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Old 23rd January 2008, 04:01 PM   #1
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Default Cascading gain stages in a tube preamp

Help anyone? I am looking to scratch build a tube preamp for guitar use. I have found that most 2 tube units come up a little short on the insane gain level so......I was looking at the schematic for my Carvin Quad x and it has 11 stages on it's insane gain channel. That of course is just a mush sound. How do I build something that is a happy medium? I am thinking that 6 gain stages may be the magic number. I have tried every 12a-? tube in my gazzillion rack units. I have used 5751's 5963's etc etc etc but it does seem to me, (in my ignorance of course) that the circuitry is my issue in all of these off the shelf units. So I guess I need to build and just breadboard all the componets and swap around until I find what I am looking for? Suggestions as to where to begin? Simple is better ! In level Out level no tone stack just gain and level ? Help? Is someone willing to talk me through this?
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Old 23rd January 2008, 06:09 PM   #2
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Send a message via AIM to ThSpeakerDude88
http://www.ax84.com/static/corepream..._Schematic.pdf

Check out the Lead II preamp over at AX84. 6 Gain stages using 12au7's.

http://www.ax84.com/static/corepream...2tonestack.pdf

There is a full explination of it.

Also if you havent tried the High octane (Lead preamp) circuit you should. Its got a little higher gain than a marshall, but its probably not what you would call 'insane gain'.

Best of Luck!
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Old 23rd January 2008, 06:16 PM   #3
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Default Interesting

That looks cool thanks for the info !
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Old 23rd January 2008, 11:52 PM   #4
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Dave,

You can get ALL the gain you could possibly use out of just 2 "bottles". A 6922 and an EF86 are plenty. Use 1 section of the 6922 in common cathode, follow with the EF86 in common cathode, and finish off with the 2nd 6922 section as a cathode follower.

EF86 RC coupled chart here.
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Old 25th January 2008, 02:56 PM   #5
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Default Ok so.....Eli

Have you got a schematic of that? This will be my first build so I kinda need some help ya know ? Oh and the AX84 folks say that the lead II kinda sucks so they are not recomending it ?
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