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6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)
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Author:  Gio [ 11 Mar 2010, 00:08 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

Different operating points. ;)

http://tubedata.milbert.com/sheets/127/6/6418.pdf

Author:  mwhouston [ 11 Mar 2010, 02:52 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

Beftus wrote:
Gio wrote:
And it does sounds better! :headphones:

Please explain it to me like I'm a six year old... What does a higher plate voltage do? Better S/N ratio? Does a higher plate voltage always equal better sound?

I'm giving no reasons here so shoot me if you wish. But the higher plate voltage the better. Now some valves operate on low plate voltages but high current to achieve a good wattage output. Other valves can handle high plate voltages and lots of current. Transmission tubes for example.

Dynamic headroom comes into it. This is possibly why transistor amps can sound a little congested. 80Volt +/- rails (160V swing) compared to 400V plate swing. That's a crude explanation but I think most will agree its half right.

Author:  metzb1 [ 02 May 2010, 09:02 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

Hi, I'm new to this forum and found it when searching for information on the K272 headphone amp. I've been involved in the audio hobby since I was an early teen and my grandfather gave me his home-build folded K-horn loudspeaker. I have been building speakers ever since but have never built an amp kit. I am a mechanical engineer by education, so electronics are a bit mysterious to me since I can't see the workings, although I have a basic understanding and know enough to be dangerous. ;)

I just bought an iPod and haven't had a tube amp since I was a teenager (long time ago... :smoking: ). I decided to order two K272 kits from Oatey and I'm looking forward to building and trying them out. I have read that some are using an 18V supply for these kits instead of the single 9V.

One of my other hobbies is model airplanes and helicopters. The battery technology used in that arena is Li-Po. The cells are 3.7V each and come in a wide variety of capacities. They have a high energy density and are rechargeable, so they are a great choice for a portable amp. :idea:

Question: If I run a 3s (three cells in series) Li-Po battery, the amp would see 11.1V. I assume from the previous posts that this would be well within the operating limits of this amp. Does anyone see problems with this configuration?

Brian

Author:  Beftus [ 03 May 2010, 13:50 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

metzb1 wrote:
Does anyone see problems with this configuration?
I don't think that will be a problem at all.

Author:  jacy [ 06 May 2010, 22:49 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

Hi Gio and Mark,

thanks for sharing your K272 DIY project. I plan to build a headphone amp for my ipod + tripfi 10 pro. just wondering am I able get better SQ from ipod lo -> amp ->TF10? I don't have big headphone, is it necessary to use a amp for TF10 as it's a low impedance (32 ohms) and high sensitive (117 dB SPL/mW) IEM. if an amp will definitely improve the SQ. compare with this tube based amp and CMOY amp, which one would better suit for TF10? TF10 is quite cold, quick and metal feeling IMO. I'd like adjust little bit warmer, would this tube amp do the work? btw, what's the size of this PCB, would it fit into a hammond 1455 case? is it alright to carry around listen music on the go with those 2 extremely microphonic valves?

please forgive me ask so many questions. :blush: as I never tried amp before and none of my friends have one so I can test. any comment will be much appreciated.

Author:  mwhouston [ 07 May 2010, 21:38 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

jacy wrote:
Hi Gio and Mark,

thanks for sharing your K272 DIY project. I plan to build a headphone amp for my ipod + tripfi 10 pro. just wondering am I able get better SQ from ipod lo -> amp ->TF10? I don't have big headphone, is it necessary to use a amp for TF10 as it's a low impedance (32 ohms) and high sensitive (117 dB SPL/mW) IEM. if an amp will definitely improve the SQ. compare with this tube based amp and CMOY amp, which one would better suit for TF10? TF10 is quite cold, quick and metal feeling IMO. I'd like adjust little bit warmer, would this tube amp do the work? btw, what's the size of this PCB, would it fit into a hammond 1455 case? is it alright to carry around listen music on the go with those 2 extremely microphonic valves?

please forgive me ask so many questions. :blush: as I never tried amp before and none of my friends have one so I can test. any comment will be much appreciated.

Having built both the CMoy and the Oatley tube headphono amp, which I made portable, I would recommend the Oatley portable triode headphone amp. Yes I you hit the case the tubes will ring and any cell phones close will induce into it. But the sound is dreaming. Very fluid, warm, and musical. I run mine on two 9V lithium batteries in parallel and are yet to change the batteries.

My phones are the Phiaton MS400s closed back and Audio-Technica AIRs both 32ohm phones. My player is the Cowon S9.
Attachment:
HPTriodeAmpSS.jpg

Author:  jacy [ 08 May 2010, 04:08 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

thanks for you recommendation and prompt reply. I'll get one kit. hope it portable enough for carry around. Oatley should give you commition as your blog make this kit popular around world :P

thanks again and I may have more question when I get it.

Author:  mwhouston [ 08 May 2010, 18:25 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

jacy wrote:
thanks for you recommendation and prompt reply. I'll get one kit. hope it portable enough for carry around. Oatley should give you commition as your blog make this kit popular around world :P

thanks again and I may have more question when I get it.

I made mine in a solid plastic case, as you can see. The case is lined with AL foil and tar. I use mine mainly on the train so I can sit it on the seat beside me. Weight and size have not been an issue. I went for quality of sound over convenience knowing mostly how it was to be used.

From a twisted point of view I went for bragging rights. A portable triode headphone amp that runs on batteries is a unique device. One thing I did do is to ensure there is no way it is on without me knowing. Both input jacks have switches and an on/off switch at the back. So there must be connections at both inputs and the switch on before juice will flow. I used pure silver wire throughout and my list of upgrade parts right across the board.

I didn't include a pot because I can control volume from my Cowon. I just set a small amount of gain in the amp. It realy is just used as a headphone driver. I used the PT2308 chip which comes with the kit. It is designed to drive HP better than the OPA2134 which I use in this kit when I want a preamp.

Author:  Bennybuis [ 17 May 2010, 00:28 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

Hi everybody,

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.

Author:  Bennybuis [ 17 May 2010, 01:54 ]
Post subject:  Re: 6418 Tube / Opamp Headphone Amp (Oatley Electronics K272A)

Hi everybody,

I just got an e-mail from Oatley. Paul Witherly promised me to u send the missing kit right a way. Well, sounds good for the first time in month, I wanna be fair, so if Oatley does me right after all, I will tell you guys.

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