WE91A 300B Stereo
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
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:
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
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.
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
Soviet's legacy. Check out the love of my tube life.
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?
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