[David Ellis]

Frank,

I know that in some amplifiers it's possible to use a slight variation of tubes.  Would it be possible to use 6L6GC tubes in your Ultimate 70?

Dave

[rlee8394]

Yes you can. You can also use KT-77 and 5881 tubes as well. The JJ brand has released a nice KT-77 that is getting rave reviews. Now, for something completely different. I currently am using 6BG6GA's in one of my two U70's. Go here for more details:

http://www.vacuumtubes.com/6BG6.html

 If I can figure out how to post photos in these messages, I'll show you how the amp looks.  This tube does have a plate cap on it. They draw less filament voltage than a EL34/6CA7 does, can handle much higher plate voltage, is more rugged, and is close to a KT-77 in plate resistance, and has a higher plate dissipation of 35 watts. I'm using them with the adapter bases that I bought from SND several years ago. They require a higher bias voltage (more negative) than an EL-34, so if you back off the bias pots all of the way, it will be close. Just wait about 10 or 15 minutes and you will just need to adjust it up to the 100 ma reading necessary. I haven't done a side by side comparison between the two U70's but I plan to. The big factor is this a basically a "Super 6L6" and very close to the KT-77. I will also probably get a couple quad sets of the JJ KT-77's to try out as well. The big benefit of the 6BG6's are that they are dirt cheap, $40 for a matched quad! I'm listening to them right now. Been using the amp 5 to 6 hours daily for about three weeks or so. No trouble at all. Note, these are not vintage 6BG6 tubes, but the Philips/ECG units. Read the website above for more info. Hope this helps. BTW, I like your site Dave. I may have to go for a set of 1801's one of these days.

[rlee8394]

Dave,
Here is a photo of the U70 with 6BG6GA's.

[avahifi]

We have noticed that the JJ output tubes seem to have a smaller pin diameter than normal, resulting in a loose fit in some ST-70 sockets and trouble.

For that reason we have gone back to Electro Harmonix 6CA7 output tubes for the Ultimate 70 amps we rebuild here.

Frank Van Alstine

[rlee8394]

The loose pin issue was on earlier production runs, especially with the KT-77 from JJ. That has been rectified and most vendors selling them note that the newer production runs of this tube is just fine. Check the bottom of this page for the KT-77.

http://www.boiaudioworks.com/index.php?cPath=57

[richidoo]

I bought an octet of KT77s 2 months ago from Eurotubes. He sells good volume, so is not shipping old stuff. I'd heard about the pin width problem from the year previous. I mic'd them just to be sure, everything was 0.091+, and they fit fine. A little sputtery at first, though...   Nice sound, but not best for my amp. I also got some gold pin JJ 12AT7s, those are reeeal niiiiiice.
Rich

[rlee8394]

Richidoo,

Nice sound, but not best for my amp.

What amp would that be?

[rustneversleeps]

JJ 8 pin power tube with small pins is nothing new. I bought a 5AR4 JJ two years ago, and it would not fit right. instead of going through the hassel returning it, I ended up putting a coat of solder on the pins to make it fit. Adjusting the thickness of the solder coating on pins was quite a task.

After that, all the power tubes I bought were EH, they are nice fit.

[David Ellis]

rlee8394,

Thanks much for the post and insight. 

I must confess that I had already installed the tubes, and... they sounded very good.  The specific tubes were old stock Phillips double-halo tubes.  I HAD 6 of these tubes installed in my Golden Tube SE40SE.  Unfortunately, one of the tubes suffered a complete loss when subjected to the foot of a running child.  Hence, I had 5 very good tubes.  It seemed reasonable they would work well in the ST70, and I do like how they sound.  The EL34s that Frank provide were decent, but the 6L6 Phillips impart slightly better bass and a more lush tone.  And, the detail level is on par with the original El34s.  I am really not a huge fan of tube swapping, but I do like the character of the 6L6 tube.

And older gentlemen conveyed several years ago that each genre of tubes have a  sound.  I don't have much experience in this regard, but I am starting to believe him.  I suppose guys who intimately understand the guts of a vacuum tube can easily convey the reasons for this.  I am certainly not one of these guys.  Sure, I can look at the obvious specs, but it seems there are other audible reasons for what I am hearing. 

Anyhoo, thanks for confirming my suspicions regarding the 6L6 tube in the Ultimate 70.

Dave

[richidoo]

Richidoo,

Nice sound, but not best for my amp.

What amp would that be?

Oops, asleep at the wheel, sorry for the delay, rlee. I have Manley Snappers. The designer made the amp and output transformer around the GT E34Ls tubes which he also designed. So far they have been the best sounding tubes in this amp, not a big surprise. I might try the SEDs also, supposed to be very good. Still not given up on the KT77s, in this amp they have a more laid back sound compared to GT. GTs make a little more power than standard EL34 too.
Rich

[Hogg]

How does everyone like the JJ KT77's?   I tried them in my Canary 608 with an outboard tube-rectified Border Patrol PS.  It's a nice tube but I found the increase in bass was offset but a slightly less euphonic midrange.  I eventually went back to EL 34's.

                                                                                     Jim

[WEEZ]

Hogg (Jim),

You have a PM on an unrelated subject...

WEEZ

[richidoo]

I found the KT77s slightly too euphonic in midrange!!    But it is very puuuurty, and they are not fully broken in yet, gotta give 'em a chance. My amps are bridge rectified, 12aT7>7044>E34Ls
Rich

[Listens2tubes]

I like the SED Winged C EL34's in my Dynaco MkIV amps. As they offer a full, dynamic sound. I had tried a quad of Golden Dragon E34L (thin, brittle) then some Teslovak E34LS tubes, which stayed for years, then the SED quad which opened things up nicely. I had liked the layed back sound of the Teslovak's until one developed a short then retrned to the GD's until the SED's arrived. If you need to brighten up a dark, overly robust amp I can let you have the Golden Dragon's for a song.
Meanwhile I have long wondered about the KT77's and how they'd sound. So many tubes, so little money.

As always, Enjoy

[David Ellis]

I like the SED Winged C EL34's

I have found these tubes very good too my push pull amps too (2 of them).  The only bugger is that my Jolida 302 would "eat" one of these tubes about every 3 months of home use.

Dave