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Old 10th April 2004, 04:57 PM   #1
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Default 5814/12AU7 Preamp?

Hi,

I have a couple of 5814 tubes and would love to build a preamp out of them. I was thinking of something like the foreplay, any ideas?

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Old 10th April 2004, 05:15 PM   #2
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Sure. Can also use them in something like this (although the tone stack sounds best with a 12AT7).

Tim
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Old 10th April 2004, 05:26 PM   #3
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That was quick Tim . I would not need a tone control, just plain line stage is what I had in mind. Been searching the net for a foreplay schematic but can't find one except for a modified foreplay with 6N1P tubes.

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Old 10th April 2004, 10:11 PM   #4
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Buy the Foreplay manual from Bottlehead Corp., not the complete kit.

When building from "scratch", you could incorporate some tweaks initially. Tube rectify the B+, if that's to your liking. Energizing the signal tube heaters with DC for a lower residual hum is another simple change.
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Old 11th April 2004, 06:10 AM   #5
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Quote:
Originally posted by JojoD818
That was quick Tim . I would not need a tone control, just plain line stage is what I had in mind. Been searching the net for a foreplay schematic but can't find one except for a modified foreplay with 6N1P tubes.

JojoD

I don't know anything about the Foreplay so I just posted my preamp. For a straight-up line amp you can just run the 1st triode plate on to the 2nd triode's grid. Note that V1's plate voltage biases the cathode follower!

Tim
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Old 12th April 2004, 04:14 PM   #6
Mike L. is offline Mike L.  United States
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Hello,

I would recommend the preamp design published in Glass Audio by Buce Rozenblit. The article is republished in Rozenblit's "A Beginners Guide to Tube Audio Design", which is where I found it. I built it and use 5814A's. It drives a 1969 JLH 10 watt class A amp into Klipsch speakers and sounds terrific. It is also very inexpensive and simple to build (it was my first audio project).

Mike L.
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Old 12th April 2004, 04:56 PM   #7
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Hi,

Quote:
I would recommend the preamp design published in Glass Audio by Buce Rozenblit.
I think this is the one you mean:

BR GA 91

Cheers,
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Old 12th April 2004, 06:33 PM   #8
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Default Foreplay schematic, No luck

Hi guys,

I have searched extensively for the schematic but to no avail. I can't buy the schematic since it's not available anymore, only the kit.

JojoD
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Old 12th April 2004, 11:59 PM   #9
arnoldc is offline arnoldc  Philippines
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jojo, you will not find any Foreplay schematic on the web because it is copyrighted material.

bottlehead used to sell the Foreplay manual for $35 and is a great value. send them an email if they will still sell it, and ask them to ship via USPS to save cost. if they say they won't sell it anymore, i have another suggestion -

you said "like the Foreplay", now, the Berman 76 preamp is floating on the net. the Foreplay uses the same topology. you can also look at JE Labs version of it from Joseph Esmilla's site. from that schematic, you will be able to figure out how to convert it to 12AU7, all you have to do is to put in the AU7 operating points. the good thing here is that you can actually design your own. i'm sending you all my Norman Crowhurst articles (yup, i found them) which is a good starting point.

i'm sure you are deeply in love with tubes by now and i suggest an investment on SE Amp CAD and TubeCAD will be worth while. I use them a lot to give me a starting point when building something. Let's give these guys at TubeCAD a favor by buying the legit copy for a very reasonable price more information about the software here - http://www.glass-ware.com/ online purchase and other goodies from www.tubesandmore.com

cheers!
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Old 13th April 2004, 12:34 AM   #10
s2kov is offline s2kov  Canada
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Arnold,

I have a copy of Norman Crowhurst article and indeed it is a good handsout which we can use for beginners like me.

Regards,


Andy
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