(NOISE) Gainclone with bridged LM4780 - diyAudio
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Old 24th October 2007, 09:48 PM   #1
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Default (NOISE) Gainclone with bridged LM4780

Hello everyone !

I build gainclone with audiosector parts.

I buy big toroid transformer Avel Lindberg.

I build all my amp with twisted cable "normally" for reduce the noise.

The box is in aluminium

etc...etc...


When I start the gainclone I have background noise (60 hz).

Do you have TIPS to kill this noise ?
ex: nF capacitor in parallel with the 1500uF or other TIPS ?

I know many people have this trouble with her first gainclone.

P.s. it's not only when the preamp source is pluged on my amp.
it's ALWAYS !

Thanks for your HeLp !

Nick
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Old 25th October 2007, 05:16 AM   #2
CJ900RR is online now CJ900RR  Sweden
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How have you connected ground from wall to refferens ground?
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Old 25th October 2007, 01:40 PM   #3
sek is offline sek  Germany
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Hello Nick,

a picture tells more than a thousand words.

Sebastian.
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Old 31st October 2007, 08:12 PM   #4
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Hello all,

I am like Nick. i have different details though. I hope we don't become confused with the type of gainclone.

I have recently constructed a gainclone (the BrianGT). I can say that the GC design was interesting for me because I had always wanted to construct a OTL amp and the designs are very similar - coincidence? Also I had never built a solid state component before or havenít built anything for many years.

I can say that the audio characteristics are very impressive and I will experiment some more.

For now I only have some bookshelves and a pair of full-range in bass-reflex. I prefer the sound of the full range but have one concern, there is some high back noise with the full range - I believe because it is a very sensitive driver because there is less for the bookshelf. I have no audible hum (from the PS) therefore I would like to know if somebody has correctly filtered this noise or if this is possible. I have already viewed many subjects in this forum but cannot manage to conclude with this exact objective.

I have decided not to use a potentiometer but have not yet placed any input resistor. I am using a simple passive preamp with attenuator (10K) and have also tried the sound card of the PC and the noise always remains.

Thanks in advance for your advice.

M

ps. The photos I have are too large to be posted (only 800KB)
If you provide the email, or another method, I can then send
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Old 1st November 2007, 12:37 AM   #5
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Default gainclone NOISE

Thanks for your answer !


I don't have pics for you because I destroy my old gainclone aluminium enclosure to built a blend of russian plywood & plexiglass & led new enclosure to have great look.

I'm not sure but......... I try ihihihihi


Bye !
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Old 1st November 2007, 08:08 AM   #6
defect9 is offline defect9  Ireland
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I had some pretty bad hum from my last amp build. turns out I had about 4 things all working against me. Not sure if anything I did will help you, but I'll post my experience.

My first hum came from my chosen source, my computer. easily fixed by switching out the source. I knew it was the source because it got louder when I turned the potentiometer up.

My second hum issue was with improper grounding and isolation of my switches. they were grounding to my aluminum case.

My third hum came from my potentiometer as a part of the ground loop hum, again grounding to the case

My fourth hum was my headphone out, yes, once again, grounded to the case.

Basically, i had 5 ground points strewn around the case. I removed the entire amp assembly from the case and there wasnt a bit of audible hum. Admittedly, this is with a tube amp, but the principles are the same. when i do finally put it all back together I'm going to isolate everything that caused ground issues from the case with teflon, or build an entirely new face plate. Anything to keep the case from turning into a ground loop nightmare.

-Jared
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Old 2nd November 2007, 07:30 PM   #7
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Post gainclone

thanks for your ground loop answer

BUT

I'm disapointed to have many many ground trouble with this VERY BASIC AMPLIFIER.

When you take a look to the (3500$US) GAINCARD UGLY circuit and power supply with EL transformer.

I don't understand why when you take better parts you have trouble.

EL transfo (gaincard) VS toroidal (gainclone)

cheap parts VS best parts. etc.....etc.....


ByE !!!

NickThevoice

Gainclone RULEZ !!! hiihihi huummmmm i'm not sure
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Old 2nd November 2007, 08:39 PM   #8
defect9 is offline defect9  Ireland
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Could you post some pictures? perhaps we can determine the problem by looking at the build. you can email me at narcissist69@hotmail.com and I can resize them for posting.

No matter how good the parts are, one small mistake can change how good it sounds. Have you tested the amplifier without the aluminum case?

-Jared
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Old 5th November 2007, 08:01 AM   #9
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Default Gainclone photos

Hello Jared,

I have emailed you with my photos.

Greetings,
MV
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Old 5th November 2007, 10:02 PM   #10
defect9 is offline defect9  Ireland
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Posting these for mavallarino to help determine possible noise areas. More eyes are better than my eyes

Click the image to open in full size.
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Click the image to open in full size.
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