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    Building, troubleshooting and testing of these amplifiers should only be
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The days of wine, roses & WE205D

cdwitmer

Member
2003-04-17 1:10 am
Tokyo
(A Japanese friend's WE205D SE amplifier)

Because I started to get some queries about my friend's amplifer over here, I decided to start a new thread (not that I expect it to grow very long) to avoid cluttering up the thread about Feastrex speakers. So here is a quick look at what he has done:

[IMGDEAD]https://shinshu.fm/MHz/44.04/images/ThtcBtOz.jpg[/IMGDEAD]
[IMGDEAD]https://shinshu.fm/MHz/44.04/images/hCwpLkT8.jpg[/IMGDEAD]
[IMGDEAD]https://shinshu.fm/MHz/44.04/images/pMAvZn5R.jpg[/IMGDEAD]
[IMGDEAD]https://shinshu.fm/MHz/44.04/images/qjmJAQ8S.jpg[/IMGDEAD]

And his comments about it:

"It is with a sense of awe that I undertook to build an amp around this classic output tube -- a real world treasure. I decided to keep things extremely simple and easy on the tubes, going from a triode connected pentode first stage to resistance load, coupling, grid choke, and then to output stage. The grid choke was also used to take good care of the WE205D tubes. Output is about 1W. (For my cloistered existence, 1W is more than I need.)

"I did try to use excellent quality parts, such as the Noguchi Transformer "Finemet" (nanocrystalline) core OPT and choke, a stainless steel chassis, KM capacitors (cathode bypass), Vitamin Q (coupling), Dale resistors, WE capacitors (output stage cathode) Western Electric wires, etc. Back when I built this amp, I still had a job and some spending money.

"I played around with voltage amplification tubes in all stages, trying out the 6SJ7, 5693, WE717A, WE409A, etc., but it was the WE409A's overwhelming power of musical expression that surprised me. The sound of the recording venue is completely different from other tubes. I found this difference to be amazing. Ever since then I have been in love with the WE409A.

"I like the pure, tight bass and a superior vibrant midrange of push-pull amplifiers, but the unique tone of this single-ended amplifier, with its smooth harmonies and silky touch seem to grow on me as the years go by. And the years are going by . . . "

-- Chris
 

cdwitmer

Member
2003-04-17 1:10 am
Tokyo
Ask and ye shall receive . . .

[IMGDEAD]https://shinshu.fm/MHz/44.04/images/2DLMd8br.jpg[/IMGDEAD]

Follow-up comments from my friend:

"Some people say that if you're going to use the WE205D, you might as well use the 45. I'm 100% in agreement with that. The WE205D costs 10x-20x what you would pay for the 45, but the sound character is almost the same. The 45 is a wonderful tube and a great value. (Speaking of RCA here.)

"Another apparent alternative is the TJ FullMusic 205D, in a new shape without the pointy head. The pins too have been changed to the same easier to use UX type as found on the 2A3. When the power comes on, the filament lights up attractively through the mesh plate. It's a delight to the eyes . . . but not to the ears. It might be DullMusic or NullMusic, but "FullMusic" is a misnomer, unfortunately.

"The WE205D's pins are unusual, and the heater voltage is also unique at 4.5V. And on top of that it is expensive, but its sound is just ever so slightly harder than that of the 45 -- and a wee bit more refined, in my opinion."

L to R: RCA-45, TJ FullMusic 205D, WE205D
[IMGDEAD]https://shinshu.fm/MHz/44.04/images/Z6F9GJFY.jpg[/IMGDEAD]

The TJ FullMusic 205D has a beautiful mesh plate
[IMGDEAD]https://shinshu.fm/MHz/44.04/images/DWao5iTB.jpg[/IMGDEAD]

