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Old 12th September 2009, 03:30 PM   #21
SY is offline SY  United States
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Got my board today. It's very... red.

I love pentode amps. This will be fun to compare with the RLD, running the upper end of my speakers.
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Old 13th September 2009, 01:06 AM   #22
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Carbon films are less noisy and I've measured 1.2:1 SWR at 470MHz with a 2-watter. More than enough HF range for audio
Just enough... I've had oscillation at 120MHz. I was afraid that I'd have airliners crashing nearby

My only worry with the CF's would be that some may be better than others. CC's are a known quantity.

Actually I would expect a ferrite bead would work OK as well.

Pete
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Old 13th September 2009, 01:07 AM   #23
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Got my board today. It's very... red.
What, you don't like red?

Why be boring?

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Old 13th September 2009, 02:02 AM   #24
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Got my board today. It's very... red..... What, you don't like red?
I saw the output tubes today. They are very.....RED! I was planning to buy one of these boards sooner or later just to experiment with. I saw that there was only 7 left, so I just ordered one.

I got 20 6GV5's when they were $1 each so I can afford to "test" a few. Do you really think that I will run this amp at 340 volts. Nah. I'll be disapointed if I can't get 50WPC.

I probably won't get to build it until I get back from up north, but I do expect to complete the build for under $75!
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Old 13th September 2009, 03:23 AM   #25
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I had the same thought- the B+ seems a bit puny. I've got some UTC LS-54s that were just made for this amp...
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Old 13th September 2009, 04:12 AM   #26
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I've got some UTC LS-54s that were just made for this amp...
I got a pair of LS57's but I think they will go into a fully differential class A P-P amp that is slowly developing in the 6L6GC in AB2 thread. The LS54's and the LS57's are only rated for 20 watts.

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I had the same thought- the B+ seems a bit puny.
If I read the schematic correctly there are a whole bunch of different sweep tubes that will plug into this board including 6LR6's (I got some of those too). I have several P-P OPT's to try, so I will leave the power supply stuff off of the board at first, hook it up to some bench supplies, and experiment until I find something I like. Then I will figure out how to make the power supply work.

Pete calls this an "engineers amp". I am sure that he would expect a fellow engineer to do some engineering with his board.
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Old 13th September 2009, 04:21 AM   #27
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I don't use my tube amps below 110Hz, so I figure I can squeeze 35 watts easy out of 'em. With 500 volts on the plates and the idle current dropped a bit, it should be do-able.
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Old 13th September 2009, 05:15 AM   #28
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Red makes it go faster!
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Old 13th September 2009, 01:01 PM   #29
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Originally Posted by tubelab.com View Post
I saw the output tubes today. They are very.....RED! I was planning to buy one of these boards sooner or later just to experiment with. I saw that there was only 7 left, so I just ordered one.
Meme chause aussi.

Now to find a cake pan big enough to mount it in.
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Old 13th September 2009, 03:13 PM   #30
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I had the same thought- the B+ seems a bit puny.
Let's just say it's conserative

You can definitely go higher and get more power - I did on the breadboard. But keep in mind I wanted to make this fairly safe for somebody with limited experience, so avoiding glowing plates and exploding electrolytics was on the "design goals" list.

So with 450V electrolytics on the board, you can certainly up the steady-state B+ to 400V without going over 450V at cold start. If you go higher you'll need to kludge some series-connected caps in.
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