Kasuga KA-10SH tube amp kit finished
Nov 17, 2011 at 4:34 PM Thread Starter Post #1 of 9

mojo

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Evening all.
 
I finished the KA-10SH tube amp kit I bought from Kasuga in Tokyo earlier this year. It uses 6DJ8 tubes and is naturally 100V only so I use a step-down converter for 230V. The kit didn't take very long to assemble, it just took me a while to translate the instructions first (´Д`;)
 

 
More photos here: https://picasaweb.google.com/mojo.chan/15November2011?authuser=0&authkey=Gv1sRgCIbUyYPHmrDkZQ&feat=directlink
 
I have not given it a really serious listen yet because it only has about 30 hours of burn-in and they say it needs at least 100. Looking forward to my first tube amp!
 
Nov 17, 2011 at 5:07 PM Post #2 of 9

nikongod

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Neat! 
 
Can you provide a schematic? I'm always looking for other people's designs to tweak or interesting concepts to integrate into my own stuff. 
 
edited:
I googled around a bit, and found out that this has multiple output taps for different headphones. NEAT! Im still curious if there are neat feedback loops, or something cool like that. 
 
Nov 18, 2011 at 3:57 PM Post #3 of 9

mojo

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Here is the schematic and translation of the text accompanying it.
 

 
I will be going back to Kasuga next month and am thinking about getting another tube amp kit, and maybe the upgrade Alps volume pot for this one.
 
Nov 18, 2011 at 4:33 PM Post #4 of 9

nikongod

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Thanks for the schematic, that is a neat circuit. I like how the output is setup with the 40%tapped transformer as an autoformer for the high impedance headphones. 
 
I'm not such a fan of the voltages on the second 6dj8. Maybe rework it so they dont see much more than 90-100V. I lean towards lower voltages on the 6dj8, although others have run 6dj8 at voltages I consider silly for ages. Dunno. 
 
If your feeling frisky, you could do lots of stuff with the gain tube too. LED or grid bias and CCS loading the plate :) I'm kind of obsessed with grid/LED bias & CCSs because of how they change the sound of the amp (generally for the better, IMO) for so little extra money.
 
Nov 18, 2011 at 5:29 PM Post #5 of 9

liamstrain

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So this is output transformer coupled? 
 
I can't find much information on this amp, but it looks very cool. How does it sound?
 
Nov 19, 2011 at 1:14 PM Post #6 of 9

mojo

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Yes it is output transformer coupled. I am going to give it some serious listening this evening and tomorrow now that it has as reasonable amount of burn-in on it. I had a listen to the demo one in the shop though and thought it was pretty good, so I have high hopes.
 
Nov 20, 2011 at 10:46 AM Post #7 of 9

mojo

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Okay, some initial thoughts on the sound after a few hours listening. The amp has around 90 hours burn-in on it. Source is FLAC files played in Foobar with bit-perfect optical out via an Onkyo PCI 200 series card into a C.E.C. DA53 DAC. The DAC is set to x1 oversampling (i.e. none), soft digital filtering, dither on and 128FS. Might need to experiment for that as it is set up for my AT-HA5000 that has been my main amp for a few years. Connection via my own silver wire and solver solder built phono cables and jacks that I forget the name of (bought in Akiba with the amp). 'Phones are Sennheiser HD 495s. I will try out some AT-W5000s later, but at the moment I'm not using them much because they are incompatible with wearing glasses IMHO so they are waiting for some contact lenses or laser surgery...
 
First impressions are very good. I threw some modern stuff at it to see how well it would cope with the ridiculous loudness levels and as expected it coped well. The tubes do an amazing job of making fairly crap recordings sound good, and the amp seems to synergize with the '495s brilliantly. The bass in particular is fantastic, full with a good amount of slam but also musical. Seriously, we are talking about the kind of thing you get from the HA5000/W5000 combo, excellent separation and a kind of effortless power. Guitars sound realistic with that lovely tube-amp ringing (is that the right word?) that is easily lost in the "wall of sound" that seems to be popular.
 
The soundstage could be bigger but you never have trouble picking instruments out. I'm having trouble describing it, the separation is less than my HEADFIVE but in a way that makes the sound "fuller" and without hiding the detailed sounds that lesser amps lose. It does make me want to crank the volume a bit. The top end is a bit flat, somewhat expected with vacuum tubes, and the effect is rather enjoyable. You don't get the sparkle or the extreme detail of a high end solid state amp, but with some music that isn't necessarily a bad thing. For serious listening the ATs are hard to beat but when you just want to enjoy the music and relax this amp seems ideal.
 
The '495s are only 32 ohms but I tried the high impedance output anyway and felt it lacked clarity. The amp looks lovely and keeps my room warm too :)
 
Nov 20, 2011 at 11:30 AM Post #8 of 9

liamstrain

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Very cool. 
 
Do you know if this amp is available internationally?
 
Nov 20, 2011 at 1:52 PM Post #9 of 9

mojo

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It isn't available anywhere except from Kasuga as far as I know, and they only ship to Japan. I could get you one and mail it over in January. The Mk II is out now and incorporates a popular mod: 6.35mm sockets for the headphones. Additionally the case is a bit longer and the 3.5mm input socket has been removed. They talk about some kind of shielding on the PSU but I think they just mean that it is now physically a little but further away from the audio stuff.
 
http://www.e-kasuga.net/goods.asp?id=993
 
You could use my instructions because I imagine they will be pretty similar looking at the photos, and you can email bits that are different. It seems that you know your stuff when it comes to electronics and the built was fairly easy.
 
At this point I'd just like to ask that anyone who is interested please note that Kasuga don't speak English and you should only contact them in Japanese. Using Bablefish doesn't count :) Feel free to contact me though.
 

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