#1
Hi guys, it's been a while.


Okay, so I've been wanting to change the bulbs in my amp for a while, being that the ones stock are known to suck. But now it seems like I'm needing to as my JCA100h's sound has been getting staticy, brittle, lacking warmth, and losing the "edge" it's had before.

I think I can wait a little while longer before I swap out the 4 bigger light bulbs as I think they're shining okay for now. I mean, they're obviously cheapo Chinese bulbs, but I feel the preamp lights are needing it more.

What bulbs will make my amp look the prettiest? And do they make them in other colors aside from orange? It gets really boring after a while.


Okay but seriously, preamp tubes. What would you guys recommend?

JJ seem to be recommended frequently, but I've always found them to be a bit too dark. The way my amp has been is that it has that distinctive midrange bite that Soldano amps are known for, yet at the same time, smooth and creamy sounding with leads.

I fear that throwing JJ will give it too dark of a look sound, would take away the clarity, and make it sound too much like your typical modern-metal/"core" sounding amp (e.g. 6505). Plus from my experience, they make cleans sound really dull and muffled. If this is not the case, correct me if I'm wrong.

I do still play metal as my main genre of music, so I don't want to use 5751's or 12au7's or anything else that will make the amp lose it's balls/edge.

What would anyone suggest as a good mix of tubes? Like a JJ in one socket, Tung-Sol in the other, etc.
#2
Get a few different styles an mess around.

JJ803s - long plate, low noise
Tungsol- a bit brighter
JAN5781 or something..

JJs are a great quote for the price. Really mess around with the tube responsible or the 1st gain stage as it will make the most difference.

Also- tubes Make a difference in sound, albeit not that much. You could turn your EQ knob and get the same results... That being said a good tube in the right location can take the fizz off the top end, etc.. Things the EQ can't do.
Last edited by R45VT at Mar 23, 2013,
#3
Sylvania made some great bulbs, but they're a bit hard to come by for your application .
#4
Put normal JJ's everywhere and experiment with other things in V1. Maybe a JJ ECC803, a Gold Lion a TungSol, maybe hunt down a nice NOS tube. I would have said that the JJ's would be fine in a Marshall styled amp like yours anyway but just experiment with V1 until you find what you want.
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Last edited by Cathbard at Mar 23, 2013,
#5
i would almost always recommend a 12at7 in the last position unless the amp specifically says not to.

put a 5751 in v1 if you want to reduce fizz and add some clarity...also pairs well with a 12at7 in last position.

tung sol in v! is nice. i pair it with JJs following.
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#6
Thanks for suggestions so far.

I have a few leftover unused 12au7 and I believe a 5751 tubes from when my dad and I were experimenting still with that Fender Champ 12, so I might try those. If not, I'll switch back to the typical ECC83 (for the V1).

Which positions should be the center of focus? I'd imagine the V2 and V3, being those would be the gain stages, correct? How much would the 4 and 5 positions have impact on the sound?
#7
Well, the phase-splitter is important.... but just so long as you have a balanced tube, they should be fine, Tung-Sols in the phase-splitter location is a bit of a gamble, I think there are some amps where a Tung-Sol'll just crap out. That said, I've had one in my MkV's phase-splitter and it's working fine.

I personally would not put a JJ in V1... it just made my MkV sound dark, muddy and ugly. I think there Tube Depot allows you to specify the gain level and breakup characteristics of tube, try some low moderate gain tubes in your gain stages and see how you like them. I like 12AY7s in my V3, the lower output can clear up your sound.
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#8
V1 is the most important. Every stage is a gain stage, but the first stage is amplifying a very, very small signal and in most cases will have the most impact on overall tone. After that I'd say the phase splitter is second.

Not that you need a super quality tube in the splitter, but there is usually quite a difference between a 12ax7 and a 12at7 in the PI position. I don't think the balanced thing is that important, the power tubes themselves won't be balanced if there isn't separate bias control for each tube. Hell, the 10% and 20% tolerance components in there will unbalance things.
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Last edited by Kevin Saale at Mar 24, 2013,
#9
Quote by Kevin Saale
Not that you need a super quality tube in the splitter, but there is usually quite a difference between a 12ax7 and a 12at7 in the PI position. I don't think the balanced thing is that important, the power tubes themselves won't be balanced if there isn't separate bias control for each tube.


It's a nice to have IMO.

I know this local shop that does the checks and testing for free. Since I can request for a balanced set and have the tubes checked, I'd rather get a balanced PI tube
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#10
Quote by ragingkitty
It's a nice to have IMO.

I know this local shop that does the checks and testing for free. Since I can request for a balanced set and have the tubes checked, I'd rather get a balanced PI tube


No doubt. Whenever I order tubes I still usually end up paying the 2 bucks for the balanced tube
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#11
12AU7 is a pretty radical departure. 12AY7 is another to consider. It has lower gain than a 12AT7 but not as radically lower as a 12AU7. Plate voltage could a problem with a 12AU7 in that too. If it's like an actual Soldano you could be in trouble because Soldano tend to use stoopid high voltages. I'd measure it and check the 12AU7 datasheet before I tried it.

Just for your reference it goes:
12AX7 - 100
5751 - 70
12AT7 - 60
12AY7 - 45
12AU7 - 19

I think there's only one modern 12AY7 and that's an EHX. It's actually quite a decent tube for a short plate valve from the Sovtek factory. I have one in my JTM45.

Edit. A good NOS 5751 like a Phillips will often be on the high side of 70 and a modern 12AX7 is likely to be down around 90 or less. So in practice you'd hardly tell the difference - except of course that the Phillips will sound better. Gain differences are often negligible.
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Last edited by Cathbard at Mar 24, 2013,
#12
I remember when you were serious about using light bulbs....

Otherwise I'd just go with what Cath says.
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#13
I played with some Tug-sols, groovers and EHX that I had lying around, in my JCA50H.

To tell you the truth, I just stuck the stock chinese tubes right back in. They sounded so much better
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