Tubes are one cause of "noise", but we don’t know what sort of noise was experienced with the noisy Chinook. One reason the Chinook (and the Steelhead) are both exceptionally quiet for "tube" phono stages is that they are not purely tube phono stages, as I have mentioned at least twice. The gain stage is a hybrid cascode where a transistor receives the signal and drives a high transconductance tube (one half of a 6922) via its cathode. This makes for high signal to noise ratio, very high gain, very low input capacitance, and wide bandwidth. The only downside is a highish output impedance, which is obviated by adding a cathode follower downstream. That’s the basic circuit of the Steelhead so far as I can determine without having a schematic. Now, to be clear, I am not saying that the Chinook is superior to the Modwright on other grounds; I have never heard the Modwright, and I am sure it too is very good. You pay your money and you take your choice, as the saying goes. I’m only saying that the Chinook is unlikely to be rejected on account of inherent noise.
I chose the Steelhead for its capacity to handle more than one tonearm input and both MM and MC cartridges (actually two MCs and one MM), and for its adjustable input parameters. I think I made mine better by upgrading the output coupling capacitors and the phono load resistors.
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I have to wonder whether the Chinook that was said to be noisy in high gain mode might have been defective. There are many possible causes. Whatever one might say of my Steelhead, it’s very quiet in all gain modes. I can’t live with a noisy phono stage for long. The base circuit is inherently very low noise.
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theflattire, I am curious to know where you got the information that most audiophiles prefer the Modwright to the "Manley" (by which term I assume you refer to the Chinook)? Both units seem well thought of by most who offer opinions, but I have never read of a credible direct comparison between the two.
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Pindac, eddy currents and copper vs silver conductor are probably subjects for another thread.
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There is an easy upgrade to the Chinook, if its output stage is like that of the Steelhead. Just upgrade the output coupling capacitors, which are mediocre in the Steelhead and way higher in value than they need to be. I have written about this before, so I won't repeat it here. If someone wants to know, I can post a summary here or send the information by PM.
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Pindac, I do not disagree that low eddy current RCA connectors, like the KLE types, do sound good. In fact, I use nothing but KLE connectors, when it comes to RCA. The point is that one does not know WHY they sound good. The fact that the design reduces eddy currents may have nothing to do with the good results. What a physicist pointed out to me is that at the low voltages and currents we encounter in home audio, not much eddy current is ever generated. That was just one person's opinion, of course.
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Are you referring to what used to be called "Eichmann Bullet Plugs" and are more lately called "KLE"? Those are a low mass, therefore low eddy current design. They are my favorites, but they are no longer a new thing; they've been around maybe for 10 years or close to. FWIW, bona fide engineers and physicists to whom I have spoken about eddy currents in audio level signals were not credulous that eddy currents are an important problem. I have no opinion, being untrained in that discipline; I just know KLE plugs continue to sound best.
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Pindac, in what phono stage are you experiencing the benefits of tube rolling? The Steelhead and probably the Chinook use a hybrid cascode (FET/6922) for gain at the input. In that topology it’s not surprising that differences among 6922s would be muted if not inaudible.
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I did replace some of the putative MC load resistors in my Steelhead with TX2575 resistor equivalents. (TX2575 are the best most transparent phono load resistors I have ever heard and by general consensus.) That may have improved SQ in the MC circuits; I would not swear by it.
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There are two tubes that would make a difference so far as "matching" goes. Those are the tubes that provide gain in the L and R channels, respectively. In the Steelhead these provide the "top half" of a cascode where the bottom half is probably an FET. The other two tubes are used to create an output stage that is very low in output impedance; in effect they form an unusual type of cathode follower (a stage that turns voltage into current). There is no added gain in the output stage, so the sound of tubes in a cathode follower is generally thought of as not a prominent factor in the overall presentation. I think tube matching is overrated, because tubes are aging as we use them, and no two tubes will age in exactly the same way or rate. So what "matches" today may not match tomorrow. And yet, I am guilty of perceiving that some tubes of any type sound better than other tubes of the same type. In my Steelhead, I use Siemens CCa, I think. I would not shed a tear, however, if some day I had to use some other brand.
By the way, as regards the autoformers in the Steelhead, I get the feeling that my Steelhead sounds best through its MM outputs, where there is no autoformer in the signal path. Interestingly, in the Steelhead, I have read (never tried it) that you can get up to the max 65db of phono gain via the MM outputs. To me that suggests the autoformers are more for impedance matching to MC cartridges than for their potential to step up voltage. Also, if you look inside, you can see that for each input R setting available via the rotary switch, there are discrete pairs of resistors whose values match the choices offered via the rotary switch. (If the autoformers were used like SUTs, you would think that the different input impedances would be mostly the product of what pair of primaries is selected.) It's a bit of a mystery to me. Manley are very secretive and certainly will not provide a schematic; I have asked.
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Yeah, I guess you could, but not much bandwidth in a Variac.
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Autoformer, not SUT. No secondary makes a big difference. But ya got me. I forgot about that. You get 50db of phono gain without an Autoformer. Then the Autoformer(s) add up to 15db more, for a max gain of 65db. Happy holiday to all.
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Again, if the Chinook is like the Steelhead in its gain stage, it uses a hybrid cascode consisting of a transistor on the bottom and a high transconductance tube on top. This topology can develop tremendous gain, wide bandwidth, and low noise relative to an all tube gain stage and on par with most all SS gain stages. No SUT inside.
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By the way, if the Chinook is like the Steelhead, the gain stage is a tube/transistor hybrid cascode and is remarkably quiet with a very wide bandwidth.
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Define “outperform “.
Di you mean”sounds better”, “quieter “, more gain, or what?
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