Legacy Lead Channel Sound Problem - Jemsite
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post #1 of 9 (permalink) Old 09-03-2009, 12:40 AM Thread Starter
 
Join Date: Aug 2008
Location: Union, NJ USA
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Legacy Lead Channel Sound Problem

The lead channel on my Carvin Legacy head has slowly been sounding worse and worse for some time now, I think that it may be time to replace some tubes.

It sounds REALLY muddy, theres almost no more presence or treble, just one big mush. However, the clean channel, reverb and everything else seems to be working fine. Should I replace the preamp tubes with JJ/Tesla 12AX7's? Do I need to replace them as a set or just the ones giving me problems?

P.S. I'm also looking for a sound that has more saturated gain in it, without loosing the originality or overall feeling of the amp. It would be nice if I can replace my tubes and improve the tone of my amp as well (i still have the stock groove tubes). Any recommendations?? Thanks
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post #2 of 9 (permalink) Old 09-03-2009, 08:23 AM
 
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Re: Lecagy Lead Channel Sound Problem

Quote:
Originally Posted by hotwax1989 View Post
The lead channel on my Carvin Legacy head has slowly been sounding worse and worse for some time now, I think that it may be time to replace some tubes.

It sounds REALLY muddy, theres almost no more presence or treble, just one big mush. However, the clean channel, reverb and everything else seems to be working fine. Should I replace the preamp tubes with JJ/Tesla 12AX7's? Do I need to replace them as a set or just the ones giving me problems?
You do not need to replace preamp tubes as a set, that's only for power tubes (matched pairs/quads) In fact you could switch around some of the tubes to figure out if it is indeed a single tube that is giving you trouble. Preamp tubes can last a very long time.

If only the Gain channel is giving you problems, you might want to check if exchanging V2 and V4 helps, that would allow you to pinpoint the problematic tube, provided they are all 12AX7 tubes:

V1B input
V1A gain
V2A cascaded gain (clipping)
V2B cascaded gain (clipping)
V3A FX loop recov
V3B master volume
V4 A+B reverb drive/recov
V5 A+B phase inverter

Leave the V5 alone (it's part of the power amp) and it could actually be a tested symmetrical double triode.

Since the clean channel sounds ok, V1 should be ok, but you might want to check it anyway.
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post #3 of 9 (permalink) Old 09-04-2009, 07:44 AM
 
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Re: Lecagy Lead Channel Sound Problem

replace all the tubes and eject the old ones into a nearby river or pond
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post #4 of 9 (permalink) Old 09-04-2009, 01:41 PM Thread Starter
 
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Re: Lecagy Lead Channel Sound Problem

Thanks eviltwin, that was very informative. I'm gonna do that sometime soon and post back a result...hopefully I can just replace one or two.....
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post #5 of 9 (permalink) Old 09-05-2009, 05:28 PM Thread Starter
 
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Re: Lecagy Lead Channel Sound Problem

I swapped V2 & V4 like you said eviltwin and that seemed to fix the mushy gain problem! Haven't had much time to test but it still seems like the amp is not sounding its best..so I'm gonna test and replace a few tubes.

Also, I noticed that 2 of the stock tubes are 12AX7R's and the rest are 12AX7C's. So that means 3 of my tubes are Chinatubes??? And i'm guessing the other 2 are Russian or something?? Why couln't they just put all the same tubes in there?
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post #6 of 9 (permalink) Old 09-06-2009, 04:07 AM
 
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Re: Legacy Lead Channel Sound Problem

C for Chinese and R for Russian, is an internal naming scheme by GrooveTubes. Their description of the tonal characteristics of each seems contrary to commonly held beliefs, at the risk of generalisation, Chinese tubes are preferred for grainy Marshall type tones:

http://thetubestore.com/12ax7review.html#summary

but in GrooveTubes' case the Chinese ones are labelled as smooth and round...in my book smooth and round means low dynamics, which is generally attributed to Russian tubes...ymmv.

How were they originally installed V1+V2 Russian the rest Chinese? Or V1-2-3 Chinese?? The five tubes all perform radically different functions so they may be selected for their particular qualtities (linear/compressed, raspy/grainy/soggy/mushy, high gain, etc.) The input tube for example, may be set to unity gain and is only there as a buffer for the input. (maintaining the tonal character of your guitar)

Logic dictates that V3 and V4 should be linear and clean (FX recov, master volume and reverb) but using a heavily coloured tube in those locations could really define the amp or take the edge off digital effects.

With the "bad" tube in the reverb location (V4) you should be able to hear that as you crank the reverb. It also means you could "park" the bad tube there without much notice.

I still think that perhaps only one tube is failing, so spending 5*20$ is a bit silly. You could buy two radically different tubes (but both 12ax7s) and switch them around in the V1, V2 and V3 locations to fine tune your tone. The spares will keep forever.
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post #7 of 9 (permalink) Old 09-06-2009, 09:37 PM Thread Starter
 
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Re: Legacy Lead Channel Sound Problem

Wow, thanks for all the great information i really appreciate that eviltwin. Well, V1,2,3 were CHinese, and V4+5 were Russians. I swapped V2 with the Russian V4 now all sounds pretty good, reverb hasnt been affected much at all. But your right, I should invest in maybe 1 or 2 new ones. I'll keep in mind what you said about how putting different tubes with diff characteristics will affect my tone. Since V2 was my problem source, can I change it with a JJ 12AX7? Does it have to be matched as well?
Thanks
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post #8 of 9 (permalink) Old 09-07-2009, 04:44 AM
 
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Re: Legacy Lead Channel Sound Problem

Quote:
Originally Posted by hotwax1989 View Post
V2 was my problem source, can I change it with a JJ 12AX7?
You can; they appear to be rugged and decent but not brilliant.
A bit flat, but one of the cheaper ones specifically mentioned for high gain applications.
I wouldn't pick a JJ for the V1 though.

Note that only the cheapest JJ (ECC83S $10) meets the demands for a Legacy!
You don't want to risk microphonics (803S $15) and the expensive gold plated terminals (83S-Gold $20) are unnecessary if you don't have gilded mounts on the Legacy.
http://thetubestore.com/12ax70ectyp.html

Quote:
Does it have to be matched as well?
No, but if it does colour the sound much, you will get a more pronounced difference between clean and lead channels. So technically there is no need for matching , but you may want to for tonal considerations.

Looking at the specs and the tone I associate with a Legacy, I'd go for two Tung Sols in the V1&V2 position. See how that feels and sounds.

Keep the Russians in V4&V5 and the Chinese V3. That would leave you with one decent Chinese spare.
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post #9 of 9 (permalink) Old 09-07-2009, 01:19 PM Thread Starter
 
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Re: Legacy Lead Channel Sound Problem

Sounds great - thanks for all your help eviltwin. I'll probly post here in a couple days with my results, but the Tung Sols DO look like a good choice, it was either them or JJ's(I was up all night doing research lol). I didnt know about the mounts on my Legacy that was very helpful because I would have probly spent more on the gold plated versions for no reason. Again, thanks for all your replies and I will be posting again soon!

BTW, hows TubeDepot.com for service?? They are a bit cheaper than TubeStore. All i really care about is the packing, I dont want to order tubes than have them screwed up through shipping...

Last edited by hotwax1989; 09-07-2009 at 01:39 PM.
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