#1
so I have a booger 6260, and I would like to reduce the gain a tad, smooth out the sound and all that jazz. what I need assistance with is how many preamps tubes i should replace, which v spot i should put them in, if I should go with 5751s, 12at7, 12au7, etc., and what brands I like. My goal is to be able to turn the gain knob as far as I can on the lead channel and still get usable distortion, the closer to ten the better, but I also understand this amp is a gain monster, so I know this may not be possible. I just need help realistically assessing the characteristics of each tube type and what combination is going to get me closest, as I would like to get a good base before I go about experimenting. Thanks ahead of time for all the help, if anyone needs any additional info I'm sorry I forgot it.
I'm just a kickin' and a gougin' in the mud and the blood and the beer.
#2
A 5751 in V1 will tame it quite a bit but get a 12at7 also and you can experiment.

EDIT: oh yea, about the brand, get an NOS. They're cheap enough because there's not much demand for them and they will sound better than new production tubes.

I have an RCA 5751 and a Jan 12at7 I keep on hand.
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Last edited by OldRocker at Apr 3, 2011,
#3
5751 will change the gain barely at all. You will notice a slightly lower noise though.
#4
yeah I was looking at the chart the the tube store has and a 5751 is still pretty high up on the list. what Im really curious about is the different v spots. I know that placing a lower gain tube such as a 12at7 in v1 would reduce gain, but what about the rest of the spots? will the gain decrease more noticably the more spots I fill?
I'm just a kickin' and a gougin' in the mud and the blood and the beer.
#5
Yes, even more so. A 5751 is 70% of the 12ax7 and the 12at7 is 60%. Trouble is that when you lower the gain too much it'll sound cold and you may not like it.

If you put lower gain tube in the PI the power tube won't be driven as much.
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#6
The gain of the tube is lower, and its characteristics are different so the 5751 and the 12at7 tend to have smoother overdrive when compared to the 12ax7. The 12at7 is also great in the phase inverter to reduce volume a bit.

A 12au7 would also work, but is reducing gain quite a bit.
#7
ok, so maybe Ill pick up two at7s and throw them in v1 and 2? and think thats a happy medium. any brands that are particularly smooth? I know nos, but Im looking for as specific as possible. keep in mind Im thinking $2o or less per tube.
I'm just a kickin' and a gougin' in the mud and the blood and the beer.
#8
A lot of 5751's test out more around 90 in terms of gain factor even though they are supposed to be 70.

12AT7's are not great audio tubes. I've only experienced one single 12AT7 that sounded good to my ears. I would certainly never put one in V1 though.

Honestly, swapping out V1 won't do much. Here's why: you still have 12AX7's down the line which have really limited headroom. If you want to tame the preamp as a whole, it's advisable to change out more than one tube.

Example:
Let's say your input stage has a standard configuration of 300v plate supply, 100k plate resistor and a bypassed cathode resistor with a typical following load. With a 12AX7 that yields you a gain factor of roughly 61. Swap in a 12AT7 and your gain factor is 54.

Let's say the voltage coming from your guitar pickup is 200mV.

The 12AX7 stage creates a 12.2 volt output signal. The 12AT7 stage creates a 10.8 volt output signal. The difference is negligible, particularly when you have an amp with many cascading gain stages following. The subsequent 12AX7's are going to have a maximum headroom of around 4 volts before clipping.

So if you really want to tame the amp, swapping out all the preamp tubes with something like a 5751 would be more effective.
#9
thanks craig, thats exactly the sort of answer I was looking for. I will pick up some 5751s next time i get 60 or so bucks. still looking for brands though, any recs?
I'm just a kickin' and a gougin' in the mud and the blood and the beer.
#10
Quote by dementiacaptain
thanks craig, thats exactly the sort of answer I was looking for. I will pick up some 5751s next time i get 60 or so bucks. still looking for brands though, any recs?


NOS JAN-Philips 5751 is my absolute favorite preamp tube. Sooooo smooth.

bluestratplayer changed all the preamp tubes out in his Peavey 3120 with these and reported that it was incredibly worth it. Similar type of amp.
#11
much appreciated for the help, love when threads just get the answer right away. That reminds that I want a triple x xD. How much do they usually run/good place to get em?

edit: just looked at the tube store, little pricey, but if they will really make a difference, I can dig up the cash, just need the grass to grow haha. Is there any other places that have a good price? thats the best I can find on the fly
I'm just a kickin' and a gougin' in the mud and the blood and the beer.
Last edited by dementiacaptain at Apr 3, 2011,
#12
Quote by dementiacaptain
much appreciated for the help, love when threads just get the answer right away. That reminds that I want a triple x xD. How much do they usually run/good place to get em?


No problem.

The sweetness comes with a price. They typically retail for about $30 a piece. To me they are worth it, they not only sound great but are built like tanks too.

I think Tubestore has them, Tube Depot, a few other places. Luckily they are still pretty abundant. I'll be very sad when the day comes they're all gone.....

Note to self: stop recommending JAN-Philips 5751's to others...

#13
thanks man. now the debate starts over new speakers or preamp tubes first. I am gonna rob a bank
I'm just a kickin' and a gougin' in the mud and the blood and the beer.
#15
wow sounds like hes pretty hot on em haha. thanks again though, been a huge help
I'm just a kickin' and a gougin' in the mud and the blood and the beer.