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4S Tube Preamp with 12AU7 Cathode-Follower Output Stage
http://www.diyaudioprojects.com/Forum/viewtopic.php?f=9&t=5186
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Author:  lowhifi [ 12 Jan 2020, 22:18 ]
Post subject:  Re: 4S Tube Preamp with 12AU7 Cathode-Follower Output Stage

lowhifi wrote:
We are Devo.

I remplace the 33uf capacitor before the choke for a 45uf and add the DC heater supply with a .1uf cap and now the preamp is very silent. The resistors where already installed at the end of the tube supply. An other successful build. Regards.

It's recommended to put a fuse when using a diode bridge to not fry the transformer if a diode is shorted.

Author:  Hermanator [ 22 Feb 2020, 22:00 ]
Post subject:  Re: 4S Tube Preamp with 12AU7 Cathode-Follower Output Stage

Just a NOOB question, since the output signal is 180 degree out of phase, do I need to flip the speaker cable?

TIA

Author:  mwhouston [ 24 Feb 2020, 16:12 ]
Post subject:  Re: 4S Tube Preamp with 12AU7 Cathode-Follower Output Stage

If your power amp preserves absolute phase you may want to. One reviewer in Stereophile suggest see which way sounds best.

Author:  Hermanator [ 24 Feb 2020, 16:24 ]
Post subject:  Re: 4S Tube Preamp with 12AU7 Cathode-Follower Output Stage

I see, thank you Mark.

Author:  Witek [ 16 Apr 2020, 10:24 ]
Post subject:  Re: 4S Tube Preamp with 12AU7 Cathode-Follower Output Stage

Hi it's my first massage on this forum so greetings to all!
It's also my first attempt in tube DIY and i have a question: is it possible to use 12at7 tubes for both pre and buffer? I'm aware that it's not optimal but right now here in Italy i have problems to get 12au7 because of lock-down and since i have 2 12at7 tubes and A LOT OF TIME i would like to try... Can somebody tell me if some modifications must be done to the original design? Preamp will drive an T-Amp based on TA2024 chip, input impedance is about 20k. Thank you for any help and compliments for very interesting forum.

Author:  mwhouston [ 16 Apr 2020, 23:00 ]
Post subject:  Re: 4S Tube Preamp with 12AU7 Cathode-Follower Output Stage

Witek wrote:
Hi it's my first massage on this forum so greetings to all!
It's also my first attempt in tube DIY and i have a question: is it possible to use 12at7 tubes for both pre and buffer? I'm aware that it's not optimal but right now here in Italy i have problems to get 12au7 because of lock-down and since i have 2 12at7 tubes and A LOT OF TIME i would like to try... Can somebody tell me if some modifications must be done to the original design? Preamp will drive an T-Amp based on TA2024 chip, input impedance is about 20k. Thank you for any help and compliments for very interesting forum.

Should work OK.

Author:  gofar99 [ 17 Apr 2020, 08:50 ]
Post subject:  Re: 4S Tube Preamp with 12AU7 Cathode-Follower Output Stage

Hi, Yes it ought to work, the gain will be more though. In the world of tubes you can often swap the 12AU7s with 12AT7s and the reverse. Not so much that they are alike, but frequently the settings work out the same. My phono preamp uses some in the cathode follower output stage and either type will do fine there. On the other hand, 12AX7 tubes will fit in the same sockets with the same pin connections but the settings are way different. It is true they do work, just way far from optiminal.

Good listening
Bruce

Author:  mwhouston [ 17 Apr 2020, 18:58 ]
Post subject:  Re: 4S Tube Preamp with 12AU7 Cathode-Follower Output Stage

In my 6L6 SE UL power amp, “Silver Supreme” , I use a 12AT7 Psvane as the driver tube. Tried other including my fav. U7 but always came back to the T7. The amp driver design was based around the 4ST and electrically it should work but it did more than that with the T7.

https://retro-thermionic.blogspot.com/2 ... ooden.html

P.S. Bruce I sent you a PM.

Author:  gofar99 [ 17 Apr 2020, 21:52 ]
Post subject:  Re: 4S Tube Preamp with 12AU7 Cathode-Follower Output Stage

Hi Mark, No PM?

Good listening
Bruce

Author:  mwhouston [ 17 Apr 2020, 22:06 ]
Post subject:  Re: 4S Tube Preamp with 12AU7 Cathode-Follower Output Stage

gofar99 wrote:
Hi Mark, No PM?

Good listening
Bruce

Oops, email.

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