|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
73.149.50.39
I'm hardly new to tubed audio, though downsizing from large-chassis tubed separates I now own a Conrad-Johnson CAV-50 and have some questions about it and the tubes it uses. I'm liking it a lot so far. Feel like I'm on-mission - smaller, simpler, less pricey, great audio experience. So far all those boxes are checked.I would like to confirm how this unit works. It uses a single 12AU7. I'm understanding that this is used only for preamp out functions and isn't otherwise in the audio path unless I'm using the CAV-50 to drive a second output, such as another power amp. Is this correct? If it is, and I'm not driving another output, then can I remove this tube so I'm not simply burning away a 12AU7?
And, as long as I've been into tubed audio gear, I've not had long experiences with the 6SN7 and EL34/6CA7/KT77. I know something about them, but haven't lived for any substantial length of time with any of those types. C-J had for a long time used the noval 6FQ7. Without any real current supply of that tube, they've been using the octal 6SN7. The CAV-50 uses a pair of 12AX7s for the input and phase splitter tubes, feeding the 6SN7s as driver tubes. It looks like they're using the 12AX7 instead of the 5751 for the same reason - no real supply of the 5751.
So, I'm curious about tube rolling. I already have a nice selection of 12AX7s, a boat load of 12AU7s, which I'm thinking may not be really at play with this unit since I'm not planning to use the pre-out, a beautiful set of Mullard dual getter XF1 EL34s, and no 6SN7s. It's currently fitted with an RFT 12AU7, Sovtek 12AX7-WB, and Sovtek 6SN7s - all OE fitment, and I have the OE Sovtek EL-34s and Mullard reissue EL-34s.
Anyone here familiar with this control/integrated amplifier? Is this unit responsive to different tubes in different positions? Any suggestions for 6SN7s? KenRad VT-231s? Some specific Sylvania or RCA variant/s you like? How good are the current production 6SN7 offerings? EL-34, 6CA7, KT-77? How good are the current production tubes? Using 6550s and KT-88 forever, many of the new production tubes are excellent. Same with many of the current 12AX7s.
Tube rolling is per one's ears and one's gear, but I'd be happy to hear people's experiences.Oh, anyone have C-J do their C1 CJD Teflon cap upgrade to any C-J piece? Results?
Thanks!
Edits: 01/04/16Follow Ups:
Before my CAV 50 had to go into the closet due to space limitation I used 1 JJ KT77 and 1 Golden Lion KT77 per side, since you can bias each tube individually.
Otherwise I prefer VT 231 Ken-Rad, 12AX7 Telefunken smooth plate.
Never bothered with a decent 12AU7 since I did not use the pre out.
Steve, good to see you back around here. I am sure I have plenty of 6SN7s I could part with if you are looking for some. I don't really use that tube any more, to speak of, but had acquired a fair stash of them some years ago.
-Ed
Hey, Ed! Thanks for the kind welcome and the offer. I'm sending you a message now.
Cheers,
- Steven
Your amp section is the same as my Rogue, 12ax7 inputs and 6sn7 drivers.
I agree with the choice of Sylvania 6sn7W as driver tubes. Great in that spot but if your output tubes are on the brighter side they can be a little relentless. In that case something like the black glass National Unions or Grey glass RCA VT231 can be better.
I think the Sovtec 6sn7 is a brutal sounding valve I would get those out as fast as possible.
I like pretty much any Sylvania 6sn7 prior to about 1955 as drivers, which would include the VT231, the bottom getter GTs and the GTAs and WGTAs. None are as good as the Ws though. The early Tung Sols are all very good and the GTB tall bottles are also good. The tall Hytrons are also decent.
For 12ax7, I think the RCA black plate from the early 1950s is tough to beat. All the early 1950s U.S. made 12ax7 (especially the black plates) are pretty good whether from RCA, Raytheon, Sylvania, or GE. The fancy European tubes are good but not worth the price IMO.
5751 black plates from GE, Sylvania, and Raytheon are all very good. I also like the Sylvania 5751 triple mica grey plate. Once you try a good 5751 you may never go back to 12ax7. Depends on the type of sound you like.
