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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
s23chang
619 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.
sojs OP
13 posts
 
S23chang:
I could not tell the sonic changes of replacing the original caps with Dynamicaps, because I have changed lots of other parts together at the same time. I know I should have modded one part at a time. The original caps are yellow colored Rel-Caps. I have also tried Auricaps at this position, and found it sounded too forward and loose. Dynamicaps are more neutral.

I had 2 different versions of Counterpoint SA-5 preamps. One was older model with yellow Rel-Caps, and the other used white Wondercaps. The one with Rel-Caps sound significantly better. It sounded very delicate, warm, detailed, and very musical. I was disapointed with the Wondercap version (dry and transistor like sound).
s23chang
619 posts
 
Hi Steve, thx for your reply.
Yes. Both the RM-4 and the Counterpoint SA-2 I have are the yellow Rel-Caps. Exactly like what you described.
Rm-4 had additional by-pass cap to enhance or clean up high frequency response.
I guess the SS power supply is quicker and more dynamic than the tube version in SA-2.
dwbwbw
1 posts
 
I bought a RM 4 some time ago without a manual. Could someone please advise me on how to use it properly.

On the OUTPUT Gain terminals, my guess is that for each channel (say the left channel), one connects a resistor the signal (the center) to the ground (the outer) to achieve the gain as shown on the back of the RM-4. This is to be repeated for the other channel.
The gain would then be realized at the "Attenuated Output" terminals. The "Direct OUtput" terminals are for output NOT affected by the insertion of the resistors (i.e. no gain).

On the INPUT Source load, my guess is that it is for impedance matching with the cartridge. Thus, one would put a say 47 kohm between the center and ground for each channel.

I used the above setup (with about 6 db gain) and used it as a head amp, connecting to the phono input of an Audio Research SP-11 Mk2 pre-amp. It sounded really good, but it tripped the power amp (solid state Krell) after 2-3 minutes of playing. The SP-11 was not tripped.

My questions are (1) is the setup correct? (2) is the RM-4 NOT meant to be used as a head-amp?

Would someone sell me a copy of the manual?

Many thanks.

Tom
s23chang
619 posts
 
I have the SP-11 MK II and I also tried to test the RM-4 for the MC cartridge. The gain is too high that it doesn't work well with SP-11 unless you use super low output cartridge like .2mV. Make sure you have subsonic filter turn on when you use a lot of gain.
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