Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: mikek200 on April 13, 2013, 05:59:06 AM
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I bought a few 6sn7 tubes,for my crack.
Can anyone tell me,if,using a 6sn7 to 12au7 adapter,will degrade SQ?
Thanks
Mike
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Nope, it's a mechanical connection either way. An adapter saved you from rebuilding the kit.
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Thank you ,Sir,I went ahead and ordered a few 6sn7's ,before checking---daaa.
Raytheon 6sn7 WGT
Sylvania top getter 6sn7GT
And have my eye on an old RCA 5692 Red Base
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Where is the bet place to get one of those tube adapters?
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http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1313.TR0.TRC0&_nkw=6sn7+tube+adaptor&_sacat=0&_from=R40 (http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1313.TR0.TRC0&_nkw=6sn7+tube+adaptor&_sacat=0&_from=R40)
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Excellent link,TJ
Thanks
Mike
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TJ,
Saw those on Ebay the other day i was hoping to find some one on the forum that has used them. Do they work ?
Thanks
Danny
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I am expecting delivery,of this adapter ,next week..
http://www.ebay.com/itm/220742043198?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
From what I've read-they do work..maybe a more learned member can chime id here,and give you a more detailed answer.
After I get it ,and test it for a few days,I'll post back with my impressions.
For,the money,it seems like a good option???
Mike
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The 6SN7 tubes sound very good in the Crack.
But from looking at that adapter you purchased, looks like its the wrong one, or else i`m just not seeing clearly.
You need a 9 pin male going to a 8 pin female, like this one.
http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=320659633166&ssPageName=STRK:MEWAX:IT#ht_1080wt_793
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Larry,yes,I did order the wrong adapter
I contacted the seller,& he is giving me a refund.
SORRY,SHOULD HAVE CLARIFIED THIS BEFORE...
I did however,order the correct adapter...like the one you linked..& it should be here next week
Can I ask,which 6sn7 tube your using in the crack,which do you prefer?
I ordered a few,on ebay,and was shocked with the low prices..nice surprise after owning literally dozens of tubes with my Lyr
Sorry,again ,on the misinformation about the adapter
Mike
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I`m using the Electro-Harmonix 6SN7 with very good results. No worries. :)
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I use a 6SN7 adapter in my Crack and have rolled several different brands and productions. The adapter works just fine, and it really opens up the different types of tubes you can try as a driver. They are inexpensive enough to give octal's a try, w/o having to make semi permanent modifications to the Crack just to experiment.
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What are "octals"?
Do you feel that the 6sn7 tubes,give a better,cleaner sq, than the 12au7's
Which of the 6sn7's are your favorites??
Tnx
Mike
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"Octal" is a generic term for the 8-pin base on many types of tubes, such as the 6SN7.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fangela.com%2Fimages%2Fproducts%2Fdetail%2F310249166957.jpg&hash=629415303be63a88d0897e6e5f2e0ea4a6d6a456)
I was lucky enough to find 2 pair of these for $50 a few years ago; my current favorite in the Crack, as compared to the 12AU7's and equivalent 9-pins I have tried ....
http://www.ebay.com/itm/RCA-Black-Plate-Red-Base-5692-Audio-Tube-High-End-6SN7-6SN7GT-PAIR-2-/140957889014?pt=Vintage_Electronics_R2&hash=item20d1beb1f6 (http://www.ebay.com/itm/RCA-Black-Plate-Red-Base-5692-Audio-Tube-High-End-6SN7-6SN7GT-PAIR-2-/140957889014?pt=Vintage_Electronics_R2&hash=item20d1beb1f6) (Submitted only as an example of the tube I currently use, not affiliated with this listed seller. You will find dozens of different brands/types 6SN7's on the market.) I have also tried black base RCA 5692 and and Sylvania JAN 6SN7, GE 6SN7GTB, with good results.
But by all means I certainly have not tried them all .....http://www.ebay.com/sch/i.html?_trksid=p2047675.m570.l1311.R1.TR11.TRC1&_nkw=6sn7+tube&_sacat=0&_from=R40 (http://www.ebay.com/sch/i.html?_trksid=p2047675.m570.l1311.R1.TR11.TRC1&_nkw=6sn7+tube&_sacat=0&_from=R40)
YRMV, it's all personal to your ears ....
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I installed a second octal socket and wired up my crack amp for a 6SN7 right out of the box. You can see it here.
http://www.bottlehead.com/smf/index.php/topic,1222.0.html
And see some comments I made here.
http://www.bottlehead.com/smf/index.php/topic,3415.15.html
I really liked the sound but started to wonder if I was mising out on anything "magical" that the 12AU7 might have to offer.So I ordered up a set of adapters from the Lowther club in HK.
http://lowther.com.hk/ (scroll down to the bottom)
I rolled a lot of 12AU7 and 6SN7 tubes and always kept coming back to an RCA 6SN7 and a "Conn Organ" 6SN7 tube that I believe was made by Sylvania. The funny thing is that these happen to be some of the cheapest 6SN7's in my inventory. :)
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Ah,OK Tubejack
Thanks for that clarification
I'm a little new to crack & the tubes,that can & cannot be used.?
Basically,what I'm trying to find out is...does the 6sn7,produce better quality sound,with all things being equal ,vs. the 12au7
My thinking,correct me ,if I'm wrong,or,coming from left field,is,that, due to the bigger physical size,the 6sn7 should produce bigger,better SQ????
Also,most of my 6sn7's,that I've purchased,are all made in the 50,60's..& jan labelled
Weren't the tubes ,made in that era..better quality,better sound? low noise??
With that being said,yesterday,I got delivery of another tube ,a Siemens 12au7 ecc82 triplemica ,,,the quality of sound with my HD800's & Crack, ,and tung-sol 5998 ,was so outstanding,_ I listened to it for almost 12 hours nonstop
Natural sound,
Great pics......the original tube that came with my crack,was from a "Conn" organ
Thanks for those links.
Any other input/advice ,will be greatly appreciated
Mike
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correct me ,if I'm wrong,or,coming from left field,is,that, due to the bigger physical size,the 6sn7 should produce bigger,better SQ
This is kind of a gnarly misconception.
The primary difference between a 6SN7 and 12AU7 would be ten years of technological evolution (6SN7 evolving into the 12AU7). If you go backwards from the 6SN7, you'll find the single bottle 6J5, then the 76, 37, etc.
One way to judge the impact of physical size is to look at how much heat one of the plates can dissipate. A 12AU7 can burn off 2.75 Watts, while earlier 6SN7's are rated to 2.5 watts (the GTB/A can do more).
It's also worth noting that the overall geometry differences between the 6SN7 and 12AU7 lead the SN7 to have more stray capacitances, which may contribute to some of the observed sonic differences.
IMO, the very best of the 12AU7 family edge out the 6SN7, but an average 6SN7 will sound a little better to me than an average 12AU7.
-PB
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"IMO, the very best of the 12AU7 family edge out the 6SN7, but an average 6SN7 will sound a little better to me than an average 12AU7"
PB,thanks for your reply..
So,basically,size does not matter..
Key word here,might be ..edge out,.
I was guessing as much,& I'm assuming the very best of the 12au7's,might even be price prohibitive?...Lorenze, {if you can find one ?},matched & balanced Siemens tubes?
Dollar for dollar,the 6sn7,might be the way to go?
M
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Eh, the prices that tubes command can be circumvented to a large degree by buying used tubes with unusual labeling. I see a few Mullard 12AU7's with non-Mullard printing on eBay for $15, that's a nice place to start.
When you move into Siemens, Telefunken, Amperex, and Mullard type 12AU7's, then the 6SN7's that can keep up become a bit more scarce.
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Paul,
Thanks for your suggestion
I went on e-bay,& found a few tubes {12au7 }, that I might be interested in,.Amperexes Mullards,Brimar
These have odd labeling,but seem to be authentic..such as--Mullards ,made in India,and one or two others
Prices were low,& the readings were good-to like new...
Still waiting on my 6sn7 to 12au7 adapter..coming from China.
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I've used the adapter to run 6SN7's in crack. The adapters work well. I ultimately built an FPIII with 6SN7's and use a 12AU7 or variant in Crack. If I was running the Crack standalone, Im not sure where I would have ended up. Most likely the VT-231 (6SN7) primarily but I also have some favorite 12AU7's as well as some of the 12AU7 variants and 12BH7. Tube rolling can be fun ;)
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Paul,
Thanks for your suggestion
I went on e-bay,& found a few tubes {12au7 }, that I might be interested in,.Amperexes Mullards,Brimar
These have odd labeling,but seem to be authentic..such as--Mullards ,made in India,and one or two others
Prices were low,& the readings were good-to like new...
Still waiting on my 6sn7 to 12au7 adapter..coming from China.
Yea I believe mine took the same boat when I ordered, must have taken 3- 4 weeks to get them. :-\
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OK,really no luck with dealing with Chinese adapters..or,6 week delivery times.
Maybe you guys can still help?
Here is what I am looking for:
a 9pin base to 6sn7 {on top} adapter...that plugs into my 12au7 input
Does anyone know,of a seller in the USA,or,someone who can build me one ,in the USA?
Is this idea doable,safe?
Thanks
Mike
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OK found it..
Just in case anyone else may need one:
http://www.ebay.com/itm/281031554093?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
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Took less than 2 weeks for me to get those adapters from HK. I think it was the same seller too. They work fine. Of course, YMMV on shipping time.
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thanks for the link and feedback on the hongkong seller Mike and Laudanum - I was on the fence about ordering from a non-US seller but did just order one up. here's hoping it gets here in some relatively reasonable time frame!
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Well - finally received my 6sn7 adapter, and sadly I'm getting a bad buzz in the left channel (that increases in loudness as I turn up the pot). With the pot at 0, no buzz is audible.
I acknowledge that the problem could be my tube - but I only have 1 6sn7 on hand (a seemingly nice Sylvania vt-231 foil getter I picked up from tubemaze), so my money's on the adapter. It has a hex bolt on the bottom. Has anyone successfully taken one of these apart to check the connections?
My amp continues to run beautifully with all of my other input tubes.
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Never had the need to take one apart. They had it apart to build it, shouldnt be too difficult, maybe just a loose wire/bad solder joint.
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If the volume is at zero, and there is no buzz, then the problem is before the volume control. The only things that are before the volume controls are the input RCA jacks and 3 pieces of wire (it may be four pieces of wire, but I remember the input wires being braided).
Is the buzz in one channel? It could be the interconnects. Regardless, try reheating the solder joints on he inputs and the volume control.
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Thanks for the input laudanum and grainger. The buzz is only in the left channel, but to clarify, I dont have any issue when running the amp with any of my many 12au7's or 12bh7's. So I don't think the problem is with the amp, interconnects, etc.
Gotta be either my adapter or 6sn7. I'll have to see if I can open up the adapter later today. I pulled the hex nut from the bottom, but it doesn't fall open immediately. Maybe time to contact the vendor on ebay.
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Maybe time to contact the vendor on ebay.
I don't think I'd do that until you try a second 6SN7.
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Just wish I had one on hand. Hate to double down and purchase another 6sn7 tube if the adapter is no good. It took about a month for the first one to arrive.
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I'd hop onto eBay and look for 6SN7's available in your area (there are hundreds).
I see pairs around LA for ~$10, and most sellers are OK with local pickup. Even with shipping, you'll get them in a day or two
-PB
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Thanks for the further thoughts all! Per PB's suggestion, I went ahead and ordered a cheap TS 6sn7gt that should be arriving in a couple of days. That should definitely help in ID'ing the cause of the issue one way or the other.
In the meanwhile, I've gone back to enjoying my crack with a 12au7 bugle boy (that's probably a better tube than any 6sn7 I'm likely to find at a reasonable price anyway).
I wish I understood why the buzz (with my adapter and 6sn7) only becomes audible and then increases in volume as I turn up the pot. Note that this is true irrespective of whether or not I have a song playing, so it is independent of having any signal passing through the tube.
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Are the voltages at terminals 1/5 within spec? (70-90V)
-PB
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All my voltages were right on spec last I checked (following my speedball install), but admittedly, that was more than a year ago. Got held up working late last night, but hopefully I'll have a chance to grab my meter and reconfirm this evening. Then again, given that my crack always has, and continues to, work perfectly with all 6 or so of my other input tubes - I have to believe the left channel "buzz" is simply the result of a defect in the adapter or in my lone 6sn7 tube.
Either way, based on past frustrations, I am totally dreading attempting a return/exchange with the ebay seller of whichever component is faulty. I love the deals you can score on ebay, but there would certainly be benefits to working with a mainstream seller like vacuumtubes.net
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Not that it's worth anything, but my money is on the tube...
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You're probably right Adam - which is a shame given that it is otherwise a very nice sounding tube. I should know once and for all Saturday when the new tube is scheduled to land.
Also - I just confirmed that terminals 1 and 5 are both measuring well within spec (right around 80V).
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Well - my new TS 6sn7 arrived last night, and it is giving off exactly the same left channel buzz (loudness proportionate to the level of the pot) as my Sylvania vt231. Given that my voltages check out, and the amp continues to function beautifully with all my 12au7's and 12bh7's, I think the issue has to be the adapter...
Incidentally, the adapter has a hole down the center but there is a loop of insulated red wire poking out from the internals of the base into that cylindrical cavity. Is the same true for others of you own this adapter, or might this signify a wiring issue? It remains unclear to me whether or not there is actually any way to open the adapter up.
I have reached out to the seller, who responded with some initial questions about my amp, whether it is suitable for 6sn7's and whether the voltage is 6.3v or 12v. I directed the rep to this thread and explained that many other bottlehead owners appear to be using these adapters without any issues. Frankly, I hope she'll sign up and join in the discussion. It would be much easier to work through the issue here than via ebay's primitive, character limited, plain text internal message system.
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My working theory right now is that the wire to the grid pin is too close to a heater wire, so heater AC voltage is capacitively coupled to the grid. The volume control shunts that to ground, but the higher the volume control, the higher the resistance to ground and the less shunting is happening.
One of the heater wires is grounded, so if I'm right it's the other one that is close to the grid. To test this (if you want!) swap the heater wires, or ground the other end of the heater winding on the power transformer.
All theories are eventually proven false of course - it's just how long it takes, and how false they turn out to be ...
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There is no wire, red or otherwise, that can be seen peeking down the center hole of the adapter that I have. I wonder if they pinched a wire or trapped it and pulled it partially loose when closing the entire adapter up after assembly. They dont cost an awful lot and cost much less than that to make so Im not sure why they wouldnt just replace the thing. But then again, it is an HK seller and they can be a PITA to deal with, especially if the language barrier is an issue. No offense intended to them as a people, but the large volume asia based ebay sellers are quantity driven for the most part. If they hoover in the 98-99% range on positive feedback with a big volume of sales, they probably arent likely to care whether they get another negative. That said, the adapters work fine and look to be made pretty decent overall but unfortunately, it looks like you may have just gotten a bad one. Maybe they will work it out with you when all is said and done.
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Thanks for the further input PJ and Laudanum - it is much appreciated! I haven't had a chance to do any more tweaking or testing in the last few days, but I'm guessing PJ hit it on the head. I had referred the seller to this thread, and shortly after PJ posted, I received an email from ebay indicating the seller had sent me a full refund (without any suggestion or request that I ship back the part, which actually would have been consistent with their written return policy). So Icelake deserves some credit for good customer service - even though it appears I got unlucky with a defective adapter.
I think I'm going to give this another go - so here's the question. Would you go with: 1) http://www.ebay.com/itm/1x-6SN7-to-12AU7-Vacuum-tube-adapter-socket-converter-/300914409464?pt=Vintage_Electronics_R2&hash=item460fe57ff8 or 2) http://www.ebay.com/itm/6SN7-6SL7-to-12AU7-12AX7-tube-adapter-adaptor-socket-converter-brand-new-1-piece-/151045740252?pt=Vintage_Electronics_R2&hash=item232b0716dc
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The more expensive one looks like it may be easier to open up, depending on how they mounted the octal socket, if there is a problem. The Octal socket also looks to be better quality. Looks like they just stuffed a decent octal socket into a sleeve. The less expensive piece is being sold by Lowther Club of HK. I believe that they are a pretty popular group in HK, which may or may not translate to the quality of the adapter.
I doubt that you would hear a difference between either adapter assuming you get a good one. Personally, I'd probably buy the less expensive one because it's lower profile, the octal socket is flush mounted. The other one has the white socket protruding out of the top of the adapter. But if the looks of the bulkier adapter and extra 12 bucks doesnt bother you, you would be getting an octal socket that may stand up to more tube rolling. Of course, that doesnt take into account how well they wired the internals.
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I have only good things to say about lowther_club. I have some of their adapters. They are very well made and plenty robust by the way. lowther_club is also pleasant to deal with.
The usual disclaimer.
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So take 2... My adapter from lowther_club arrived yesterday, and it definitely works better than the last one!
As compared to running 12au7's and 12bh7's, I still get a little bit of audible noise with this adapter, but it is equal in both channels, and not audible until the pot is turned up higher than I would want to listen in any event (with the exception of a few classical albums I have that seem to have been recorded at very low volume).
I really like the aesthetics of the crack with a 6sn7 up front, and it is always fun to experiment with different tubes. But from the standpoint of sonics, my initial impression is that I like the sound of most of my 12au7's and 12bh7's better than either of my 6sn7's. Hoping to do some more real listening in the coming days to see if this holds true.
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I just got one from Lowther club and one of the pins had a glob of solder on it and the socket is crooked. Junk! I 'm in the process of a dispute with them on e-bay.
Hopeful,
Check your lighting in the room where your Crack is being used I got some audible noise on my crack and then isolated it to a dimmer on that circuit.
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Thanks for the suggestion danosol. I don't have any dimmers in that room, but it is full of other electronic equipment that couldn't potentially be causing issues. Anyone have a suggestion for a cheap power conditioner/isolator? I used to run my crack from an audio port on my belkin pf60 - which worked reasonably well, but we moved and my amp migrated from my family room entertainment area to our guest bedroom/office.
I get no noise at all when I'm running 12au7's/12bh7's - so it seems like it has to be an adapter issue, but cleaner power couldn't hurt.
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You can pick up Furman stuff for cheap on craigslist like the PL-8 Plus. Look for the stuff with Lift technology if you decide to used (all the new stuff has it). It should be around $80 used. Kinda big because it's rack mountable stuff but it's well made stuff.
Someone else will probably chime in with another suggestion I'm sure. I'm just familiar with Furman as I use it on my guitar rig. You can always call Rob at Furman and tell him I recommended you. Rob and the rest of the team are great guys and know their stuff. By the way my name is Ajay.
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Hi everyone,
Can anybody confirm if the tube adapter in the picture below works on the Crack or not? I'm confused because the white words printed on the base of the adapters indicate that this one is to convert the 6SN7's to 12AX7's, not 12AU7's, I called the seller and he said that this would work just fine with the 12AU7's. These adapters are sold in the local audio shop, so it doesn't take too much time for me to drive there, give them cash and bring them home, much faster than buying and waiting for shipping on Ebay :)
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi148.photobucket.com%2Falbums%2Fs36%2Fdungaudio97%2FIMG_9539.jpg&hash=a041b864c74bb6ad0326bb9c5f9ba32246be9ffc)
( Adapter number 03 )
Thanks in advance!
Kratos.
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Ok, the tube pin assignments are the same for a 12AX7 and a 12AU7. The tubes are not equivalents.
The reason the adapter says 6SN7 to 12AU7 is that they are equivalent tubes, one octal one noval. If you use a 6SN7 where a 12AX7 was you will not be setting the 6SN7 up properly.
Does that make sense?
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Ok, the tube pin assignments are the same for a 12AX7 and a 12AU7. The tubes are not equivalents.
The reason the adapter says 6SN7 to 12AU7 is that they are equivalent tubes, one octal one noval. If you use a 6SN7 where a 12AX7 was you will not be setting the 6SN7 up properly.
Does that make sense?
Hi Grainger,
Thanks for your reply.
I'm sorry, but my English is not so good, so I don't understand what you mean very well. I consider that the tube adapter number 03 in the picture I posted above can be used perfectly for the Crack, because the function of tube adapters is just for converting the tube pin assignment from the 8-pin 'octal' of the 6SN7's to the 9-pin 'noval' of the 12AX7/12AU7/12AT7, etc, and it does not matter what kind of 'noval' tube your amps are using?
Thanks again,
Best regards,
Kratos.
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The 6SN7 to 12AX7 6.3V adapter in the photograph would be the correct one (by specification).
Grainger is very correct - the 12AX7 and 6SN7 would not be operationally interchangeable.
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FWIW, I have two 6SN7-->12AU7 adapters that would appear to be from the same manufacturer. Both are VERY, VERY noisy in my Crack, which is generally silent with my 12AU7s, 12BH7s, and E80CCs.
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FWIW, I have two 6SN7-->12AU7 adapters that would appear to be from the same manufacturer. Both are VERY, VERY noisy in my Crack, which is generally silent with my 12AU7s, 12BH7s, and E80CCs.
Did you ever end up trying a 6V DC wall power supply to feed the 9 pin socket?
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No. By the time I saw your suggestion, I had already ordered another (i.e., 3rd) adapter. I'll wait for that to arrive. And frankly even if that one is still noisy, I'm not sure that it is worth the effort for me to explore using a separate power supply. Are 6SN7s really all that likely to sound better than the various 12AU7s and 12BH7s available?
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It's not a matter of better or worse IMO, there are just a lot of different varieties of 6SN7.
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Yep, I already have more of them than I know what to do with...
My next step for my Crack will be to install those 200uf Icar films caps in place of the first two power supply caps, and the two 100uf motor run oiler caps in place of the stock electrolytic (currently bypassed with a film cap) for the last power supply cap. After that, I think I will be tapped out on Crack mods...
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Paul Birkeland said it. The 6SN7 and 12AX7 are not interchangeable tubes. They are not equivalent. They don't have the same gain, need different voltage and current to operate properly. But the 12AU7 and 12AX7 have the same pin assignments. That means that the plates, grids, cathodes and heaters all use the same pin numbers.
But just because they have the same pins and holes to go in it does not mean that they are the same.
The tubes will work but not well and not as designed.
Does that make sense?
Grainger
Ok, the tube pin assignments are the same for a 12AX7 and a 12AU7. The tubes are not equivalents.
The reason the adapter says 6SN7 to 12AU7 is that they are equivalent tubes, one octal one noval. If you use a 6SN7 where a 12AX7 was you will not be setting the 6SN7 up properly.
Does that make sense?
Hi Grainger,
Thanks for your reply.
I'm sorry, but my English is not so good, so I don't understand what you mean very well. I consider that the tube adapter number 03 in the picture I posted above can be used perfectly for the Crack, because the function of tube adapters is just for converting the tube pin assignment from the 8-pin 'octal' of the 6SN7's to the 9-pin 'noval' of the 12AX7/12AU7/12AT7, etc, and it does not matter what kind of 'noval' tube your amps are using?
Thanks again,
Best regards,
Kratos.
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To summarize:
12AU7 and 12AX7 are not interchangeable, because they have different gain, etc. You generally can't use a 12AU7 where a 12AX7 is called for. BUT, they do have the same pinouts. So a 12AU7 will fit in a 12AX7 socket, even if it shouldn't be used there.
6SN7 and 12AU7 are sonically interchangeable. In theory, you can use a 6SN7 where a 12AU7 is called for, and vice versa. But the problem is that they have different pinouts and sizes. So you have to use an adapter.
Because 12AU7s and 12AX7s are the same size and use the same pinouts, you should be able to use a 6SN7 --> 12AX7 adapter in order to use a 6SN7 tube in place of the 12AU7 in your Crack (provided you get a 6.3V version of the adapter, not a 12V version). This is because an adapter doesn't (or rather, shouldn't) have any characteristics of its own, it just rewires the pins assignments, which are the same for a 12AU7 and a 12AX7.
See, isn't that simple? ;D
Best regards,
Adam
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Paul Birkeland said it. The 6SN7 and 12AX7 are not interchangeable tubes. They are not equivalent. They don't have the same gain, need different voltage and current to operate properly. But the 12AU7 and 12AX7 have the same pin assignments. That means that the plates, grids, cathodes and heaters all use the same pin numbers.
But just because they have the same pins and holes to go in it does not mean that they are the same.
The tubes will work but not well and not as designed.
Does that make sense?
Grainger
Hi Grainger,
Thank you for clarifying.
But I have one more question, you said that the 6SN7 tubes will work but not well and not as designed because 6SN7 and 12AX7 are not interchangeable, so what are the 6SN7-12AX7 tube adapters used for? They are not equivalent, so in theory you can not use a 6SN7 where a 12AX7 is called for. Why do people make the adapters which sonically can't be used because of the tube characteristics?
Thanks again, and sorry if my question is too silly :(
Best regards,
Kratos.
To summarize:
12AU7 and 12AX7 are not interchangeable, because they have different gain, etc. You generally can't use a 12AU7 where a 12AX7 is called for. BUT, they do have the same pinouts. So a 12AU7 will fit in a 12AX7 socket, even if it shouldn't be used there.
6SN7 and 12AU7 are sonically interchangeable. In theory, you can use a 6SN7 where a 12AU7 is called for, and vice versa. But the problem is that they have different pinouts and sizes. So you have to use an adapter.
Because 12AU7s and 12AX7s are the same size and use the same pinouts, you should be able to use a 6SN7 --> 12AX7 adapter in order to use a 6SN7 tube in place of the 12AU7 in your Crack (provided you get a 6.3V version of the adapter, not a 12V version). This is because an adapter doesn't (or rather, shouldn't) have any characteristics of its own, it just rewires the pins assignments, which are the same for a 12AU7 and a 12AX7.
See, isn't that simple? ;D
Best regards,
Adam
Hi Adam,
That is a superb detailed and helpful reply and explanation. I guess I'll come to the local audio shop and try this adapter out. I can't stand the fact that I'll have to wait for nearly a month to get the adapter on Ebay >:(
Thanks in advance!
Cheers,
Kratos.
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Aeolus,
I expect that they are just to keep you from having to un-solder the 9 pin tube socket and put in an 8 pin socket. At that time if you were converting from 12AX7 to 6SN7 you would need to make resistor changes at the same time.