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 NEW  Bruce Heran outlines the details and construction of his simple DIY 6DJ8 (ECC88) Tube Hi-Fi Headphone Amplifier Project.

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PostPosted: 27 Jan 2011, 05:01 
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Joined: 11 Jan 2011, 02:52
Posts: 22
Location: Melbourne, AUS
Hi all,

As promised previously, here is my build log for the K16LS kit from S5 electronics.
I purchased the kit straight from S5 and also purchased the Tone Module that goes with it.
I will show the steps I took to arrive at a built amp kit and show a couple of minor mistakes that I made along the way - lots of pictures!

First up - the contents of the amp kit:
Image
The kit includes pretty much everything you need to be able to make the amplifier except solder. The extra tube in the picture is the one that comes with the tone control module (1 box for shipping)

The kit comes with an American power plug which of course is useless in Australia (Where I live) but luckily this kit has been rigged to be compatable with 240V supply. The switch that comes with the kit appears to be rated for 120V so also can't be used for an Australian build.

I originally wanted to get the K12G kit even though it is a little less powerful due to the mixed reviews of the lower powered 'LS' series kits, but after speaking to S5 and reading around it seemed like it would be quite painful to replace the power transformer for one that would work on 240V and the only real option was a 240-120V step down transformer. I came to the conclusion that it seemed like a lot more trouble than it was worth so I elected to get the K16 kit with tone control (a bonus compared to the K12G)

So - away to the building. I will walk through the steps in the S5 build manual - my version of their words though..

3a) Install R1 through R11 and R13 through to R24 flush to the board.
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3b) Install Tube sockets.
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3c) Install input RCA's.
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3d) Install R26 with room for heat dissipation.
3e) Install R12 and R25 also need space for heat dissipation.
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3f) Install the rectifier chip.
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3g) I had a problem here - the S5 manual states "Install C1 through C6 and C8, C9 solder and clip leads"
So I in my bleary minded state interpreted this as meaning the 6 red drops marked 224K should go in C1 to C6 and that the other caps would be 8 and 9... THIS WAS WRONG!! dammit - luckily I hadn't trimmed the legs too short!

pic below = WRONG!
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The pic below has the red drops in the right positions:
Image

The C8 and C9 caps are the ones towards the back of the board although I forgot about them until the end :o

3h) Install the power filtration caps, making certain of the polarities.
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3i) Install the fuse holder.
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3j and k) Install the volume control and it's grounding lug.
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3l) As I wanted to try the amp without the tone control to start with, I had to bridge the Ain/out and Bin/out areas of the board - these are really just L and R signals I believe.
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4) Install 'jumper(s) to define grid power type (240V or 120V)
From the manual it looks like 2 horizontal ones = 120V and 1 vertical = 240V
Image

5a) Install the output trans body grounds.
Image

6&7) Install the 'banana' posts for the speaker wire connects.

8) Check it all


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PostPosted: 27 Jan 2011, 05:02 
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Joined: 11 Jan 2011, 02:52
Posts: 22
Location: Melbourne, AUS
9&10) Connect the power transformer - twisting the leads to try to help reduce AC noise.
Image

11,12,13) Connect the output transformers.

14) Connect Mains Cable.

15&16) Mount the PCB to the wood.

17) Install switch (not on mine due to 120V only and I'm on 240V)

18) Install the Vacuum Tubes.
Image
Image

And there you have it - your completed K16LS amp.

So at this point I decided to power on using my 'disposable' speakers just in case adn found that the sound was better than I was expecting after seeing the K8LS review. But DAMN heart sank - only my right channel was working! After a laborious fault finding mission is eventually managed to figure out that one of my output transformers has a slightly dodgy connection from one of the wires to the actual coils! Thankfully though there are plenty of angles of wire at which it works! after that I was able to enjoy it and test out how it sounded - more on that later.


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PostPosted: 27 Jan 2011, 05:10 
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Joined: 11 Jan 2011, 02:52
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Location: Melbourne, AUS
Now for the Build of the Tone Control Kit:

Again I will walk through with my words on the build order of the S5 manual.

First up the kit.
Image

again everything except solder is included...

3a) Install the resistors.
Image

3b) Install C2 through C5 and C8 through C11.
Image

3c) install the tube socket.
Image

3d) Instal the red drop caps C1, C6, C7 and C12.
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3e) Install C13 - the eletrolytic and remember to be certain of polarity.
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3f) Install the 2 tone control modules - they are the same so it doesn't matter which one goes where.
Image
Image

3g) Install the grounding lugs.
Image
Image

You now have a completed tone module :)
Image


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PostPosted: 27 Jan 2011, 05:23 
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Joined: 11 Jan 2011, 02:52
Posts: 22
Location: Melbourne, AUS
So yeah - that's the building of it all.... You can see the linking wires between the amp and the tone module - they are white jumping accross the two PCB's
Image

So at this point I fired it up again with the tone control... I was amazed at least a bit - I think that without even really changing the tone control pots the amp sounded better with the tone module installed!

