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 Post subject: My KT88 Build
PostPosted: 05 Sep 2017, 19:43 
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Joined: 30 Oct 2015, 07:44
Posts: 82
Let me first say, my apologies if I'm not following any rules for posting. I've posted questions and submitted a few photos of the chassis build for this project in other areas of the forum but I thought to post my entire build here in a single location. I'm not a regular forum poster so I'm not sure of the rules and such.

I built the KT88 essentially as shown here http://diyaudioprojects.com/Tubes/KT88/ but there were some very minor deviations due to the power transformer selection, chokes and that I plan to use my 4S Universal Pre-Amp for drive control.

The project did take a lot longer than anticipated due to a move and then some work related distractions but in the end, it was very easy and very satisfying. The end result is a wonderful addition to my sonic collection. I highly recommend it. Something new for me was the wood working which also added to the enjoyment of this project. I look forward to your comments and suggestions.


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 Post subject: Re: My KT88 Build
PostPosted: 05 Sep 2017, 19:49 
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Joined: 30 Oct 2015, 07:44
Posts: 82
Layout...not a lot to say here except I read plenty about ground system layout (I prefer a distributed/logical buss) and transformer orientation. In the end, my need for a symmetrical layout drove the layout. The second factor was the size and weight of the transformers. The output transformers were much larger and heavier than expected. This really dictated the size of the chassis.

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 Post subject: Re: My KT88 Build
PostPosted: 05 Sep 2017, 20:11 
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Joined: 30 Oct 2015, 07:44
Posts: 82
Wood working:
To me this was going to be the fun part. I've not done much wood work before and this gave me the excuse to purchase a router. I chose walnut, made a few test cuts on the saw and learned how to setup it up. In the end a simple but square box. The next trick to cut the relief (rabbet) edge with the router which again, much easier than I expected. I also learned about making a table saw jig to even further fancy up the corner joints.

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Maybe too much worry about nothing but I wanted the supply section in the middle and because it's all wood except for the top I thought to get some copper shielding tape and wrap the center sections to help keep the noise down.

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Here's the fancy it up a bit part. The rose wood is really hard stuff, I thought I would be able to just sand it down but that's not the case at all. I invested in a Japanese hand-saw to get nice and close.

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 Post subject: Re: My KT88 Build
PostPosted: 05 Sep 2017, 20:24 
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Joined: 30 Oct 2015, 07:44
Posts: 82
The top plate;

I wish I had taken more photos of the top plate. This is where the work really started to happen. I purchased the top plate at Home Depot. It's a steel top. I prefer steel because it's easier for me to work with. Aluminum is hard to cut and make clean edges (it's my experience or lack thereof). I have a really cheap set of hole punches from Harbor Freight that punched the socket holes out very nicely. Unfortunately, I found that the steel plate from Home Depot wasn't really square so, I ended up grinding and filing.

I also wanted to try a hammered finish paint. This didn't go well at all. I followed all the precautions/recommendations but in the end, I learned that the primer I was using wasn't compatible with the paint and had to sand to bare metal and start all over again. I'll say this, I went into this very confidently because on the day I went to buy the paint, the product rep was in the store and said "all our paint products are compatible"...yeah...not so much. I ended up with a self-etching primer which really turned out kind of cool. The flat G.I. green looks pretty neat.

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And finally putting some of the mounting points onto the top plate;

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 Post subject: Re: My KT88 Build
PostPosted: 05 Sep 2017, 20:29 
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Joined: 30 Oct 2015, 07:44
Posts: 82
A little more wood working;

I wanted to use an IEC chassis connector. This would test my resolve because it would require the use of a chisel. I had never done this before but it seem really simple...sharp blade, whack it with a hammer...a whole new respect for those who work with wood. I also added the in/out connectors;

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 Post subject: Re: My KT88 Build
PostPosted: 05 Sep 2017, 20:49 
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Joined: 30 Oct 2015, 07:44
Posts: 82
First rough look;

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And with some oil and finish;

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 Post subject: Re: My KT88 Build
PostPosted: 05 Sep 2017, 20:53 
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Joined: 30 Oct 2015, 07:44
Posts: 82
Putting it together;

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 Post subject: Re: My KT88 Build
PostPosted: 05 Sep 2017, 20:56 
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Joined: 30 Oct 2015, 07:44
Posts: 82
All put together;

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 Post subject: Re: My KT88 Build
PostPosted: 05 Sep 2017, 21:04 
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Joined: 30 Oct 2015, 07:44
Posts: 82
Final notes;

As they say, it's all in how it sounds but the numbers are still important. The amp is being driven by my s4 Universal driver and connected to a pair of Klipsche Heresey II speakers. It's plenty for me and my living room. Sounds great.

Utility Power Input: 122.5 VAC
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Thanks for watching...thanks to those who offered advice and comments along the way.



-Steph


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 Post subject: Re: My KT88 Build
PostPosted: 06 Sep 2017, 15:59 
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Joined: 29 Apr 2017, 15:14
Posts: 43
That was a remarkable effort, and a good completion on your part,
I wish I could have done all that preliminary work, in your objective.
must be really satisfying. hope you enjoy the sound, good show.


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