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Post by jbgtr on Jun 26, 2008 11:12:08 GMT -7
I've read a number of threads on here, with people saying that certain tubes will offer more headroom than others. In terms of preamps, I've seen many say that using 12bh7 or 12AY7's offers more headroom than 12ax7's. Any other thoughts on this?
In terms of output, are there any particular brands or models or EL84's, 6v6's, or El34's which offer a significant amount more?
For that matter has anyone found that a particular 5y3 or GZ34 provides a significant amount of clarity?
I know that how an amp is voiced tends to be a much larger factor, but any insight on this would be great. Thanks!
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Post by billyguitar on Jun 26, 2008 14:16:12 GMT -7
I think 12AX7s are just a harsher tube in general than the lower gain tubes. For instance if you use AX7s in an old tweed Fender that calls for AY7s, their is more gain but more harshness. I recently bought an Allen Brown Sugar from a forum member here who sold it because he said he couldn't get enough clean headroom out of it. When I got it I could agree with him. I replaced V1 and the phase inverter tube with 12AY7s and cleaned it up a lot! It also smoothed the overall tone by quite a bit. My Maz jr reverb head gave me more clean headroom when I put a 12AU7 in V1. That's pretty extreme though and an AY7 is about right. A GZ34 is much stiffer than a 5Y3. It can almost feel like a solid state rectifier. With output tubes just use as high a rating as you can find and then you'll probably need to rebias.
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Post by beauzooka on Jun 27, 2008 11:32:30 GMT -7
Try 5751's too. They are about 70% of the gain of 12AX7's, as opposed to 50% for the 12AY7 and 20% for the 12AU7.
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Post by johnnyl on Jun 28, 2008 13:14:24 GMT -7
I use a 12bh7a in V2 in my Ghia and I could definitely hear the increased headroom. I like the way it responds to my pedals as well.
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Post by bustertheboy on Jun 30, 2008 14:33:14 GMT -7
Not sure I'd use it all the time, but a NOS 5751 in V1 and 12BH7 in V2 is very sweet and clean right up to 12 o'clock on the Ghia. Alternatively try different 12AX7's- I have an old Brimar at the moment in V1 which is much lower gain than my NOS GE- or maybe leaner in the mids. Brett
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Post by deaconblues on Jul 15, 2008 13:04:40 GMT -7
I agree with buster on the 5751 in V1 and the 12BH7 in V2 of the Ghia. There's a noticeable difference. I notice that the amp runs much quieter, also.
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Post by myles on Jul 16, 2008 9:17:10 GMT -7
I agree with buster on the 5751 in V1 and the 12BH7 in V2 of the Ghia. There's a noticeable difference. I notice that the amp runs much quieter, also. Less front end gain will always give any amp a better signal to noise ratio ... the amp will have less background noise.
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Post by myles on Jul 16, 2008 9:21:20 GMT -7
Keep in mind that one factor in clean headroom that is often overlooked is the phase inverter ... and I am not talking about changing the type of tube but talking more about having a proper spec tube in a given tube type. Today's 12AX7s as an example have a general current output of 0.6-0.8mA ... and 1.2mA is spec. Right off the bat we are in the toilet 30-50% when it comes to trying to properly drive our output tubes.
I select tubes for phase inverter use in a very different way than I select tubes for a gain stage.
12AT7s made today are just awful too for the most part as a side note.
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Post by shizzaq on Jul 18, 2008 4:40:10 GMT -7
Myles, Ive been looking everywhere for your recommendation on a NOS 12ax7. Doug has some JAN Phillips that he really likes but Mike at KCA NOS recommends the mullards that are twice as expensive. Are the mullards twice as good as the JAN Phillips?
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Post by myles on Jul 18, 2008 8:55:14 GMT -7
Myles, Ive been looking everywhere for your recommendation on a NOS 12ax7. Doug has some JAN Phillips that he really likes but Mike at KCA NOS recommends the mullards that are twice as expensive. Are the mullards twice as good as the JAN Phillips? The JAN Phillips are OK tubes ... stay away from any date codes of 1988 or later. They are just OK in my mind, a good workhorse tube. Considering how long preamp tubes last I would listen to Mike at KCA and go his route as in the long run the cost difference would be a non-consideration.
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