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suitable preamp for a tube amp (kt88+12ax7)

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kevinkuang

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Joined 2005
Hello, I am totally new for tube amp. Just brought a tube amp 40wch, with KT88 + 12AX7. I really don't know how to choose a "suitable" preamp for it. What makes a preamp good? Should I look for tube preamp or ss preamp? what's their difference? My budget is $300-$500 (for used). Thanks for input
 
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Sherman

Member
Joined 2004
kevinkuang said:
Hello, I am totally new for tube amp. Just brought a tube amp 40wch, with KT88 + 12AX7. I really don't know how to choose a "suitable" preamp for it. What makes a preamp good? Should I look for tube preamp or ss preamp? what's their difference? My budget is $300-$500 (for used). Thanks for input
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I think for your amp any good preamp with a gain of 4 to 6 would probably work just fine. You need to decide on what features you want/need such as input selectors (some may have only a single set of inputs), phono stage (rare these days as a built-in feature) etc.

If you are looking to build one yourself the Bottlehead Foreplay kit would be a good choice. A ton of them have been built and there is a large community of builders/users to turn to for help and ideas on mods.

Also Lighthouse Electric has a suitable preamp kit the STA-1LG for about $100. With the LE kit you have to supply the chassis. I built one this winter and it had a fairly annoying 60 Hz hum but I converted the heaters to DC (not a bad idea for a preamp anyway) and the hum is gone. It now drives my KT88 SE monoblocks quite nicely.
 
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Sherman

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Joined 2004
kevinkuang said:
should I look for tube preamp or ss preamp for the KT88? thanks
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Yeah, not very specific about which was best was I? But honestly it depends on whether you intend to build or not. If you want something already built you have a lot of options but not quite as many as if you will build it.

The "tube sound" will still be there if you use a SS pre but I just like the idea of tubes end to end. If I were you I would build either the Bottlehead Foreplay or the Lighthouse Electric STA-1LG.
 
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Sherman

Member
Joined 2004
kevinkuang said:
how important is the preamp in the whole system? will a good or bad preamp make how much the sound better or worse? thanks
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That actually depends a lot on the power amp and how much gain you have to get from the preamp in order to drive the power amp. A bad preamp can make a good power amp sound bad but a good preamp can't make a bad power amp sound good.

I would say one of the most important things a preamp can do (or actually not do) is hum. Any hum from the preamp will be amplified by the power amp so it is important to have a quiet preamp. Most power amps don't require a lot of gain from a preamp, so a preamp with a gain from unity to maybe 6 should be fine.

Another function of many preamps is input source selection. If you regularly listen to more than one source (I use a tuner, CD player and turntable) it is nice to be able to switch between sources without having to change interconnects around.
 
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