cm16600
61 posts
Feb 05, 2009
10:39 AM
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Hi, i need to change 2 tubes amps, the stock one are chinese unbranded and i'd like to buy better ones.I need a EL84 and a 12AX7 .Which brand would be best for harp playing ? I am playing , blues rock ,pop,funck and some brass pops too.
I've read as well that it is possible to swap the 12AX to a 12AU7 what would be the difference?
Thanks
Chris
Last Edited by on Feb 05, 2009 12:05 PM
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Oxharp
68 posts
Feb 05, 2009
10:56 AM
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Hi Chris if you go to http://www.watfordvalves.com
they have a great deal of info for you and are very reliable.
There are several different pre amp valves all with different Gain Factor. A lower gain will get your tube amp to break up at a lower volume but this is a mix and match affair and needs some research on your amp before you go and buy a load of pre amp valves.
For example the Fender Bassman 59 comes with a Rectifier GZ34 for example 2 6L6 Power tubes and 3 12Ax7 pre amp valves (stock). Thats great for a guitar but way too bright for the good old harp so people swap out the pre amp valves to get a lower gain value and push the pre amp stage harder in the chain. The result is a better sweet spot at lower volumes before feed back occures. Basically better tone at lower volumes means you dont have to turn it up too loud to get that crunch.
Beware though changing all the pre amp tubes can be detramental to your other valves. its worth doing but research is the key.
Typical gain factors are.
12Ax7 = 100%
12AT = 70%
12AY = 40%
12AU = 18%
I have messed around with different combinations and you have to be pretty good at listening to hear some of the differences.
Hope this helps.
Russ
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cm16600
62 posts
Feb 05, 2009
11:16 AM
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Thanks a lot Ox this helps a lot.
chris
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TBone69
39 posts
Feb 05, 2009
11:43 AM
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Hi Chris,
I am just guessing here but it sounds like you have an Epiphone Valve Jr as thats the tubes it has in it.
Before modding the electronics I swapped the preamp tubes around using some old NOS tube I found. I found the 12AU7 to give a nice mellow sounds but you need a HOT mic to really drive this one. I used this one for playing with the church band.
For nice gritty blues I found the 12AT7 to lower the feedback enough on my MIC so I could crank up the volume.
Now that I modded/revoice the amp for HARP playing I am back to the stock 12AX7, though I want to try a better quality tube.
With all that said grab a couple different tubes and test them out.
Good Luck
Tom
I never
Last Edited by on Feb 05, 2009 11:43 AM
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cm16600
63 posts
Feb 05, 2009
12:03 PM
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Hi Tbone, thanks for your tips i did order a Blackheart little giant, i know it is set with low quality tubes so i wanted to know a little bit more.
Thanks.
chris
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Oisin
107 posts
Feb 06, 2009
10:05 PM
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NOS Mullards are a very good tube. See 'em quite a lot on ebay.
Oisin
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Bluzdude46
9 posts
Feb 07, 2009
2:17 AM
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I chose the Tung-Sol gold re-issue 12ax7 in both my Epi Vjr's very warm sound breaks the eminence speakers nicely. With a good CM mic you can push it hard without it getting too nasty. If you use a crystal or ceramic element mic you really need to push the amp
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Bluzdude46
10 posts
Feb 07, 2009
2:20 AM
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Chris? Let me know how you make out on the Blackheart I'm set with the Epi's for low watt amp and there is more modification info on them. I'm a harp player not an electrician so I went the easier route. I know Guitarists like the Blackheart a little better, but guitarists are NOT looking for the same thing in amps as us lucky few.
Last Edited by on Feb 07, 2009 2:20 AM
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cm16600
66 posts
Feb 07, 2009
4:28 AM
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Hi ,Bluzdude46, i will let you know after i try it a couple of weeks .As i understood the valve junior and blackheart are quite similar, it is the same engineer that made them. The most obvious differences is the blackheart have an 3 knob equaliser, a 12 inch speaker and a 3 to 5 watt switch .
I e-mailed Thomann to know the size of the magnet (12cm)and tell them it was for harp,thay replied that a lot of harp players in germany are pleased with it,so i decided to give it a go .Worst senario i will have to return it.
chris
Last Edited by on Feb 07, 2009 4:29 AM
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LIP RIPPER
28 posts
Feb 07, 2009
5:05 AM
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LOOK UP VACUUM TUBES.NET. GREAT INVENTORY, PRICE AND KNOWLEGIBLE STAFF. I BOUGHT AN RCA AND A SYVANIA NOS "5965" WITH A 47 GAIN FOR $3 EACH. YOU MIGHT GIVE THEM A CALL.
IT'S MY UNDERSTANDING THAT WE DON'T NEED SAY, TELEFUNKEN QUALITY FOR OUR AMPS. THAT QUALITY TUBE IS MORE FOR HIFI EQUIPMENT.
LR
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cm16600
67 posts
Feb 07, 2009
5:09 AM
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thanks Lip Ripper
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