BAT comes immediately to mind. Never heard 'em.
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Several phono stages do balanced in. Ayre, Aesthetix Io, BAT are a few. I have a BAT VK P10SE super pak and have tried it with a din to rca and a din to XLR. The XLR input lowers the noise floor some and details pop out a little more. I think it really depends on the rest of your system whether this is way the way to go... |
Agree completely with Jfrech. I use balanced as much as anything because it's a more secure and firmer fitting connection for my oversize cables, less likely to strain connections than the light weight RCA's. I do think the balanced in on my Aesthetix Io is a bit better but not enough that I would suggest a person sell off their RCA to change. Next time you upgrade I suggest going for the XLR though, assuming your preamp supports it. My turntable is the Walker, I ordered a spare (brass) connector plate for it and bored it for XLR. I kept the original RCA connector plate version in case I ever needed to switch back. |
Depends. Many products convert balanced to single-ended after the input and then process the signal in single-ended mode. Other products are single-ended all the way thru and then have an additional stage at the output that provides a balanced out. In either case, it is unlikely to be advantageous to use the balanced in or out, as compared to the SE inputs and outputs on the same piece of gear. Only a few phono preamps are truly balanced from input to output. AFAIK, these include BAT, Ayre, Aesthetix Io (in spite of what someone wrote below), and Atma-sphere. In my opinion, there ARE some advantages to a balanced circuit in the latter case, noise and distortion cancellation being two of those advantages. Before purchasing a "balanced" input phono preamp, it would be wise to make inquiries as to what is really going on inside the unit. I think a lot of the reason folks are indifferent about the advantages of a balanced circuit is that they have not really heard one properly implemented. |
There is an exception to every rule I reckon. I've got a VKP10SE and I like it a lot better with the input connection unbalanced. To the second half of the original question, I think the answer is no. Some great phono stages give you the balanced input option and some do not. A drawback to the balanced input approach is that to convert a two wire device (cartridge) to a three wire device you have to cut the signal in half which creates opportunity for more issues with signal to noise ratio and amplification error (i.e. for a 1.0 mv cart the unbalanced input is 1 mv, the balanced input is 0.5 mv on each leg). |
Your conception about what is happening to the output from the cartridge when interfaced with a balanced input is flawed, insofar as you see it to be a negative. The signal is not "cut in half" per se, and there is no conversion of the signal from "two wires" to "three wires". The ground in a balanced input is independent of the + and - inputs. The cartridge sees only the + and - inputs and does not know the difference between +/- vs hot/ground in an SE input. One could make an argument that the output of a cartridge is inherently balanced in the first place; the choice of hot and ground is arbitrary, really. However, your impression that your BAT phono sounds best with an SE input is not one I would challenge, since I don't know the particulars of that unit and you are entitled to your opinion. You might discuss your finding with BAT, however. Nor is it my intention to argue that all truly balanced circuits are better than all SE circuits, not by a long shot. |
Jeff_jones: I've heard from others that some people do like the SE ended inputs better if you are using the transformer step ups. I'm curious if you are? Also, are you using the single ended outputs or balanced out to your preamp... I am not challenging your observations...just more curious. Thanks.. good luck |
Jfrech - No step up. Gain switch to high. Balanced output to pre (full balanced through pre to power amp). Shelter 90x. To my ear the main difference is reduced background noise. Lewm - didn't mean to say that balanced was bad just that there were trade offs. Circuit wise, balanced ain't balanced unless it is balanced :). Do not have the Bat schematic but at some point they have to split the signal from each channel with something like a center grounded resistor to get equal strength (balanced) + to ground and minus to ground signals. It would be interesting to look at the schemativ or ask Victor, the signal splitting might occur exactly the same way regardless of which input connection you are using, so in this particular case we may be talking about no difference except in cabling between the table and phono pre. |
Not to beat a dead horse, but you wrote, "Lewm - didn't mean to say that balanced was bad just that there were trade offs." Not only did I not say that balanced was bad, but I was trying to say that I prefer it and why. Also, I was trying to convey the idea that one must be cautious in interpreting what manufacturers claim about their equipment, especially now that balanced circuits seem to be in vogue as never before. Try to find out whether the circuit inside is truly a balanced one (if you care about the issue at all), because in a lot of gear an XLR input or output is derived from what really is a single-ended circuit internally. Many CD players pull this trick by adding a chip at the output, which not only is a phony way to do it but also will likely degrade the sound a bit compared to the SE outputs on the same piece of gear, due to the added active device which is typically a middle grade op amp, at best. Even my former Accuphase DP75 (a $10K cdp when new) and the Sony SCD1 used this approach to obtain a balanced output. For this reason, when someone says they don't hear any advantage to a balanced output, I have to first wonder what they have been listening to. |
I have a PH2 from Audio Research. It is completely balanced from input to output. A quick look at the schematic and it's easy to tell. The ground runs right down the middle of pin 2 and pin 3. I can't say from experience yet that it sounds better than single ended because I'm running mine into a single ended line stage, but theoretically noise picked up from cartridge output pins throughout a balanced chain will be common mode rejected giving you a lower noise floor and less interference/interaction from outside sources. Good idea given the lower output of phono cartridges |
Many CD players pull this trick by adding a chip at the output, which not only is a phony way to do it but also will likely degrade the sound a bit compared to the SE outputs on the same piece of gear I agree, but would like to point out that since the data on the CD is single ended, any CD player with a balanced output has to "create" the inverted signal in some manner. Some use more DACs, some use inverters after the DAC, but in every case there is no such thing as a balanced CD player from front to back since the data on the disc isn't balanced. |
-And since phono cartridges are balanced, it is actually surprising that balanced phono sections did not appear sooner! When we built the first one in 1989, we thought that someone had done it before us, as it seemed the logical thing to do. But apparently the idea of balanced lines was/is foreign to high end audio, which is a shame because they have been so successful for over 50 years in the recording industry. Balanced lines were created with the intent of eliminating cable problems and differences but the high end community has preferred to throw money at single-ended cables instead. While the techniques has proven successful, it has hardly been economical :) Balanced operation also gives you lower noise both in the cable and in the circuitry. A differential amplifier, one of the basic building blocks of a balanced phono circuit, has *6db* less noise than its equivalent single-ended circuit! In practice you get a little less than that, but over successive stages of gain this means a lot- 10 db less noise for example in only 2 stages of gain. This allows for greater simplicity (less stages of gain) which translates to being closer to the music. |
Atmasphere - I never understood why it is said that phono cartridges are balanced, given that they are a two wire device. For the particular connection between two wire cart and pre amp ,i.e. signal still single ended until split into balanced at the pre, there shouldn't be any advantage in common mode rejection. Once the split is made (downstream of the input connection at the pre amp) I understand your point. N803nut - If I understand the circuit you have described correctly, it is electrically the same as an unbalanced connection except that you are using two wires in parellel on the grounded side of the unbalanced connection. |
Jeff_jones, you are correct. The signal encoded on the vinyl disc is also single ended. Balanced is hype. Long (and I mean really long) signal runs can benefit from balanced but not typical home setups. ALL sources are single ended. All speakers are single ended. Your ears are single ended. All sound is single ended. There are no balanced instruments or sounds. |
Herman, I think I agree with you :^). I have some balanced stuff and run it with balanced cable because I think it's a little bit better that way. But who knows, perhaps if it had been designed from day one as single ended it would sound better than it does now in balanced. Interesting comments for sure. |
A balanced electrical interface is almost immune to spurious signal pickup: eg: hum. When using single ended interconnects I have never had a problem with noise pickup, but I have had a phono cartridge circuit pretend it's a radio. Balanced configuration makes more sense for a high gain phono input than for any other part of the system. Actually, I do use some balanced wires, but this is because the equipment is pro sound stuff, and that's the way it is made. I have used some of this equipment single ended, and it worked fine that way also. |
>>And since phono cartridges are balanced<< This is simply not true. I'm suprised you would continue to actively propogate this myth. If anyone understands the beauty of balanced circuits and signalling, it's you. You get it. So why pretend a two-wire device is balanced? It's not. A cartridge is floating single-ended. Balanced operation require three terminals: a common (mid-point, average, reference), a positive polarity, and a negative polarity. You don't have that with a cartridge. Nonetheless, as I pointed out in another thread, a proper receiver can force a cartridge into balanced mode. This is done by using a center tap on the primary of a step-up transformer. The center tap connects to ground. The windings then force the cartridge to act as if it were balanced (but without the 6dB gain). I wonder how many of these so-called balanced phonostages actually do this. And how many simply connect one cartridge tap to ground and pretend? jh |
Dear Pedrillo: Jeff, Herman and Hagtech are totally right the cartridge is not a balanced device. I was surprised at Spencer place when I read in the Atmasphere operation manual that the cartridge is balanced, it is not. Herman, balanced it is not hype: in a fully differential well made design the distortions/noises are canceled inside the circuit ( I'm not talking here of interconnect/speaker cables ) and this subject is extremely critical in a Phonolinepreamp, could you tell us why is only " hype " ? Hagteck, our design is real input to output balanced one, no " charlatan " seudo-balanced design. Regards and enjoy the music. Raul. |
Raul, good to hear from you. What is this "our design" you speak of? I agree there are some theoretical advantages to differential designs; however we both know that many balanced devices are not differential. I believe Atmasphere's are but many (most?) are not. By hype I mean the advantages are outweighed by the complexity of the circuits, and the ability to reject common mode noise is simply not needed in the home environment. The only exception I can see where it might come in handy is the very early stages in a phono stage. Otherwise, why take an inherently single ended source, convert it to balanced, and handle it that way only to recombine the 2 polarities at the speaker? Most of those who are trying to sell balanced equipment take advantage of the fact that the average consumer doesn't understand the circuits. They tout the advantage of noise rejection (which isnÂ’t needed) and love to point out that pro audio uses it (which isnÂ’t relevant.) As you may know I feel simplicity is the key to good sound. Balanced circuits donÂ’t fit in with this philosophy. My amplifier has 3 SETs directly coupled. My phono stage has a step up followed by 2 stages of amplification with the RIAA in between. With high efficiency speakers this is all you need. |
All right, everyone, a little lesson about why all phono cartridges are balanced and how balanced operation works. Cartridges are balanced as they have 2 wires per channel, neither of which has to be tied to ground for it to work. Proof? invert the phase of one channel of your cartridge in your system and see if it hums (it doesn't). Hagtech, the ground is the tone arm itself. Have you ever wondered why the phono is the only hookup in your system that requires an extra wire for grounding (else it hums)? This is the result of trying to operate a balanced source in single-ended mode. Other examples include tape heads on tape machines, the light pickup on a laser head, most microphones and nearly anything with a transformer-coupled output. You don't need a 'center-tapped transformer' to 'force' the cartridge to be balanced. Any differential input will accept the cartridge without any such work! I've been doing this now for nearly 20 years with my cartridge and we've been building phono sections like this for 18 years. It works. All of your recordings were made in the balanced domain. All of them. They only get converted to single-ended in playback- if you allow that to happen. For a long time, you had no choice- now you do. The benefits are lower noise with less gain stages (blacker background lower distortion wider bandwidth) from the phono preamp, and less buzz/humm/RF from the pickup wiring. There are no tradeoffs if executed properly- often the signal path is simpler! Herman, single-ended/balanced has nothing to do with sound in space, quite simply the analogy falls apart and becomes a logical fallacy. SE/balanced has everything to do with how recordings are made and played back: that is where we need to be focused. |
Have you ever wondered why the phono is the only hookup in your system that requires an extra wire for grounding (else it hums)? This is the result of trying to operate a balanced source in single-ended mode. That is simply not true. It is not required. A cartridge connected to a single ended input sometimes will hum with the ground connected and sometimes without. Sometimes the ground connection makes no difference. After playing records for almost 40 years I have proven this to be true. While it may be true that balanced equipment might have been used in the recording process, the groove in the disc is not balanced. Balanced has 2 signals of opposite polarity per channel so a stereo signal would require 4 separate signals. There is no medium (tape, vinyl, digital, etc.) that provides these balanced signals so all sources are single ended. Why even imply that vinyl is balanced? |
Dear Herman: Our design is the Essential 3150 Phonolinepreamp that you can follow at this link: http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1166047312&openflup&49&4#49 The Essential 3150 is fully diferential input to output and has two gain phono stages with out step-up transformers. Ralph, I understand your cartridge balanced explanation but it is not clear to me, how a coil/inductor can be balanced? Regards and enjoy the music. Raul. |
>>Proof? Invert the phase of one channel of your cartridge in your system and see if it hums<< You're kidding, right? >>Balanced is hype<< There is more to balanced circuitry than is obvious to the casual observer. One significant advantage is PSRR. Or the way it interacts with a power supply. Think holistically for a moment, everything is inter-related to everything else. I can walk through an example here. What is the best type of regulation? Many will say shunt. Why? Because it offers a lot of line rejection and can be made very fast. It is also class A. What is better than shunt regulation? What if (pretend it is possible) instead of reacting to a load variation, as a shunt regulator does, that you could know in advance what the variation will be? What if the regulator acted precisely at the same moment and without phase delay to a load transient? And without feedback. Would that not be better? Imagine correcting the supply rail perfectly in response to the music. Well, that is basically what a balanced differential stage does. One way to look at it is a single-ended stage mated with a shunt regulator. You can actually run it that way. There isn't any other topology out there that can top that. Now take it even further. You can add passive line regulation (no feedback). In a balanced phonostage I once designed you could take a variac on the ac line and crank it up and down (simulating line disturbances), and the dc output level from the amplifier doesn't budge. Yes, the power supply rails move in response to the variac, but the output doesn't. Well, at least not at a 1Hz variac rate. The point is, there are tricks you can pull with differential topologies that you can't use anywhere else. It ain't hype. Unfortunately, there is a big price to pay. It takes double the number of devices. Cost goes way up. jh |
Atmasphere, agreed. The notion that balanced circuits are more complex that single-ended is a myth. In fact, balanced operation in comparison gives you twice the voltage (+6 dB) than single-ended, which in many stages would allow you to eliminate one gain stage (or several, with multiple stages)! Also, a symetrical circuit presents supply current variations in opposing polarities, so cancellation takes out and supply demands are drastically reduced. Balanced circuits are more elegant from an engineering standpoint, etc. As a final bonus, the signal-to-noise ratio improves by +3 dB (not +6 dB). You can definitely notice that. |
Speaking of a phono cartridge, it's just a floating coil with 2 wires. As the coil is floating, you have the choice to operate it as either single-ended or as a true balanced signal source. If you connect the negative terminal to ground, and use the positive terminal as signal, then you have normal single-ended mode. To better understand the advantage of a cartridge working in balanced mode, I will quote a paragraph from my book "Noise Reduction Techniques in Electronic Systems" by Henry W. Ott: "A balanced circuit is a two-conductor circuit in which both conductors and all circuits connected to them have the same impedance with respect to ground and to all other conductors. The purpose of balancing is to make the noise pickup equal in both conductors, in which case it will be a common-mode signal which can be made to cancel out in the load". According to this definition, we can confidently say that a pickup cartridge truly acts as a balanced source, because when the cartridge is connected to a normal phono cable (with 2 wires and 1 grounded shield), the impedance of both wires with respect to ground is the same. Further, the noise pickup is equal in both wires, forming a common-mode signal that a differential input stage (or a center-tapped transformer) will easily cancel out. Please notice that differential mode is not the same as balanced mode. In fact, an input circuit working in differential mode is a pre-requisite for balanced mode. As said, this circuit could be: 1) A center-tapped transformer, or 2) a differential input stage (tubes or solid-state). As you can see, balanced mode has obvious advantages over single-ended mode in phono cartridges. |
