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PostPosted: 28 Jun 2010, 01:08 
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gofar99 wrote:
The KT120s seem to be great tubes. I'm now working on a design and prototype of an "Oddwatt" that uses them to their full ability. The transformers used in the original projects can not provide the power needed (I tried - they run out of gas) and the outputs should be a higher rating and initially I determined that the impedance ought to be in the 6-6.5K region for Oddwatt use not the 8K of the other amps..

Be still my beating heart. Just in time for my next build :)

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PostPosted: 28 Jun 2010, 03:49 
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Cold Macaroni wrote:
gofar99 wrote:
The KT120s seem to be great tubes. I'm now working on a design and prototype of an "Oddwatt" that uses them to their full ability. The transformers used in the original projects can not provide the power needed (I tried - they run out of gas) and the outputs should be a higher rating and initially I determined that the impedance ought to be in the 6-6.5K region for Oddwatt use not the 8K of the other amps..

Be still my beating heart. Just in time for my next build :)

Let me put an end to your suffering.

Simple build this amp http://www.diyaudioprojects.com/Schematics/Mikael-Abdellah-SE-KT88-Amplifier.htm But remove the KT88 and insert and freshly purchased matched pair of Tung-Sol KT120s. Change the cathode resistor to 300ohms. Nothing else has to change. Just ensure the power tranni can deliver about 300mA because my amp consumes 112mA per tube. And you have a small current drain for the 6N1P. Also make sure you OPTs will handle the idle current.

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PostPosted: 30 Jun 2010, 07:28 
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mwhouston wrote:
Cold Macaroni wrote:
gofar99 wrote:
The KT120s seem to be great tubes. I'm now working on a design and prototype of an "Oddwatt" that uses them to their full ability. The transformers used in the original projects can not provide the power needed (I tried - they run out of gas) and the outputs should be a higher rating and initially I determined that the impedance ought to be in the 6-6.5K region for Oddwatt use not the 8K of the other amps..

Be still my beating heart. Just in time for my next build :)

Simple build this amp http://www.diyaudioprojects.com/Schematics/Mikael-Abdellah-SE-KT88-Amplifier.htm But remove the KT88 and insert and freshly purchased matched pair of Tung-Sol KT120s. Change the cathode resistor to 300ohms. Nothing else has to change. Just ensure the power tranni can deliver about 300mA because my amp consumes 112mA per tube. And you have a small current drain for the 6N1P. Also make sure you OPTs will handle the idle current.

I had planned on building a set of Odd blocks, but I'm starting to think that amp might be a better choice for my first ground-up build... I'm sure I'll be picking your brain down the road. Thanks!

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PostPosted: 30 Jun 2010, 09:13 
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Cold Macaroni

If you build oddwatts or oddblocks you will have no trouble. The amp in the link requires a little more hand holding. Some parts will have to be specced better than the simple guide I laid out. Happy to help though.

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PostPosted: 01 Jul 2010, 00:32 
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mwhouston wrote:
If you build oddwatts or oddblocks you will have no trouble. The amp in the link requires a little more hand holding. Some parts will have to be specced better than the simple guide I laid out. Happy to help though.

I know the oddblocks/watts will be a smoother build in the sense that I won't have as much of my own work to do on the circuit, but I think I would benefit from some having to learn some theory and more about how these things work. The amp in the link you provided is visually pretty simple, and even if I don't actually build it in the end, it might be fun to "bench race" with it a little. I'll go ahead and remove myself from this thread no since it's a KT120 thread, if I have any questions, I'll send 'em your way mwhouston

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PostPosted: 01 Jul 2010, 03:43 
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Cold Macaroni wrote:
I know the oddblocks/watts will be a smoother build in the sense that I won't have as much of my own work to do on the circuit, but I think I would benefit from some having to learn some theory and more about how these things work. The amp in the link you provided is visually pretty simple, and even if I don't actually build it in the end, it might be fun to "bench race" with it a little. I'll go ahead and remove myself from this thread no since it's a KT120 thread, if I have any questions, I'll send 'em your way mwhouston

Anytime I can help. Why not build the simple amp I sent the link for. The KT120s are an excellent tube but so are: 6L6, 6V6, El34s, KT88 and even 5881. Think about it. It is a very easy amp to build.

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PostPosted: 01 Jul 2010, 04:28 
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mwhouston wrote:
Cold Macaroni wrote:
I know the oddblocks/watts will be a smoother build in the sense that I won't have as much of my own work to do on the circuit, but I think I would benefit from some having to learn some theory and more about how these things work. The amp in the link you provided is visually pretty simple, and even if I don't actually build it in the end, it might be fun to "bench race" with it a little. I'll go ahead and remove myself from this thread no since it's a KT120 thread, if I have any questions, I'll send 'em your way mwhouston

Anytime I can help. Why not build the simple amp I sent the link for. The KT120s are an excellent tube but so are: 6L6, 6V6, El34s, KT88 and even 5881. Think about it. It is a very easy amp to build.

I think I was a little unclear before, I intend to build it :)

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PostPosted: 01 Jul 2010, 04:33 
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What to do, what to do???

I've got these 6.6K 100 watt Edcor trannys with secondary taps in my oddwatt that some (nobody here) say "I wasted my money on". And this insane 2 Amp PS tranny! That's madness! Lunacy I tell you.

Who wasted their money now??? :D :D :D

Of course, in a way I screwed myself when I purchased those - now I have to upgrade - I have no excuse. Wait. there's the cost of the CCS resistor I need to replace. Forgot about it - can't do it now. Too expensive. :(

The plastic finally comes out tomorrow. :sick:

Call me an abuser. If I'm buying these they will be PUSHED HARD. Otherwise there's no point I can see.

I want 50 watts. Doable you think with higher B+ (got taps on my power tranny to raise it if needed!) and higher bias current, with lower impedance high power tranny?

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PostPosted: 01 Jul 2010, 16:18 
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Hi, Possible, but pushing it. Class A amps are inefficient (right). With a U/L connection about the best you can see is 35% efficiency. In pentode mode about 5% more. So to get 50 out you need to put in around 150. That's 75 per tube which exceeds the ratings for dissipation. In U/L mode I figure the best you can expect is about 40. Loudness wise not much of a difference.

Good listening
Bruce

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PostPosted: 02 Jul 2010, 02:16 
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gofar99 wrote:
Hi, Possible, but pushing it. Class A amps are inefficient (right). With a U/L connection about the best you can see is 35% efficiency. In pentode mode about 5% more. So to get 50 out you need to put in around 150. That's 75 per tube which exceeds the ratings for dissipation. In U/L mode I figure the best you can expect is about 40. Loudness wise not much of a difference.

40 solid clean watts would work. The difference in volume would be very small between 40 and 50.

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