12ax7 replacement question

H

How Hendrix

New member
Hi everyone!

I just recently picked up a Kustom Tube 12a.....GREAT lil' combo amp! Made the switch from digital modelling.....and there's NO GOING BACK!! Anyway, I'm curious about switching the tube for something else. There's only 1, so I'm looking for suggestions on what you would put in a combo this small...or would it even make much difference? I play mostly metal (80's, 90's etc...) AND blues.

The clean sound on this amp is pretty bright (to my ears). There's a button to engage the gain circuit...and when that happens, there's a muddy mess once you turn the knob past 3...and I'm using low output pups and pedals for distortion and overdrive. I've done a bit of research....but all I'm finding is info for amps with pre and power tubes.

I'm trying to get a tighter "chug" sound under high gain....but still keep it warm and round for when I play the blues......is this even possible with one preamp tube?

Thanks for your help!
 
Re: 12ax7 replacement question

hard to say. if the tube is actually running at real voltages then changing the tube will have noticable effects, if its running in a starved plate configuration changing it will have significantly less effect on the tone but should still make a noticable difference. im am not farmiliar with that amp so maybe some one who is will chime in
 
Re: 12ax7 replacement question

You can't get a hi-gain metal sound with one preamp tube, unless there is some silicon gain stages in there too. But you're NEVER gonna get a fat chug sound with a lil 8" speaker. Sorry, bro. Welcome to the forum.
 
Re: 12ax7 replacement question

I probably shoulda mentioned.... most of the time, I run the headphone out to a mixer and monitor from there...so the speaker can be bypassed (have a 4 month old!).

I also have a Vox AD30VT...same scenario...use the headphone out to mixer. I know the tube is bypassed in that case. I guess I'll just have to pick up a couple different tubes and see what happens!
 
Re: 12ax7 replacement question

My cousin had that amp. If memory serves. I believe that amp uses the single 12AX7 at real voltages and represents the input and tonestack buffers. But the gain circuit is a diode boost between each triode. the 12watt output section is purely solid state.

I would just ignore the onboard gain function since its a diode anyways. dial in that clean sound and use your pedals for drive sounds and push that 12AX7. maybe find where that output section sounds the best too and keep in there.

is the 8" speaker still a celestion? am i thinking of the same hybrid kustom practice combo?

goodluck.
 
Re: 12ax7 replacement question

Over a few brain grenades one night we swapped out the 12ax7 in my buddies amp just like that one. The EH sounded the best in it with a Ruby coming in a close second.
 
Re: 12ax7 replacement question

Yes....it still has the 8" speaker. Where could I find the EH and Ruby tubes you're talkin' about?

Thanks for all the quick replies!
 
Re: 12ax7 replacement question

I just thought about this..... if the output on the Kustom is all solid state, doesn't that make this amp the same as the Vox AD30VT?? ( without the modelling and effects obviously! ...and the fact that the tube is bypassed when the headphone line out is in use)

They both have (1) 12ax7 preamp tube and solid state output?? Am I correct here?
 
Re: 12ax7 replacement question

How Hendrix said:
I just thought about this..... if the output on the Kustom is all solid state, doesn't that make this amp the same as the Vox AD30VT?? ( without the modelling and effects obviously! ...and the fact that the tube is bypassed when the headphone line out is in use)

They both have (1) 12ax7 preamp tube and solid state output?? Am I correct here?
Click to expand...

no the AD30VT uses the 12ax7 in a different way. its after the digital korg preamp and before the solid state power section. its actually used as a low wattage power tube section. it helps give that cranked tube tone and not just preamp saturation. which is why the vox is the better of the modelers.

so its Digital preamp-12ax7 micro power section->solidstate power section

the Kustom has a Tube Preamp. which is just used in the preamp section. and only will produce preamp breakup.

so its 1st 12ax7 triode-Diodes for Distortion function-2nd 12ax7 triode-solid state preamp.
 
Re: 12ax7 replacement question

I think speakers make a much much bigger difference then tubes do in a all tube amp mind a hybrid and like said before your just not gonna get metal chug out of a 8" speaker. On a help side of things what od/dist pedals are you using?
 
Re: 12ax7 replacement question

I have a Maxon OD 9 Pro+ (stock), a Metal Zone modded by Wampler (aka Indyguitarist), a Blues Driver (stock), and a DS-1 modded by Monte Allums. I see you have the Pinnacle 2 by Indyguitarist....how is that for high gain?

With the exception of the Maxon, all the other pedals sound like poo thru the clean setting of the Kustom.....even the modded ones. I had a cube 30X....just sold it....now I kinda wish I hadn't. It was so easy to just plug in and play....and get great tone!

I tried a Behringer GDI (Sansamp GT2 knock-off) and had better results, but it was a bit noisy.

Now, I'm reading the cube RX is BETTER than the 30X !! :banghead:

There seems to be no end in sight when you're chasing tone!
 
Re: 12ax7 replacement question

I know this is a birdwalk from the original post, but If you can't get good chugga-chugga from an AD30VT, you're doing it wrong.

I can (and do) rock the house with a close mic'd AD15VT, it has plenty of bass and "chug," but again, I'm mic'd and not direct out.

If you're up for a lifestyle change (:laughing:) start mic'ing your amp and run that signal to your mixer. There's no substitute, seriously.



Bypassing the tube (power amp) in the VOX may affect your ability to rock.


Conclusion: buy a few tubes and try them all ---
 
Re: 12ax7 replacement question

I'll have to give the micing a shot....didn't know it would make that much difference! The main reason I use the headphone/line out is too keep volume to a minimum.
 
Re: 12ax7 replacement question

Did you change the tube in your Vox AD30VT? ...I changed the speaker in mine (Warehouse 10") but not the tube. What tube would you suggest for that?
 
Re: 12ax7 replacement question

Ive had many in mine and Ive come back to the Sovtek LPS and EHX tubes.

if you want to stay lowest noise go for the EHX.

if you want some vintage edge the LPS is key.

if you want some more breakup try a newer Chinese 12AX7 or get a hi-gain selected tube.

the rest just seemed to mess with the overall voice in a bad way.

Ive tried Tung-Sol RI, EHX, LPS, every other sovtek(Noisey), Mullard RI (new sensor and GT), TAD(just a relabeled China Tube), the bigger plate and regular JJ and a NOS JAN 5751.
 
Re: 12ax7 replacement question

LoFiBrian - I have a question... what kind of sound are you going for? Are you a metal head who plays weeedly weedly style guitar? Just curious, cuz I have only tried the JAN 5751, Mullard RI, and short plate JJ's...
 
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