tube substitution for preventing pre amp distortion. VHT AMP

[tonequester]

Greetings.

I just purchased a VHT Special 6 Ultra(mod-friendly) hand-wired amp. It came with generic Chinese tubes. The bottles are black, and you can't even see the insides. The tone is not good. I am replacing all 3 tubes. My intention is to be able to play clean, of course, but I also want to overdrive the power tube WITHOUT overdriving the pre amp. My tube dealer told me that I should replace the 12ax7 in position 1, with a 12ay7 to achieve this.

I would be pleased to get ANY comments or opinions on this change. I believe that this will lower the output. What about the tone ? Will the gain still be sufficient to overdrive the 6V6 power tube. Will this truly prevent pre amp distortion ? Any opinions or advise is very welcome.

tonequester.

[Zippy]

It came with generic Chinese tubes. The bottles are black, and you can't even see the insides.

Some 6V6 tubes are like that - it doesn't matter.

The tone is not good. I am replacing all 3 tubes. My intention is to be able to play clean, of course, but I also want to overdrive the power tube WITHOUT overdriving the pre amp. My tube dealer told me that I should replace the 12ax7 in position 1, with a 12ay7 to achieve this.

I would be pleased to get ANY comments or opinions on this change. I believe that this will lower the output. What about the tone ? Will the gain still be sufficient to overdrive the 6V6 power tube. Will this truly prevent pre amp distortion?

No, it won't absolutely keep you from overdriving the preamp - that will still be a function of how much signal your pickups generate and the gain structure of your amp. But the 12AY7 is a step in the right direction.

I don't know that your goal is realistic. Replacing the frail 6V6s and trying a variety of preamp tubes is a good place to start.

Edit: I just looked up the description of your amp. "With its additional preamp gain stage, amazing variable Watts control, unique Depth control and tube-driven effects loop, the new high-gain Special 6 Ultra rockets the popular Special 6 platform to the next level." That tells me that you are at odds with the intent of this amp. It's designed for high gain - just the opposite of what you say you want (like a Fender Champ). Even the sound clip at VHT, "57 clean mellow", gets dirty way too easily.

[rock_mumbles]

What kind of guitar/pickups are you using?

I first started reading your post and immediately I thought 12AY7 ...

...

Using the clean input, Power control on full power, Boost off, and maybe guitar volume backed off, the amp should be clean

My brother has both the Special 6 and the Ultra 6 ... I know he prefers his modded Special 6 because it's a lot smaller and lighter ...

[tonequester]

Greetings Guy's.

Thanks for your comments. it gives me alot to think about. Overall, I like the amp and it's tone. I'm hoping that the 12ay7 will reduce the gain enough to be able to avoid pre amp fuzz. I believe that the 12ay7 has a gain of 45, compared to the 12ax7's 100. Perhaps I might go with a 12au7. My pickups are not considered very hot and I never use any type of boost pedals(except perhaps that which came with the amp. If I remember right the 12au7 has a gain of less than 20.

ANYWAY, thanks for your time in posting. I truly appreciate it.

tonequester.

[Zippy]

G'luck!

You might like it with "less gain" rather than your original (difficult) goal.

Let us know how a lil' tube swapping goes.

Cheers!

[rock_mumbles]

Are you running the power control on full?

There should be no preamp fuzz with the power control on full power ...