[mhamel]

And secondly, one of the Amperex tubes makes a sound through the speaker it is on the side of, when I tap it with my finger. I can't hear anything unusual at any other time. Is this anything to be concerned with?
I need to do some more A-B testing with the stock ECC82 before I can speak to the difference in sound. I do think it is a subtle difference, however.

 
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

 

[JK-47]

   
Still burning things in, but so far the combo of 1950s Sylvania black plate 12BH7 and reissue Gold Lion KT-88 is my favorite.  I need to put some more hours on some of the other tubes before doing any sort of meaningful comparison.
 
  -Mike

What are the advantages/benefits of the 12BH7 tube? I've heard folks from other forums speak highly of them compared to the 12AU7...

 

[JK-47]

I've been emailing Peter at Maxi Test over the last several days, and he has been quick to respond. They offer a 10% discount if the MaxiMatcher II and MaxiPreamp II are purchased together, but they don't have the MaxiPreamp in stock until Mid March. I asked if I bought the Maximatcher II now for full price, and the MaxiPreamp II in March when they were back in stock, if they could apply the full $165 discount towards the Maxipreamp II. The only reason I asked if this was possible, was because Peter told me the MaxiMatcher II would most likely be sold out by the end of this week, and didn't know when they would be in stock again. He turned down my offer, and I felt like he was continuing to pressure me to buy the Maximatcher immediately as well as the back ordered Maxipreamp... not my cup of tea (he came across as very pushy the last few emails) . I still might go with the MaxiTest combo, but I'm considering biting the bullet and have just contacted Amplitrex...

 

[Effusion]

 
What are the advantages/benefits of the 12BH7 tube? I've heard folks from other forums speak highly of them compared to the 12AU7...

 
I haven't personally tried the 12BH7 tubes, therefore I can't comment on how they sound, however I would check with Victor and possibly Mr. Fujita first to make sure they are compatible.
 
There seems to be some varying opinions on their substitution for the 12au7, as some have said the the heater draw is nearly twice that of the 12au7... so, better to check first before trying as you may just blow a FET like I did, which is never a good thing.
 
Post below from the following link:  http://www.head-fi.org/t/183771/what-kind-of-tubes-are-compatible-with-12au7
 
6/22/06

1. [img]http://cdn.head-fi.org/1/13/100x100px-LS-13ca4a84_3133-IMGP1613_resize.jpg[/img]

1. sacd lover
2. 
3.  
4. offline

1. 8,220 Posts. Joined 8/2002
2. Location: Ohio

Quote:

Originally Posted by Ferbose Thanks for the links. It is still unclear to me if putting a 12BH7 into a 12AU7 position is a good idea.

The heater current draw of the 12bh7 is twice that of the 12au7 .... I wouldnt without knowing more about the circuit. But, in the tube substitute lists, I checked, the 12bh7 IS listed as a sub for the 12au7. However, its not listed as a preferred substitute ... which means in some circuits the 12au7 and 12bh7 will not be compatible.

 

[Effusion]

  I've been emailing Peter at Maxi Test over the last several days, and he has been quick to respond. They offer a 10% discount if the MaxiMatcher II and MaxiPreamp II are purchased together, but they don't have the MaxiPreamp in stock until Mid March. I asked if I bought the Maximatcher II now for full price, and the MaxiPreamp II in March when they were back in stock, if they could apply the full $165 discount towards the Maxipreamp II. The only reason I asked if this was possible, was because Peter told me the MaxiMatcher II would most likely be sold out by the end of this week, and didn't know when they would be in stock again. He turned down my offer, and I felt like he was continuing to pressure me to buy the Maximatcher immediately as well as the back ordered Maxipreamp... not my cup of tea (he came across as very pushy the last few emails) . I still might go with the MaxiTest combo, but I'm considering biting the bullet and have just contacted Amplitrex...

 
I've heard mixed opinions regarding the Maxi testers, but they are generally not seen as being as versatile as other testers, as the tests they perform are pretty basic.  Also, since you have to essentially buy two testers, they are not a very cheap option, but since they are newer, you wouldn't have to worry about restoring or fixing them first and they would come with a warranty.
 
The Amplitrex AT1000 is a pretty amazing tester and when hooked up to a computer can provide the most detailed analysis of how a tube does/will perform; however they are very expensive and are generally a bit of an overkill unless you have a ton of expensive tubes or are in the business of selling them.
 
My recommendation would be to try to get one of the better older testers that is already restored and have it professionally calibrated.  Many will do everything and more than you would need and even with calibration, they will generally cost you much less than the Amplitrex or both Maxi testers.  I prefer Hickoks (I have a gold plate 533a), but there are several other brands that are pretty good as well, such as Sencore and B&K.
 
Below is some info on older testers:
 
http://www.tubewizard.com/recommended_Hickok_testers.htm
 
http://radiolaguy.com/Showcase/TestEquipment/Gallery-Hickok-Test-Equipment.htm
 
http://www.alltubetesters.com/articles/tester_guide.htm
 
Hope this helps!!

 

[mhamel]

   
The heater current draw of the 12bh7 is twice that of the 12au7 .... I wouldnt without knowing more about the circuit. But, in the tube substitute lists, I checked, the 12bh7 IS listed as a sub for the 12au7. However, its not listed as a preferred substitute ... which means in some circuits the 12au7 and 12bh7 will not be compatible.

 
I think I've been the guinea pig on this one.  FWIW, I've got around 50 hours with 12BH7s in the amp so far without issue.
 
   -Mike

 

[Effusion]

Very cool and very good to know... after 50 hours, the circuit of the Elekit can definitely handle any differences they might have!
 
What type/brand of 12BH7 are you using?  Any impressions on the sound signature they provide?
 
Edit:  Sorry, just noticed that somehow I missed the last 4 posts or so on page 6, I guess I wasn't paying attention

.  Let us know what your ultimate verdict of the 1950s Sylvania black plate 12BH7 tubes are!

 

[Effusion]

JK-47,
 
Not sure if this helps at all, but I remembered reading about some of the issues that were found with the Amplitrex AT1000 and found the link again, below:
 
http://jacmusic.com/Tube-testers/Amplitrex/index.htm
 
Now, it is more or less his opinion (as he states), but I remember after reading it, even though I'm not sure about all the technical aspects he describes, it kind of made me cross-out the Amplitrex AT1000 as a possibility, at least for me (other than the really huge price tag).
 
Also, to clarify my post above, I got confused between the Orange VT1000 and the Maxi Preamp tester (long day), as it is the Orange tester that is very basic in its test, whereas the Maxi is quite elaborate and would make a fine tester for your uses.
 
In addition, if you were wondering at all, I purchased my Hickok 533a for $350 and it had seen very little use over the years and was in really nice cosmetic shape; generally a professional recalibration will cost about $150, but you have to ship the unit if you can't find anyone locally.  After recalibrating, you can use special calibrating tubes (~$50) and a specific process to keep the tester in calibration; best to test once or twice a year if under use, but supposedly using these tubes/process correctly you will not need another full calibration, at least for a long time.  Now, the 533a is probably the cheapest of the better Hickok testers out there, but there are better models, however at higher prices.

 

[JK-47]

mhamel,
 
I asked Victor if 12BH7 tubes were ok... he said "NO", please be careful.
 
Effussion,
 
Thanks for the great info, I will be weighing all my options over the next few weeks before I make my final decision. I ran across the recommendations from alltubetesters.com a while ago, and found most of the Hickok models difficult/near impossible to find, or expensive buy it now auctions ($1000-$1500 for Hickock 539 series, or high $$$ bidding wars). If I saw something similar to yours, I would be all over it, but if I'm going to spend $1500+ I'm leaning towards the MaxiTest pair still.
 
There was an auction that just ended ,for an original untested (seller only said it turned on) MaxiMatcher. The original retailed for $500, and this well worn (badly faded face plate) sold for a little over $500 with shipping, crazy! I've seen models sold over the last year in much better condition on audio/tube sites for apprx $400. I lost interest in the latest auction as soon as the bids went over $200.
 
I looked into the Tube Imp also, and for $500, It doesn't quite sell itself to me, definitely $300-$350, maybe $400...
 
Geez, this quest for a tester is almost as bad as chasing tubes, lol
 
Greg70,
 
Is your amp back up and running?

 

[Effusion]

Good to know Victor has worries and said not to use them.  I'm wondering if maybe over time they will start to cause issues or eventually wear a component out.  When I used the QV05-25 power tube, it only took about 5 min. or so to blow the FET, but later I found out that the plate voltage for this type of tube is out of spec, so that may have been more of what did it so fast, compared to the potential heater draw issue with the 12BH7.  Plus, it was a power tube and not a signal, etc... but I'm definitely not an expert on the Elekit's circuit design.
 
