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GM70 SE amp project
GM70 SE amp project
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Old 25th October 2020, 04:26 PM   #1
dave123 is offline dave123
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Default GM70 SE amp project

Hey guys

Actually two of my friends and I are working on a single ended integrated amplifier so we thought why not to write about it here in order to use group wisdom as we are not expert in electronics.

OPT and power transformers are made by a friend whos job is pretty good in building tube amplifiers:

photo_2020-10-07_12-58-24.jpg

photo_2020-10-07_13-09-32.jpg

he suggested to use 6n6/6H6 as input tube and two 6E5P Russian tubes do drive one GM70 but without any further details. here are PSU and amplifier schematic I got so far:

photo_2020-10-20_22-59-02.jpg
photo_2020-09-14_16-49-23.jpg

I'm not sure about using 6N6/6H6 and 6E5P. I may consider other tubes if I have access to. any idea is much appreciated.
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Old 25th October 2020, 05:38 PM   #2
v4lve lover is offline v4lve lover  Netherlands
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Location: Surrounded by glass, no really my room is full of tubes
GM70 SE amp project GM70 SE amp project
I can comment on the heater supplies, 20VAC rectified with a 50A diode block will give you more than 20VDC output, and the voltage will vary with the mains voltage.

I have developed a heater regulator that is capable of glowing a GM70 as well, this may be just the thing for you. Dropout can be set very low, and if your heater windings are beefy. E.G. capable of 5A AC these will drop right in.

Attached picture is that of the module glowing a 813 10V 5A load.

As far as the high voltage supply goes, i need to look at that better to see if there are no drawing errors. I think you are using a GZ34 as the tube rectifier, correct?
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File Type: jpg photo_2020-10-23_05-12-05.jpg (231.1 KB, 553 views)
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Old 25th October 2020, 05:46 PM   #3
v4lve lover is offline v4lve lover  Netherlands
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GM70 SE amp project GM70 SE amp project
Default Free gerbers for boards

V4lve lover's free gerbers thread.


check post 11 for a nice board for your HT cap supply.
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Old 15th November 2020, 07:24 PM   #4
Francois G is offline Francois G  United States
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Quote:
Originally Posted by dave123 View Post
Hey guys

Actually two of my friends and I are working on a single ended integrated amplifier so we thought why not to write about it here in order to use group wisdom as we are not expert ...

I'm not sure about using 6N6/6H6 and 6E5P. I may consider other tubes if I have access to. any idea is much appreciated.
Very interesting project. One that I might try one day, if you get the kinks worked out here. 😁 Best wishes and please keep us informed of your progress.

Iím a novice with SE GM70, and had been eyeing designs on the internet, especially the Tsaar. See:
https://www.audio-creative.nl/wp-con...M70-schema.jpg
I assume you have looked at other GM70 SE designs too.

One question - what is the primary impedance for your output transformer?
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Old 15th November 2020, 07:31 PM   #5
audiowize is offline audiowize  United States
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A pair of Meanwell LRS-150-24 power supplies turned all the way down will happily heat your GM70s, especially since you are using fixed bias.
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Old 15th November 2020, 11:05 PM   #6
gideon1990 is offline gideon1990  Netherlands
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Nice looking transformers, I need friends who can wind those too
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Old 16th November 2020, 03:26 PM   #7
bobikdartanan is offline bobikdartanan
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Originally Posted by dave123
Quote:
Hey guys

Actually two of my friends and I are working on a single ended integrated amplifier so we thought why not to write about it here in order to use group wisdom as we are not expert in electronics.

OPT and power transformers are made by a friend whos job is pretty good in building tube amplifiers:
I would not recommend SRPP. It has negative and positive feedback,if you do wan't feedback.
Non Linear Behaviour of Shunt Regulated Push-Pull @ PAEng

Last edited by bobikdartanan; 16th November 2020 at 03:45 PM.
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Old 16th November 2020, 04:03 PM   #8
Schmitz77 is offline Schmitz77
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Quote:
Originally Posted by gideon1990 View Post
Nice looking transformers, I need friends who can wind those too
We all know, between nice looking and nice sounding is a distance that equals earth to the moon. To wind a mediocre sounding transformer isn't too hard, one can do it mostly by learning on the internet in one day.
To wind a supreme sounding transformer bears many hidden secrets thats mostly not free knowledge to achieve the easy way. I would just mention the anealing of the transformer core laminations and its process. With C-cores its different, but even C- cores sound different. In the end its a project with many unknown variables and when doing with no great circuit engineering knowledge, it could end anywhere. Maybe good or bad experience.
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File Type: jpg lafon-gm70-21.jpg (98.6 KB, 321 views)

Last edited by Schmitz77; 16th November 2020 at 04:05 PM.
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Old 16th November 2020, 04:16 PM   #9
bobikdartanan is offline bobikdartanan
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Oh of course,I agree with you
Tube Output Transformer Concept / Pictures | TTRadio
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Old 16th November 2020, 04:38 PM   #10
Schmitz77 is offline Schmitz77
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Quote:
Originally Posted by audiowize View Post
A pair of Meanwell LRS-150-24 power supplies turned all the way down will happily heat your GM70s, especially since you are using fixed bias.
I wouldn't recommend high freq. switching PSU for tube amps.
They are just a cheap and ready made solution, but they contaminate the whole amp with garbage frequencies that no one with a clear mind would prefer to have in such a unit.
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