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Old 28th April 2007, 10:19 AM   #1
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Default K-12G First Time Build

K-12G Stereo Tube Amplifier

Hello to all that love valve amplification. Well I finished my amp kit with most of the mods per Voltsecond. First I have to commend this person for his comprehensive site on this amp, working with tubes in general, and electrical safety. By the way his mods do work with the "G" model. As this was my first build I did a lot of research paying close attention to the hazards involved. I took an electronics course right out of high school. The first thing next to Ohm's Law was. Don't become part of a circuit. I dropped out after DC circuits. Math was too hard at the time. Should have stuck with it.

Any way when I fired this thing up it was awesome. No problems at all. It has been on for 14 hours continuous now(plan is to burnin for 24 hours). I connected my iPod to it and the sound was incredible. One thing I noticed was without any input there was a very slight hum with the volume all the way up. With the iPod connected, total silence. Being a newbie I don't know if this is normal. I don't own an occiloscope but would like to eventually get one. Any economical suggestions? I just want to say that lots of research, proper soldering and triple checking everything along the way will pay off. A can of air is a must have.
I have some pictures to include but don't know how to insert as I'm a newbie to diy. Thanks Voltsecond. I have better amp because of your site.
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Old 28th April 2007, 01:35 PM   #2
Sherman is offline Sherman  United States
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Join Date: Feb 2004
Location: Chicago area
Congratulations on successfully completing your amp!!! Welcome to the wonderful world of tubes.

A very slight hum with the volume pot all the way up and no input connected isn't unusual and shouldn't be cause for concern.

One note of warning- you have just stepped onto the slippery slope and my prediction is that you will not be able to stop now! Soon your residence will begin to fill with tubes, sockets, resistors, capacitors and the occasional working amp. Within two or three years you'll be able to heat your house just by turning on your tube amps.

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Old 28th April 2007, 04:54 PM   #3
jduffy is offline jduffy  United States
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Right on, nice job.

I'll second Sherman's thoughts:

So what's your next build?
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Old 28th April 2007, 07:15 PM   #4
drj759 is offline drj759  United States
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Join Date: Jul 2006
Default Re: K-12G First Time Build

Congratulations on your build.

Originally posted by TubesRule6656

I don't own an occiloscope but would like to eventually get one. Any economical suggestions?

There's lots of advice on buying scopes on this site. A couple of threads on the subject:
Kofi Annan in: "Oscillatin' in the Bevois Valley'"

This a good beginner 'scope?

In summary from what I've gathered on this site: Buy an analog scope. Stay away from digital and PC based USB types. Minimum of 50 MHz bandwidth, dual channel. Best would be a 100MHz or better (high bandwidth is recommended in case you need to troubleshoot an amp that oscillates).

Best bet is a Tektronix. I would not recommend buying anything older than a Tek 465 (no boatanchor 500 series). You could probably find a Tek 465, 2213, 2215, 2235 for $50 to $250 on ebay that may or may not need some repair (buyer's luck). Probably twice that price range if you buy from an ebay store that guarantees working units. Shipping may end up being more than the scope price so you need to factor that into your risk assessment of what and where to purchase. Other sources are local hamfests, tech surplus sales.

Mine is a Tek 454 that I picked up at a hamfest for $20. It amazes me how rock solid it performs despite its age of 40 years. I had to replace one cap in the power supply though. It's got a bunch of those cute little 6CW4 nuvistors inside.
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Old 28th April 2007, 07:56 PM   #5
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Thanks. I believe your right. Im hooked. I knew I could do it as I built my own computer.
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Old 28th April 2007, 07:56 PM   #6
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Join Date: Apr 2007
Thanks this is the next project when i get the $s. Anyone know how to post pictures. Can't tackle that challenge. Thanks
Amp is cranking Dokken. Very fat sound

Audio Vista Inc:

Model 1 Full Kit

500-0001FKIT Model 1 Amplifier Full Kit comes with everything you need to assemble the working amplifier with two tubes per channel for increased output power. You only need to build a chassis and provide power cord and interconnect cables. The kit contains:

1 x 500-0001ABD - Model1 Basic Amp. Board Kit

1 x 500-0001UPGD - Model 1 Ful lPack Upgrade

1 x 500-0002 - Power Supply Kit PS-1

2 x 250-0001 - Output transformers 2.5k/0-4-8 ohm and UL tap

1 x 250-0002 - Standard toroidal power transformer

(for optional shielded power transformer, please add $10.00)
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File Type: jpg full_pack_1.jpg (70.0 KB, 181 views)
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Old 29th April 2007, 03:24 AM   #7
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Location: Los Angeles
Oh dear God!

I started exactly the same way!! You are doomed.

I'm on the 3rd amplifier already AND buying transformers for the next big DIY.

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Old 29th April 2007, 07:17 PM   #8
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Wow. Yea I can see me getting to that point. I started out investigating the Velleman stereo kit. At about $1400 put the kaibosh on that. I saw this little amp for $160. Love at first sight.
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