In output tubes, the best EL34/6CA7 tubes I have tried is the Treasure Black bottles from China. Costly but better than XF2s in my amp. The JJ KT77 is my economy choice, a great sounding valve at under $100 a quad. The EH 6CA7 is also a decent sounding tube but I prefer the JJs.
Hope this helps.
Enjoy the roll!
Thanks! So many 6SN7 variants. So you have tried at one of the premium Chinese tubes, the Black Treasure. There are some lovely "looking" premium tubes out of China, and they are costly. I haven't tried any because of the prices and I've been very pleased with many of the other Chinese tubes. Of course I am very curious about how they sound and work.
I have a perfect quad of Mullard dual getter XF1 EL34s that I rescued from my father's Dynaco ST-70 (along with all the other premium tubes from his scantly-used Dynaco gear). Haven't tried them yet.
I'm rollin'!
The 6CG7/6FQ7 is still in production, the Electro-Harmonix tube (quite good!) is available in standard or gold pins.
The 12AU7 Tung-Sol and B749/12AU7 Genalex reissues are really good too.I use and recommend both highly.
The KT-77 Genalex reissue is off the charts, a superb tube. I cannot recommend it more highly. The 6CA7 EH is another terrific tube, and the Tung-Sol EL34B is quite good as well. The other current EL34s are good tubes too, but those 3 stand out IMHO.
The current generation Tung-Sol 6SN7GTB tube is quite good as well. Is it as good as NOS? In some cases yes, but probably not the very best of the NOS. Of course, the price is not like NOS either. The only beef I have is a number of them have slightly tilted glass bottles, which is cosmetic only but still I wish they were straight!
In your case the replacement of the Sovtek 12AX7s would be my #1 move, followed by a set of KT-77 Genalex. You may like the Sovtek 6SN7s with a warmer toned 12AX7 in place - if not at least try the current Tung-Sols.Your RFT is a FINE tube, leave it.
My $0.02 antway...
I would second Jim's Gold Lion KT-77 recommendation I've been using them the last few years in my pushpull EL34 amp nothing comes close to them. Lots of good 6SN7's out there I am running Sylvania 6SN7GTB's in my amp they sound great and seem very rugged. Good luck with your amp and have fun tube rolling!
Hey, Jim:Thanks for the recommendations. Always appreciate your insights. Looks like quite a few good current production EL34s/6CA7s to choose from. And the current generation TS 6SN7GTB. I know about the EH 6FQ7. It is quite good. I'd be plenty happy that C-J had continued to use the 6CG7/6FQ7. From my decades of using C-J and ARC gear, I've got just about every variant of these tubes ever made - and there were a lot of them - so I have a huge inventory of them! But now I'm lookin' at 6SN7s.
Absolutely agreed on the RFT 12AU7. Oustanding tube in every way. I've been on a bit of an audio avocation hiatus. Before this, though, searching this Asylum you'll find plenty of posts from me about that tube. I'm not sure I need to be running that 12AU7 at all in the CAV-50. Apparently, it's only there to drive some output functions, and otherwise isn't in the audio path. I think just to see how it works I'll hook up a separate amp and use the CAV-50 as a low gain linestage. I'd prefer not to burn a 12AU7 if I don't have to.
I am quite enjoying the CAV-50 with its OE tube complement. Just can't resist exploring a bit with some tube rolling. Seems clear that the Sovtek 6SN7 isn't a favorite.
OH, how about the Chinese EL34/6CA7/KT77s and 6SN7s? I haven't had anyone mention any Chinese tubes. I LOVE the sonic performance of the Shuguang 6550s (particularly the 6550A-98 and 6550B) and KT88s (GEKT88 and KT88-98). I even really like some of the 12AX7s and 12AU7s.
I'm checkin' out your recommendations now.
Edits: 01/05/16 01/05/16 01/05/16 01/10/16
I had intended to stock the EL34B Shuguang as an economical EL34 choice, but my source of supply discontinued them! I've heard a lot of good about the tube, it seems like a nice bargain.
I've not dealt with the expensive Chinese tubes at all, so I have nothing to base an opinion on.
Thanks, Jim. I haven't tried any of the more premium Chinese tubes, either.
