#1
So I decided to do a little experimenting and bought a Line 6 pod HD pro and a Peavey classic 120 power amp (Tube power amp with 6L6 tubes). I figured i'd try a digital preamp with a tube power amp and see what I get. The first thing I did was replace the ancient stock tubes with Tung-Sol 6L6 tubes. But to my surprise, the power amp also took preamp tubes. I didn't any, so i kept the old stock preamp tubes in. I'm running these 2 units through a Custom Omega 2x12 cab with 1 Eminence Swamp thang and 1 Eminence Wizard.

I'm currently very unhappy with my tone. It's like no matter what i do, It sounds like my amp is inside a box or something. Also, 120 W tube amps usually go A LOT louder than what this power amp is currently pushing out.

Would any of these problems possibly be better with new preamp tubes? Also, what exactly are preamp tubes doing in a power amp? Or is it just the item combination i chose that is just not a good overall rig?

Just want to learn. Thanks to anyone who can help!
#2
A power amp is more than just power tubes and a voltage source. We only call preamp tubes "preamp" tubes colloquially because that is where they are most often found in your average tube amp, but they're not only for preamps. There are three "preamp" tubes in the C120. One is the phase inverter, which splits the signal into two parts so the power tubes can amplify it more efficiently. The other two tubes are (probably, don't have the schematic in front of me) driver tubes that bring the signal up to the optimal strength for the power tubes to amplify.

So, long story short, there's sort of a condensed preamp in the power amp, but there's also no strict rule that what we commonly call preamp tubes can only be used in a dedicated/integrated preamp circuit.

As to the actual issue, tubes are always suspect when your output is low. That said, it could be either the pre or power tubes, and you may just be expecting more power than an amp designed for clean output may be able to give.
#3
Quote by nor.omar.9


1) Would any of these problems possibly be better with new preamp tubes?

2) Also, what exactly are preamp tubes doing in a power amp?

3)Or is it just the item combination i chose that is just not a good overall rig?


1) it could possibly be the 'preamp tubes'. buy a couple and replace them to see if it helps

2) i would guess the 'preamp tubes' would be the phase inverter for the power amp. if the power amp is an class A/B power amp then it could use a dual triode for the phase inverter

3) is the cab emulation turned off on your emulation software? i would do that. what type of speaker cabinet are you using? it's gonna take some experimenting to get the sound you want from such a setup
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#4
Don't rule out using some YouTube videos that contain settings for the tones you want out of your POD. I couldn't get anything I liked out of the one I had, then I resorted to YouTube, and using others tones helped me figure out how to tweak it to get decent sounds.
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#5
Go with fresh tubes all around and make sure your power tubes are biased to the amp. Tone restored.
#6
Quote by gumbilicious
1) it could possibly be the 'preamp tubes'. buy a couple and replace them to see if it helps

2) i would guess the 'preamp tubes' would be the phase inverter for the power amp. if the power amp is an class A/B power amp then it could use a dual triode for the phase inverter

3) is the cab emulation turned off on your emulation software? i would do that. what type of speaker cabinet are you using? it's gonna take some experimenting to get the sound you want from such a setup



Yeah my cab simulation is off. I'm running it through a custom omega 2x12 with 1 Eminence Swamp Thang and one Eminence Wizard. Youtube hasn't really helped me much because everyone I find seems to be using them directly and in studio mode. Also, for the very few cab demos i'v found, I haven't seen any with any similar cabs to my own. I'll try replacing the preamp tubes and see what I can do. Thank you!
#7
I also don't really know much about a phase inverter or anything like that, but will it help my volume to have these tubes changed? I just ordered a set of 12ax7 either way.
#8
Quote by nor.omar.9
So I decided to do a little experimenting and bought a Line 6 pod HD pro and a Peavey classic 120 power amp (Tube power amp with 6L6 tubes). I figured i'd try a digital preamp with a tube power amp and see what I get.
Would any of these problems possibly be better with new preamp tubes? Also, what exactly are preamp tubes doing in a power amp? Or is it just the item combination i chose that is just not a good overall rig?


I've used a Pod with a Carvin TS-100 (50W/50W stereo amp that can be bridged to 100W mono) for years. It can use EL34 or 6L6 power tubes -- you can actually use a different pair of tubes in each side. And it's got four 12 AX7s onboard. You DO need to replace those as part of the re-tubing process.

Worth noting that it will take some tweaking before you're happy with your Pod sound, though I found it a lot easier to get everything organized when I started using a more FRFR-type setup. Youtube isn't going to help you there as much as just doing the reading and finding people who are successful at using the things. There will be a lot of little "aha!" moments. It's not at all like plugging in one of the old guitar tube preamps.

There's no particular benefit to using a tube power amp. Much as you'd like to think that it would "warm things up" or add some kind of tube magic to things, I found that the Carvin, at least, had much tighter THD specs than the power section of your usual guitar amp. So it was more like a hi-fi or PA power amp in that regard. Eventually, I just switched to a 1500W solid state power amp (lighter, less fragile) that could handle whatever I tacked onto it.