistors really mounted dry as they appear to be in your pictures?
-Chris
Are your output transistors really mounted dry as they appear to be in your pictures?
-Chris
Yes they are 😀 , but just for a short period. They don't get that hot - i can put my hand on top of them and they are under 50C. The radiator is colder. This is because i don't listen to loud and have a huge vent (same size as the radiator) that blows air from 5cm.
After i get back from my vacation I'll make the second amp, build a nice box and also put some thermal grease between the transistor - mica - radiator.
I really like the sound of this amp. Never had something like it before. Now I realize that some mp3 files coded at lower bit rate sound worst then ones with 320 kbps.
Well this is my last post for 10 days - until then have a good time. Bye and thanks for the help.
After i get back from my vacation I'll make the second amp, build a nice box and also put some thermal grease between the transistor - mica - radiator.
I really like the sound of this amp. Never had something like it before. Now I realize that some mp3 files coded at lower bit rate sound worst then ones with 320 kbps.
Well this is my last post for 10 days - until then have a good time. Bye and thanks for the help.
You need to shorten the wires to the main transistors as short as possible. The output stage of the P3A is a Sziklai pair and these are sensitive to oscillation. Long wires will set that off.
I would say your output transistors are fakes too... certainly the one with the ON logo is. They look nothing like the genuine ON parts I have here. I would say they are MJ2955/2N3055 instead, which will work, but dont push it. No 4 ohm loads, and keep the power supply to +/- 35V
I would say your output transistors are fakes too... certainly the one with the ON logo is. They look nothing like the genuine ON parts I have here. I would say they are MJ2955/2N3055 instead, which will work, but dont push it. No 4 ohm loads, and keep the power supply to +/- 35V
Hi jaycee,
LOL!
-Chris
LOL!
That was to be my next comment. Probably why it isn't oscillating right now.
-Chris
Are you sure that they are fake. Because if so... in Romania probably there are no original transistors this way. 🙂 I'm happy that it sounds good.
Can you give me a picture of an original ON transistor?
If they were original, you say that i would have problems (oscillating because of the long wires)
Can you give me a picture of an original ON transistor?
If they were original, you say that i would have problems (oscillating because of the long wires)
Hi adi81bv,
If you go to www.onsemi.com and call up the data sheet, the specify the package and markings in the datasheet.
-Chris
If you go to www.onsemi.com and call up the data sheet, the specify the package and markings in the datasheet.
-Chris
Originals I recieved from OnSemi samples programme about 4 years ago:
Also, Rod Elliot's page on counterfeit transistors, specifically the MJ15003/4 pair:
http://sound.westhost.com/fake/counterfeit-p1.htm#mj15003
Really, no matter what transistors you use, you need to keep the wires to the output transistors as short as possible. If you were using faster power transistors then you would definitely have issues (the main reason I don't like the Sziklai pair output stage!)
An externally hosted image should be here but it was not working when we last tested it.
Also, Rod Elliot's page on counterfeit transistors, specifically the MJ15003/4 pair:
http://sound.westhost.com/fake/counterfeit-p1.htm#mj15003
Really, no matter what transistors you use, you need to keep the wires to the output transistors as short as possible. If you were using faster power transistors then you would definitely have issues (the main reason I don't like the Sziklai pair output stage!)
OK, thanks for the advise. I will shorten the wires but after I build my amp box, to be sure what radiator I'll use and construction method. For now I'll just keep it at lower volumes.
From the photo you posted..... your sample seem strange, because of the bad orientation of the markings. (the text is not very strait? or it spreads in the right part) And my ON transistor has very good orientation of the text.
The reason way the text is so thin and one could not read easily all letters is because I tried to wipe it with acetone, and rubbed like 10 seconds to see if the text will be removed. I also mention that I had no success in removing the paint with my nail, thats why i tried the acetone.
Again my transistors:
-the ON tr. seems original, i don't know about Motorola (but I hope that it is a old stock)
From the photo you posted..... your sample seem strange, because of the bad orientation of the markings. (the text is not very strait? or it spreads in the right part) And my ON transistor has very good orientation of the text.
The reason way the text is so thin and one could not read easily all letters is because I tried to wipe it with acetone, and rubbed like 10 seconds to see if the text will be removed. I also mention that I had no success in removing the paint with my nail, thats why i tried the acetone.
Again my transistors:
-the ON tr. seems original, i don't know about Motorola (but I hope that it is a old stock)
Hello, unfortunately they look fake to me too. Take a photo of the bottom side of the transistor and also from the side (showing the thickness of the mounting plate). Then, I can confirm......
I tried to make some photos. Here they are:
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I also measured the thickness of the legs, diameter of the blue epoxy, the distances between the legs. They all are in the specifications of the ON data sheet. Also they are steel cases (I saw one in aluminum in my town 😀 a cheap store, and I said the guy that is a fake and he look at me very angry)
Bye bye for 10 days 🙂................
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I also measured the thickness of the legs, diameter of the blue epoxy, the distances between the legs. They all are in the specifications of the ON data sheet. Also they are steel cases (I saw one in aluminum in my town 😀 a cheap store, and I said the guy that is a fake and he look at me very angry)
Bye bye for 10 days 🙂................
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