Note the TJ FullMusic 205D's more conventional UX 4-pin configuration
[IMGDEAD]https://shinshu.fm/MHz/44.04/images/yME8jrKT.jpg[/IMGDEAD]
 

kmaier

Member
2007-07-12 1:42 am
Chris, thanks for the schematic post and the feedback on the TJ 205D, etc. It would seem many people have the opinion that the RCA 45 is preferred variant... while I'm not going to disagree, I will point out that many branded 45s out there are not manufactured by the manufacturer labeled on the base, RCA included. The pair of 45s in the pic appear to have different internal construction, and from what I can see, neither is a "real" RCA made 45. I actually have a NOS pair of RCA branded 45 triodes in the original boxes with matching date codes on the base. One is RCA made and the other is not. Note that this was common practice between manufacturers to re-label tubes... simple economics of setting up the manufacturing line for a particular tube type.

I'm lucky enough to have pretty large collection of 45s... many different brands, mostly ST-glass (which I prefer) and some balloon types. I'll try and get some decent pics of the internals and post them with some descriptions. Granted, I do not consider myself an expert on the 45, but I probably have more of them to experiment with than most people. I can show at least 5 different internal constructions in ST glass and 2 internal constructions in Balloon glass that are different. I also find there are some sonic differences between them. As for my personal (current) favorite, I'll put that in the post too.

Regards, KM
 

cdwitmer

Member
2003-04-17 1:10 am
Tokyo
How about that . . . I guess tube amps are like potato chips, you can't have only one. Now my friend is ready to start on his next project, 50 watts single ended out of the RCA 805 . . . here are a good 10+ kilograms of transformers to get him started --

[IMGDEAD]https://shinshu.fm/MHz/44.04/images/C9d3l03x.jpg[/IMGDEAD]

I'm glad I can vicariously enjoy all this through him, because my wife would have me living in the dog house if I started building tube amps . . .

-- Chris
 

limono

Member
2007-03-02 8:04 pm
I built Yamamoto inspired S-08 pair of monoblocks .No as pretty as the one pictured but also using penthodes 717A as an input stage .While I have RCA 45s and other brands too VT-52 is just head and shoulder above 45 even with filament DC supply .
I should not post that but the prices are so inflated already that I can't afford them anyway :
Regards, L
 
I should not post that but the prices are so inflated already that I can't afford them anyway

That reminds me of why I stopped subscribing to Vacuum Tube Valley. One page details the history of the 45 tube and the last paragraph says they recommend people conserve to keep the supply around as long as possible. The next page is a project using eight 45s!
 

kmaier

Member
2007-07-12 1:42 am
Yes, I tend to agree that there are still 45s around, how many are all that great is a matter of opinion and personal subjectivity. As for running the filament, I prefer AC, not DC... and I think a DC filament will run them down quicker. For me, this means I reject a good percentage of the ones I have based on extensive testing and matching of pairs.

When I fit tubes for an amplifier I match in complete sets, not just the 45s, but the input/drivers and rectifiers as well. To get the best possible sound from a zero-feedback design, you need to spec groups of tubes for the amplifier(s). I match in complete sets for gain, noise, distortion and voltage before any listening is attempted. Testing for mechanical noise is also crucial.... can't tell you how many tubes I've found to be so sensitive to mechanical vibration (including the music itself) to make them useless in an amplifier.

While I fully realize 2 watts is only 2 watts, the requirement for ultra high sensitivity speakers (104dB) and a lower limit of 200Hz is also a matter of opinion (as you pointed out). For the 45 designs I've completed... I consider 50Hz the lower useful limit but ensure proper operation down another octave. I also like to see a flat response to at least 40KHz with 50KHz being the preferred 1db down point.

Also, the more sensitive your speakers are, the more critical the output noise of the amplifier becomes. This defines the useful dynamic range of the system in addition to having hum and noise as intermod distortion with all low level detail. A signal to noise ratio of 80dB (referenced to 1-watt) is a bare minimum... and with high sensitivity speakers, it's really not enough.

