Question about input impedance and input sensitivity.

That's interesting the points you raise #3 and #4 which my MX110 is exhibiting neither of those maladies. Volume control tracking in fact is excellent throughout the range as verified on the MPI 4, whereas on the MX113, tracking is only accurate in the 12:00 - 3:00 range. (Maybe I just got lucky - :dunno:)

- I've never observed any noises associated with the illumination of MPX Stereo on my example either. In fact I've always found the MX110 relatively free of crosstalk issues and interference in general.

- I cannot comment on the flatness of the tone controls except to say 12:00 seems to work fine to my ears..

Otherwise, I have no major criticism of the MX110's overall performance but I will also add that MX110s that are still essentially original which only received bare minimum servicing to keep operational over the years - it's unlikely to be performing to spec and won't be long before a full fledged restoration will be needed. I still appreciate the MX110 for its classic beauty but much like a classic car, it definitely needs a fair amount of attention! :)

.

All I can say is what I found on my 110. However....it’s entirely possible considering the complexity of these units, normal production variation and running production changes that unit to unit variation is greater than we’ve come to expect from today’s highly automated assy. So luck may indeed be a factor. And as the old proverb goes, “I’d rather be lucky than good any day”.

Regarding stereo light noise, I found it resulted from AC rectification noise generated in the light driver transistor. Fixed it using shielded wiring and basic reroute. This was annoying to me because I typically use high eff speakers with the 110 so faint noise is exaggerated. Ultimately I’d like to redo that entire circuit but not high on list of priorities.
 
Regarding stereo light noise, I found it resulted from AC rectification noise generated in the light driver transistor. Fixed it using shielded wiring and basic reroute. This was annoying to me because I typically use high eff speakers with the 110 so faint noise is exaggerated. Ultimately I’d like to redo that entire circuit but not high on list of priorities.

As I do a lot of FM listening with the MX110, that would bug the bejesus out of me too. Selectivity is only so-so with the MX110; much better with the MX113 I've noticed. (Of course the MR80 trounces either! :D) I do consider 110's phono section superb.

To be frank, I'd probably have gotten out of the MX110 long ago were it not for its physical appearance which I love dearly. A major refurbishment back in 2014 kept it going for a good three years but needed to go back to Audio Classics 3 times in the last year alone. This was partially my fault as I was endeavoring to keep as much of the unit original as possible but that soon becomes a losing battle if you have any aspirations of using one of these things daily.

After all the money I've spent, I probably have one of the most thoroughly gone-through, up-to-spec MX110s on the planet. Much like a beautiful woman, looks are expensive!
 
The loudness feature on vintage gear was never intended to be hi-fi. Boomy is normal. It was designed to boost low end for listening at low levels (for example during the evening in an apartment).

What amp did you mate the MX110 with?
Understood. However, the unit shouldn't need the Loudness engaged so that it doesn't sound lean. As the MX110 was my only serious preamplifier for several years, I ran it with every power amp that I owned - MC240, MC275, MC2505, MC2300, MC2500, etc. I bought a C29 for a 2nd system in the den and then it quickly displaced the MX110.

Over the years, I've had something like a dozen of them - several in near mint condition. The MX110 is a collectors' piece no doubt, but as a serious HiFi preamp, it falls short.
 
Understood. However, the unit shouldn't need the Loudness engaged so that it doesn't sound lean. As the MX110 was my only serious preamplifier for several years, I ran it with every power amp that I owned - MC240, MC275, MC2505, MC2300, MC2500, etc. I bought a C29 for a 2nd system in the den and then it quickly displaced the MX110.

Over the years, I've had something like a dozen of them - several in near mint condition. The MX110 is a collectors' piece no doubt, but as a serious HiFi preamp, it falls short.

Interesting. Were all your MX110's restored (power supply and signal path electrolytics replaced)? Were tubes to to spec? Odd that they all sounded anemic.
 
I also felt bass had been lacking somewhat in the MX110 but seems to have been improved considerably after the last remaining original caps were replaced. Rarely use the loudness switch now.
 
I also felt bass had been lacking somewhat in the MX110 but seems to have been improved considerably after the last remaining original caps were replaced. Rarely use the loudness switch now.

Which caps being replaced improved the bass? Power supply caps or audio path caps?
 
Found this additional info on the Steve Hoffman forums. A member states that Terry said: "you can go down to 1000 ohms and there will be no mismatch."

