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Old 14th May 2012, 05:27 AM   #11
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Quote:
Originally Posted by Einric View Post
@ Wave, with 450V B+ on the Simple SE GU-50; do you think that is a good application?
What do you suppose I could expect, power wise & quality wise?
I am in the process of building some 96db efficient speakers so I don't need a heap of power.
Do you know how to use plate curves and load lines?

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Last edited by Wavebourn; 14th May 2012 at 05:31 AM.
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Old 14th May 2012, 05:35 AM   #12
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You can find some tips in this discussion: www.wavebourn.com • View topic - GU-50 Single Ended Amplifier Design
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Old 14th May 2012, 05:57 AM   #13
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Quote:
Originally Posted by Einric View Post
@ Wave, with 450V B+ on the Simple SE GU-50; do you think that is a good application?
What do you suppose I could expect, power wise & quality wise?
I am in the process of building some 96db efficient speakers so I don't need a heap of power.
Good morning!
We highly recommend an excellent scheme (personal conception), even if you're new tube amplifiers, making this scheme will give you full satisfaction.
Pentode mode you get up to 18W with low THD, power that will move your 96dB speakers very well.
The scheme is realized in many copies and the results are excellent.
Is relatively small voltage Ua (Ua = 500V), but must be careful, danger is still very high.
You signal the drawings and as 8 ohm load, operating schedule, construction data for OT and supply scheme.
Because floors are pre-outs and attack SRPP, filament power supply must be made as illustrated.
Again, GU50 is a great tube, but it is uglier than the classic series EL ** or KT**.
hoping that I was helpful, thank you for your attention
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Last edited by LAZAROIU; 14th May 2012 at 06:06 AM.
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Old 14th May 2012, 06:12 AM   #14
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Quote:
Originally Posted by LAZAROIU View Post
Again, GU50 is a great tube, but it is uglier than the classic series EL ** or KT**.
I prefer when tube works nice even if looks like trashcan, rather than when it looks nice, but works like a trashcan.

However, tastes are different...
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Old 14th May 2012, 06:58 AM   #15
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Originally Posted by Wavebourn View Post
I prefer when tube works nice even if looks like trashcan, rather than when it looks nice, but works like a trashcan.

However, tastes are different...


Right you say I prefer the tubes (GU50), like everything is a challenge.
GU50 and 6C33C tubes are made ​​to go and play "shoot tank gun" and when MiG (aircraft) is at 10.000Km, so a quiet GU50 function to a good home is very simple ... right?
I made ​​a joke, but honestly I prefer Russian tubes for their robustness, but also its quality in the audio and more.
I believe that a GU50 in a project like the above may work for many years without problems.
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Old 14th May 2012, 12:03 PM   #16
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Originally Posted by Wavebourn View Post
And for an output stage I would consider grid currents to occur, even if only on peaks, so I personally tend to avoid coupling capacitors to 1'st grids of any output tubes when possible.
When you point at blocking distortion when grid current occurs, the combination of coupling capacitor / high ohm-ish grid leak resistor is more responsible. Replacing the grid resistor by a low DCR grid choke should work OK, also with a coupling capacitor.
Better drive still will be there with an interstage transformer IMO.
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Old 14th May 2012, 01:09 PM   #17
Einric is offline Einric  United States
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I don't quite understand how to read the trace curves.
I know how to read a graph but I don't know what the lines mean.

BTW, I think the GU-50 looks Badass!
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Old 14th May 2012, 01:40 PM   #18
Einric is offline Einric  United States
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My other thought would be to use my Aikido 6CG7 x 6CG7 to drive the GU-50's directly.
This would be wired P2P and I have no problem with that.
As a matter of fact it may simplify my build and save me $45 on a PCB that I can use for parts.
I was thinking maybe 2 Parallel GU-50's for a little more output since I don't need to buy a PCB.
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Old 14th May 2012, 03:01 PM   #19
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Originally Posted by pieter t View Post
Better drive still will be there with an interstage transformer IMO.
No, source follower is better. IMO.
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Old 14th May 2012, 03:15 PM   #20
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No, source follower is better. IMO.
Depends IMHO.
Source follower is the champion in current drive, no question.
With a 1:1 IT the driver tube will be able to deliver higher voltage swings, and current drive will improve with IT step-down (at cost of voltage swing).
It's all a matter of solid engineering; with different approaches equally good results can be obtained IMVHO.
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