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PostPosted: 09 Oct 2013, 20:41 
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Location: South East US - Tennessee
Stick with the batteries. If you want to "upgrade" the PS, just use larger 1.5 volt batteries for the filament. It's equipped to run on AA batteries for the filament, upgrade to C or D type. But if you insist, use a wall-wart of about 24max DC and then regulate the DC voltage using regulators. The regulators will make filtering easier since they are generally designed with that in mind. You will need 2, one for the 18volt rail and one for the 3volt rail. I don't recommend an SMPS power unit. You can get good quality DC wall-warts from JAMECO. They'll have some filtering already, so what you add will be minimal. You won't need more than 1amp, in fact you can probably get by pretty easily with a 500mA type, like this one (click here). And here is a recommended LDO regulator, also available from JAMECO and other online retailers: LM1086CS, or a standard adjustable regulator LM317T

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The key to a successful build is to keep the smoke IN the circuit.
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We cannot solve our problems with the same thinking we used when we created them. - Albert Einstien
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LM380 Bridged Guitar Amp, Oatley K301 Phono Pre-amp, Oatley K272 Headphone Amp, Tube proto-board


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PostPosted: 11 Oct 2013, 10:32 
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Joined: 20 Dec 2011, 17:43
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Location: Czech Republic
Okay, thanks a lot for your input! I'll chime in as soon as I have some results to share..


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PostPosted: 19 Oct 2013, 21:01 
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Joined: 19 Oct 2013, 20:46
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Hi Mark, my name is Phil B. I ordered an upgraded K272 kit and an assembled stock K272A from you personally back in early March of '12. Still loving my original build and use it pretty much everyday. In recent research, I see that this K272C kit is in production now. Out of curiosity, are there some matching resistor values in the newest kit to the original K272? I I still have extras and it would be nice to stay on the cheap, as it were.

Cheers,
-Phil


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PostPosted: 20 Oct 2013, 17:28 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
e_phil_b wrote:
Hi Mark, my name is Phil B. I ordered an upgraded K272 kit and an assembled stock K272A from you personally back in early March of '12. Still loving my original build and use it pretty much everyday. In recent research, I see that this K272C kit is in production now. Out of curiosity, are there some matching resistor values in the newest kit to the original K272? I I still have extras and it would be nice to stay on the cheap, as it were.

Cheers,
-Phil

Phil: not sure if there are some same resistor values but for me metal film 1/2W resistors are $0.46 for a pack of 8. I don't even look through my old resistor box when collecting parts for an amp, I just purchase new. It takes less time and the small outlay is worth it. You should be able to download the schematic for the K272C and check it out.

About the K272C it is a huge improvement over the earlier models both in performance and usability. The kit is $40 plus shipping. If you can accommodate another kit or move your old one I'd do it. You will be pleased with the new model.

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Projects: "Grace" - Psvane 6SN7-SE Globe preamp | | "VoXUno" - Single driver MarkAudio 12P speaker | | "Lagoon Take 2" - Single stage tube preamp | Website: retro-thermionic


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PostPosted: 24 Oct 2013, 20:34 
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Joined: 05 Jan 2010, 21:16
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Location: Las Vegas Nevada USA
I've tried the JAN6418. It's highly microphonic and it is VERY non-linear. It basically specs out HORRIBLY although that doesn't mean it doesn't sound good. The ONLY reason I can see for using this tube is battery operation for something like a portable tube headphone amp.

I like the sound the JAN6418 makes. It distorts nicely. If it weren't for the microphonics I would have used them in my Harmonic Sweetner 2.0. To me this device is no different than the one below only it's smaller and draws less power. The basic premise of using a very non-linear tube to create that "tube sound" is the same.

http://www.diyaudioprojects.com/Forum/viewtopic.php?f=9&t=4566

The 12AX7s are cleaner than the 6418 so I had to get creative. The sonic results of driving the 6418 and a 12AX7 hard aren't that different. The 6418 uses a tiny fraction of the power though and runs on very low voltage. I had a design that would have fit INSIDE my guitar, but when I built it all I got was microphonic feedback. Bummer. Even a loud speaker can infiltrate the 6418 although I discovered that a low impedance source on the grid can reduce the microphone effect.

Nice build. I may try one. Thanks for sharing.

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Last edited by sampleaccurate on 24 Oct 2013, 20:50, edited 1 time in total.

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PostPosted: 24 Oct 2013, 20:49 
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mwhouston wrote:
[I don't even look through my old resistor box when collecting parts for an amp, I just purchase new. It takes less time and the small outlay is worth it.


That's definitely the case with me. I know I have the parts but I can't find them in all the junk boxes I have - too many parts to sort through. :confused:

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PostPosted: 24 Oct 2013, 20:56 
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mwhouston wrote:
The earlier images really did show how this whole little project hangs together. The lid is under the preamp doubling as a stand.
Attachment:
K272C.jpg

Very cool. I'd love to see what the outcome would be if a toaster had been thrown at you, one of the old chrome plated vintage types. The stand feature worked out perfectly. I love novel cases and chassis.

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PostPosted: 24 Oct 2013, 21:22 
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Nobody posted the schematic? It IS available on Oatley's website for free download. Publication here should be considered fair use - it is not copyright infringement. If Oatley asked to have it removed however I would do so. Schematic can be found here:
http://secure.oatleyelectronics.com//product_info.php?products_id=1027&osCsid=dgi9fua64sct2lkd29im6jbul6

Image

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PostPosted: 25 Oct 2013, 14:37 
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This thread has convinced me to order this kit. I plan on putting the two channels in series to be used as a distortion generator or simply add another tube stage with the JAN6418s I already have on a daughter board and keep it stereo. The 6418 characteristics are perfect for generating "inaudible" distortion. The only requirement is that they be acoustically isolated when being used. I'm thinking about putting the entire thing is a sound proofed box. The monitors I have can get pretty loud and feedback into the tubes.

I built the original kit. Sometimes the tubes would "ring" producing a relatively clean sinusoidal output. Has anyone had this problem with the new kit? Other than the microphonics and ringing I do like the sound of this tube - it very gracefully rounds off the signal peaks without clipping unless it's pushed to it's limit. I makes a nice signal conditioner for recording instruments on a digital audio workstation. It "removes" the "harshness" of accurate reproduction and actually improves the sound by the way it rounds off the signal peaks without clipping.

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PostPosted: 25 Oct 2013, 17:35 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
I have built about 6 or so K272s including three K272Cs. All those tubes are microphonic but once settled the preamp\headphone amp dies perform well. I think the K272C the best yet. I even have a K272B which never went to production. Oatley also has some tube buffers. Worth a look.

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Projects: "Grace" - Psvane 6SN7-SE Globe preamp | | "VoXUno" - Single driver MarkAudio 12P speaker | | "Lagoon Take 2" - Single stage tube preamp | Website: retro-thermionic


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