OldVet said:
I have a question. I am new to this forum, I have read that the input impedance of the power amp connected to a MX-110 should not be less than 100kohms. Someone said there would be "deleterious effects". I have a Emotiva XPA-2 with an input impedance of 33k ohms. So I wouldn't be able to use it with the MX-110, right?

OldVet said:
I also read another post where the poster said that anything over 10k ohms would be no problem, would like some feedback on that. I think it came from Terry Dewickt or somebody like that on another forum.

OldVet said:
I talked Terry today and he said using my power amp is no problem, he said you can go down to 1000 ohms and there will be no mismatch. My amp is 26000 ohms so at least I can use it with the MX110 until I can afford a mc240.
 
It is often referred to in this and other forums the "synergism" of the parts of a system working together, creating a sum that seems greater than it's parts. Conversely often times when units don't sound good together the lack of synergy is blamed.

Vintage gear designed 5 or 6 decades ago certainly can be expected to not match well with modern designs......this just has to be expected. If this hurts some collector types in their wallet for expected resell, well get over it. It is what it is.

Even though DOB gave me his precision output resistor network for my Soundtech after a amp clinic I hosted decades ago I can remember no discussions about impedence matching......

The only in depth published test results I have seen on this issue involved the testing of a Dynaco PAS3 by Regenisis as part of their evaluation of that preamp.

I would suggest that the only true way to evaluate this issue would be actual bench tests of this preamp/tuner driving a number of amps and measuring the pairings output frequency response.

All else is pure speculation.
 
FR will probably not suffer all that much. The main issue is mismatching between the preamp and gain structure of the amp. If input impedance is too low, higher volume settings will be necessary resulting in a higher noise floor. Other option is to crank the amplifier gains way up to compensate for this but that also winds up creating more noise as well. (Assuming the amplifier has GAIN controls to being with.)

If the amplifier lacks gain controls, then you're really stuck as far as the ability to deal with the situation, which can be worsened depending the sensitivity of the loudspeakers. Frankly, I would never even THINK of using an MX110 with modern amplifiers if they did not at least have gain controls - which the MC275 VI does not.
 
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FR will probably not suffer all that much. The main issue is mismatching between the preamp and gain structure of the amp. If input impedance is too low, higher volume settings will be necessary resulting in a higher noise floor. Other option is to crank the amplifier gains way up to compensate for this but that also winds up creating more noise as well. (Assuming the amplifier has GAIN controls to being with.)

If the amplifier lacks gain controls, then you're really stuck as far as the ability to deal with the situation, which can be worsened depending the sensitivity of the loudspeakers. Frankly, I would never even THINK of using an MX110 with modern amplifiers if they did not at least have gain controls - which the MC275 VI does not.

True within reasonable limits. In the case of an MX110 there is a 1uF blocking cap at the CF output and this becomes a very real limit to minimum load that can be driven w/o response anomalies. In the case of a 1K load suggested in another post, -3fB point would be ~ 160Hz probably quite audible along with assoc phase shift issues that may or may not be audible. And then there’s the issue of whether or not the output stage can drive nec current into the load at reqd output voltage with low distortion. Output iimpedance is just one of many characteristics of a good output stage.
 
Impedance matching is ALL about frequency response.......

I suspect mismatch or possible positive synergism for accepted altered sound and the thin bass, boomy bass or other issues with or without the Fletcher-Munson equal loudness compensation switch, might be based in impedance mismatching beyond just the inside joke about disliking your speaker bass output.

The loudness bass boost is based on excepted research on human hearing.......liking or disliking it's effect with your speakers at louder listening levels is very much whatever floats your boat.

A proper multiband EQ should do a better job of correcting that.
 
I collect vintage tube hi-fi equipment, and I’m a classical music fan. I’m not a technical expert.

I own two MX110Z, because I think they’re handsome, and they were reasonably priced compared with other vintage McIntosh tube preamps. Both of my MX110Z were electronically restored (to differing degrees) before I bought them.

In my living room system, I have an MX110Z mated to an MC275 MkV. FWIW, I believe in synergy between amps and speakers, and the MX110Z / MC275 MkV sounds good driving my Snell Type CV. (I have the MX110Z loudness off, treble slightly attenuated, bass slightly boosted.) In this same system, I have a pair of MC30s that I use without a preamp – driven directly from an Oppo universal player – and this configuration sounds great.

