ARC Reference 5 SE with Mcintosh MC1.2KW amps ? ....

joeinid

joeinid

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The Ref 5 SE's output impedance is 600 ohms balanced and the MC1.2KW's input impedance is 10,000 Ohms. Has anyone either heard this combo, or think it would be okay?
 
Joe-It should be okay. The input impedance of the McIntosh amps are greater than 10x the output impedance of the Ref 5SE.
 
Mark,

Thank you so much. I thought so, but wanted a more experienced/professional opinion.
 
I wouldn't try the 5SE with the Mc amps. The 600 is nominal reading at 1KHz. It does vary across the freq spectrum and can get up into 1.5Kohms at some point I believe (have to look it up in Stereophile measurement). A reviewer of the Ref 5SE on Soundstage.com (even though the review was not very impressively done) did complain about wooly bass when he paired up the 5SE with MC501s. If you can demo before pulling the trigger fine but I would say stay away if trying out blind. If you look at all of ARC amps they all have minimum input impedance of 100Kohms. I am guessing that the Mc tube pres have much lower output impedance than ARC's to make sure they are compatible with their amps.

Here is link to the Soundstage.com review mentioning wooly bass with MC501s: SoundStage! Hi-Fi | SoundStageHiFi.com - Audio Research Reference 5 SE Preamplifier

and this character was clearly on display no matter what power amps I plugged it into, provided the amp’s input impedance was greater than 20k ohms, balanced. Otherwise, the bass was ill-defined, recessed, and woolly -- as I found when I partnered the Ref 5 SE with the McIntosh Labs MC501 monoblocks, which have an input impedance of 20k ohms, balanced.
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From Stereophile measurement section:

At high and middle frequencies the Ref 5's output impedance was slightly higher than specified, at 628 rather than 600 ohms balanced and 322 rather than 300 ohms unbalanced. However, at 20Hz the impedance rose to 1447 ohms balanced and 637 ohms unbalanced, which, with an extremely low load impedance of 600 ohms, rolls off the low bass by 3dB at 15Hz (fig.1, cyan and magenta traces).
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Ok so output impedance goes up to 1447 at 20Hz so theoretically you may hear some bass frequency attenuation but not sure with the MC1.2KWs and the 3dB roll off in the bass at 15Hz was into a 600ohm load not 10Kohm load like the MC1.2KW but there is enough here to suggest you want to hear them together before pulling the trigger.

Just my 2c Joe.
 
mep said:
Joe-It should be okay. The input impedance of the McIntosh amps are greater than 10x the output impedance of the Ref 5SE.
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Mark,
The oversimplified generic "thumb rule" of the x10 should not be applied to preamplifiers that use capacitor coupling in the output, specially in the case of tube preamplifiers. ARC advises to use a minimal input impedance of 20 Kohm, but I know of people who used the REF5 Se with lower input impedance amplifiers with great success in their systems. Factors such as of the gain of the amplifier and the sensitivity speakers will also affect this matching, the only reliable way of knowing is trying.

Edit - I see now that while I was typing there was another post from cmalak on the subject. We fully agree on this one!
 
microstrip said:
Mark,
The oversimplified generic "thumb rule" of the x10 should not be applied to preamplifiers that use capacitor coupling in the output, specially in the case of tube preamplifiers. ARC advises to use a minimal input impedance of 20 Kohm, but I know of people who used the REF5 Se with lower input impedance amplifiers with great success in their systems. Factors such as of the gain of the amplifier and the sensitivity speakers will also affect this matching, the only reliable way of knowing is trying.
Click to expand...

+100 :thumbsup:

Joe...in your case trying does not mean buying and then trying, it means demoing before buying...:D (at least that is my advice)
 
microstrip said:
Mark,
The oversimplified generic "thumb rule" of the x10 should not be applied to preamplifiers that use capacitor coupling in the output, specially in the case of tube preamplifiers. ARC advises to use a minimal input impedance of 20 Kohm, but I know of people who used the REF5 Se with lower input impedance amplifiers with great success in their systems. Factors such as of the gain of the amplifier and the sensitivity speakers will also affect this matching, the only reliable way of knowing is trying.

Edit - I see now that while I was typing there was another post from cmalak on the subject. We fully agree on this one!
Click to expand...

Notice I said "should be okay." ;) Unless you are using a preamp from a manufacturer that was designed to go with an amp from the same manufacturer, there could always be issues. I no longer care to mix and match a preamp from one manufacturer with an amplifier from another manufacturer. I wouldn't hesitate to use the Krell preamps I used to own with damn near any amp though. The KBL had an output impedance of .5 ohms and should drive any amplifier known to man. The KRC-HR has an output impedance of 5 ohms which is still incredibly low. Did I mention they both have a great bottom end? I was able to achieve a better match with a much better bottom end with a certain tube amplifier than I could with the tube preamp that was designed to go with the amplifier which violates my current rules for purchasing gear.
 
mep said:
Notice I said "should be okay." ;) Unless you are using a preamp from a manufacturer that was designed to go with an amp from the same manufacturer, there could always be issues. I no longer care to mix and match a preamp from one manufacturer with an amplifier from another manufacturer. I wouldn't hesitate to use the Krell preamps I used to own with damn near any amp though. The KBL had an output impedance of .5 ohms and should drive any amplifier known to man. The KRC-HR has an output impedance of 5 ohms which is still incredibly low. Did I mention they both have a great bottom end? I was able to achieve a better match with a much better bottom end with a certain tube amplifier than I could with the tube preamp that was designed to go with the amplifier which violates my current rules for purchasing gear.
Click to expand...

Some people will tell us that an extremely low output impedance is not a good design practice. Most designers fit resistors in series with the output, as the intrinsic low impedance of the active circuit is too low. Krell KRC HR avoided these resistors - it is why in the Stereophile review there was a 10% mismatch between left and right output impedance parameters.

BTW, I fully agree with you - in principle we should not mix and match. But sometimes we must do it, as we can not always start from a full reset.
 
I used to use the ref5se with MC501's and the results was just ok. I recently bought a pair of ARC ref250's and the difference was staggering. I never thought that the synergy was that far off with the 501's. After having both amps in my system, I would agree with cmalak. In the end.it's all about the synergy of the gear.
 
Rscotth said:
I used to use the ref5se with MC501's and the results was just ok. I recently bought a pair of ARC ref250's and the difference was staggering. I never thought that the synergy was that far off with the 501's. After having both amps in my system, I would agree with cmalak. In the end.it's all about the synergy of the gear.
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Do the 501s every sound anything better than "just OK" regardless of which preamp is used? :rolleyes:
 
I've used the 501's with a C2300 and with the MX150 with much better results than the ref5se. It's been my experience that the ref5se sounds best with ARC power. I can't put my finger on it, but once I switched the 501's to the ref250's, the entire sound improved in every aspect. I know it was going from SS to tubes, but I believe that the impedance has to be taken into account for the synergy of the 2 components to play well together. YMMV.
 
I know my CJ GAT will be superb with everything but sometimes I wish for a balanced preamp. Not that I think it would be any better but because sometimes I'd like to put some distance between the front end and the amps.
 
That would be an obvious choice but sometimes I like to mix it up. C500 is under consideration. I need to hear the MC1.2KW's again anyway, just thinking out loud.


Paul said:
Why not the C1000T ? I always find the McIntosh sounds best with their own brother :)
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joeinid said:
That would be an obvious choice but sometimes I like to mix it up. C500 is under consideration. I need to hear the MC1.2KW's again anyway, just thinking out loud.
Click to expand...
Joe, Maybe send an email to Rick would help. The Master of McIntosh :)

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Paul,

I have emailed him. That's why I want the MC2KW's and be done. I've wanted them forever.
 
microstrip said:
Mark,
The oversimplified generic "thumb rule" of the x10 should not be applied to preamplifiers that use capacitor coupling in the output, specially in the case of tube preamplifiers. ARC advises to use a minimal input impedance of 20 Kohm, but I know of people who used the REF5 Se with lower input impedance amplifiers with great success in their systems. Factors such as of the gain of the amplifier and the sensitivity speakers will also affect this matching, the only reliable way of knowing is trying.

Edit - I see now that while I was typing there was another post from cmalak on the subject. We fully agree on this one!
Click to expand...

I also think another issue that's not being considered is the IC length. As the preamp's output impedance increases, the length of cable becomes more important. At least for SE apps.
 
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