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6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)
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Author:  Robbie7 [ 28 Feb 2010, 12:25 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

Hmm,
Regarding the cap's. It looks like a trade-off.
To tell you the truth I am not sure witch way to go now with this information.
What do you think , any suggestions?
This will be my first kit and I would like the best of all worlds Sound, Quality, and Portability.
And yes I know, from an engineering standpoint. Nothing is free !
I might have to give this one some more thought...

Author:  matt1234 [ 01 Mar 2010, 00:09 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

Hi,
Regarding the Caps (you mean the 220 uF right?)

there should be no problem for 12.5 mm, maybe with a bit of leg-bending but should fit quite ok on the 272A in my opinion.

I've changed the resistors to 1% Metal-foil type(after the tubes, because it is not amplified and rather static), installed an OPA2134 and it reduced the background noise. But using them with 32 Ohm headphones there is still some.

So my question would be if Silmics would give another improvement (I also wonder why there even are such big Caps in the Signal Path, maybe someone could give me some info on that)?

Another idea is to apply a higher Voltage to the Opamp to have more choice regarding this part.

Matt

Author:  deniss [ 01 Mar 2010, 02:08 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

I just put an order in to Oatley through their website for a K272. Reading previous posts, I guess this means that I'll be getting the original kit, not the newly revised one. I emailed paul@oatleyelectronics to ask whether that is the case.

Anyhow, I'm planning to use this device as a pre-amp in my audio system, which consists of an Onkyo DVD receiver/player with 6 pre-outs and 2 integrated amplifiers (Onkyo A-RV401 and Yamaha DSP-E492). While I do already have pre-amps as integrated components, obviously, I wanted to use this DIY preamp to boost the signal going from the DVD receiver to my integrated amps (long story). Will this *tube* preamp be compatible with the rest of my audio components, which are all *solid-state*? Or is this pre-amp intended to drive tube amps only?

Cheers
-Denis

Author:  mwhouston [ 01 Mar 2010, 06:23 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

Robbie7 wrote:
Do these new kits have a rev. number ?, so when I order the kit I would like to receive the newest kit available :thumbsup: .

Robbie7- I only have the old kits.

Guys - these Kits have put Oatley on the world map. They claim they ship near two kits a day all over the world, particularly Asia!!

Also I have used 470uf low ESR caps on the output with no space issues.

Author:  Beftus [ 01 Mar 2010, 07:16 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

mwhouston wrote:
Guys - these Kits have put Oatley on the world map. They claim they ship near two kits a day all over the world, particularly Asia!!

Stock up on JAN6418 tubes now, before they will be prohibitively expensive! :mrgreen:

Author:  Robbie7 [ 01 Mar 2010, 10:35 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

Great,
Where can I go to buy it now and extra tubes ?
How many tubes do you suggest for spares, I am thinking (2) ?
I sent the e-mail previously for where to buy with up-graded parts, however I have not received an e-mail on that one, so I have been holding off. It may have been lost in cyber-space.

Author:  mwhouston [ 01 Mar 2010, 16:09 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

Robbie7 wrote:
Where can I go to buy it now and extra tubes ?
How many tubes do you suggest for spares, I am thinking (2) ?
I sent the e-mail previously for where to buy with up-graded parts, however I have not received an e-mail on that one, so I have been holding off. It may have been lost in cyber-space.

I have spoken to the owner of Oatley, Branko, about the poor response to international e-mails. A few have bought the kits from me because they couldn't get a response from Oatley. Just keep trying.

I will e-mail Banko directly again to let him know others are trying to contact the company.

Author:  Gio [ 01 Mar 2010, 23:00 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

matt1234 wrote:
Another idea is to apply a higher Voltage to the Opamp to have more choice regarding this part.

A higher voltage, especially with the OPA chips will help quite a bit. The OPA213x sound good at +/-9V.

deniss wrote:
Will this *tube* preamp be compatible with the rest of my audio components, which are all *solid-state*? Or is this pre-amp intended to drive tube amps only?

Yes. Mark has used the kit as a preamp so he should be able to provide a few comments using it in this role.

Author:  Robbie7 [ 01 Mar 2010, 23:28 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

Wow,
That's new information that I have not heard off.
Please post more information !

Author:  mwhouston [ 02 Mar 2010, 01:19 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

Guys, this is where the designer has been quite clever: he uses the opamp chip (unity gain) as a driver. I use the OPA2134s for preamp specific use and the standard chip for HP drivers. The tubes cannot drive so the chip does all the grunt work.

You should have no drive problems regardless of power amp etc.

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