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The "Herniator", WE91A 300B Stereo

JJ 300Bs, NOS 6C6, NOS Chatham 5R4

Sophia Electric's WE core OPTs

Built for Jouni S. of Finland

Completed on 2/16/09


"Hi Min, after some 3 weeks of use it's propably time to give some real feedback of your WE91 amp. I think it's rather useless and impossible actually give you a detailed head to head comparison against some other 300B amp. But, what I can say without the slightest hesitation, your amp got my Omega 8"XRSs' to fully blossom :) like no amp before (incl. some very respected and much more expensive commercial 300B hi-end amps). The presentation is powerful, smoooooth, clear, with beautiful (very natural) midrange and extended top end and  bass range with real impact and articulation, it's more like 2A3 or 45 amp in some regard. I've owned and auditioned lots of (different) amps, ss and tube and this definitely is one of my favourites if not the best. My highest recommendation, Min! You build me such a terrific amp, really! Best, Jouni."  - Jouni S. of Finland 



This is an interesting build for two reasons. First, it was built to use in Europe. Luckily, Hammond makes 378CXs (400-0-400 465 DC mA) that has universal primary taps. This is basically the same as 278CX with a 120VAC primary, except it's 0.5" bigger all around and weigh 17.5 lbs.  With a pair of those potted OPTs that weigh 12 lbs each, I couldn't name the amp anything else but "The Herniator".

Another reason why this build is interesting is that I am trying out a new pair of OPTs. I have been buying loads of Sophia Electric's time delay circuit from Washington Audio, who is an authorized dealer of Sophia Electric products. Their product line include delicate sounding carbon and mesh plate 300Bs and 2A3s. I got to learn that they sell OPTs that are customized for the WE91A circuit. William of Washington Audio was confident that those OPTs will beat anything that I have tried so far, including the Hashimotos. Naturally, I got curious. He provided the following info:

Sophia transformer
Core:  vintage Western Electric core(from WE chokes) and modern core mix,  
Wires: US made OFC
Natual fiber(cotton) made papers and no-mag stainless steel screws
Hermatically potted in a metal case.
Sound:  excellent high end extension, seductive mids and good bass.  Magical!  at least in my amps.
By comparison:  Lindual is too plain, Electroprint is not as information rich, not as extended, Tango is not close to overall, These three were not as expressive, not as musical as Sophia Electric transformers. 
Very close to real Western Electric sound.

Keep reading....


Fully potted Sophia Electric's WE-cored OPTs. These are around 12 lbs each.


All parts mounted, ready for wiring. The amp has a 17.5 lbs PT and a pair of 11 lbs OPTs. I get my workout for the day flipping these guys over a couple of times.


Here is the finished amp. I usually take my amps outside for pictures, but it's been raining in Nor Cal non-stop for last four days. I really detest my camera (a cheap Samsung with the crappiest flash light) and all these pictures of the amp doesn't do any justice.


Beats me, but the wiring in this amp looks more complicated than my other builds. It's dead quiet, has no oscillation, and plays music beautifully. That's all I care about, so whatever.


Soviet's legacy. Check out the love of my tube life. Got oil?


Notice the Solen cap as the first cap then the discrete second caps. I wanted to be able to fine tune the B+ by using non-electrolytic right off the rectifier. I am also using a choke per channel, so I thought discrete caps might be a good idea to keep things separated. I usually use a 10uF 500VDC Sprague Atom lytic for the first cap then a multi-section cap for the second cap.


Time for action! Check out my super duper hi fi Klipsch Forte speakers. A $350 Craigslist find. They are efficient (99 dB/W/m), reasonably sized, has a decent WAF (wife acceptance factor), has horns, and does a great disappearing act, thanks to the passive radiator in the back. Great for SET nuts like me. It does its job. I might sell these and upgrade to a pair of Klipschorns one of these days, so please buy more amps from me!


The aftermath of 300B amps...I seriously know where everything is in this organized mess.

Ok, here is my verdict. Those OPTs do actually sound very nice. I mean VERY nice. I honestly can't tell if these are siginificantly better sounding than the Hashimotos, if at all, since I don't have an amp with Hashimoto OPTs to make the comparison. But I get the same goosebumps when I hear these WE-core OPTs as I did when I auditioned Paul's amps. It's all there- excellent high end extension, seductive mids and good bass.  Most importantly, they are very natural sounding and musical. I am spinning some Jazz records as I am typing this and I can't remember for how long the amp has been on. It's been playing music for hours, but I didn't notice it because the sound is so comfortable. Hope I remember to turn it off before going to bed!  Will I recommend these for future builds? Sure. After all, shouldn't a WE91A deserve WE sounding OPTs?

I don't know how many people will actually end up reading whatever nonsense I am writing here, but if you do, please let me remind you that what I write here is purely based on my personal observations, which are very subjective. It's my hope that what I add here will serve as a useful reference should you find yourself shopping for parts to build 300B amps. -Min

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