Not sure if this is any help or even something you didn't already know, but this is a quote from a 1998 review for Soundstage!
"One 12AU7 is used for the preamplifier line out (and is therefore not in the signal's path unless you use the tape/EQ loop)."
As to the C1 CJD Teflon cap upgrade. I had it done by them for my Premier 140 power amp. While not exactly cheap ($2,300), I thought it was worthwhile in just about every aspect. Naturally what one person thinks is worthwhile...Plus, don't know what the cost would be for the CAV-50.
Joe
Hi, Joe:
Thanks for your note, and sharing the link and your experience with the C1 upgrade.
I have read these reviews, which is where my understanding of the 12AU7's operation comes from. In the C-J preamps I've owned that were fitted with a phonostage, over time I used the phonostages (and usually very good phonostages) less and less and would often run them without the tubes. Bill Thalmann said that was okay to do, and it seemed to be. Didn't really want to just be burning up a handful of tubes without essentially using them. Wondering whether I can do the same here with the 12AU7.
I've heard only good things about the C1 cap upgrade, but noted the prices. I've emailed C-J asking them what the price is for the CAV-50.
People actually are getting responses from C-J these days? I've been calling/emailing a couple years now, trying to order replacement tube sets (or failing that, get their recommendations). The one time I called (probably a couple years ago now), the guy was rude. I emailed them about 2 months ago about recommended tube brands for my CAV-50 (since they don't seem to sell replacement sets any more). No reply. Also probably emailed about 3 years ago. No reply. Worst customer service ever.So here I am, rummaging through the internet to find what I can. Bought my unit new back in 2002/2003. Love it, but it's suddenly difficult to find replacement tubes and the prices have shot through the roof (it seems). I last bulk bought back in 2009 and rotated through tubes since then.
Edits: 12/23/17
One does not need conrad-johnson to get replacement tubes.
Any decent tube distributor could supply what you need. If you
contact mr mcshane i'm sure you will get good quality well matched tubes.
Another good source is eurotubes.com
Seems to me you got good advice regarding the output/power tubes and the 12AU7.
The 6SN7 as Jim pointed out might be improved upon by using NOS or just good OS tubes. The Ken Rad is well known for it's excellent low frequency emphasis, so if you like bass this is a good tube to use. It doesn't matter if it's a black glass tube, or a clear glass tube, they sound the same. The difference is that black glass looks better in some peoples mind.
I will cut to the chase and just tell you my favorite, the Sylvania 6SN7W or original Chrome Dome early top getter GT. People think the metal base tall bottle W is the best, it may be. I think the real bargain however in Ws are good condition short bottle regular base tubes. These have have been selling for as little as $50 or less. They have superb holographic imaging in the upper and mid frequencies, and glorious tone, it has proportional bass but not like the Ken Rad.
You know as much as anyone, about 12AX7s and other small signal tubes, but it does seem that current production is coming very close to the better old tubes. I will say that if you need a 12AU7 at some point my vote is for Amperex, if you don't use current production.
Good Luck and pleasant listening.
Thanks for your input. Yes, it's the 6SN7s I'm least familiar with (deeply familiar with them in their noval form ;) ) The way you describe the Sylvania 6SN7W checks all my preference boxes. Any notable variants of this tube? Anything to pay attention to to make a positive ID different variations? On the Ken Rads, what are the details on different ones to look out for?Agreed on current production. Lots of good tubes, and in the last handful'ish of years a lot of stuff has been introduced that I haven't tried of the types I've typically used. There seems to be quite a bit of adoption of both the KT120 and KT150 power tubes. I'm not anchored to the dogma that older is better. I do like the Heerlen-made ECC82s. Long or short plate. I like 'em. A tube always on my 12AU7 short list. Of the short plates, I find myself favoring the Gf7, Gf8, and Gf9 types, but all are wonderful.
The 6SN7 is a wonderful tube. I'd enjoyed it for decades in the noval 6CG7/6FQ7 bottle. I'd tried to steer clear of the 6SN7 because it is a pretty heavily trafficked audio road with prices following the popularity. Now I'm traveling this road, too.
Cheers!
Edits: 01/10/16
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: