[jeffreybehr]

My newish trio of EM7 amps.  Left and right are the new EM7-12 monoamps; in the center is the EM7-5 which I converted from a '2.5.  I've replaced a few parts in them with higher-quality ones, but they sound basically the same as stock ones.  (Parts replacements almost never change the basic character of amps.)  The '5 drives the tweeters while the '12s drive the bass/midrange of my open-baffle, line-array speakers.  The system sure does sound good.  TY Roger for making such great-sounding equipment so affordable.

Full disclosure--Roger has turned into a friend over the last year or so, and he stayed at my house for almost a week last fall, but I still have to buy his stuff.

[Ericus Rex]

Sweeeeeeeeet!

The tops of the 12's look slightly raised.  Is that for ventilation or to fit larger trannies?

Sonically, are the 12's and the 5 much different?

[chadh]

When Roger upgraded my 2.5w version to a 5w version, he also had to raise the top.  He told me this was to accommodate the transformers, and that improved ventilation was simply a bonus.  I can only guess the same is true for the 12w monos.

Chad

[jeffreybehr]

Ericus, good observation.  Yes the 12s' covers are spaced off the chassis.  I use little self-adhesive cork pads that my framing-glass company uses.

The '12 is left; the '5 right.  Chad is correct; the '5's power transformer won't fit in an original '2.5 chassis; the newer chassis are a little taller (and thinner-walled, too, which I think is a great idea).  The power transformers in the '12s (and that in the '5) run quite hot, and Roger already had added 4 ventilation holes in the bottom of each end of the new chassis...

I felt that allowing a little more convection can't hurt anything, and later probably I'll add a few more holes in the bottom around the PT.

Also visible in the lower pic are a couple of my additions/changes.  The black-tape-topped can, top-center, is a 6/370VAC GE motorrun cap in parallel with the main-PS 2nd cap (which feeds the output transformer), and the upper-right cap is a 22/350 BlackGate replacing the same-value decoupling cap feeding the frontend tubes.  I think the amps sound a little cleaner/quicker, but I don't know--I never do before-and-after comparisons.   

What I do know is my system just gets better and better sounding, and that's what matters.

[Ericus Rex]

Would it be too much trouble to give us a full view of the guts of one of them?

[jeffreybehr]

Here are the 6 new vent holes...


...and here is the amp.


The most-obvious changes are the addition of the previously mentioned 6/370VAC motorrun bypass cap and the replacement of the decoupler with a BlackGate.  I've also replaced the cathode-bypass caps with BlackGates, the binding posts with one pair of the now-discontinued Edison Price MusicPosts (the output-transformer windings are soldered in parallel), the input-series resistor with a Vishay S102-type substitute, and the power inlet with a Furutech.  I've added an AudioNote silver-plated RCA input jack (with PRP load resistor) in an empty bindingpost hole.


I LOVE how easy this is to work on.

[Ericus Rex]

Wow...ultra simple and to the point.  What's the deal with 3 RCA plugs?  Are they crossovered inputs?

[jeffreybehr]

Ericus, "ultra simple and to the point" is exactly what I would call these amps; maybe that's why they sound so good, in my system at least.

The 3 RCA jacks are 2 originals plus my add-on.  The 2 originals include a full-range input, the upper this time instead of the lower as in the '2.5, and one with a hi-pass filter cap in series for a 100Hz filter point.  I left all of the original stuff there, disconnected, and added the AudioNote jack, PRP load resistor, and Vishay-S102-type series resistor, the latter without extension wires.  IOW, the jack is connected to the tube socket's tab by only the resistor and no other wire and extra solder joint.

[Ericus Rex]

Beautiful!  Thanks Jeffrey