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Old 21st January 2017, 10:17 PM   #1
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Default 50W monoblock "Engineers Amp"

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As some of you already know I designed a PCB for a 50 watt monoblock version of the "Engineer's Amp". It uses 6HJ5 tubes, B+ of about 410V, and does an easy 50 watts out into 8 ohms.

You can see the details on my web site: Engineer's amp 50W monoblock

I have one assembled into a chassis now. I will be doing more measurements soon. It works very well

Pete
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Old 22nd January 2017, 02:13 AM   #2
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Quote:
I used the 6HJ5 sweep tube for the outputs. I am using 6GU5 tubes for the input/driver. Thanks for the idea George!
And only 50 watts.........
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Old 22nd January 2017, 02:58 AM   #3
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I hope there's more of those tubes left. George and friends might have burned up a few working on those 100 Watt and up earth shakers.

21LG6, 17KV6 and 26DQ5 are fairly similar tubes except for pinout and socket. Might be useful to allow for some pinout re-assignments and optional plate caps. And then there's bigger TV tubes.... 1/2 KW dreams-obsessions

Last edited by smoking-amp; 22nd January 2017 at 03:23 AM.
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Old 22nd January 2017, 03:55 AM   #4
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Maybe the -bias V should have a Zener regulator, if the screen V is regulated.
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Old 22nd January 2017, 04:06 AM   #5
hooman is offline hooman  Iran
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work very well..... tv tubes in hifi sound .
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Old 22nd January 2017, 04:21 AM   #6
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the incredible unfairness of living on the bum of the world.

FOMO.
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Old 22nd January 2017, 06:05 AM   #7
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Quote:
Originally Posted by aardvarkash10 View Post
the incredible unfairness of living on the bum of the world.

FOMO.
yeah, but you get the really cool accents and great words like bum.
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Old 22nd January 2017, 07:03 AM   #8
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There is a Hammond 291FX upgrade xfmr ($114) for the presently specified 290FX ($92). It's more expensive, but has 29M6 laminations for quieter running.

I assume the rather more expensive 300 series (373FX, $182)) has M6 laminations too. Weighs 1.5X as much. Must run at lower flux density.

The EDCOR XPWR247 looks like the only similar XFMR, but only rated 325 mA (versus 450 mA for 290FX) and it doesn't have enough current for the 6.3 VAC heaters.

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"the incredible unfairness of living on the bum of the world."

As long as Atlas doesn't take a break, you should be fine.

Last edited by smoking-amp; 22nd January 2017 at 07:19 AM.
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Old 22nd January 2017, 09:22 AM   #9
AJT is offline AJT  Philippines
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for some reason i could not get his boards, still having fun with point to point wiring...


Quote:
but has 29M6 laminations for quieter running
i use 0.35mm H18 and rm18 taiwan laminations for power traffos that
i use in my tube amp builds....
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Old 22nd January 2017, 10:30 AM   #10
Schultz is offline Schultz  Croatia
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Excellent.... Maybe I am gonna try....

Can you post ebay link for pcb's.....?
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