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RM-4 vs. MCP-33

I have recently purchased the Audio Research MCP-33 phono pre-pre amp, and compared it to my heavily modified Music Reference RM-4 pre-pre(Dynamicaps, Vashay nudes, Blackgate caps, fred diodes, premium power cord, etc) RM-4.
Here is the listening impression so far. My regular phono preamp Counterpoint SA-9 is out to Mike Elliott for upgrads, so I have borrowed my friend's Wright Sound WPP-200C for the audition.

My modified RM-4:
very transparant, lots of details without sounding bright, a little polite sounding, instruments a little thinner than the ARC unit, very smooth and silky, better micro dynamics

MCP-33:
I had to change the tubes to Amprerex Buggle Boy 6DJ8s since the stock Telefunkens sounds too thin and bright to me.
This unit has definitely more macro dynamics than the RM-4, so it is more suited for jazz and pop with rhythm. The RM-4 is more polite and silky smooth sounding, so classical music is good with the RM-4.
So, the MCP-33 has somewhat more apparant (macro) dynamics, a little more foward in the midrange, a little thicker sounding than the RM-4, while the RM-4 is more transparant, smoother and has better resolution and more detail. Occasionally, I felt a little hardness in the high frequency from MCP-33, but I need more listening before I can be sure. Guess the premium parts installed on the RM-4 has paid off (parts alone cost over $1000). The MCP-33 indeed sounds very good, and I am sure stock MCP-33 would outperform unmodified RM-4.

If I had to pick one of them, I would pick the RM-4 because the transparancy of RM-4 is quite addictive. Maybe I would change some parts on the MCP-33 and find out if it gets better.

Any thoughts on the comprasion?

My system is VPI TNT 5/JMW 12.5/Shelter 501 II/Modified Acoustat Servo OTL power amps/Acoustat model 8
Steve
sojs
sojs OP
13 posts
 
Don is right about Vishays. I have noticed the RM-4 to be extremely quite after installing Vishays (along with Caps).
My cartridge has about .4mv output, so tube hiss is not audible at normal listening level. So, my analog setup is deal quite at the listening position. It's pretty amazing with all tube head amp and phono preamp. With about .2mv output cartridge I would get slight tube hiss with regular NOS tubes. Low noise tubes will be dead quite, but it's hard to find NOS with low noise. Registers can be soldered to change input impedence. The RM-4 has about 30db of gain, which is a little too high for me. I am using SA-9 phono preamp volume control (providing only 0db to -15db range), and I have to use the lowest volume setting and it's not low enough for me.

I have compared the RM-4 to Counterpoint SA-2 about 15 years ago. Counterpoint sounded too thick and colored. It also emitted DC voltage when the AC line voltage changes slightly, which the factory could not fix and recommended usage of power conditioner. Even with the power conditioner my Apogee Duettas bass panal was moving badly.

I heard good things about the HK Citation One. Will try it if I have a chance.

I have ordered Bent audio TX-103 transformers and will post how it compares if you are interested.

Steve
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rauliruegas
13,090 posts
 
Dear Steve: Something that can do an improvement on your RM-4 is to change the Dynamicaps for V-caps. This ones can do a great difference ( for the better ) in the quality sound reproduction.

Regards and enjoy the music.
Raul.
sojs OP
13 posts
 
Raul:
I have thought about using V-Cap oil caps. The Teflon caps are too expensive in my application since the RM-4 uses 5.0uf value. A very reputable person in audio modification told me that V-cap teflon is 9 if Dynamicap is 10. So, I am holding off that mod for now.

Thanks,
Steve
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rauliruegas
13,090 posts
 
Dear Steve: Before I use the V-caps I try: Wima, Sonicaps, Aeon, Solen, MIT, Audicaps, Dynamicaps, Hovland, etcc.. on my speakers crossover.

For me, the V.caps hands down any of the others ones. I think that you have to try, not with the Teflon ones but the metallized prolypropylene ones. High recomended !!!!!

Regards and enjoy the music.
Raul.
s23chang
620 posts
 
The V-cap oil caps were not as preferred as the dynamicap by some reviewer on AA. He gave V-cap TFTFs 2 thumbs up. However, Teflon version doesn't come in 5 uf size from Chris's website. It will probably be surper expensive to make a teflon version that size.
Steve,
I wonder if you loose the warmness after replaced the original caps with Dynamicaps.
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