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Call it good enough?
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Old 12th June 2019, 09:16 PM   #1
Troy Madden is offline Troy Madden  United States
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Default Call it good enough?

Would you call this good enough? These are the distortion numbers on my amp project, loosely based on the GEC 400 watt tube amp plans. I'm using 4 KT120's in parallel push pull, and instead of cathode followers driving the output tubes, I'm using paralleled 6SN7's with CCS plate loads. Output trans is Hammond 1650T. Measurements taken with Keithley 2015, at 1 Khz.

3 watts-.07% , 5 watts-.11%,
10 watts-.17%, 20 watts-.29%, 30 watts-.31%,
40 watts-.28%, 50 watts-.22%, 60 watts- .27%,
75 watts-.52% 90 watts-.61% and starting to clip

Last edited by Troy Madden; 12th June 2019 at 09:59 PM.
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Old 12th June 2019, 09:32 PM   #2
Wavebourn is offline Wavebourn  United States
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Call it good enough?
Yes, it is pretty good, if you keep it far from clipping, like 25W average output.
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Old 12th June 2019, 10:15 PM   #3
nigelwright7557 is offline nigelwright7557  United Kingdom
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Lots of lovely valve distortion is good.
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Old 12th June 2019, 11:08 PM   #4
Wavebourn is offline Wavebourn  United States
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Call it good enough?
It is for "Musical Instruments" forum.
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Old 12th June 2019, 11:41 PM   #5
Bigun is offline Bigun  Canada
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Call it good enough?
Looks good enough to me, but the proof would be in the listening. How does it sound ?
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Old 13th June 2019, 12:06 AM   #6
Troy Madden is offline Troy Madden  United States
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I haven't listened to it yet, I just got the hum/noise down to acceptable levels.
I'll put some music through it tomorrow!
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Old 13th June 2019, 02:26 PM   #7
Troy Madden is offline Troy Madden  United States
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DAAANG....finally put some music through this thing, test speaker is a Eminence 12" full range in a true infinite baffle, its in a very solid plywood wall of my shop with a whole adjoining room for it's enclosure. This thing is very listenable with some EQ. Enjoyable, foot tapping, surprising. Make me wonder if I have gone off-track with my home theater....

It has way more than enough power for the Eminence 12 of course. Bass is surprisingly good, sure sounds better than it looks on the scope when square wave testing...Mids are present and real, highs are pleasant but of course constrained by the speaker. Might have to throw a tweeter on.
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Old 13th June 2019, 03:22 PM   #8
Troy Madden is offline Troy Madden  United States
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Default Front end

Here's the front end of my amp project...look good?? The circuit I mean, not the cobbled drawing...LOL
Cathode bypass cap is actually 100uf Sanyo Oscon
This is driving 4 paralleled push pull KT-120s.
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File Type: jpeg B3FDF2CF-A0B2-4E1B-9DE1-A619641D2F2F.jpeg (150.0 KB, 397 views)

Last edited by Troy Madden; 13th June 2019 at 03:32 PM.
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Old 13th June 2019, 06:21 PM   #9
Alllensoncanon is offline Alllensoncanon  United States
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Call it good enough?
My 2 cents, The effective "2M" grid leak resistor for the 6SN7 is out of spec and aggressive. Unless there is a reason, 450V B+ seems high and unnecessary. 10nf couple capacitors might cause issues with low frequency NFB.
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Old 13th June 2019, 06:35 PM   #10
petertub is offline petertub  Sweden
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Call it good enough?
Quote:
Originally Posted by Troy Madden View Post
Would you call this good enough?
Is this without NFB ? If so good!
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