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 NEW  Bruce Heran outlines the details and construction of his simple DIY 6DJ8 (ECC88) Tube Hi-Fi Headphone Amplifier Project.

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 Post subject: Amp noisy
PostPosted: 15 Apr 2014, 03:17 
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Joined: 26 Sep 2008, 03:50
Posts: 89
Hi there. I am not too active here as I am not a very big DIY guy after trying my hand at a couple of things, just to see if it is for me. I did assemble a tube amp a couple of years ago and it still works!! :P

But, it is a bit noisy. It sounds like a dull buzzing sound coming through the speakers. The sound stays the same loudness regardless of volume level or if there is an input connected or not.

Where does one start looking? It is a push-pull amp using 6l6gc tubes and is based on the dynaco designs according to the designer of the kit. I will try and attach a schematic.

Question: The 6.3v ac line for the filaments/heaters, can one filter that as well maybe?


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 Post subject: Re: Amp noisy
PostPosted: 15 Apr 2014, 03:40 
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Joined: 08 Aug 2009, 03:11
Posts: 1301
Location: Chilliwack, BC
Hi,

Could possibly be a dried-out capacitor (a couple years old, unlikely, but manufacturers to put out the odd lemon ;) ) or a solder joint gone bad.

Cheers!

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 Post subject: Re: Amp noisy
PostPosted: 15 Apr 2014, 04:21 
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Joined: 26 Sep 2008, 03:50
Posts: 89
Ok, which ones do you think I must have a look at first? The ones in the PSU section I guess? C6,7,8 ?


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 Post subject: Re: Amp noisy
PostPosted: 15 Apr 2014, 05:45 
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Joined: 02 Mar 2009, 12:41
Posts: 790
Location: Vänersborg, Sweden
When talking about the wiring for the filaments - twist the wires, keep them far away from all signal circuitry as much as possible.

There are also some ways to "de-hum" the circuitry but a balance pot and by lifting the relative level above cathode voltages:

Image

Image

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 Post subject: Re: Amp noisy
PostPosted: 16 Apr 2014, 06:18 
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Joined: 26 Sep 2008, 03:50
Posts: 89
Just a quick update, going through some tips given by the designer, a lot of this noise is actually coming from my 12au7 tubes... Replacements on their way.....


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 Post subject: Re: Amp noisy
PostPosted: 17 Apr 2014, 10:01 
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Joined: 04 Jun 2008, 20:59
Posts: 2237
Location: Arizona, USA
Hi, 12AU7s? the schematic shows 6U8s. I would concur that the filters capacitors might be the cause. A constant hum regardless of volume is a really good indication of insufficient B+ filtering. I would also do the modification to raise the heaters from ground potential. This can really quiet an amplifier.

Good listening
Bruce

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 Post subject: Re: Amp noisy
PostPosted: 22 Apr 2014, 04:31 
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Joined: 26 Sep 2008, 03:50
Posts: 89
Yup, they are 6u8's. I got confused between the version 1 and 2 of this kit.


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