I need to get a bit of a better listen to this amp! I was using it with my old art studio bookshelf speakers, which sounded the best I've ever heard them sound - however, they are hardly that special. I don't want to connect it to my main system as yet as I'm waiting on a DAC since my old amp had a dac and this one of course doesn't.
I strongly suspect that with the new DAC and my better speakers that this amp will sound great.

Notes on Hum - yes I have some. not tooooo bad - doesn't really interfere with the music but it would be nice if I could find a way to dampen it somewhat. I think I may need to investigate getting some better filtration caps and moving the transformers away from each other (I will do this when I get round to making a proper enclosure for this)

So.. now for my thoughts on the kit.

I think this kit is good for the money, it was for the most part well written instructions, it has some power, it sounds fairly decent and also the PCB is well marked making it easy to match the instructions to the actual board.
There are some things that could be improved however - the leads on the transformers really are too short - it means you can't move the transformers around very much and when you get an enclosure for the amp will have to splice in new wires to be able to complete your install. But yeah even on the wood board that comes with the kit you barely have enough length to accomplish the job.
One other 'niggle' I have is the banana posts. They're really not that good - I think this kit could really be benefited by at least a modest step up from these posts.

All in all though I am pleased and I enjoyed the build - now I'm going to enjoy thinking about what modifications I can make to make it sound even better and count the minutes until my DAC arrives and I can switch this amp over to the main spot in my stereo system.

Hope this has been of interest to you all! Regards,
S


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PostPosted: 27 Jan 2011, 12:07 
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Joined: 18 Jun 2010, 12:46
Posts: 284
Location: Northern VA
Excellent posts!

Thanks! :D


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PostPosted: 27 Jan 2011, 13:29 
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Joined: 03 Jan 2009, 10:44
Posts: 121
I commend you for taking the time to document your build. Although these kits are pretty straightforward, your pics will make people more comfortable taking on one of these projects.

And I agree with your niggles...the transformer wires are way too short. And the banana posts won't stay tight when you start attaching speaker wires. For this reaons I suggest using banana plugs. The pots are pretty cheap, too.

At some point you may want to upgrade the capacitors as suggested in the K12-G postings. This made a big difference according to folks. There are other changes you may wish to consider while dealing with the hum...these too are posted in the K12-G mods project by Bruce Heran (our hero) with support from Gio (our super hero).

Thanks again for your post!
Lofton

PS I forgot to compliment you on your soldering. Beautiful work, there!


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PostPosted: 27 Jan 2011, 23:20 
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Joined: 18 Feb 2010, 10:52
Posts: 86
Location: Menifee, California U.S.A.
Great post,
Thanks for sharing your experience with your kit.


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PostPosted: 28 Jan 2011, 10:56 
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Joined: 14 Oct 2008, 17:35
Posts: 901
Location: Dartmouth, Nova Scotia
Very nice tutorial :thumbsup:

A big worth while upgrade to that kit would be those tiny output transformers and some bigger power supply capacitors to remove the hum you have. I imagine the frequency response of those outputs is not the greatest.

_________________
My Mini 12AU7 Tube Preamp, Pioneer SX-D7000, JVC XL-V221BK, JBL L80T, DCM TF700


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PostPosted: 28 Jan 2011, 15:43 
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Joined: 03 Jan 2009, 10:44
Posts: 121
I am using the original S5 OTs (and PT) in my K12-G without any hum and I have plenty of output. Probably the same iron as in the K16 kit. I'd upgrade the caps, though. Also, add snubber caps to the heaters. These are easy mods. As suggested, see this project and be sure to read Bruce's conclusions:

http://diyaudioprojects.com/Tubes/K-12M_bh/index2.htm

Lofton


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PostPosted: 28 Jan 2011, 16:32 
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Joined: 11 Jan 2011, 02:52
Posts: 22
Location: Melbourne, AUS
Thanks guys!

I'll definitely be reading the threads for further mods :)

I've read the Neets module - but I want to know more about how one chooses or defines the values of the various resistors and caps to go with a given tube. What should I read next to try to get my knowledge up to a point where I can adapt schematics to suit a given set of tubes?

Cheers,
s


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