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    Building, troubleshooting and testing of these amplifiers should only be
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Uesugi 211 (vintage 1971)

Hi all

I‘m planning to resume an old project based on a schematic of a designer called Y Uesugi in the early 1970s.

The schematic was published in Hiraga’s French book on tube amps, on Claudio Bonavolta’s audio pages, and sometimes briefly described in some articles including one on a contemporary variant presented here https://worldradiohistory.com/Archive-All-Audio/Sound-Practices/Sound-Practices-1994-08-Summer.pdf
Where the Uesugi original schematic is published.

Amp is based on 6AU6, 12BH7, 211SE with 5k OPT, extremely simple concept, voltage doubler for B+ etc

I’m looking for feedback from knowledgeable people on
  • Mr Uesugi’s work (sometimes confused with current Uesugi Bros creations?)
  • the amp itself from people who have built it, how does it perform (musically and electrically - hiss, hum etc)
 
Uesugi-211-1971-schematic-1280x900.png
 

45

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Amp is based on 6AU6, 12BH7, 211SE with 5k OPT, extremely simple concept, voltage doubler for B+ etc
Keep in mind that the original Uesugi design could use both 845 and 211. If you have decided to use the 211 then, in the very same circuit, should go for 7-8K. The difference in output power will be small but much better in all other areas with 7-8K. This OPT will also work fine with the 845, in case you decide to change.

Otherwise, increase the plate voltage and use 10-14K but this will require some re-design. Keeping the same kind of circuit you might need to change the 12BH7 cathode follower with a bit higher voltage tube like a 6BX7 or 6BL7. That will depend on how you re-think the power supply. Nothing too difficult if you have some experience.
 

45

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Anyway I would personally change several things, starting from the power supply. Back in 1971, buying 211s and 845s was cheap, today it's not. So building a cheap/simple 211 amplifier amp makes much less sense.
I would look at the Ongaku as a (much) better platform to start with.
 
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Thanks for your advice, 45. I confess I did not mean to open a discussion on a complete tweaking of the original design starting with another OPT, powersupply, tube selection, etc and ending ultimately with building a silver/gold wired Ongaku instead... o_O I actually bought all the components for the original Uesugi back in the mid 1990s already, but left the project aside for various reasons including disapointment with most (all?) big triode amps heard here and there :censored:, lack of practice with wiring a 900+V device etc). Now I think it's a waste to leave all the components unused. But the Ongaku would certainly have been another interesting option.

It's the second time I read that the Uesugi amp was meant to be used with 211 or 845 interchangeably (without any adjustment, apparently); first was in the Sound Practices article from 1994 mentioned in my first post. That's quite interesting. Would love to hear more about the designer, his goals, the company he created. And as pointed out in the first post: actual experience of people with the original schematic.
 
I spoke to the builder of that amp through another channel who said it was nice but he had not tried the original schematic and went straight to upgrading / modding the power supply stage.

I prefer his hybrid power supply with tube rectifier and diodes. To cut down on cost, I would use an easier to find power transformer with one high voltage winding, 800VCT or 400V-CT-400V or similar, with a center tap you can use its half voltage for the driver stage or variation of that, like below. Regardless how you build it, it's going to be heavy with irons and costly. Good luck!

211-pow-sup-mod-schematic-720x720.png
 
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It is time to remind some people about the techniques of Double Blind Testing.
So get busy, and figure how to set up a Double Blind Test for your local audio club.

Some devices that are compared really are significantly different, others not.

Warning:
After a well designed and properly implemented Double Blind Testing session, there still are two opinions:
1. Oh, there is no discernible sound difference
2. Yes, But . . .

I have designed and carried out a couple of Double Blind Test sessions, so the above notes are just my opinions.
 

45

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Building an Ongaku amplifier implies using silver wire output transformers. Anyway you may not like the sound of cathode follower driver.
I was talking about the circuit, not the silver wire which is frankly irrelevant.
I have built several amplifiers using a cathode follower driver and they sound just fine. I have come to the conclusion that those people who talk about the bad sound of it couldn't make it work....
 
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I may go extreme and say an amp may sound different depending the time of the day or the mood of the listener. The true character of an amp reveals after minimum 30min of listening, if you want to switch it off or leave it on, there are the differences.
I am a believer, once I was not.
 
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I was talking about the circuit, not the silver wire which is frankly irrelevant.
I have built several amplifiers using a cathode follower driver and they sound just fine. I have come to the conclusion that those people who talk about the bad sound of it couldn't make it work....
I have an Ongaku style amp using E86C-6N6P-211and copper transformers, it sounds fine.
 
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filenet,
and
elac310,

Correct, If elac310 has All the original parts, and If the schematic is completely correct, he should first build it as original.
After building, testing and measuring, and then listening, Only then should he consider modifications to the original.

Note, In reference to the statement made in Post # 8 above:
(*) Any article that states that this amplifier with 52V bias on the output tube is able to use Either a 211, Or an 845 interchangeably is incorrect.
The amplifier schematic clearly shows that the bias voltage to the output tube is fixed, not variable.
A 211 versus an 845 Both with 960V B+ do require a different bias voltage . . .
Unless you want the 845 to draw about 2X the plate current and about 2X the plate dissipation; versus the 211 at the same B+ and bias voltage.
. . . Good luck with that concept.

I hope I do not need to quote the u, transconductance, and plate rp differences of the 211 versus the 845, in order to justify and prove my statement above (*).
 
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45

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The article is correct. The schematic is for the 211, the schematic for 845 will have different resistors but the circuit is the same. At a very quick look I think that simply changing the 50K cathode resistor of the 12BH7 follower to 39K it will already get in the ballpark for a 845 ( in the range of -110 to -120V). It is not a plug and play tube rolling amplifier. Fixed bias does not imply the use of a trimmer or variable resistor. Several times, after testing and refining the bias I change the trimmer with fixed resistors that are better quality and more reliable.
 
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