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Old 1st January 2010, 04:33 PM   #1
imagios is offline imagios  Czech Republic
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Default 6418 tube preamplifier - Oatley Electronics

I just finised my tube entry project
the AN6418 Valve (Tube) Preamplifier / Headphone Amp Kit
its quite nice and really affordable, for the sound it self I subjetively must say it sound very clear I was missing nothing, therefore im satisfied with the kit.
see the image of the amp here http://hex.dan.sweb.cz/minitubeamp/DSC_0837.JPG

does anyone here made it as well?

For the begining I builded it as it came, but I would lilke to make a few changes so I would like to get the experience from someone else as well.

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Old 2nd January 2010, 12:26 AM   #2
kevinkr is offline kevinkr  United States
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Looks interesting, how about some information on where to get it, and a link to the seller's website. It's unfamiliar to me and probably a lot of others here.
"Extraordinary claims require extraordinary evidence." - Carl Sagan
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Old 2nd January 2010, 12:41 AM   #3
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This looks like it:
Raytheon JAN6418 Valve (Tube) Preamplifier / Headphone Amp Kit
"It is hard to imagine a more stupid or more dangerous way of making decisions than by putting those decisions in the hands of people who pay no price for being wrong." ~Thomas Sowell
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Old 2nd January 2010, 12:58 AM   #4
Brit01 is offline Brit01  United Kingdom
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This looks like it:
Raytheon JAN6418 Valve (Tube) Preamplifier / Headphone Amp Kit
Yep was just about to say this.

I came across this the other week. Interesting miniaturized pentodes.
I wonder how they sound compared to the common size tubes that we use.
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Old 2nd January 2010, 01:11 AM   #5
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Neat. The filament/VR2 setup on V2 is kind of odd though.
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Old 2nd January 2010, 11:02 AM   #6
imagios is offline imagios  Czech Republic
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I bought it on australian Ebay: K272 - STEREO TUBE PREAMPLIFIER - HEADPHONE DRIVER KIT - eBay Tube, Valve Amplifiers, Amplifiers, Audio, Electronics. (end time 18-Dec-09 15:46:10 AEDST)
as Oatley Elec. do not ship to Czech Republic.

Its easy to build, sound for a amateur nice. But I never lisened to a tube amp therefore please take this with some distance. newer the less I have a headphone amp self made from a kit based on the TDA7053 chip and personaly I like these tubes more than the chip. (but this must say nothing)
Im not much knowledgeable in electronics, so I build only kits. But I would for sure change some parts on the board. a potentiometer would be fine...

I would be interested to know the THD at the amp... but have no equipment to measure it.

But as a introduction to tubes I think its great 1-easy to build, few parts that you can hardly mix up, 2- low voltage (Im not skilled egnouth to play with deadly voltages) 3- good sound (subjetively on common headphones) I will as well conect this as a preamp to mi tripath amp from 41Hz to see what difference it will make.
Never the less I was not sorry to instal golden cinch to the amp and a quite expensive jack connector as you might see here http://hex.dan.sweb.cz/minitubeamp/DSC_0836.JPG

as well for thouse who might be interrested the "shine" of the petodes:
(ISO 200; 30 seconds exposition)

the biggest problem with the amp is the ring sound comming from vibrations they suggest to use rubber grommets, that I dont have and that are not a par of the delivery(thats a pity) but I dont know how much bether it will become. I can not imagine to use this as a travel amp in a bus,car, train as I think it would ring... but to have it on stable place makes it a quite nice travel amp, desk at work, library, waiting room, what ever ...
One common 9V battery can power the amp for good 10 hours without loose of "power"
but I think to buy a Li-ion batery and make it a travel amp with rechargable embeded batery. Quite easyer than to exhange bateries.
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Old 13th January 2010, 02:57 AM   #7
poynton is offline poynton  United Kingdom
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Anyone know about Oakley's K261 preamp Kit.

It seems to use a smal smps to supply the 30v HT.

Oatley Electronics
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If it ain't broke, break it !! Then fix it again. It's called DIY !
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Old 13th January 2010, 09:54 PM   #8
Beftus is offline Beftus  Netherlands
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I have one too and decided to upgrade some of the mediocre quality parts since I want to use it as a preamp with my mini Aleph in the living room.

Here's my BOM
Resistors: all resistors 1% metalfim types
Caps: C1,C2,C4,C5 MKP1837 0.1uF C7,C8 Elna Silmic ARS 220uF 25v
Trimpots: Piher 1M
Opamp: OPA2134PA

I replaced the opamp socket with a better one and connected a decoupling cap (a "104") to the supply pins on the reverse side of the PCB.

For the tubes I came up with a diy socket. I butchered a large IC socket to make two 5-in-line sockets for the tubes. Tube (re)placement now is quick & easy.

The Elna's are 12.5mm diameter and they just barely fit. I plan on using MKP1837 0.01uF bypass caps on the Elna's once I have them.

As for tube dampers I use a short piece (~32mm) of clear silicon tubing with the side cut open.
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File Type: jpg DSC_0363.jpg (54.3 KB, 947 views)
File Type: jpg DSC_0366.jpg (91.9 KB, 939 views)
File Type: jpg DSC_0367a.jpg (120.0 KB, 947 views)

Last edited by Beftus; 13th January 2010 at 09:58 PM.
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Old 13th January 2010, 10:04 PM   #9
Beftus is offline Beftus  Netherlands
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Imagios, take a look at a piece of your photo. The stray strands are a shortcircuit waiting to happen... Cut them!
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Old 13th January 2010, 10:30 PM   #10
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All -- Good info here --

Raytheon JAN6418 Valve (Tube) Preamplifier / Headphone Amp Kit

There also are several great threads on the forum for this site.
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