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Thread: Pre amp tubes

  1. #1

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    Pre amp tubes

    Hi all,

    I have a Blackstar HT20 combo and have been wanting to tinker with a preamp replacement. I was wanting to get away from this amp's darker sound to something a bit more open, 3D'ish...if I said that i wanted to get a sound similar to VH's first album, you would all say get the same equipment, as a start!

    Well I was hoping to turn "water into oil" with what I have got, with the exception of changing the preamp tubes. So I've done some searching and there is much to choose from and of course depending on the amp. One that was recommended to me yesterday was the NOS RFT ECC83 12AX7. This was recommended as it broke up earlier and considering the HT20 only has two preamp tubes it sounded logical. Other potential candidates include the Sylvannia 12 AX7WA and the JJ EC83.

    If there are any HT20 users who have gone down this route i'd like to hear your about your results.

    On the speaker side of this amp, i swapped out the Rocket 50 for a WGS Vet 30, big change!

    Thanks in advance,
    Stevie

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  2. #2

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    Personally, I think changing tubes is akin to snake oil - sure changing old knackered tubes is like changing old guitar strings, anything will be an improvement, but there is not the huge difference in tone between brands that people will tell you (and convince themselves of). Difference are small at best and going from a HT 20 to an EVH Marshall sound by changing tubes is, IMO, never ever gonna happen.

    The EVH sound (apart from the way he plays) is about the amplifier circuit design, the speakers and cab he used (4x12 closed back vs 1x12 open back is VERY different), and on the recordings the microphones used and their exact placement (which as we all know, and inch one way or another can give far more dramatic changes to tone than preamp tubes ever will).
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  3. #3

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    Thanks Dr.

    That was always my thinking.

    I guess if anyone with a HT20 could chime in if they have changed their pre amp tubes and their thoughts on the result.
    Stevie

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  4. #4

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    It depends on the circuit of the amp. In some amps a different tube can make a huge difference, but in most cases the difference is very small.

    Having said that, the HT-20 has a lot of gain but only 2 preamp tubes (and I believe the second one is used as a phase inverter too). I'm not an expert in guitar amps and electronics, but there's no way that amount of gain is achieved by the tubes only. There must be some solid-state circuit that helps with the gain stages and that's nothing new, I've seen other amps with similar design, I even owned some of them too. I never tried a HT-20, but I've played through a HT-5 and while it sounds amazing, there's something a bit solid-state-like in the amp's feel and response which only confirms my doubt about that circuit thing.

    So I would assume that a tube change won't make a huge difference in this case, since it's not the tubes that shape the sound all by themselves if you know what I mean. The HT range is voiced to be modern, dark and compressed - which is exactly what the classic VH tone is not.

  5. #5

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    Blackstar do nice amps but they never quite turn me on. One of the rehearsal studios I use has them the three-channel heads and depending on the cab they are paired with the clean channel can be quite nice. The gain channels are perfectly useable but nothing special for my purposes. The Infinte Shape thingy is useless IMHO. One night the studio had a 5150III head and cab in the room we used and it was like bang, all I wanted to do was play "Eruption" and I was never an EVH fan and don't even like "Eruption". The tone was right there. Astonishing! But after 5 minutes I had to get down to work and I fired up the Blackstar to get clean tones that suited the classic soul I was playing for the next three hours.
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  6. #6

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    All good points given in the previous posts....Might I suggest a few more...

    In my experience, the main difference that you can hear or feel in a preamp tube is either 'gain' or 'compression'.
    There are lesser gain tubes that you can put in place of a 12AX7. In some circuits it will take some of the mud out of higher gain settings. Some brands can give you a more compressed feel. JJ higher gain tubes will do that.

    You may get closer to that Eddie tone by picking up a nice Plexi pedal and run it into the clean channel or in a channel w/ a lesser gain setting. OD on OD / Distortion doesn't always work, you just have to experiment....
    But hey, that's 1/2 the fun : ) -

  7. #7

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    Some 12AX7 brands or tubes are more noisy than others, then again there's a gain change as well.

  8. #8

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    Ive always gone with three JJEC83 and one EC803. That's just my preference though.

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