I'm always very glad to help, when I can and you are taking the best approach by weighing all options first.  The Hickoks go very fast and some demand a high price, mainly because those who are buying them want to use them to test tubes in order to sell them, as Hickok results seem to be trusted more, especially for high price tubes.  There are other options such as the Sencore and B&K, which are both pretty good too.  A pretty basic Sencore will at least tell you that a tube doesn't have shorts/leakage and has life left, however some models won't give you an accurate MC reading, which is helpful when matching pairs and buyers may not bid high when using its test results (probably a maybe though).  Also, for the price the Orange tester just doesn't do enough to justify the cost, but it will tell you if the tube is dead or has a short.
 
Keep up the search and try to learn as much as you can to make the most informed decision possible.  Probably best to view the tester as an investment if you plan to buy a lot more tubes in the future, plus if the resale value of the Maxi testers looks to be high, you could always sell them if you find another better option down the road.  Anyway, the Maxi's should work great if you decide to go with them.
 
Let us know what you ultimately decided to do and good luck on the search, you never know when a nice 533a might pop up for sale!

 

[mhamel]

I had sent an email to Elekit Japan to get some more details on the heater circuit current capacity, but haven't heard anything back yet.
 
So, I probably should have dug into this before just plugging them in, but here's what I found... I think I'm looking at this correctly:
 
From the schematic it shows 4A from the transformer on the 6v tap, but I don't know if that's the max spec for that transformer or not.  That tap powers the DC heater circuit for the pre tubes and directly powers the heaters of the power tubes via AC. The DB107 rectifier for the pre tube heater supply is 700v / 1A. It's probably ok doing 1.2A @ 6v, but I haven't done a thermal check on it yet. It would be simple to drop in a 50V 1.5A rectifier in the same DIP-8 package to be safe, they're $0.46/ea from Mouser... so I think I'm going to do that.
 
Combining the 12BH7 with some of the supported output tubes looks like it will exceed the 4A rating on the schematic.  Checking the heater current draw for supported tubes:
 
Pre:
12AU7 - 0.3A parallel
12BH7 - 0.6A parallel
 
Power:
6L6GC - 0.9A
6550  - 1.6A
KT88  - 1.6A
KT66  - 1.3A
EL34  - 1.6A
KT90  - 1.6A
 
It looks like the way I'm running it right now exceeds the 4A spec on the schematic by 400mA.   I haven't had any issues, but to stay completely within spec, at least until I hear back from Elekit, I'll probably drop back to the 12AU7 family tubes if I stick with the KT88, 6550, EL34 or KT90, which would draw 3.8A.  Switching to the KT66 with 12BH7 would also draw 3.8A, so should be ok.  The 12BH7/6L6GC combo draws even less, at 3A.
 
If Elekit responds that the 6v tap on the transformer can handle 4.4A or higher, there may be no issue at all running 12BH7 tubes with the higher draw output tubes.  I'll share whatever I hear back from them.
 
 
    -Mike

 

[Effusion]

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!

 

[JK-47]

mhamel,
 
I emailed Elekit in Japan a while back regarding a power tube (I can't remember which one), and they gave a response within 24hrs. I'm amazed how quickly Elekit and Victor respond...
 
Thanks for the technical update regarding the current draw of the various tubes. I can barely read a schematic, not to mention I forgot one was included in the instruction manual.

 

[satwilson]

Been following this thread for a while, don't have the Elekit yet but plan on purchasing soon. The Schiit Lyr was my gateway back into tubes, and I have many sets of Amperex, Telefunkens, etc for rolling. My comment today is regarding tube testers. A few months back I picked up a Sencore TC154. While not as accurate as an Amplitrex or some others, it certainly does a great job performing your basic tests for shorts, grid leakage and emmissions, and matching sets of tubes. I bought mine on Ebay, "in good working order" and after getting a calibration module and repair manual, am very pleased with its performance. All told less than $160. The key is getting one in good condition. All I needed for mine was to calibrate it, which is pretty easy. Here is an article at Tubesound detailing the Sencore "Mighty Mite" testers   http://tubesound.com/2007/10/24/sencore-mighty-mite/

 

[Effusion]

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.