So far, I'm pretty happy using my 45 amps to drive the Feastrex D5nf. Yes, there is a definite upper SPL limit, but depending on the room, personal levels, etc. it can be more than adequate, but you're not going to get the last 2 octaves in full glory regardless... limits are still, well... limits.

Regards, KM
 

limono

Member
2007-03-02 8:04 pm
Thank You
Such a nice post , I don't have resources nor dedication to go to that extent of matching tubes and checking technical performance .I do use separate filament transformer with electrostatic shield and AC heating also PT and choke are somewhat separated from chassis and tube sockets (ordinary) use rubber grommets. The hum although noticeable when close to the driver is not an issue .I'd rather worry of those HF noises . At present I use Lowther DX4 in 204 Azura horn and even if I will probably tear the setup apart in the near future to address some inherent mid-bass , top end weaknesses it sounds really sweet.
Regards, L
 
Aarghs from the abyss: WE 211E ecstasy & agony

The owner of the amplifier and tubes shown above is now working part-time for Feastrex. All the people connected with Feastrex are big fans of tube amplifiers and at any given time there always seems to be at least one interesting amplifier project going on, albeit at the personal enjoyment level rather than as part of their business per se. I have a backlog of "Feastrex-related, tube-related" items that I'll try to add to this thread as time permits.

Some of these items will also be peripherally related to Feastrex speakers, such as what I'm going to write today -- that in some instances simply changing a certain type of tube from one brand to another could change the way the speakers are driven, to the degree that one feels a loudspeaker enclosure design modification might be in order to accommodate it. (I have not confirmed this myself and am in no position to defend that last statement -- I'm simply passing on what another person has written about his experience.)

Anyway, the experience has proven rather mind-blowing, because nobody who has heard this tube would have expected it to make such a huge difference. The tube is the original Western Electric 211E.

The "ecstasy" is in the sound that these tubes produce -- beyond compare to any other 211 type tube that these people have encountered. The "agony" is their high price and the difficulty of maintaining a reliable supply of them today.

oqYXDXSg.jpg

GldncLuU.jpg


One of the monobloc amplifiers to which the above tubes have been added (the tube shown is of a different make):
oJSsGyjq.jpg

L8s0DL2o.jpg


Here are some comments from the amplifier's owner:

"Until we hooked up this amplifier, we thought the enclosure that we had designed for the prototype Feastrex field coil driver housed in it was just about perfect. We have found that when the driver and enclosure are properly matched to each other, problems arising from enclosure resonation seem to simply disappear. It's as if all the energy inside is coming out the port effortlessly and there is no residual energy to excite the enclosure itself. But when we hooked up this amplifier, the previously well-behaved enclosure started to act up. There was clearly a lot more energy to be dealt with here, and it really drove home to me the fact that in some cases at least it is not enough to think of the driver and enclosure as 'the loudspeaker system'; rather, for best results the driver, enclosure, and amplifier need to be all considered together. That means the choice of amplifier could have implications for the enclosure design. In some cases, to get truly optimum results, one might be forced to do several cut-and-try variations on a speaker where the differences are measured in millimeters. This experience has left a deep impression on me, because we have tried this combination of driver and enclosure with a wide range of amplifiers, and gotten basically similar (excellent) results with all of them, until this one came along. This amplifier seems to clearly have the potential to sound better that all the others, but it may very well mean modifying the enclosure in order to be able to take advantage of it.

"The other thing that comes to mind is that a good fullrange driver loudspeaker can be like an 'audio stethoscope' that really reveals everything in your system. A powerful tool for music reproduction is also a powerful tool for revealing every quirk and change in your system. Living with such a loudspeaker may not always be easy, but that's part of the price of admission to a world of better music reproduction.

"Anyway, this WE 211E is really amazing, and the WE 331A that came along with it perhaps even more so. These great old tubes from half or three-quarters of a century ago -- if we can put a man on the moon, why can't we produce modern tubes that are able to equal these?"

http://museum.ehost-services112.com/211e.html
http://museum.ehost-services112.com/we331a.html

-- Chris