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PostPosted: 17 May 2010, 03:15 
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Joined: 06 Jun 2008, 18:23
Posts: 5134
Location: Australia
Bennybuis wrote:
beware from Oatley, you may buy something from them and never receive it, they will not answer your e-mails and laugh at you at the telephone. This kit I never got turned out expensive now, counting all the phone calls to Australia. Even my very dear friend Mark, having a good relationship with Oatley, couldn't help to solve the situation, Oatley lied to him as well. I ordered 3 kits from them, one of it I just never got.

I believe Oatley has sent the kits but for some reason Benny does not receive them. I am hoping to talk with the owner of Oatley shortly to see what is happening. I and a number of others have all bought kits from Oatley which have all arrived.

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Projects:"retro2308" - chip based headphone amp | ”Calibre 834” - tube phono MM preamp | ”najah” - Raw 180W Tripath Class D power amp | "Icon" - Shuguang CV-181Z preamp


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PostPosted: 18 May 2010, 07:07 
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Joined: 02 May 2010, 08:45
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I just received my two K272A kits in the US less than two weeks after ordering FWIW.


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PostPosted: 18 May 2010, 07:39 
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Joined: 28 Oct 2009, 02:34
Posts: 501
Location: Utrecht Nederland
Hi everybody,

now at least Oatley admitted to Mark that they screwed up and never sent the kit to me. Supposedly it is all fixed now. Well, we will see.

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Greetings from Holland, Ben

My DIY Audio Projects:
- Single-Ended 12B4A tube amp with ECC802S driver
- DIY Push-Pull KT88 tube amp (OddWatt amp from scratch)
- 832 / GU32 tube push-pull amplifier project


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PostPosted: 18 May 2010, 07:42 
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Bennybuis wrote:
now at least Oatley admitted to Mark that they screwed up and never sent the kit to me. Supposedly it is all fixed now. Well, we will see.

Benny it may take a couple of week for the kits to show.

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Projects:"retro2308" - chip based headphone amp | ”Calibre 834” - tube phono MM preamp | ”najah” - Raw 180W Tripath Class D power amp | "Icon" - Shuguang CV-181Z preamp


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PostPosted: 25 May 2010, 16:36 
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Joined: 24 May 2010, 10:50
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Hey all, I'm new to the forum :)

I just built the kit! I added the option to switch between TRS and RCA-connectors.
Attachment:
CLOSED.jpg

Attachment:
OPEN.jpg

However, there's always a low-volume background hiss, regardless the headphones I use. I tried Sennheiser HD485 (32 Ohms), Westone UM1's (25 Ohms) and some cheap earbuds.

Also, when using the UM1's, the basses are really boomy and sound distorted (clipped). Does anyone know what may cause this and how to fix it?


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PostPosted: 25 May 2010, 19:35 
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Strange with these preamps/headphone amps, some people get hiss other don't. I only finished one for a repeat customer in Singapore the other night and it is perfect.

Try turning the gain down. And try a totally different battery. I only use lithium batteries.

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PostPosted: 26 May 2010, 04:40 
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Joined: 24 May 2010, 10:50
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mwhouston wrote:
Try turning the gain down. And try a totally different battery. I only use lithium batteries.

The gain doesn't seem to have any effect on the hiss at all. Changing the batteries does not help either. I even tried hooking up an external power supply, but the hiss does not diminish.

Also, as you can see in the pictures, I lined the inside of the box with alu-foil to provide some shielding & reduce hum. It doesn't really seem to have any effect at all... when I touch the foil you can hear a loud buzz as well.

Any other ideas?


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PostPosted: 26 May 2010, 05:10 
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Electrically connect all the foil areas. Connect all the foil areas to the RCA ground and battery ground. Try that.

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PostPosted: 26 May 2010, 06:06 
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Joined: 24 May 2010, 10:50
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mwhouston wrote:
Electrically connect all the foil areas. Connect all the foil areas to the RCA ground and battery ground. Try that.

Did that, does not do much either.

I tried rewiring my circuit so that the switches are bypassed and I just have TRS-to-TRS connection, but the soft hiss is still there :bawling:


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PostPosted: 26 May 2010, 06:12 
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Hiss will ocure in most tubes at various levels. It can also be controlled by reducing the filament voltage/current. See if you can reduce the filament volatge by 0.1V. A series resistor with the filament should work.

What voltage is across your filaments at the momment?
Is the hiss the same in both channels?

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