#1
I'm sure it's been asked but I am unable to check at the moment...

I have a Fender HRD that needs to be completely retubed. Which ones sound best? JJ's, mullards, etc? I've heard a lot about those 2 and they're the only ones I can think of at the moment.

I also have an early 90's crate V50 3x10, same deal. Anyone have one of these and do you have any pointers?

What do you guys suggest? I've never had one of my amps retubed so I'm totally new to this!

Thanks guys!!!
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#2
SED are better than JJ but JJ are better value for money.
My usual plan of attack if I'm not using NOS everywhere is to start with all JJ and then experiment with different others in one or two positions, mainly V1 and the phase inverter.
Gilchrist custom
Yamaha SBG500
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Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#4
So once the power tubes are happy in paradise (they're EL84's), the V1 preamp makes the most difference? It is the first tube hit with signal in the pre section right? Or am I totally off?

From the discussion about the 12at7 eh, it sounded like all the tubes you guys listed were mostly interchangable. I'm interested in the 5751's. Lower gain, higher headroom, different feel? I'm wanting to keep my cleans super clean and the OD smooth and organic. It certainly wasn't bad before, but it is a crate and could be better. Is Sovtek the big one for these?

I'll be getting all this done as soon as I can get the amp out to a tech to properly tickle the amp's girly parts. Might be a couple weeks so I have some time to hash out the details beforehand. I'll definitely be back on how all this works out regardless of what ends up happening with the amp.
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#5
Look at TAD tubes.
2002 PRS CE22
2013 G&L ASAT Deluxe
2009 Epiphone G-400 (SH-4)
Marshall JCM2000 DSL100
Krank 1980 Jr 20watt
Krank Rev 4x12 (eminence V12)
GFS Greenie/Digitech Bad Monkey
Morley Bad Horsie 2
MXR Smart Gate
#6
Higher gain = more headroom. I think I had it backwards... Maybe 5751's aren't what I was looking for. I might come back to this after having the work done if I feel like there's something to be desired still.

I read through the tubes thread and still feel like there could be more clarification. JJ's are said to have dark 12ax7's but absolutely brilliant 84's. Tung-Sol is good but there isn't really anything to compare to others. Mullard is expensive.

How do the 3 brands compare on the 12ax7's?

The JJ's sound like the best bet for the 84's. I did find a matched pair of Mullard 84's that was about $30. Worth looking into?

OR is there a noticeable difference between any of the brands at all? Just curious.

Do most amps use a phase inverter? I assume from the circuits/physics jargon I just sifted through, that yes most do. Pretty much you need it so you can run your OT at whatever watts using more than 1 channel? That's kind of what I got at least... The stuff I read also mentioned a push-pull circuit. Does push-pull apply to run of the mill class AB amps? I assume that mine is an AB.

All that to ask, what kinds of tweaks to your sound do you get out of changing your PI?

I'm on overload since anything tube beyond the big 4 types is ENTIRELY new to me. Sorry for all the questions.
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#7
Don't think in terms of headroom as much as in terms of gain and it will make more sense. Gain is the cause, headroom is just a result. Gain is simply the amplification factor so Voltage out divided by voltage in. So if you have a gain of 100 1V in would create 100V out. Now we wash off some of that gain with circuit design but a larger gain tube will cause a bigger signal to hit the next stage in the same circuit.
So if you stick in a 12AX7 it will present a bigger signal to the next triode and be more likely to distort it. That could be called less headroom. Here are the gain figures for the most common tubes:
12AX7 - 100
5751 - 70
12AT7 - 60
12AY7 - 45
12AU7 - 19 (12AU7 will not always work as a direct replacement in all amps)

In my opinion JJ 12AX7's kill other modern valves. They tend to be mid heavy and good bass making them sound "dark" compared to other tubes. People will often put a different valve in V1 to add in a few highs that are lacking from the JJ's. In most Marshalls that just isn't needed and a full set of JJ will usually kick arse.
V1 usually makes a big difference because that is the valve dealing with the smallest signal and responsible for getting it all up to a useable level.
Russian TungSol and Mullard preamp tubes (not to be confused with the old NOS tubes of the same name) are pretty brittle sounding. An amp tubed with nothing but those will end up sounding a bit like a tin can. They are ok in small doses to add in some highs.

There was a bit of a scare about JJ EL84's quality control recently but that seems to have died away and I've had no problems myself. I only buy JJ EL84's. With EL84's it JJ, NOS or gtfo. The scare had me quite worried I can tell you.

A phase inverter is only in A/B (and B but you'll never see a B) amps. It is the driver for the power amp, it isn't actually a preamp tube per se. It provides the correct waveforms needed for the push/pull power tube section to function. A/B and B amps are push/pull, Class A aren't. Push pull means that one power tube drives the positive half of the signal and the other tube drives the negative part of the cycle.
If you have an A/B amp it has to be push/pull by definition and will therefore need some type of phase inverter.
The phase inverter can introduce some of it's own distortion (as can all tubes) so trying different tubes in there can also dramatically change the sound. They also tend to wear out the fastest of all the small signal tubes in the amp. A lot of people will therefore try to put as good a tube in there as they can afford. A popular choice are NOS military valves like the JAN Phillips 5751 (JAN stands for Joint Army Navy - lots of old manufacturers had JAN tubes back in the day)

If you really want the best preamp tubes you hunt down NOS tubes from Germany, Holland, Britain or the US.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
Last edited by Cathbard at Feb 18, 2012,
#8
I think I've got it now! The description of the 5751 didn't really make it sound that way. But this makes more sense. If I feel like I need to smooth it out more, I might look into it.

I finally found someone with a version of my amp. He made it sound like Tung-Sol was the way to go for V1 and then use JJ's for the rest, both pre and power. It seems to go with what you're saying to, so I'll probably go with it.

Is the PI what people are talking about when they mention a cathode follower?

Thanks for all the extra info as well! Its a lot easier to understand when you're not trying to read through formulas before you have the theory down.
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