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Tube Pre-Amp Schematic Needed

Wharf_Creek

Member
2007-11-27 1:07 am
I'm hoping someone out there in audio-land has what I'm looking for. I'd like to find a VERY basic circuit upon which to build and learn. I've heard of something called a 'Spice' circuit....but I'm not sure if that's what I'm looking for either. For some reason, that sounds a bit 'exotic' to me....... Anyway, looking for something that would use perhaps two 12AX7 type tubes.....similar to what Dynaco used in their PAS 2/3 pre-amp. I'd like to do a point-to-point build and have the pre-amp deliver the usual contingent of controls; volume, balance, and possibly 3 levels of tone (bass, mid, treble). If anyone has such a circuit, please let me know. If possible, I'd love to have a file emailed to me at [email protected]. As always....many thanks to all who read this. Happy soldering!! TSD
 
Spice is a simulaton program that allows one to build virtual circuits and test them without actually using hardware.

LTspice from Linear Technology is very popular, in part because it is free.

Linear Technology - Design Simulation and Device Models

What would you drive the pre-amp with? Phono? CD? Ipod?

This determines how much gain you need in the pre-amp. If no gain is needed it becomes a line stage rather than a pre-amp.

Adding all those controls is going to complicate the circuit considerably. I suggest doing searches for schematics of old tube receivers and look at their circuitry as a starting point.
 
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Wharf: Is there a reason that you are looking to build something with 12AX7's? These are high gain tubes and you may struggle to find them in many modern line stage designs..........

Do a search here for the Aikido and the 12b4 preamps, both very popular with lots of threads and info.

As mentioned, you need to determine how much gain you need (if any). A line level pre has relatively low voltage gain say 1-20 or so, and a phono pre typically has a voltage gain of 70 or so. A phono pre also needs RIAA equalization, adding more components.

The tone controls will also add complexity (and are somewhat out of fashion these days).

The Aikido is designed by John Broskie and you can buy PCB's for this project at his website: John Broskie's Guide to Tube Circuit Analysis & Design You can also build this point-to-point, but for a first project, one of the PCB solutions makes a lot of sense for little $$. The Aikido also offers lots of tube (and gain) choices.

Use a decent volume pot, and be prepared to chase down and eliminate hum during your build.

If you are set on 12AX7's, You could always find a PAS 2/3 preamp schematic and clone that also....
 
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Wharf_Creek

Member
2007-11-27 1:07 am
Wow, I'm amazed at the 'sound advice' that arrives in such a short time from this group! MANY THANKS to all who contributed!! I should back up a bit and mention that indicated that I'm kind of 'hooked' on old separates...like the Dynaco, Eico, and Heathkit power amps and their respective pre-amps. However, from a 'pre-amp' perspective, I've found that all those old units DID contain a phono stage....which I do not need or want. And, they all had multiple inputs....which is also a function that I don't need. At best, I'll do a simple toggle switch for two sets of inputs...the classic 'A' & 'B' thing. My plan is to drive the thing with a CD player......and perhaps down the road add XM or Serious radio. I attempted to subscribe to a few PC based music providers, but didn't get much satisfaction in the programming. And, after having Serious in a company car I had while employed.....I did enjoy some of the talk-show stuff on that venue as well as the music channels. But....for now....it's just the CD player. And...if any this is any help, I hope to build a set of 6V6 mono-block amps AFTER I build this pre-amp project....and the pre will be used to drive those amps. I've not seen any really good examples of what any builders did with the 6V6 tube in most anything other than console or suitcase type amps...... Most all the Dyna, Eico and Heath stuff all seems to revolve around either the EL-84 or on to the 6L6/EL-34. So, I'll be looking for a GOOD yet Simple circuit for that amp next!! I do have transformers....so good to go there! Again...thanks for all the help! I'll check out all the leads (no pun intended). Tom D.
 
And...if any this is any help, I hope to build a set of 6V6 mono-block amps AFTER I build this pre-amp project....and the pre will be used to drive those amps. I've not seen any really good examples of what any builders did with the 6V6 tube in most anything other than console or suitcase type amps......


If you are looking for a PP 6V6 power amp, check out Poindexter's 6GK5/6V6 Music Machine, about 6W of PP 6V6 triode power. There are a couple of versions of this; the 6GK5 driver version is the latest one.

http://www.diyaudio.com/forums/tubes-valves/149211-6v6-music-machine-build-help.html

AudioTropic: * State-of-the-Art Audio Under the Banana Tree.

IIRC, Eli Duttman's El Cheapo and Gingertube's Baby Huey may also be around in 6V6 variants. Do a search here. There's also SY's Red light district.....the BH is UL around 12W, and the RLD is pentode, around 15W using EL84's.
 

ray_moth

diyAudio Moderator Emeritus
2004-01-27 8:55 am
Jakarta
I found the Fun With Tubes site useful for basic and not-so-basic amp and peamp information. It's aimed at the hobbyist and isn't too technical.

If you want something really comprehensive (and also readable), you could do a lot worse than buy Morgan Jones's Valve Amplifiers, available to order online from Amazon and other sources.