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KT120 Class A Push-Pull U/L Mono-Blocks [message #67330] Sat, 30 April 2011 21:34 Go to next message
gofar99 is currently offline  gofar99
Messages: 1393
Registered: May 2010
Location: Southern Arizona
Illuminati (3rd Degree)
Hi Everyone. The Prototype KT120 mono-blocks are up and running and will be demo'd at the LSAF. Powerful, even with zero time tubes they sound rather good. Look for a diy project on them as well as future kits. These amps are not for the faint of heart nor weak back. In the present configuration (chassis is too small) they weigh in at over 28 pounds each. Power output is approximately 40 watts RMS. Testing to follow as soon as I can.

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Good Listening
Bruce
Re: KT120 Class A Push-Pull U/L Mono-Blocks [message #67334 is a reply to message #67330] Sat, 30 April 2011 22:21 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17357
Registered: January 2001
Illuminati (33rd Degree)

That is one meaty amplifier. Looks great! Can't wait to hear 'em...

Re: KT120 Class A Push-Pull U/L Mono-Blocks [message #67349 is a reply to message #67334] Sun, 01 May 2011 16:31 Go to previous messageGo to next message
gofar99 is currently offline  gofar99
Messages: 1393
Registered: May 2010
Location: Southern Arizona
Illuminati (3rd Degree)
Thanks, They still need a bit of taming, but in the raw form right now can develop 46 wrms into 4 or 8 ohms. Initial spectrum analysis shows more thd over about 1/2 power than I would like, Confused but that is just a detail and can be cleaned up.



Good Listening
Bruce
Re: KT120 Class A Push-Pull U/L Mono-Blocks [message #67887 is a reply to message #67330] Fri, 27 May 2011 22:12 Go to previous messageGo to next message
gofar99 is currently offline  gofar99
Messages: 1393
Registered: May 2010
Location: Southern Arizona
Illuminati (3rd Degree)
Hi Everyone, The KT120 amps were in use for a while at the LSAF. As you might expect, they really put out serious sound. Shocked The design process is on going and a number of refinements underway. These are shaping up as mega power amps (at least for a class A tube design. Power output is coming up to spec in the 40-45 watt RMS range. They are so mighty that one smoked my test load bank. Uh Oh The smell of smoldering plastic was the first clue. Oops. I have some upgraded parts on order and expect the design to be finalized in about 2 months. Kits will follow at a later date (it takes time to source things like circuit boards and chassis). In accordance with the way I design, as soon as the design is finalized I intend to post it under group builds as a diy project for those of you who like to build from scratch. My experience is that there are at least two types of audio enthusiasts, those who build from scratch and those that don't. I like to cater to both.


Good Listening
Bruce
Re: KT120 Class A Push-Pull U/L Mono-Blocks [message #68201 is a reply to message #67887] Thu, 16 June 2011 17:15 Go to previous messageGo to next message
gofar99 is currently offline  gofar99
Messages: 1393
Registered: May 2010
Location: Southern Arizona
Illuminati (3rd Degree)
Hi Everyone, I'm still waiting for bigger power transformers for the amps. I have made some design improvements since the LSAF. Even with the under sized transformers they deliver close to 40 W RMS. These amps should be just the ticket for folks using thing like Maggies that are power hungry. Stay tuned for developments.


Good Listening
Bruce
Re: KT120 Class A Push-Pull U/L Mono-Blocks [message #68422 is a reply to message #68201] Fri, 01 July 2011 22:13 Go to previous messageGo to next message
gofar99 is currently offline  gofar99
Messages: 1393
Registered: May 2010
Location: Southern Arizona
Illuminati (3rd Degree)
Hi, Power hungry listeners. Rolling Eyes I have installed the new transformers and the amp behaves quite well. Unfortunately, I smoked my PC based DSO and can not do accurate measurements on it until I get another one. The stand alone DSO I have just can't keep up with the PC one. I sent the fried one off to the repair shop and they called back and wanted to know what I did to completely smoke the board and make it un-repairable. I suggested that test gear should be protected against 175 volt spikes on the ground. They didn't see the humor in it. Anyhow the KT120 amp sounds quite nice and has lots of muscle. Using my back up test gear I show a power output right on design spec at 45 watts rms. Now all this comes with a lot of heat as the B+ is 440 and idle current is 310ma. Each mono block consumes roughly 190 watts to make 45. About right for a class A U/L amp. More to follow as soon as I can replace the scope.

Good Listening
Bruce
Re: KT120 Class A Push-Pull U/L Mono-Blocks [message #68425 is a reply to message #68422] Fri, 01 July 2011 22:55 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17357
Registered: January 2001
Illuminati (33rd Degree)

Bummer on the PC card smoke. Can't wait to see the results when you get it back going again!

Re: KT120 Class A Push-Pull U/L Mono-Blocks [message #68580 is a reply to message #67330] Sat, 16 July 2011 20:16 Go to previous messageGo to next message
gofar99 is currently offline  gofar99
Messages: 1393
Registered: May 2010
Location: Southern Arizona
Illuminati (3rd Degree)
Hi Everyone, Progress is in the offing.... I got the replacement DSO and now can get back to the KT120 Oddblocks. Smile One is now on my bench. I expect some good news in a week or so. The new transformers are in place and initial measurements show right on 45 wrms in class A U/L mode. Right on target for the design. These amps really demonstrate the thermo in thermionic equipment. Rolling Eyes Folks in the north will love them in the winter. Down here in Arizona, well...... not needed at this time of year.

Good Listening
Bruce
Re: KT120 Class A Push-Pull U/L Mono-Blocks [message #68728 is a reply to message #68580] Mon, 25 July 2011 22:33 Go to previous messageGo to next message
gofar99 is currently offline  gofar99
Messages: 1393
Registered: May 2010
Location: Southern Arizona
Illuminati (3rd Degree)
Hi Everyone, A progress report. These amps are beasts. My personal sense is I would like to be able to roll tubes in the outputs, but with a sole brand this is not possible. Powerful certainly, detailed the same but I would like a choice of flavors. I have a question for any who care to respond .... opinions on monoblock kits at about $800 each? Slightly more than the cost of the KT88 amps. Rolling Eyes

Good Listening
Bruce
Re: KT120 Class A Push-Pull U/L Mono-Blocks [message #68729 is a reply to message #68728] Mon, 25 July 2011 22:38 Go to previous messageGo to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 17357
Registered: January 2001
Illuminati (33rd Degree)

Oh, man, that's an excellent price. Very competitive. Looks good and sounds great too! What's not to love about that?!!

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