I guess you’re saying that the Aqvox provides for continuous adjustment of gain anywhere between some lower and upper limits. The BMC (as you likely know) has internal jumpers that allow for "low", "medium", and "high" gain. Those should be sufficient for most situations; you would choose your setting once, to match the particular cartridge you are mating to it, and then forgeddaboudit. I looked up the Nibiru, too. Although it accepts RCA connections for input and output, implying SE, one cannot be certain that the actual business is not done in the balanced mode; there is just no information provided, and the phono circuit is hidden from view by a copper shield. Anyway, I feel like we might be guilty of hi-jacking the thread, for which I apologize to the OP. Thanks for responding to my question about current drive in the first place. I am tempted to try one out in my system.
I read Fremer's reviews in the course of my recent research. He certainly did seem sincere in his praise for the MCCI, even in comparison to some very much more expensive units that he is known to adore. In his summation, it seemed he had to backtrack to come up with some reasons why the $30,000+ units he compared it to are a slight bit better than the MCCI. Surely, the MCCI had better measurements than the megabuck units. (As I recall, the Boulder 2008 is pretty noisy.) |
My last post is more than 30 min old, so I am blocked from editing it, but I did go and read Fremer’s review of the BMC, and apparently the input resistance of the BMC is "less than 3 ohms", but not zero. This solves my own conundrum; I couldn’t figure out how one would create a zero ohm input. Fremer seemed to really like the BMC, but he could not bring himself to say it was the equal of two $30K-ish phono stages (Ypsilon and Boulder), although he admitted it was very close to those two. |
I keep forgetting that the Aqvox is one example of a phono stage driven by current output of the cartridge. It makes sense that it would operate in balanced mode, because my search on the topic led me to designs that are balanced topology too. It may be a requirement for current drive. As my present phono stage has true balanced inputs, I have already converted to balanced tonearm outputs, in one of my two systems; that's no problem.
You mention that the load cannot be changed. Actually, the load is fixed at zero ohms, is it not? What troubled me with my very basic understanding of circuits is that the input impedance of the phono stage should need to be a multiple of the output impedance of the cartridge, so the cartridge can drive the phono stage. But I think this is required in "voltage world". Current-driven phono stages are in "current world".
What's the BMC? |
What about "current-driven" phono stages for very low output MCs? This is either a new bit of jargon conjured up by manufacturers or a really new idea. So far as I can tell, allowing the cartridge to drive the phono stage by virtue of its current output amounts to building the stage with a very low or zero input impedance. This would seem to require a solid state device for the first amplification stage; tubes don't do well with very low value grid resistors or no grid resistance (grid connected to ground) unless you drive the cathode. |
Swampwalker, Among commercial phono stages that do have built-in SUTs, the Allnic H3000 does provide a choice as regards gain, probably by internally selecting primaries or secondaries that afford different turns ratios. Of course, the H3000 is not a "budget" product.
For manufacturers of MM phono stages that do not incorporate SUTs to facilitate the use of MC phono cartridges, there really is not much more they could do, except possibly allow for a choice of load resistances so as to accommodate a wide range of turns ratios in whatever SUT is chosen by the end user. |
A very recent experience: Last week my neighbor emailed me, as he usually does when he has a question about his very expensive audio system. He recently purchased a new $30K phono stage (39db gain according to mfg spec) which is fed by a SUT suited to his previous phono stage (which had 42db gain, minimum). Between the phono stage and his amplifiers, he was using a very high quality passive attenuator. With his new phono, he was noticing that the sonics were occasionally anemic during orchestral crescendos and on similar demanding passages, and he wanted me to help him decide which of two more powerful power amplifiers he should now buy, in order to fix his problem.
I noted that he currently owns an 8W SET powering a pair of speakers rated at 105db(!), and I told him his problem should hardly be an indication of a need for more amplifier power. (8W should produce 107db spl at 10 feet from a 105db speaker, based on my calculations.) Instead, I advised him to save his $$$; I guessed that his upstream components were not driving his amps to their full output. Indeed, if I assumed that his SUT was providing about 5.0mV at its outputs (i.e., the voltage output of a typical HO MM), I calculated that the signal voltage delivered to the amplifiers via the passive attenuators was less than 0.5V, not enough to drive most amplifiers to full output. To prove the point, I lent him my vintage Quicksilver preamplifier which can provide quite a bit of gain via its active linestage section, although I don't know precisely how much gain in db. Once we inserted the Q into his signal path in lieu of the passive attenuator, all was well, and I left it with him for a couple of days. I have no intention of parting with my Q, so he bought an (expensive) active linestage of his own. Now he's "cooking with gas". What was striking to both of us is that the active stage made his system sound better in all respects, not just on musical peaks. And strangely, this applies also to digital, where gain should not have been a problem.
The story has no moral, because he has now also made a deposit on a more powerful amplifier even though I proved to him he did not need it. I am happy to help him, because, besides the fact that he is a nice guy, listening to his system after each "upgrade" allows me to educate myself on the price/performance ratio prevalent in high end audio, at no cost to me. |
roberjerman, I cannot argue with your thesis, because it is after all based on your own opinion, but with all due respect, the Levinson JC1, while it is historically significant, is ancient in design and parts used, compared to the best modern high gain phono stages, like Raul's and Almarg's, and dare I say my own. (JC1 was a pre-preamplifier or "head amp", as I recall, or was it a phono stage with high gain? I used to own a Counterpoint SA2 head amp, which is now easily beaten by many top caliber high gain all in one phono stages.) But I am not taking the position that all high gain phono stages are to be preferred compared to all SUTs plus low gain phono stage combos, even though the former is my decided preference. I am only saying that either approach can be superb, done right. |
It's interesting that guys who build equipment from scratch very often talk about building for minimal or just barely enough gain, because in their way of thinking, gain is inevitably accompanied by added distortion and after all you're throwing away energy by sinking it to ground through a resistance, when you use a volume control to tame excessive gain. (They do not like attenuators.) I have educated myself about circuit design, and I do a lot of tweaking of circuits but not much building from scratch. Yet I have found in practice in my system that an excess of gain always has sounded "better" to me than having just "enough" gain. Dynamics are better, signal to noise ratio seems to be better. The trade-off is that you need to have a very excellent and transparent attenuator to realize all the benefits of the surplus of gain; the attenuator becomes a critical piece of the puzzle. (I have heard my own Atma-sphere MP1 phonolinestage both ways, with barely enough gain for a LOMC and now with prodigious gain, sufficient even to run an Ortofon MC2000 [.05mV output] without a SUT. I like the high gain version much better but only after upgrading the attenuator.)
On the other hand, I disagree with you in dismissing active gain stages as compared to using a SUT, to achieve sufficient gain. I am not saying that a SUT cannot give a great result, but so too can a properly devised active gain stage, for dealing with low output cartridges. The experience you relate here has to do with one particular sample of one phono stage, not enough data to support a general conclusion on the merits of phono gain stages. (Nor does my anecdote support a generalization, I admit. It only suggests there is more than one path.)
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