300B - first SET experience

John Frum

Secret Society Member
I’ve been enjoying the hell out of my Almarro A205A MK2, and have had no plans to upgrade.

Until this amp fell into my lap:

CEB1E7ED-8CF1-4823-8CE0-32AAC85CB85A.jpeg
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I haven’t even hooked it up yet. Hand-made in Japan sometime in the last ten years, and it’s supposed to be based on a Western Electric design. Tubes are Genelex Gold Lion 300B with 8 hours and Svetlana 10(?)12C, with GE 5U4GB rectifier. OPTs are Tango U-808, filament is Triad, and PT Is Luxman. Liberal use of vintage components - this is how I would build stuff if I had time, money, know-how, or talent. Top plate is sagging under PT, though.

Do any of you recognize this amp, or have any idea who built it? Thoughts, both on this amp and on diving into SET-land? Do you think I’ll need a preamp?

I’ll be powering Zenith 49CZ802 and, when the cabinets are finished, Altec 604-8G.

I’m floored, and had’t expected to make this step for a long time, if ever.
 

Attachments

It looks a bit like a WE Model 91.

Some thoughts: This does indeed look like it was handmade in Japan within the last 20 years or so. It appears to have good but not top of the line parts quality. The Tango U808s are not their best effort. I recall a 300B transformer shootout in Sound Practices that compared the Tango U808 with a potted Tango, two Magnequest models, and I think an Electraprint. I recall the reviewer (who could have been Herb Reichert) describing the sound as “wiry”, and not in a good way. I think Joe Esmilla also did a comparison of the U808 with the similar looking Hashimoto H203S, preferring the latter. Another concern is the Luxman power transformer. Are you sure that the primary is 120v and not 100v?
 

gable

Senior Member
Yes, first order of business is to check the PT primaries are 120v.

Looks like a nicely built amp, and a nice low parts count as mentioned. Could be a great playground to try some upgrades, and diy mods.

Congrats!
 

je2a3

Junior Member
+ 2 on the checking the primary connections! :)

I’ve been enjoying the hell out of my Almarro A205A MK2, and have had no plans to upgrade.

Until this amp fell into my lap:

View attachment 24999
View attachment 25000

I haven’t even hooked it up yet. Hand-made in Japan sometime in the last ten years, and it’s supposed to be based on a Western Electric design. Tubes are Genelex Gold Lion 300B with 8 hours and Svetlana 10(?)12C, with GE 5U4GB rectifier. OPTs are Tango U-808, filament is Triad, and PT Is Luxman. Liberal use of vintage components - this is how I would build stuff if I had time, money, know-how, or talent. Top plate is sagging under PT, though.

Do any of you recognize this amp, or have any idea who built it? Thoughts, both on this amp and on diving into SET-land? Do you think I’ll need a preamp?

I’ll be powering Zenith 49CZ802 and, when the cabinets are finished, Altec 604-8G.

I’m floored, and had’t expected to make this step for a long time, if ever.
Very nice amp, I like that kind of build!

Congrats!

It looks a bit like a WE Model 91.

Some thoughts: This does indeed look like it was handmade in Japan within the last 20 years or so. It appears to have good but not top of the line parts quality. The Tango U808s are not their best effort. I recall a 300B transformer shootout in Sound Practices that compared the Tango U808 with a potted Tango, two Magnequest models, and I think an Electraprint. I recall the reviewer (who could have been Herb Reichert) describing the sound as “wiry”, and not in a good way. I think Joe Esmilla also did a comparison of the U808 with the similar looking Hashimoto H203S, preferring the latter. Another concern is the Luxman power transformer. Are you sure that the primary is 120v and not 100v?
Wasn't the OPT comparison part of J-Rob's WE91 DIY article in SP issue 1? And yes, I preferred the Hashimoto H203S to the U808 when I compared them. But unlike J-Rob, I didn’t find it wiry sounding. It just so happened the H203S was better overall. The U808s are in the Radiotron SE2A3 amp I left behind in the attic. I miss it. 😞
 
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John Frum

Secret Society Member
Good call on the line voltage. It came with a nice 2000w Nissyo step down transformer and a new Dynakitparts.com PA-060 in case I ever want to swap out the PT.

I missed the @J-ROB shootout In SP, but caught the @je2a3 post tepidly comparing the U-808 to the Hashimoto. Safe to say there’s not too many English-language builders importing or using the U-808 these days. Oh well. Still excited. 😕
 

John Frum

Secret Society Member
My Cyrillic is rusty, but I believe the Svetlana preamp tubes are labeled 10Z12C - not entirely sure about that “Z”, as Google is not turning up anything.
 

je2a3

Junior Member
Good call on the line voltage. It came with a nice 2000w Nissyo step down transformer and a new Dynakitparts.com PA-060 in case I ever want to swap out the PT.

I missed the @J-ROB shootout In SP, but caught the @je2a3 post tepidly comparing the U-808 to the Hashimoto. Safe to say there’s not too many English-language builders importing or using the U-808 these days. Oh well. Still excited. 😕
I still believe the Tango U808 is a very fine OPT. I was just surprised it could be bettered. Besides, yours look like it also came from the original Hirata production line. Those are classics!
 

John Frum

Secret Society Member
That is a 310A equivalent with a different filament voltage.
Apparently the Cyrillic translates as 10J12S (or 10J12C?). Fooled me. From what I’m reading, it’s a drop-in for the 310A, with both needing 10V on filaments.
 

John Frum

Secret Society Member
I found the thread from 2016 where the person I got the amp from asks some questions. I hadn’t realized that he bought it new from the builder. Apparently he only put about 8 hours on the amp total.

The same guy (in Cincinnati) is looking to offload pairs of 414, GPA’d 802, 32B, utility 614, and @je2a3 crossover components from an aborted build, if any of y’all are looking for a speaker kit.
 

paulbottlehead

Active Member
You aren't going to need more gain with that amp, as the 91A is super sensitive. That circuit doesn't exactly have the flattest high frequency response, so you may find it worth it to triode strap the driver tube and tweak the circuit accordingly. I just helped a local fellow do this with his Angela 91A monoblocks and he was far happier in terms of gain and sound quality with the triode strapped driver.
 

John Frum

Secret Society Member
The 4A60 power transformer has a 110V tap on the primary, so you should be able to use it without a step down transformer.
I had the same thought. In the thread linked above, there was a lot of worry about “today’s line voltage”. I wonder if the situation is the same in Japan, and if the designer compensated.

My voltage stays 117V fairly consistently. I’m inclined to try the 110V taps on PT and FT at some point soon.
 

Thermionics

Post Whore In Training
I had the same thought. In the thread linked above, there was a lot of worry about “today’s line voltage”. I wonder if the situation is the same in Japan, and if the designer compensated.

My voltage stays 117V fairly consistently. I’m inclined to try the 110V taps on PT and FT at some point soon.
Pretty much all vintage US gear was designed for 110V, so if you are comfortable running an old Fisher or Eico, you should be fine.
 
I found the thread from 2016 where the person I got the amp from asks some questions. I hadn’t realized that he bought it new from the builder. Apparently he only put about 8 hours on the amp total.

The same guy (in Cincinnati) is looking to offload pairs of 414, GPA’d 802, 32B, utility 614, and @je2a3 crossover components from an aborted build, if any of y’all are looking for a speaker kit.
i might be interested in the 32b's if the price is right and it's cool to ship- can you please link me to where they are being offered for sale?
 
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