#1
I posted in the electric guitar forum, so you can look there if you want more details, but here's the dirty:

I have two guitars, both have problems with the g string sounding weak through the amp (clean and distorted). If i plug into the effects loop, then the cleans sound great on all strings. So do i need to start replacing preamp tubes? Amp is Peavey 6505+ combo.

Thanks.
Last edited by In_Black_Flames at Aug 6, 2015,
#2
Buy a few and roll them through. There's no downside, you should have extras and experiment anyway.

Try out a 12AT7 or a 5881, they help tame the unnecessary gain and noise in the 6505.
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#3
G-strings in general are problematic. They are definitely not the best sounding strings on my guitars and you can find lots of info on G-strings issues. Can you play your guitars on someone else's amps? It would surprise me if the amp had anything to do with it. I would buy a wound 3rd string and see if that helps.
#4
I am working on taking my guitar to a friend's house, so maybe. I do actually have a wound 3rd string, but I don't want to take off the current one to try it out. Maybe when it is close to time to changing strings.

Do you need to bias preamp tubes? Or just power tubes? I hear people say the 6505+ doesn't have much bias, but anything I can do to help the tone I will try.
#5
You don't bias preamp tubes, just power tubes. And I think the 6505+ is self biasing. Your issue is in the preamp section, since using the effects loop bypasses the preamp. Try a 12AX7 in all of the spots to find the bad tube.

And likely that wound G string is of different tension. It highly doubt it's the guitar.
#6
Quote by Offworld92
Buy a few and roll them through. There's no downside, you should have extras and experiment anyway.

Try out a 12AT7 or a 5881, they help tame the unnecessary gain and noise in the 6505.

5751 not 5881 (5881 is a power tube TS) I know that was just a typo Offworld

You can also try using a boost pedal.

What are your settings?

You don't need to worry about biasing your amp, Peavey does not alow much bias adjustment any way
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Last edited by Robbgnarly at Aug 6, 2015,
#7
Pre - 6.5
High - 7.5
Mid - 6
Low - 5.5

Also, I guess I need to figure out what the 5 different preamp tubes do before I start replacing them. I am not sure which one to put "low gain" tubes in and which one to put regular tubes in.. I don't even know what regular tubes are.
Last edited by In_Black_Flames at Aug 6, 2015,
#8
Quote by In_Black_Flames
Pre - 6.5
High - 7.5
Mid - 6
Low - 5.5

Also, I guess I need to figure out what the 5 different preamp tubes do before I start replacing them. I am not sure which one to put "low gain" tubes in and which one to put regular tubes in.. I don't even know what regular tubes are.

well your in the right place

your amp uses five 12ax7 preamp tubes. these tubes are also called ecc83 tubes (they are the exact same type of tubes)

The 12ax7 closest to the input of the amp is V1.

one of the 12ax7's is for the FX loop and the 12ax7 closest to the power tubes is the phase inverter (PI)

The V1 and the PI can make a big difference in the sound/fizziness

You can buy a few 12ax7 tubes and start substituting them one at a time, this is called "tube rolling".

Different brands will have slightly different characteristics to their sound. Notice I said slightly, but sometimes certain amps respond better to certain tubes over others.

Your power tubes are 5881/6L6

But a boost pedal like a tubescreamer can help thicken up single string notes
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#9
Quote by In_Black_Flames
Pre - 6.5
High - 7.5
Mid - 6
Low - 5.5

Also, I guess I need to figure out what the 5 different preamp tubes do before I start replacing them. I am not sure which one to put "low gain" tubes in and which one to put regular tubes in.. I don't even know what regular tubes are.


That is quite a bit of gain on a 6505. With a boost, i don't think I ever went over 4.5.
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#10
JJ 5751 tubes in V1 and phase inverter are like magic for these amps. Follow Robgnarly's advice on where those are located.

5751 preamp tubes are slightly lower in gain than a standard 12ax7, but there's also a different character to them. They sound clearer and warmer; it's hard to describe. But putting one in V1 gives you a little more headroom and makes your preamp gain knob more usable (you can still get way more than enough gain). It'll also improve your cleans. Putting one in the phase inverter position also improves cleans further but doesn't sacrifice any "oomph" in your high-gain sounds. Those two positions make the biggest impact on your tone, but eventually think about changing the other three preamp tubes to better 12ax7s. (I use all JJs in mine with zero complaints -- they sound much better/richer than the Shugyangs the amp came with).

Power tubes in this thing don't need to be rebiased because the amp is biased very cold. I've always just bought MATCHED pairs and put them in. Done deal. JJ 6L6s are money.
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#11
I don't know what matched pairs means.. I did order some JJ tubes last night. Also, did you do the mod to bias your amp warmer? I heard about people doing that but haven't talked to anyone about it.
#12
^^Matched pair only applies to power tubes. It just means that when you replace your power tubes, you need to buy them in pairs that have been tested at the same output (or in matched quads if your amp takes 4 power tubes). Even tubes of the same type and manufacturer can have variances in output. To keep your amp healthy and sounding good, you want those to be matched as closely as possible.

I have not done the bias mod, no. I don't know of anybody who has with the 6505+ 112, nor have I seen a tutorial on how it's done. I have heard some people who have done lots of mods on the 5150/6505 family say that they prefer it biased the way it is from the factory. The plus side to it is that it saves you money on power tubes, as running them hotter wears them out faster.
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#13
Quote by KailM
^^Matched pair only applies to power tubes. It just means that when you replace your power tubes, you need to buy them in pairs that have been tested at the same output (or in matched quads if your amp takes 4 power tubes). Even tubes of the same type and manufacturer can have variances in output. To keep your amp healthy and sounding good, you want those to be matched as closely as possible.

I have not done the bias mod, no. I don't know of anybody who has with the 6505+ 112, nor have I seen a tutorial on how it's done. I have heard some people who have done lots of mods on the 5150/6505 family say that they prefer it biased the way it is from the factory. The plus side to it is that it saves you money on power tubes, as running them hotter wears them out faster.


I ordered two JJ power tubes and didn't ask for them to be matched.. Should i still use them?

And yeah, maybe that mod wasn't for the combo, I'm not sure..
#14
Quote by In_Black_Flames
I ordered two JJ power tubes and didn't ask for them to be matched.. Should i still use them?

And yeah, maybe that mod wasn't for the combo, I'm not sure..

where did you order from?
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#17
Quote by In_Black_Flames
Tubedepot.. Where should i be ordering from?

send them an email quickly and ask them to make sure they are matched. Tubedepot is a good site and they will probably match them if they have not shipped yet

or call them 877-289-7994

but do it ASAP
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Last edited by Robbgnarly at Aug 7, 2015,
#18
I called and the guy told me typically if you order a pair they will be matched, so i think i am ok.
#19
Quote by In_Black_Flames
I called and the guy told me typically if you order a pair they will be matched, so i think i am ok.

cool, they are a good site, I have ordered many tubes from them with great results
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#20
Ok, so i switched the tubes and it didn't really help.. I put a wound g string on and it sounds fine. Is this something in the groove on the bridge then?