IME, some power amps sound good without a preamp, whereas some sound better with a preamp. Both of my KT88 amps (MC275, and Scott LK150 in a different system) sound better with an MX110Z. (I prefer inevitable colorations to be “warm”.)

Bottom line, I’ve never concerned myself with input and output impedances of amps. Rather, I go with what sounds good. And, with my Snell speakers – and the music I like - I think the MX110Z pairs well with an MC275 MkV. (I have no experience with the MkVI.) That’s my 2 cents …
 
Hi robert_kc - thanks for sharing. Have you ever tried driving your MC30s with an MX110? If so, how would you describe the sonic differences vs driving the MC275 MkV with the same MX110?
 
Bottom line, I’ve never concerned myself with input and output impedances of amps. Rather, I go with what sounds good. And, with my Snell speakers – and the music I like - I think the MX110Z pairs well with an MC275 MkV. (I have no experience with the MkVI.) That’s my 2 cents …

Thanks - It appears the MC275 MkV input impedance is 90k ohms unbalanced. http://www.mcintoshcompendium.com/Compendium Docs/Power Amplifiers/PDFs/MC275MKV.pdf

The MC275 MkVI is 47k ohms unbalanced.
 
Hi robert_kc - thanks for sharing. Have you ever tried driving your MC30s with an MX110? If so, how would you describe the sonic differences vs driving the MC275 MkV with the same MX110?

This morning I conducted a brief listening comparison of my MC30s and MC275 MkV, both driven by my MX110Z.

I decided to listen to the stereo mix on this Blu-ray – specifically, the second movement of the Rodrigo guitar concerto featuring Pepe Romero.

41+EYqMSRUL.jpg


"Rafael Frühbeck de Burgos Danish NSO”, a collection of recent performances captured in high-res audio and video and delivered on 3 Blu-ray discs:

  • Ludwig van Beethoven: Symphonies Nos. 1–9
  • Joaquín Rodrigo: Concierto de Aranjuez
  • Hector Berlioz: Symphonie fantastique, Op. 14
  • Richard Strauss: Eine Alpensinfonie (An Alpine Symphony), Op. 64, TrV 233

(Yesterday, I finished listening to the surround-sound mix of this entire Blu-ray box set, on a different system: my vacuum-tube-based surround-sound system in my basement. I highly recommend this Blu-ray box set.)

I think it’s important to first explain my perspective on accuracy vs. subjectivity: Accurate, Detailed OR Warm and Smooth OR Somwhere in the Middle Pole.

My listening tests this morning were NOT level matched via SPL meter. Not blind testing, let alone double blind. In other words, not scientific comparisons, just brief impressions (that validate many hours of previous listening comparisons).

I used the unbalanced connections on the MC275 MkV. (IIRC, several years ago I tried the MC275’s balanced connection direct to an Oppo BDP-105, but I preferred having the MX110Z in the loop with the MC275, which of course uses the unbalanced RCA connections.)

Let me first say that my assessment is that the MX110Z is compatible with both the MC30s and MC275 MkV, based on my subjective listening (not a technical assessment of the circuitry).

My assessment of MC30s vs. MC275 MkV (both driven by the MX110Z) sound quality: it depends on your choice of music, your speakers, and your preference for trade-offs in sound quality. If you want the quintessential vintage tube sound – what I’d describe as “rich, warm” sound – then IMO you can’t beat the MC30s. If you are an aficionado of high frequencies, and you prefer “accurate” sound, then you might prefer a modern MC275. (IMO, the MC275 MkV sounds more like a solid-state amp. IMO the MC30s do a better job delivering the richness of stringed instruments (e.g., violin, viola, acoustic guitar). OTOH, the MC275 MkV delivers the impact of a grand piano better than the MC30s.)

With a pre-amp in the loop, you can use the tone controls to bring the two amps’ sound closer together. As I said earlier, I use the MC30s without a pre-amp (i.e., connected directly to the variable output of an Oppo player), and I use my MC275 MkV with the MX110Z (with the treble slightly attenuated, and bass slightly boosted). But that’s with my Snell speakers (with treble pots turned down), my ears, etc.

Now, if I wanted to really stir the pot, I’d bring up the MC225. :)

That’s my 2.5 cents …


P.S. I just realized that we had a similar discussion last fall in this thread: http://audiokarma.org/forums/index....ge-mac-stereo-tube-amps.793377/#post-10965870
 
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