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Jean Hiraga 12AX7 - KT88 Single Ended Class A Amplifier
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=6337
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Author:  Dan [ 16 Sep 2018, 04:30 ]
Post subject:  Re: Jean Hiraga 12AX7 - KT88 Single Ended Class A Amplifier

And since it is traditional to check the heaters at this point of a tube amp build.................. :hot: :hot: :hot: :)

Author:  ILoveHiFi [ 16 Sep 2018, 20:41 ]
Post subject:  Re: Jean Hiraga 12AX7 - KT88 Single Ended Class A Amplifier

This looks good

Author:  Dan [ 16 Sep 2018, 21:33 ]
Post subject:  Re: Jean Hiraga 12AX7 - KT88 Single Ended Class A Amplifier

ILoveHiFi wrote:
This looks good

Thanks for the nice comment ILoveHiFi

I fired it up last night finally,
After a few tweaks I.e. removal of an issue in the feedback loop by removing the feedback loop. I am very happy with the sound so far, here is the internal:

Author:  Dan [ 17 Sep 2018, 07:34 ]
Post subject:  Re: Jean Hiraga 12AX7 - KT88 Single Ended Class A Amplifier

Ok so the feedback circuit issue was swapped plate and b+ on the output transformers fixed now works with and without feed back...

Author:  mwhouston [ 17 Sep 2018, 07:57 ]
Post subject:  Re: Jean Hiraga 12AX7 - KT88 Single Ended Class A Amplifier

I see you used cat5 solid core for sig path.

Author:  Dan [ 18 Sep 2018, 21:20 ]
Post subject:  Re: Jean Hiraga 12AX7 - KT88 Single Ended Class A Amplifier

Here is the working circuit, and the amp running,
Not quite finished yet but very close, I caught a little blue glow on the kt88s too :)

-Dan

Author:  Dan [ 18 Sep 2018, 21:22 ]
Post subject:  Re: Jean Hiraga 12AX7 - KT88 Single Ended Class A Amplifier

mwhouston wrote:
I see you used cat5 solid core for sig path.

It is stranded ;) only from the pot to the input, I used shielded signal lead from the input connectors to the pot.

Author:  mwhouston [ 19 Sep 2018, 02:26 ]
Post subject:  Re: Jean Hiraga 12AX7 - KT88 Single Ended Class A Amplifier

Dan wrote:
mwhouston wrote:
I see you used cat5 solid core for sig path.

It is stranded ;) only from the pot to the input, I used shielded signal lead from the input connectors to the pot.

Not a fan of shields wire. Twisted Cta5 pairs are usually enough in a power amp. Or I make up twisted wire-warp wire pairs. Where I have had a small hum in anything and thought just twisted, unshielded wire was the problem and replaced it with shielded wire it has made no difference. And now I have inferior wire in the signal path.

Author:  invaderzim [ 19 Sep 2018, 17:04 ]
Post subject:  Re: Jean Hiraga 12AX7 - KT88 Single Ended Class A Amplifier

that is really a nice clean build

Author:  ILoveHiFi [ 22 Sep 2018, 19:16 ]
Post subject:  Re: Jean Hiraga 12AX7 - KT88 Single Ended Class A Amplifier

I prefer sheild wires cause I found twisted pairs to have zero noise attenuation and it increased disotrtion of music sigan, like about 1 meter long wire when used as audio input cable.
Was a fancy one with like multiple twists like I think 4 or 6 "special" wires
I spent like 30-45 minutes on each cable and on the same song to hear the diffrence and come to the conclustion that the fancy twisted one increased distortion and noise

Dad got it as a present from a audipophile wich owns very expensive equipment and thinks that wire is good while its not good and standard sheilded cables work better.
The expensive audiphile also thinks hes the man at sound testing and comparing amplifiers having good ear.

In theory twisted pairs only reduce noise when both noise signal appears on both +- cable, in audio systems most are not balanced system. -signal is grounded, noise never appears on ground cable to noise directly appears on positive wire.

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