Thank you so much for your write up of the Rhumba 1.2 Extreme. I've always been curious about these preamps. I may have to hear one in my own system. :)
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You are welcome as it was a pleasure to write about my
experience with Backert Labs and their products, both of
which I consider superior in every aspect.
As for the tubes I have 4 different pairs and another on
the way. All tested at NOS levels.
#1 - 1955 RCA 3 mica black plate D getter 5814A, way too
lush. May be good in a bright system but not my thing.
#2 - 1959 RFT long plate halo getter mil spec12AU7, it is
basically a Phillips/Amperex made in France and sounds
like it. Nice tube, does everything well but doesn't
distinguish itself. I'm on the fence with this one.
#3 - 1952 Raytheon 2 mica, short black plate, D getter, 5814
, This is "The Bomb". Great extension top and bottom.
The mids are rich and meaty. Extremely detailed and
focused throughout. My only criticism is when driven
extremely hard the top end gets a bit grainy but we
are talking very, very loud, not where I listen. I liked
these so much That I bought another pair from the
same batch while I could.
#4 - 1958 CBS/Hytron short black plate, 2 mica, D getter 5814.
I can see why these are well thought of. A bit more
polite than the Raytheons. Better on a bad recording,
not as good on a good recording. They are an easier
listen but ultimately not as satisfying to me. A definite
keeper to me.
#5 - ON THE WAY, 1958 Amperex marked Beckman 7316
long plate, D foil getter CT0 ^8L. We will see if all the
hype is deserved.
Look up Mike Bower on Ebay, extremely knowledgeable
and honest on 12AU7, 5814, 6189's
" I was going to highlight some of the differences between the Rhumba
and the Rhumba Extreme but this is already much longer than I had
intended and I felt compelled to write it. I can do a follow up post if anyone wishes on what separates the two."
Woody, can you share more about the differences between the base 1.2 and the Extreme?
While repairing and modding tube equipment for years, Bob
has developed two mods/circuits, one that he incorporates into
all three preamps and the second which is included in the top
The first is the "Green Force" power supply which
uses a series of film caps in place of a large group of
electrolytic caps, this is patented. I initially had reservations
about how it would do on the bottom end, after hearing it I can't
believe how much more of a deep and focused bass I have.
The second is the "Auto Bias" tube circuit which does what
its name implies whether your tubes measure at NOS levels,
getting near minimum or anywhere in between. Now to the
Rhumba 1.2 MSRP $3500.00 usd
#1 - Polystyrene caps in the "Green Force"
#2 - REL PPT Theta output caps
#3 - J/J 12AU7 tubes
#4 - "Auto Bias" circuit NOT included
#5 - Polypropylene caps in "Green Force" regulator circuit
#6 - Rubber feet
#7 - Sound dampening applied inside of top cover and sides
as well as the outside of the "Tube Gondola", more on
Rhumba 1.2 Extreme MSRP $5500.00 usd
#1 - Upgraded polystyrene and Mundorfs in the "Green Force"
#2 - Mundorf 2015 MCap Supreme EVO Silver, Gold, Oil outputs
#3 - Psvane 12AU7 tubes
#4 - "Auto Bias" circuit IS included
#5 - Upgraded polypropylene caps in "Green Force" regulator
#6 - Four, Edensound "Terracone" footers
#7 - Premium Dynamat applied in same manner as #7 above
A few final thoughts:
#1 - The "Tube Gondola" is accessible via a clear plexiglass
cover on the topcover secured with two thumb screws.
It is a gondola shaped well with raised sides so none of
the innards are visible except the two ceramic sockets
and the axle connecting the front mounted input selector
knob to the actual switch which is toward the rear which
passes through it between the sockets. The Furutech
goldplated IEC with integral fuseholder (both models)
is on the back panel so any adjustments or changes
can be done externally - well thought out and implemented.
#2 - Apparently some of the Rhumba 1.1's were slightly noisy
and this is no longer an issue as circuits were tweaked,
dampening was added as well as strategically placed
gasketing (Terracone feet on the Extreme). With the volume
turned all the way up and tapping anywhere on the case
you hear NOTHING out of the speakers, it is completely
#3 - This is a tube preamp so it's going to be at least warm if not
hot right? WRONG, in my 72 f room with my Snap On
infrared thermometer it measures 82 f while my Wadia 15i
measures 80.5 f and my Genesis Digital Lens is 84.3 f
#4 - After spending 2 months with the Extreme I'm completely
satisfied with the added performance and enjoyment that
it has afforded me. Too often in this hobby you spend a lot
to get a little. I spent a lot, got a lot and I'd do it again in a
Happy listening, Woody
I did not compare head to head. I can say
that when I first heard the base Rhumba 1.2
in Bob's workshop system I was very
impressed and that is what got me going on this.
I only auditioned the Extreme in my system as
by the time I added the "auto bias" circuit,
upgraded caps in the "green force" and outputs,
and the Edensound terracones to the price of the
base model it just made sense to spring for the