|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
71.126.132.235
In Reply to: How do you find substitutes for rolling? (that are unlike the tubes they're replacing) posted by Mark Tinordi on April 10, 2007 at 09:01:03:
Is it "safer" (that is, less stupid) to be more reckless with sticking any nine-pin miniature tube into that socket? I've searched this board, of course, and discovered that Very Bad Things can happen if you replace certain power tubes with other power tubes, especially if you don't adjust for the bias.But provided that preamp tubes area so dinky in comparison, do they pose nearly as much danger to your person/gear?
Follow Ups:
Forgive me if I, in any way, gave you the impression that it was okay to plug any old tube into any socket in which it would fit. That is not the case at all!When I mentioned picking up a lot on ebay I was talking about a lot of assorted 12au7's.
With regards to the 6cg7 swap....go to tdsl and look up the 12au7. Down at the bottom of the page pick the link for Dave Crittle's site (retrovox). Read the second paragraph on the first page of the tube data sheet. It states the 12au7 is very similar to the 6sn7. The 6cg7/6fq7 is a 6sn7 in a nine pin mini bottle. The only difference in pinout/wiring is your 12au7 has pins 4&5 tied together and one heater wire there and the other heater wire on pin 9. To convert remove the jumper between pin 4&5 and attach the hetater wire on pin 9 to the vacant pin, either 4 or 5. Repeat, the heter wires for the 6cg7 are pins 4&5. But be forewarned the 6cg7 needs twice the heater current and I don't know if the foreplay 2 has the ability to handle it. The foreplay 1 didn't but the foreplay 3 does.
Also, if you check the bottlehead forum you will see the 6cg7 conversion is quite popular. I have heard it and can vouch for it being an upgrade.
In time you will learn how to look at data sheets and determine if another tube could be suitable. And of course there are places that list subs. In general it is best to ask the company that makes your gear and not to blindly trust others....including me:) Info on the web isn't always to be trusted and even tube data sheets have errors!
Forgive my cluelessness as a tube naïf! I decided to not even try substitutions or exact matches, but just stay with the 12AU7 proper until I get bored... holding off on NOS until I make the rounds of current-runs as well as I can.I just got back from a guitar shop and, uh... the Electro-Harmonix tubes kick ass. I wasn't all that impressed with their 12AX7 but the AU is stellar. The tubes that came with the Foreplay were a pair of Eis and were entirely, skull-crushingly pedestrian. I knew there was better out there because they couldn't get much more MOR, and I found some better ones. Hooray. Great buy.
If you don't care to post that in public email me at rbrunt(at)mercymiami(dot)org. Perhaps I can suggest someone in your area to hook up with.You really should head over to the bottlehead forum. A lot like RCA cleartop 12au7's (too bright to me). The brimar (forget the number) is a big time favorite. Personally I kinda like the siemens. My 2 buds both have foreplays so I have heard a buch of tubes in them. But neither have the foreplay 2. And yes, you want to use the foreplay if you possibly can. Properly tricked out it kicks the crap outta the other stuff.
And hey dude, don't worry about coming off as clueless. That is what we are here for. You can't learn if you act like you know it all and don't ask them dumb questions now and then:) So ask away and feel free to email. I am glad to explain things. And ofcourse do search the archives here before asking them dumb questions for tons of great answers. Ditto on the asylum FAQ's
Russ
P.S. Ei made a killer 12ax7 in the past but quality control went to shit about 3 years ago.
...RCA clear tops, RCA 5963 black-plates, Tung-Sol 12au7a's, Toshiba 5963's and ecc82's, and various three-mica 5814's. It's also fun to try some of the relabeled organ pulls (Conn, DuMont, Baldwin, etc). Of course, then you can get into the real esoterics wih price to boot (is the next 10% worth 3 times the price?). Lots of value and enjoyment in the basics!
And more, here:
Yes they do. If you look at the tube data you can tell if two tubes have the same pin out. You can also tell how much current they will draw in your circuit and what the gain will be, etc...Tube swapping (between different types) is not done "willy-nilly".
The 12au7 and the 6cg7 are very close and are (for the most part) electrically interchangeable but that doesn't mean you can just pull the 12au7 and jam the 6cg7 into the socket.
Do not install a tube unless you know for sure that it will not burn up your unit.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
This post is made possible by the generous support of people like you and our sponsors: