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Dirty-South Blues Harp forum: wail on! >
Wich 12AX7? Wich EL84?
Wich 12AX7? Wich EL84?
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rogonzab
99 posts
Sep 02, 2012
8:33 AM
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Hi,
On Friday afternoon a received my first tube amp, a Buguera V5. The amp have 2 tubes, one 12AX7 and one EL84, and sounds really good whit harp on a clean-to-dirty setting. On a dirty-dirty setting I didn't like it that much, but is good enough (keep in mind that is a really cheap amp).
I read on the internet that in this amp the stock tube are kind of lousy, and everyone agree that a tube upgrade makes a significant improvement on the tone of the amp.
So, I have 3 questions:
1) To lower the gain on the preamp, I am looking for a 5751 tube right? or a 12AT7?
2) Any brand in particular? (I am planing to replace both tubes)
3) In order to make the tube swap, I need to unplug the amp, unscrew the protective cover of the tubes, pull off the old tubes whit my hands, put in the new ones? Is that easy, or do I need extra precautions whit this?
Thxs!
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5F6H
1329 posts
Sep 02, 2012
9:02 AM
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Hi Rogonzab,
1) Yes, you might also want to try 12AU7 & 12AY7... possibly skip the 12AT7 sub as 5751 tend to be warmer? When trying find the tube with the gain that works best with your mic, the tube's designation/type is more critical than brand, but...
2) 12AT7 JAN Phillips, GE5751, EH12AY7/6072, 12AU7 again JAN Phillips but even a cheap Chinese version will tell you if this tube is in the ball-park. EL84 don't need much drive voltage so any of these should work to a greater degree. Different brands of tube do sound different, but if you like say a 12AY7, there is no brand of 12AX7 that will sound like a 12AY7. Going too low on gain will soften the sound, possibly too much.
EL84 again, different brands (& tubes within a brand) will vary but you will get less variation by subbing the power tube compaed to the preamp tube...to the point, that I would concentrate on the preamp tube first...when happy there, explore power tubes if you think it necessary (EL84 are a popular guitar tube so good NOS models are expensive, JJ are a bit stiff, so it's possible that stock Chinese & Russian EL84 can sound as good as any current production brands)...no point buying a cheap amp then matching the cost of the amp in tube subs! ;-)
3) Make sure that the amp & tubes are cool to the touch (10-15mins from turn off should be fine), it's a good idea to unplug from the wall before doing anything to an amp that does not require live voltage. Change one tube at a time - 12A#7 & EL84 both use 9 pin sockets, but ARE NOT interchangeable, get the tube positions wrong and you will kill something.
New sockets tend to be stiff so use a firm but gentle rocking & rotating action to get them out, careful about using too much force, as then it's easy to inadvertently smash the tube you have removed against a speaker magnet/etc.
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Thievin' Heathen
20 posts
Sep 02, 2012
1:34 PM
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On one of those internet tube supply sites (tubestore.com??? something like that) I selected NOS, which was described as non-specific old stock, kind-of-a grab bag. What I received was old G.E. Kinda fun, I recommend it. Just add another couple of $8 tubes to your order and see what you get.
I have a couple of Peaveys which I am trying to tweak to taste and found the AT7(as recommended) in the clean pre-amp is getting me close to what I'm looking for. Volume, clean breakup and little feedback. A pleasant surprise was the 12AU7 in the lead channel, which makes it useable without feedback with all kinds of nasty overdrive potential.
Turning guitar amps into harmonica amps seems to involve quite a bit of experimentation. And then you find yourself at a concert where a really good harp player is doing it acoustic through the PA, who then takes a walk around the bar, rocking the place completely unamplified, and you find yourself wondering if you might be going in the wrong direction.
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rogonzab
100 posts
Sep 02, 2012
2:54 PM
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If i get it right, the best thing to do is try diferents tubes (pre-amps first) and find one that I like, right?
So, I better buy 3 or 4 low cost (8-10 dollars) instead of one $30 tube?
5F6H, there is a corelation betwen impedance of the mic and gain of the amp?
It is something like a hotter element can handle less gain on the amp (because it drives more signal to the pre-amp)?
I have a ceramic mic, whit a Sonotone CM10 element in it, and 1Meg volumepot.
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5F6H
1330 posts
Sep 03, 2012
1:44 AM
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Yes, for testing & getting in the ball-park, I wouldn't blow a big wedge on a $40 NOS preamp tube...once you are settled the type of tube that you prefer, then maybe splash out, but remember, tubes sound different but not always better, taste is a personal thing...because omeone had good results with a certain tube in one amp doesn't mean to say that you will in yours.
Not so much specifically the impedance of the mic (assuming it is Hi-Z, as yours is), but more relating to the signal level & most importantly tone - you can measure loads of aspects from mic to mic, but it's always the tone that tells the story. Big signal from a mic batters the preamp tubes, smaller signal stays cleaner & allows more sweep...lower gain preamp tubes distort in a smoother, less fuzzy way. But again, the tone of a preamp tube getting battered by a big mic signal is one of the things that people like about amplified harp ;-)
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Old Hickory
42 posts
Sep 03, 2012
2:25 AM
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One other thing you need to keep in mind when you're doing the tube swap is making sure your bare fingers don't come into contact with the tube if you can help it. Leaving an oily fingerprint on a red hot tube can cause the glass to bulge and fail. Try using a clean dry cloth (t-shirt, wash rag) to install the new tubes but if you do accidentally touch it be sure to wipe it down with alcohol. It's also a good idea to treat the tube pins with some kind of protectant to keep them from burning in the socket over time. I'm not sure what the name of the stuff is but the guy I get my tubes from (Lord Valve in CO) always includes it for free whenever I order tubes.
Last Edited by on Sep 03, 2012 6:21 AM
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5F6H
1331 posts
Sep 03, 2012
3:40 AM
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@ Old Hickory - "One other thing you need to keep in mind when you're doing the tube swap is making sure your bare fingers don't come into contact with the tube if you can help it. Leaving an oily fingerprint on a red hot tube can cause the glass to bulge and fail. Try using a clean dry cloth (t-shirt, wash rag) to install the new tubes but if you do accidentally touch it be sure to wipe it down with alcohol."
This is an old wive's tale and quite untrue. The only reason to avoid touching the tube with your bare hands is to avoid getting burnt. The only time I have seen the glass on tubes fail is when dropped onto a hard floor, hit with a socket wrench, etc.
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Old Hickory
43 posts
Sep 03, 2012
5:59 AM
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@5F6H...I've seen this argument before on other forums and I won't dispute you especially since I'm sure you know a lot more about tube amps than I ever will, but I will say this...I've done television and film lighting for a living for the past 30 years and I've seen it happen dozens of times with the smallest 200watt lamps all the way up to 20,000watt lamps. And I'm not just talking about quartz halogen bulbs either. In fact every replacement lamp we use comes with a protective sleeve to keep you from touching the glass while your installing it. Now whether or not a vacuum tube gets that hot I don't know, I guess some tubes run hotter than others but in my business hot glass and oily fingerprints are a bad combination so I've always carried that logic over to my vacuum tubes. I've got a decent collection of high dollar tubes and I'd rather not take the chance.
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tmf714
1230 posts
Sep 03, 2012
6:20 AM
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I concure with Old HIckory here-I have seen the glass fail from fingerprints left behind by careless installers.
The quality of the glass may also have been of a lesser grade for some NOS tubes with early dating.
Power tubes more frequently than preamp tubes,but I have witnessed failures from both from "fingerprinting"-
The newer Halogen automotive and motorcycle light bulb applications come with a warning in the package to not touch the glass with bare hands-not only for light dispersment,but from the salt and oils on your hands etching into the glass,causing a chemical reaction,and leading to early failure.
Last Edited by on Sep 03, 2012 6:25 AM
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5F6H
1332 posts
Sep 03, 2012
7:14 AM
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@TMF714 - Amplifier tubes, as used in common musical instrument amplifiers, are not subject to the same protocols & weaknesses as halogen bulbs, which as far back as I can remember have carried warnings regarding handling.
How exactly did you determine the tubes failed specifically because of "fingerprinting"?
I can only assume that, having seen so many, you are unusually unlucky. If tubes regularly failed due to being handled by humans, then there would be no working amplifiers...anywhere.
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Last Edited by on Sep 03, 2012 7:48 AM
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tmf714
1231 posts
Sep 03, 2012
7:33 AM
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@5F6H- A good freind of mine,who has been working with/on electronics that require tubes for close to 50 years ,pointed out some failures to me that were related to mishandling-i never stated the failures were purely from the handling by humans-thats your illogical deduction-
Mishandling in the terms of dirty or greasy fingerprints-someone could have been eating chips,or some other greasy food for lunch or dinner,then decided to work on the equipment without cleaning his hands first-thats what my freind stated,andI beleive him ,after working side-by-side with him for over 20 years-
Last Edited by on Sep 03, 2012 7:34 AM
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5F6H
1333 posts
Sep 03, 2012
7:51 AM
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TMF714"-i never stated the failures were purely from the handling by humans-thats your illogical deduction-"
Hey don't shoot the messenger, I didn't "deduce" anything, you clearly wrote: "I have seen the glass fail from fingerprints left behind by careless installers" & "Power tubes more frequently than preamp tubes,but I have witnessed failures from both from "fingerprinting".
Thanks for clarifying that normal, careful handling is not an issue.
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rogonzab
101 posts
Sep 04, 2012
8:05 AM
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I bought this tubes:
1 Tung Sol 12AT7
1 EH 12AT7
1 JJ 12AY7
And
1 EH EL84
I gues that woul give me a few choices.
One question:
Do I need to bias if I want to put the EH EL84??
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bloozefish
43 posts
Sep 04, 2012
8:25 AM
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I don't know about the Bugera, but my Kalamazoo 2 had an EH EL84 in it. I picked up a New-Old-Stock (NOS) Amperex EL84 off the 'Bay for about $15 USD, and it made a HUGE improvement in the tone.
I bet your TungSol 12AT7 will be a kickin' preamp tube.
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5F6H
1336 posts
Sep 04, 2012
8:45 AM
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@ Rogonzab - No you won't need to rebias, most (all the affordable ones anyway) single-ended (one power tube) 5W amps are cathode-biased, so the power tube bias is already pre-set by a resistor, same as for preamp tubes - just plug in & play. Cathode bias is less fussy than fixed bias in big amps.
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spackle20
26 posts
Sep 04, 2012
12:52 PM
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I will offer a thought. I think this is one of those areas where expectations may cause one to hear an improvement where there is none.
When I got curious about different tubes a while back (in a guitar amp) I recorded the sound of each one, so I could go back and review them back to back.
IIRC, the Electroharmonix I had was in the middle tone wise. JJs from Europetubes were less bright / warmer. Sovteks were a bit brighter. But if I were just to walk up and hear the amp, I doubt I could tell you which was in it.
Another things to consider is how much gain the tube has (it varies). Also, a major factor for me was the circuit the tube lives in. Most tube circuits let too much bass into the input of the tube which causes a loose / sloppy / molten lava kinda sound. It causes the tube to swamp and produce blocking distortion. A lot of folks like this vintage sound but I find it annoying. The fender amps are terribly loose on the bottom. The Mesa Boogie Mark IV is incredibly tight, FWIW.
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rogonzab
123 posts
Oct 03, 2012
5:37 AM
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Update:
On Monday I received the Tung Sol 12AT7, so yesterday I opened my amp and give it a try.
Impressions:
The gain on the amp is now much lower than before. Whit the previous tube, I played whit the volume on 10 and the gain on 3, now I can get to 10/10 and no feedback in my room (on a 0.1 watts).
It does sounds better (I think) whit more definition. One thing that I noticed is that before when I put the gain on 10, and the volume on 1-2 it sounded kind of harsh. Now is a more warmer sound.
I need to adjust my settings to this tube. I hope that the rest of the tubes arrive soon.
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Rick Davis
770 posts
Oct 03, 2012
7:51 AM
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rogonzab -- When I did the Fender Pro Jr project harp amp at The Blues Harp Amps Blog I found that the standard EH EL84 had a warmer tone than other tubes I tried. I would suggest a JAN Philips 5751 for the preamp tube. The 12AT7 tubes are not good tone generators.
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-Rick Davis
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rogonzab
124 posts
Oct 03, 2012
9:22 AM
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Rick Davis,
Thx for your advice!. I read the tread about the tone of the 12AT7, but that was after that I buy the tubes. I am going to wait for the other tubes arrive, and then buy other.
I found that in over here in Chile the tubes are very expensive ($40 for a EH EL84) so I can resell this tubes fairly easy (I pay like $15 for mine whit shipping).
Also I need to ork on my tone,I bet that is going to make a big difference.
Last Edited by on Oct 03, 2012 9:35 AM
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rogonzab
162 posts
Nov 29, 2012
6:54 AM
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Update Nº2:
The best combination that I found was this:
Tung Sol 12AT7
EH El84
Much more bass and presence in the sound than the stock one.
Rick Davis advice was to get a Jan Philips 5751, so I look on EBay but I didn't buy the tube because I like the Tung Sol 12AT7 and I didn't fell like waiting 4 weeks for the tube to arrive.
A few days ago I made a google search for the Jan Phillips 5751, and I found an add in a local website. I send the guy an email, he give his phone number so I call him to ask him where do we met to make the transaction.
Turns out that the guy is the amp tech for the good guys in my town, and is a luthier and a guitar player since the last 30yrs and harmonica player for the last 2. We talk for almost an hour about gear, harmonicas, guitars, tone, music. He told me that I better took the amp to his house to test it and he told me that is going to let me play his 63` Fender Vibroverb.
So, I went to his house, and we test the new tube. Whit the Jan Phillips 5751 the amp sounds so much better, the sound has more definition and the distortion is warmer.
He pull out his guitar and turn on the Vibroverb, he says: lets play!. We start jamming, we play for 10 min or so, and then he ask me if I am in a band. I say no, and this is the first time that I ever play whit a guitar player. He look at me and says: we should make a band.
That was so great, this guy is a great player, and he ask me if I wanna play whit him. It was so cool.
(by the way, the Vibroverb is awesome whit harp)
Last Edited by on Nov 29, 2012 8:47 AM
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TetonJohn
8 posts
Nov 29, 2012
10:47 AM
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Great story. I bet that felt great! Congrats.
The lesson of course is that if you were not gear obsessed hunting down the best tubes, and instead had stayed home practicing, you would not have been invited to start a band!
;-)
Last Edited by on Nov 29, 2012 10:49 AM
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Georgia Blues
6 posts
Nov 30, 2012
7:18 AM
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I plugged a couple of Mullard EL84s into my Bjr and it made a big improvement in tone and response. Reportedly less clean headroom in these so earlier breakup. Seems to be true.
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