[mhamel]

  Thanks for the comment about the Sencore "Mighty Mite", those are really great inexpensive testers that definitely get the job done.  They really do all that you really need, even if the emissions test is a little harder to use to match than a true MC rating; matching, to a point, isn't the most important thing all the time.  As long as you can test for shorts and leaks and a pair is both similar in make and also close on emissions you should be good to go.  I may be wrong on this, but I believe a huge plus to the "Mighty Mite" is that it is fairly easy to calibrate accurately yourself, unlike most of the Hickoks, which require a bit of complex know-how.
 
Let us know if you have any questions regarding the Elekit before you purchase.  It is a great amplifier and even though I've never owned the Lyr, I don't think you'll be disappointed in the Elekit at all, especially if you are into tube-rolling as the options are almost endless.

 
I've got a Lyr 1... it's a great amp, and the 2 is supposed to be even better.  However, even after rolling an insane number of tubes through the Lyr, I never quite got it to sound right with my LCD-X. Interestingly enough I liked the Lyr with the LCD-2, but I thought it made the X sound too thick and closed-in. At this point the Elekit has pretty much shelved the Lyr.

 

[mhamel]

  Thanks for doing the research and for contacting Elekit.  It would appear that something is at least working well with them, since you have so many hours safely logged, but I guess you never know over time or when using different output tubes, etc.; probably best not to chance it until you know for sure.  The great thing about this hobby is that you learn something new everyday!
 
I'll be anticipating Elekit's response, as you've intrigued me into trying a pair to see how they sound and how they compare to other variants; that is, if it is determined to be safe to use them with the stock components.
 
Thanks again for digging deeper!

 
Sure... happy to. That's part of the fun of DIY to me.
 
I did hear back from Elekit, but I also sent a few more questions. While the pre tube heater circuit was designed for the 300mA/tube draw of the 12AU7, it can handle a limit of 450mA/tube. They said that running the 600mA draw of the 12BH7 over time "may" eventually damage the transformer, but that it should be ok to test out.
 
From that, my additional questions were:
 
1. Is the preamp heater circuit limit due to the overall 6v output of the transformer (which is what it sounded like) or a limit of that specific part of the overall heater circuit?
2. If #1 is true for the transformer load, is it then safe to run the 12BH7 when using power tubes that draw less heater current like the KT66 and 6L6GC with no other changes to the amp?
3. Would replacing the 1A rectifier in the preamp tube heater circuit with a 1.5A part make sense?
 
I'll update again when I hear back.
 
   -Mike

 

[teamrushpntball]

Was curious if anyone has gotten to compare this and the Woo WA2 by chance?  Not real concerned about the speaker amp portion, albeit that is a nice bonus.  
 
These 2 have become my likely next upgrade amp.  Hoping to get a few opinions before making a purchase since it's unlikely I'll ever get to hear this amp unless I bought it.

 

[mhamel]

  From that, my additional questions were:
 
1. Is the preamp heater circuit limit due to the overall 6v output of the transformer (which is what it sounded like) or a limit of that specific part of the overall heater circuit?
2. If #1 is true for the transformer load, is it then safe to run the 12BH7 when using power tubes that draw less heater current like the KT66 and 6L6GC with no other changes to the amp?
3. Would replacing the 1A rectifier in the preamp tube heater circuit with a 1.5A part make sense?

 
More updates from Elekit.
 
The limit is a combination of the output capacity of the transformer and the rectifier in the pre tube heater circuit. They suggested using a rectifier with approximately 2x capacity of the expected current draw for the heaters. I ordered a 1000v/2A rectifier to drop in but if that runs too hot I will go up to a 3A, which will require a bit more work to fit as the package size is completely different. As long as the rectifier is upgraded, it should be fine to run the 12BH7 with lower-draw power tubes to keep the total load on the 6v secondary < 4A.
 
I've also reached out for a couple of quotes on a custom transformer to replace the one that came with the kit, with the 6v secondary winding supporting 4.5A.
 
    -Mike

 

[catcherfly]

This is called "microphonics" and is fairly common in tubes. Some tubes will be so microphonic that any small vibration will set them ringing. If you're only getting it when tapping directly on the tube, then just don't tap the tube.    If you have a set that's very microphonic you can also use tube dampers.  They range from simple high-temperature silicone o-rings to much more elaborate/expensive devices. Check out Herbie's Tube Dampers and the dampers offered by Brent Jesse Recording.  As with most things audio, you'll find endless debate on which may or may not work (or if they're worth using at all), but that's a debate for the sound science forum. 

If you want to get more in depth on the subject, this is a good read:  http://www.thevalvepage.com/valvetek/microph/microph.htm

             -Mike

Thanks for your reply Mike. I really appreciate it. I am aware of microphonics but didn't know what degree is "acceptable" with tubes and if it is a sign of a bad tube.

 

[JK-47]

   
More updates from Elekit.
 
The limit is a combination of the output capacity of the transformer and the rectifier in the pre tube heater circuit. They suggested using a rectifier with approximately 2x capacity of the expected current draw for the heaters. I ordered a 1000v/2A rectifier to drop in but if that runs too hot I will go up to a 3A, which will require a bit more work to fit as the package size is completely different. As long as the rectifier is upgraded, it should be fine to run the 12BH7 with lower-draw power tubes to keep the total load on the 6v secondary < 4A.
 
I've also reached out for a couple of quotes on a custom transformer to replace the one that came with the kit, with the 6v secondary winding supporting 4.5A.
 
    -Mike

 
Nice!!! Are you going to show us all a few pics when you do the transplants?

 

[LingLing1337]

Will this amp be good for speakers that are 91 db sensitive at 8 ohms? I will keep it for headphones either way but if it could power my speakers that would be a nice bonus.

 

[Effusion]

The Elekit ran my Energy RC-10 monitors, which are 91 db at 8 ohms, great and with plenty of volume for a smaller room in Triode mode.  Unfortunately, I haven't been able to use the Energy RC-10s much as I've loaned them out recently, but the Elekit seemed to drive them just fine and they sounded great!
 
Info on the RC-10s:
http://www.energy-speakers.com/bookshelf-speakers/?sku=RC-10
 
You can always change the jumper to Ultra-Linear mode in order to squeeze out a little extra juice, but if your speakers are similar to the RC-10s, it shouldn't be an issue in either mode.
 
I believe quite a few other owners here use the Elekit regularly with their speakers as well... does anyone want to share more details on the speakers they run with the Elekit and how they sound?

 

[JK-47]

I have Fostex FE168EZ (94.5dB sensitivity) drivers in Madisound BK-16 folded horn enclosures. My TU8200DX can drive them to very loud levels in Ultra Linear mode with the volume at 11-12 o'clock, more than I'm comfortable with, playing in my apartment (downstairs neighbors complained about bass when volume was at 10 o'clock).

Flat EQ, I very rarely EQ the music I listen to.

 

[mhamel]

   
Nice!!! Are you going to show us all a few pics when you do the transplants?

 
I definitely will. The custom power transformer is being built now, it will take a couple of weeks to get here after it's finished. I also tracked down the connectors being used so I can wire up the new transformer to plug into the existing connectors on the boards. Those are probably another week or two out, too. I have the new rectifier here, but will do it all at once when all of the parts are in.
 
   -Mike

 

[LingLing1337]

Thanks for the impressions. I will pick one up tomorrow and ill be sure to post impressions with my paradigm monitor 7.

 

[vkung]

Here are the latest trend in Japan to modification TU-8200 with Amtrans AMRG 3/4 W AMRG Carbon Film Resistor

 http://www.amtrans.co.jp/products/amrgj/index_e.shtml
 
Stereo Sound offers TU-8200 with the following upgrade parts (only 22 3/4W AMRG)
http://store.stereosound.co.jp/products/detail.php?product_id=2062
 
AMRG 3/4W skeleton 
12 ohm: R3,4,19,20,21,22
180 ohm: R37,38
1K ohm : R5,6,11,12,35,36
22K ohm : R29,30
100K ohm : R1,2,15,16
330K ohm : R9,10
AMRA 1W 27K ohm :R7,8,13,14
AMCH  3300PF : C17,18
AMCO  0.1μF: C3,4,9.10
 
 
 
I  installed  TU-8200 PCB 1 with  all Amtrans AMRG 3/4 W except  :R7,8,13,14 with AMRA 1 W
 

 
This PCB installed with Amtrans AMCY oil coupling caps.

 
 
For PCB Unit -2
This section is important for Headphone lover
TU-8200 is using  4 resistors tapped to the OPT.  
I installed  15 ohm 2W  AMRG  plus all 3/4 W AMRG plus 2 AMCH 3300pf

 

[LingLing1337]

Im going to grab new production psvane tubes all around, kt88 and 12au7. Can anyone recommend some NOS tubes also? Mostly looking for synergy with Grados.

 

[JK-47]

Just got back home from work, and picked up a literal mountain of boxes from the post office. Included in that mountain were my Maxi-Matcher 2, and Maxi-PreAmp 2 tube testers. The Maxi's are very easy to use, and have already made a difference when it comes to weeding out poor performing NOS tubes. Some readings were very close when measuring transcondcutance, but the plate current's were almost double in some cases (supposed matched pairs). Will the amps auto Bias make up for the difference in plate current or should I not bother putting them in?
 
I'm rolling through the power tubes today. GE 6L6GC's, RCA 6L6GC Black Plates, Gold Lion KT88's, Philips 7581A's, Sylvania 6L6GC's, GE branded Mullard EL34 XF2's (beware the fakes, I sent back a pair already, with no complaint from the seller. He must have known...). Impressions later tonight, and input tube will be done tomorrow.

 

[Greg70]

Im going to grab new production psvane tubes all around, kt88 and 12au7. Can anyone recommend some NOS tubes also? Mostly looking for synergy with Grados.

For me, the EL34 family was by far the best with my Grados. The EL34 mids compliment the Grados.
 
The KT88s were very impressive with a short listen, but overbearing in the bass department and quickly became fatiguing.. better in Triode mode but still more than I could bear.
The Mullard re-issues will tell you if EL34s are the right choice for you, and from there the NOS Mullards are the way to go.
 
BTW- if someone's looking for PSvane KT-88s, I have a pair here with only a few hours on them.. first grade direct from PSvane.