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Old 2nd January 2012, 07:41 PM   #1
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Default GU50 Prototypes

Some time ago, me and friends decided that we make a few prototypes with GU50. The idea was to test as many different combinations. For input tube we decided for 6SN7, 6SL7, 6N1P, 6N23P, 6N6P, D3a, 6C3P, ECC83, ECC85, ECC81.

We made some SE prototypes, one of the PSE and the PP one. As the input tube we test: D3a, 6C3P (the best two), 6N23P, 6SN7, 6N6P (also very good - not enough gain), ECC83, ECC85 (not so good). The project is continuing. Now I'm working on the development of housing.

We found that the GU50 is one of the best, for me better than EL34 or EL84.

A couple more pictures of prototypes:
Attached Images
File Type: jpg GU50 SE2 zgoraj.jpg (407.9 KB, 600 views)
File Type: jpg GU50 SE2 Spodaj.jpg (440.2 KB, 571 views)
File Type: jpg PSE GU50 zgoraj.jpg (458.9 KB, 555 views)
File Type: jpg GU50 PSE notranjost.jpg (698.1 KB, 543 views)
File Type: jpg IMG_2288.JPG (351.2 KB, 518 views)
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Old 8th November 2012, 12:25 AM   #2
fabioab is offline fabioab  Brazil
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Hi, my prototype is a mix of Fender AB763 with 12Ax7 as phase inverter, and two Gu50 at the power.

ry50 - 80W - YouTube
Only volume pot.

Almost finished!
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Old 8th November 2012, 12:58 AM   #3
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Quote:
Originally Posted by matejsirk View Post

We found that the GU50 is one of the best, for me better than EL34 or EL84.
Me too.

Also I found that it is better than that 6L6 clones like KT-88.


Here are my prototypes:

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Last edited by Wavebourn; 8th November 2012 at 01:00 AM.
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Old 8th November 2012, 05:05 AM   #4
Junm is offline Junm  Philippines
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nice work sir wave,

I'm also planning to do a PP gu50 with 6n6p drivers or 6n1p....any schematics suggestion for a 50w amp?
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Old 8th November 2012, 07:45 AM   #5
Jaap is offline Jaap  Netherlands
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Quote:
Originally Posted by matejsirk View Post
Some time ago, me and friends decided that we make a few prototypes with GU50. The idea was to test as many different combinations. For input tube we decided for 6SN7, 6SL7, 6N1P, 6N23P, 6N6P, D3a, 6C3P, ECC83, ECC85, ECC81.

We made some SE prototypes, one of the PSE and the PP one. As the input tube we test: D3a, 6C3P (the best two), 6N23P, 6SN7, 6N6P (also very good - not enough gain), ECC83, ECC85 (not so good). The project is continuing. Now I'm working on the development of housing.

We found that the GU50 is one of the best, for me better than EL34 or EL84.

A couple more pictures of prototypes:
Schematics ?
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Old 17th November 2012, 11:20 PM   #6
fabioab is offline fabioab  Brazil
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Hi, I would state some "strange" behavior of my ampli.
When I cranck (or close cranck) the volume pot, it starts a riiiiiiizzzzzzz. Obvioulsly the amplifier is totally saturated and crunched. It happens without the guitar plugged too.

Some Ideas what could cause this effect. The circuit was based in the Fender 6G8 circuit end AB763. The PI tube is a 7025 as in 6G8.

Thanks a lot who try give-me an explanation!
I'm sending some pictures.
FAB
Attached Images
File Type: jpg P1060517.JPG (97.5 KB, 58 views)
File Type: jpg P1060516.JPG (92.5 KB, 55 views)
File Type: jpg P1060515.JPG (98.2 KB, 40 views)
File Type: jpg P1070085.JPG (88.5 KB, 41 views)
File Type: jpg P1070086.JPG (97.6 KB, 60 views)
File Type: jpg P1070081.JPG (99.3 KB, 89 views)

Last edited by fabioab; 17th November 2012 at 11:28 PM.
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Old 19th November 2012, 10:12 PM   #7
fabioab is offline fabioab  Brazil
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nobody has some idea ???
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Old 19th November 2012, 10:31 PM   #8
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I have an idea. It is probably the result of some parasitic feedback, either capacitive between close input and output wires, or some common wire (so called ground) is soldered in the wrong place.
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Old 19th November 2012, 10:40 PM   #9
fabioab is offline fabioab  Brazil
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Thanks Wavebourn, some day I will try fix the problem! But I would like to have some idea about what could cause the problem.
For the time being, I'm playing to have some fun!
Cheers FAB
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Old 28th November 2012, 07:32 PM   #10
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Hi Wavebourn, as I pm'd you months ago, still waiting for your 30+ Watts design with this endvalve .
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