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Old 18th September 2011, 04:03 PM   #11
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Hello

Thank you for all of you the precious reply (post)
Now I see the schematic much better, I understand almost 100%.
A couple question still I have.
The transformer I buy does not have bias voltage, but I'll use a separate transformer for that purpose.
Unfortunately the bias voltage unknown here. Can be -100V? He use 63V capacitors.
I found another (improved version) of he's schematic at his website. He use choke and 3 transistor in each chanel. I have some choke at hand 30H 50mA probably that would be enough because only goes to the driver tube.
Probably he designed these PS to that schematic that is why one bias per one chanel..
The truth is I want to keep those choke to my GM70 tube amp.
Later I'll want build that amp (I have most of the parts) for that BUT to get back to tube world I want to start with a smaller amp. The last 10 years I built only SS amps. Before I did tubes to but 10 years a lot of time. To start with a GM70 1KV a bit dangerous.
If I use the first (not the improved schematic) basically I need 4X the red box parts 22k trim pot, 10k resistor some electrolytic capacitor bypassed probably 1uF MKP capacitor.
That is correct?
With the 22K set up the bias (he wrote each channel 100mA) That mean one GU50 run 50mA on plate or both 100mA on plate.
Did someone built amplifier with GU50? He can let me know the correct bias.
I like these schematic all do I started to collect parts for another GU50 at first and after I found these.
That is on the forum but there is no PS..I wrote a PM to the designer but never got a answer. He use 6SN7 (I have the tubes and sockets) to drive the GU50. Missing capacitor value (red, the designer put that in red) to not just the PS.
There is one tube version and two tube also. I think bot need that capacitor unfortunately missing.
I post that schematic to. How I stated I like these Russian design all do the the 6E5P tube has only 500 hours life time (it is cheap on Ebay) not a problem.
How close the tubes have to be matched, or not well because the separate bias?
The improved version has one bias per tube..
All do that is improved still I like the first posted version because it much simple. Later I can improve it me to if there will be need for..
Thank you so much
Greetings Gabor
Attached Images
File Type: gif gu50se6e5p2.gif (10.2 KB, 721 views)
File Type: gif gu50sebp.gif (7.8 KB, 652 views)
File Type: jpg GU-50 SE Triode.JPG (45.9 KB, 655 views)
File Type: jpg gu50.jpg (56.9 KB, 646 views)

Last edited by gaborbela; 18th September 2011 at 04:09 PM.
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Old 18th September 2011, 04:12 PM   #12
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Dear quikie22
If you use 2 GU50/ channel probably that would be more than enough in triode mode to.
Am I right?
Greetings gabor
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Old 18th September 2011, 09:23 PM   #13
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yes, 2xGU-50 would be able to increase the power, but then I would need a different OPT (lower pri impedance), matched tubes, higher current requirements from my PT, a higher Miller capacitance for the output stages which will load the driver stages, a new and larger chassis to fit an extra tube....

Too much trouble.

Pentode is just a wire and a resistor and some zeners.
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Old 18th September 2011, 11:57 PM   #14
AJT is offline AJT  Philippines
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Quote:
Originally Posted by quikie22 View Post
yes, 2xGU-50 would be able to increase the power, but then I would need a different OPT (lower pri impedance), matched tubes, higher current requirements from my PT, a higher Miller capacitance for the output stages which will load the driver stages, a new and larger chassis to fit an extra tube....

Too much trouble.

Pentode is just a wire and a resistor and some zeners.

really? you can use the same output transformer, just use the 16 ohm tap to connect your 8 ohm speaker and you have a lower impedance primary....the power transformer may have enough capacity already...the chassis may need re-thinking....

matching tubes? using fixed biasing, this is not really needed....what with individual biasing pots.....

so you see, it is not really extra trouble if you have the parts on hand....

the only extra i can see are 2 GU50's and sockets....
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Last edited by AJT; 19th September 2011 at 12:08 AM.
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Old 19th September 2011, 01:46 AM   #15
Timofey is offline Timofey  Russian Federation
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>> Unfortunately the bias voltage unknown here. Can be -100V? He use 63V capacitors.

