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Tung-Sol KT120 users and abusers
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Author:  rock4016 [ 29 Sep 2011, 08:17 ]
Post subject:  Re: Tung-Sol KT120 users and abusers

Did you have an updated schematic yet?

Author:  gofar99 [ 29 Sep 2011, 10:05 ]
Post subject:  Re: Tung-Sol KT120 users and abusers

Hi, Yes, it is attached. Notice the changes in the driver stage. (Tube, voltages, resistor values and NFB values). These are essential to get the level of quality performance wanted. Also the different output trannie (do not use the 60 watters as they can't handle the current). The LM317s are connected pin for pin and share a single sense resistor.

Good listening
Bruce

Attachment:
Odd-Block-HP Sept 9, 2011.PNG

Author:  mwhouston [ 04 Oct 2011, 01:35 ]
Post subject:  Re: Tung-Sol KT120 users and abusers

The bread Board amp (Be Bamp) built some time back had swapable driver stages: 6N1P in a timber box and 6SN7 on cast Al base. Both had the same inter-stage caps (Russian military PIO) and both were driven from a common PS. I was asked which driver stage I prefered but had never taken the time to compare. But now I have.

The test arrangement was a laptop playing 24Bit 88.2khz Flac files through a high rez D2A, BoZSE into each driver stage (6N1P and 6SN7) then powered by the Be Bamp (KT120 tubes), Speakers were KEF IQ30. A rock track, single piano and orchestral track were played over and again through the two different driver stages. I could not really pick the difference until I played the single piano tracks.

The pick has to be the 6N1P in the Twinnings Tea box. This driver stage brought the piano forward and focused it well between the speakers. It WAS an single paino and apart from open and deep reverb into the recording hall nothing alse. The 6SN7 wanted to place the piano more balanced into the hall and make the reverb sound like a second or third instrument producing a very smooth mix of solo instrument and reverb/hall. With the 6N1P there was no mistaken the fact that you were listening to just one piano, reverb and hall decay were a result of the instrument and not a part of it.

The 6N1P had been picked by a freind when I demonstrated the Be Bamp at his place. His discription was "more open". The 6N1P is a punchy tight little tube. I have used it in other amps which have been pruchased on a single audition. Well the Russians got something right.
Attachment:
Testss.jpg


This post has been posted else where on this forum.

Author:  rock4016 [ 04 Oct 2011, 07:43 ]
Post subject:  Re: Tung-Sol KT120 users and abusers

what is the operating point for your 6sn7, and what is it's load resistor and next stage grid resistor?

Author:  mwhouston [ 04 Oct 2011, 07:52 ]
Post subject:  Re: Tung-Sol KT120 users and abusers

rock4016 wrote:
what is the operating point for your 6sn7, and what is it's load resistor and next stage grid resistor?


Without pulling it down I really don't know. It was built some time back but I take a look tomorrow.

Author:  rock4016 [ 04 Oct 2011, 12:34 ]
Post subject:  Re: Tung-Sol KT120 users and abusers

Try to adjust the Plate voltage to 150V and run it at about 8 mA.

Author:  mwhouston [ 04 Oct 2011, 20:05 ]
Post subject:  Re: Tung-Sol KT120 users and abusers

rock4016 wrote:
Try to adjust the Plate voltage to 150V and run it at about 8 mA.

Are you talking plate to cathode voltage?

Author:  rock4016 [ 05 Oct 2011, 09:51 ]
Post subject:  Re: Tung-Sol KT120 users and abusers

Yes. However your cathode voltage shouldn't be too high. So even not taking that into consideration you'd be fine.

Author:  gofar99 [ 05 Oct 2011, 16:52 ]
Post subject:  Re: Tung-Sol KT120 users and abusers

Hi Mark, I agree that 150V/8ma is a pretty good place for 6SN7s. A good rule of thumb is that your anode current ought to be somewhere between 1/3 and 2/3 the tube rating. I find that tubes that can handle current in the 25 ma range seem to like to be toward the 1/3 end. Tubes that are in the 3ma and down range seem to run well right at about 1/2 their rating. There certainly are exceptions, but if you stay in these areas it will almost always sound good. B+ on the anode should typically be about 1/2 the rating for good results. If you run a load line on the tube with these values it will usually fall close to the most favorable linearity range. I like the 6N1P as well. I just have not found any particular application yet, too much gain for a line stage and not enough for my phono preamps.

Author:  7_V [ 27 Sep 2012, 05:45 ]
Post subject:  Re: Tung-Sol KT120 users and abusers

mwhouston wrote:
Just one image of the KT120s in the Be Bamp.
Attachment:
KT120ss.jpg

Mark, I'm interested in building a KT120 SE amplifier.

Looking at your schematic, your amp seems to runs in UL mode, while Alex Gendrano's has the option of running in triode mode.

Can your amp run in triode mode and what are the pros and cons of doing so? Please excuse my ignorance if I'm asking a silly question but I'm new to this SET thing.

Regards
Steve

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