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Just finished my SE KT88 amp!
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=166
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Author:  bsgd [ 18 Sep 2008, 16:59 ]
Post subject:  Just finished my SE KT88 amp!

Hello all!

So, I finally had some time to finish my SE KT88 amp.
The circuit is just like Mikael Abdellah's Single Ended (SE) KT88 Tube Amplifier Schematic.
Image

For the supply I used some UF5408 for the B+ and a couple 6A10 for the heaters (they are heatsinked as they dissipate a lot of power). Bypass caps for the driver stage are some Rubcon ZL and for the power stage standard Nichicon caps. My B+ is also lower to make sure tubes will live a long and happy life.

I'm getting some hum from it (and that was expected) because I didn't use any chokes. But I will put a pair of chokes in there as soon as I get them. Right now all filtering is RC.

Here are some pics:
Image
Attachment:
DSC02041small.JPG

Attachment:
DSC02048small.JPG

Author:  Gio [ 18 Sep 2008, 19:14 ]
Post subject:  Re: Just finished my SE KT88 amp!

Hi Bernardo, that looks great. What are you using to control the volume?

Author:  bsgd [ 18 Sep 2008, 20:01 ]
Post subject:  Re: Just finished my SE KT88 amp!

Gio wrote:
Hi Bernardo, that looks great. What are you using to control the volume?

Hi Gio!

I'm using my DIY 5687 Tube Preamp.
Image

This time I decided to build just a power amp, no integrated volume control. I have way too many preamps and I need to put them to use :shock: .

Author:  billp [ 18 Sep 2008, 23:28 ]
Post subject:  Re: Just finished my SE KT88 amp!

Nice, clean and simple. Interesting use of those ferrite cores.

Author:  aroS3 [ 19 Sep 2008, 05:50 ]
Post subject:  Re: Just finished my SE KT88 amp!

Simple and effective. Congrats. I have only one point to argue if you allow me.
Please twist the fillaments cables to the tubes.

Regards,

George

Author:  bsgd [ 19 Sep 2008, 06:15 ]
Post subject:  Re: Just finished my SE KT88 amp!

billp wrote:
Nice, clean and simple. Interesting use of those ferrite cores.

Thank you billp!
It also sounds very nice too. So different from my PP amps.

Author:  bsgd [ 19 Sep 2008, 06:17 ]
Post subject:  Re: Just finished my SE KT88 amp!

aroS3 wrote:
Simple and effective. Congrats. I have only one point to argue if you allow me.
Please twist the fillaments cables to the tubes.

Thanks George! Please, do argue, that's why I started this thread!

Here there is no need to twist the filament wires cause I'm using DC. That big blue capacitor is a 10.000uF cap for the heaters.

Author:  bsgd [ 19 Sep 2008, 23:08 ]
Post subject:  Re: Just finished my SE KT88 amp!

Update:

Just added a pair of chokes, added some 10uF filter caps and a X2 noise supression cap at power input. I also added a white led at the bottom of the 6N1P driver tube so I have a clear indication that the amp is on. Also ran a separate wire from the inputs to ground to reduce hum (thanks Bruce) and now I believe this project is complete.

Heres a picture of the inside after the mods:

Author:  Gio [ 20 Sep 2008, 09:41 ]
Post subject:  Re: Just finished my SE KT88 amp!

Hi Bernardo,

Any comments on sound relative to your Push-Pull KT88?

Cheers

Author:  bsgd [ 20 Sep 2008, 12:04 ]
Post subject:  Re: Just finished my SE KT88 amp!

Gio wrote:
Any comments on sound relative to your Push-Pull KT88?

Hi Gio!

Yes, I've been listening to this amp for quite some time now, and the word that best descibes the sound is 'fat'. The sound fills the room is such a way that my PP amps just cant. Its a very, very different sounding amp (this is my first 'high quality' SE amp).
Unfortunately top end is not so clean and soundstage is also a little worse when compared to my KT88OD. But then again, I wouldnt say after all this amp sounds worse than my PP amps. It catually sounds terrific, but in a very different way!

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