This scheme is "voltage doubler" - it's not bad for small load. Capacitors has to be 1/2 output voltage only, also 2x63 V good enough for 100V.

>> I found another (improved version) of he's schematic at his website. He use choke and 3 transistor in each chanel. I have some choke at hand 30H 50mA probably that would be enough because only goes to the driver tube.
Probably he designed these PS to that schematic that is why one bias per one chanel..

"Best is enemy of just good" - any modifications and improvings may be keep for future? When you'll have working good amp already.

>> The truth is I want to keep those choke to my GM70 tube amp.
Later I'll want build that amp (I have most of the parts) for that BUT to get back to tube world I want to start with a smaller amp. The last 10 years I built only SS amps. Before I did tubes to but 10 years a lot of time. To start with a GM70 1KV a bit dangerous.

O?! Yes, GM70 is beautiful tube, but it has a bit too high anode voltage.


>> If I use the first (not the improved schematic) basically I need 4X the red box parts 22k trim pot, 10k resistor some electrolytic capacitor bypassed probably 1uF MKP capacitor.
That is correct?

Yes, it is.

>> With the 22K set up the bias (he wrote each channel 100mA) That mean one GU50 run 50mA on plate or both 100mA on plate.

100 mA for each GU50 tube. Bias has to be something about -75 V (See in attach plate curves for GU50 in triode mode)

>> I post that schematic to. How I stated I like these Russian design all do the the 6E5P tube has only 500 hours life time (it is cheap on Ebay) not a problem.

6E5P lives much more then 500 hours usually, without massive overloads of course.

>> How close the tubes have to be matched, or not well because the separate bias?

If you'll find tubes "from one box" (the same vendor and manufacturing date) - they has enough close parameters. Don't care too much about matching with separate biasing.

>> The improved version has one bias per tube..
All do that is improved still I like the first posted version because it much simple. Later I can improve it me to if there will be need for..

Golden decision, Gabor! (It is no joke).

Good luck!
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Old 19th September 2011, 09:10 AM   #16
Jaap is offline Jaap  Netherlands
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Quote:
Originally Posted by quikie22 View Post
Agree with arto. Have built another amp with 6e5p and gu-50. It gives a very clean and detailed sound. Mine is cathode bias instead of fixed bias. But I run both in pentode mode but with local feed back.
What is your operating point ?
Schematic ?
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Old 19th September 2011, 02:14 PM   #17
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I also plan to build this project. I have a OT with the impedance 1200. Could be applied to such project? I already have GU50 and 6E5P. I also have 6C45P - could I use this tube instead of 6E5P?
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Old 19th September 2011, 06:35 PM   #18
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Thank you for your answer!
Those who interested in similar schem, here is with the same tubes but only one GU50/ channel.
http://www.goodsoundclub.com/pdf/6E5P_Swedish.pdf
Please roll done after you open the page.
Greetings
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Old 19th September 2011, 09:42 PM   #19
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Quote:
Originally Posted by matejsirk View Post
I also plan to build this project. I have a OT with the impedance 1200. Could be applied to such project? I already have GU50 and 6E5P. I also have 6C45P - could I use this tube instead of 6E5P?
For 2 GU50 in parallel , 1.2ΚΩ is correct! And it is a simple design, you can use any tube that can do 80 Volts drive signal with high current. 6C45P looks good, I haven't used it, but I think it's OK!
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Old 21st September 2011, 01:06 PM   #20
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@Tony, if you read my post, I am using cathode bias. NOT fixed bias. I do not have another secondary on my transformer for bias voltage.

As for the OPT, it is limited a single 8 ohm tap.

As for the power trans, I could try to run it at max dissipation or exceed it slightly but at what possible risk?

So... before u decide to lampoon my reasons, please be polite and find out the real situation.
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