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4S Universal Tube Preamp Project (12A*7)
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=4628
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Author:  gonzalo guerrero [ 29 Mar 2019, 04:06 ]
Post subject:  Re: 4S Universal Tube Preamp Project (12A*7)

mwhouston wrote:
gonzalo guerrero wrote:
i'm bulding a 4s preamp,but here i only have linear 250k pots,can i use it? or will degrade the sound?
thanks to all. :evil:

No fine.

yeah!!! thanks!!! the 4s is alive,loud'n'proud...i'm using solid state power suply,and dc in filaments,was lost on the grouns wirings,and pickup a little hum,but now is all ok,nice sound! the best sonics to me,12au7 and 12bh7.
:lildevil:

Author:  ILoveHiFi [ 29 Mar 2019, 06:03 ]
Post subject:  Re: 4S Universal Tube Preamp Project (12A*7)

gonzalo guerrero wrote:
i'm bulding a 4s preamp,but here i only have linear 250k pots,can i use it? or will degrade the sound?
thanks to all. :evil:

Linear pots means its hard to get accurate and tight volume control, this means its harder to get the volume to your desired volume.
Log pots have the curve where you turn say 10% and volume increases 10% as hearing is logarmitic.

Linear then turn 10% maybe increase 5% or 15% volume or even worse

Author:  gonzalo guerrero [ 29 Mar 2019, 06:10 ]
Post subject:  Re: 4S Universal Tube Preamp Project (12A*7)

ILoveHiFi wrote:
gonzalo guerrero wrote:
i'm bulding a 4s preamp,but here i only have linear 250k pots,can i use it? or will degrade the sound?
thanks to all. :evil:

Linear pots means its hard to get accurate and tight volume control, this means its harder to get the volume to your desired volume.
Log pots have the curve where you turn say 10% and volume increases 10% as hearing is logarmitic.

Linear then turn 10% maybe increase 5% or 15% volume or even worse

I`m using the 4s pots in max full signal and controling the level in the power amp...

Author:  gonzalo guerrero [ 03 Apr 2019, 23:56 ]
Post subject:  Re: 4S Universal Tube Preamp Project (12A*7)

hello...just change the pots to log,and add a led status...he's more happy now... :D :lildevil:
the sound with a miniwwat 12au7 and the oddblock with sovtek kt88,and the NGF of,is a very beauty sound...
thanks to all.

Author:  Raph [ 27 Dec 2019, 12:12 ]
Post subject:  Re: 4S Universal Tube Preamp Project (12A*7)

Hi all! I am building an electrical cello with custom magnetic pickup, and I was wondering if I could use this design to preamp it? Would love to build the tube in the cello :) also, I am not sure I understand the schematics right, are there only three connections to the 12A*7? And which pins?

Author:  mayapop [ 03 Jan 2020, 02:04 ]
Post subject:  Re: 4S Universal Tube Preamp Project (12A*7)

Great design
If I use a 5K single-ended output transformer and there is no 40% super linearity, what changes need to be made to the circuit diagram?
Thank you

Author:  EmptyPockets [ 14 Feb 2020, 16:03 ]
Post subject:  Re: 4S Universal Tube Preamp Project (12A*7)

Following this build project guidelines I built my own throwing it in a cedar cigarbox. I used a EHX 6VA4 and a balanced Millard 12AU7. Hot Damn, I tried preamp on my SE 807 and SE EL34 and those amps just sprang to life. I’m using old school Infinity’s so they are not the most efficient but the sound is so much better and no need to crank anything.

Author:  mwhouston [ 16 Feb 2020, 00:55 ]
Post subject:  Re: 4S Universal Tube Preamp Project (12A*7)

EmptyPockets wrote:
Following this build project guidelines I built my own throwing it in a cedar cigarbox. I used a EHX 6VA4 and a balanced Millard 12AU7. Hot Damn, I tried preamp on my SE 807 and SE EL34 and those amps just sprang to life. I’m using old school Infinity’s so they are not the most efficient but the sound is so much better and no need to crank anything.

Man after my own heart. Nice build. A hint of steampunk.

Author:  Suncalc [ 16 Feb 2020, 10:48 ]
Post subject:  Re: 4S Universal Tube Preamp Project (12A*7)

EmptyPockets wrote:
Following this build project guidelines I built my own throwing it in a cedar cigarbox.
Nice!

I really like the feeling of vacuum tubes and the wood in the box. Well done!

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