Everyone here is getting the terms differential and balanced mixed. Differential signal is when you have the same signal 180 degrees out of phase showing up on two signal legs. Balanced signal is the differential signal referenced to a ground. Balanced signals are useful in that typically, you get the benefits, i.e common mode rejection, 6db higher signal, you also get disadvantages, the circuitry essentially doubles, you have make sure that the amplification stages of the two opposites of the signal are treated absolutely equally, not just statically, but dynamically and through the aging process that a piece of equipment will go through over years. Anyone want to take a guess at what happens to a volume control or switched attenuator after a few thousand rotation cycles. Phono Cartridges and loudspeakers are inherently differential devices and a case could be made to treat them in balanced mode at the inputs and output stages of amplification equipment. There are advantages and disadvantages to all topologies and outstanding examples of design for both. My personal opinion is that the currents involved in the phono (specially mc) stage are small enough and the inertia of the generator is small enough that exceptional results are available with either topology, in the amplifier output stage, for reasons of symmetrical feedback, reduction in ground current etc, it may be that a balanced output is the preferred method of operation. Although my current amplifier output is operated in SE mode (ie the negative terminal is tied to ground) and I am really happy! |
That is simply not true. It is not required. A cartridge connected to a single ended input sometimes will hum with the ground connected and sometimes without. Sometimes the ground connection makes no difference. This is consistent with balanced operation: you may not always get hum when converting to SE. However there is a reason why nearly every turntable manufacturer has a 5 wire system rather than 4, to prevent ground loops (IOW the ground is not mixed with the signal- this implies that the minus output of the cartridge is actually the inverting output, and in balanced systems the inverting signal is often denoted by a minus sign). Even BSRs and Garrards from the 60s and 70s are set up that way. As a result they can all be run balanced since the ground is not ground looped with the signal. While it may be true that balanced equipment might have been used in the recording process, the groove in the disc is not balanced. By that measure, neither is it single-ended! Once the sound is mechanically encoded, you have the same conundrum that you have with actual sound- it is neither SE or balanced- it simply is. It is the way we handle the sound, once it exists as an electrical signal, that makes all the difference (no pun intended :) |
Ashly pro audio equipment uses what some would call "pseudo balanced" outputs. (Inputs are true differential balanced circuits). In the "pseudo" configuration, the wire that would normally (in a single ended interface) be ground is isolated from ground by a resistor of the same value as the output impedance of the active circuit, in my case 100 ohms. This wire is carried to the (-) differential input of the following electronics, along with the signal wire (+), and a ground wire. This scheme will give the same imunity to noise pickup as a "true" balanced output. This approach could be used with a phono signal if the preamp had a true differential input. |
it is neither SE or balanced- it simply is You lost me there. I'll have to think about that one, but I would argue that the record groove as well as sound itself is single ended. I don't think something is balanced unless you have a pair of signals of opposite polarities. Since nothing in the home stereo meets this requirement unless we create the opposite signal, it is single ended. I'll have to ponder the situation of a cartridge hooked up to the inputs of a diff amp as noise rejection at this low level makes sense. I may try that myself, but I see no compelling reason to go balanced after that. |
>>Everyone here is getting the terms differential and balanced mixed<< That would be me! Perhaps we are all in agreement technically, just not semantically. For me, "balance" is like a scale (in the original sense). Or akin to a see-saw. Two ends, and a solid pivot point in the middle. Remove the pivot and ... well ... you have a cartridge. http://en.wikipedia.org/wiki/Balanced_line Calling the turntable ground as the "third wire" is disengenuous. As was pointed out above, it is not part of the signalling. jh |
OK, now my brain hurts. Here's an interesting read. http://www.ultracad.com/articles/differentialrules.pdf It would seem to support Ralph's assertion that a cartridge is balanced IF you accept that differential signals are the same as balanced. If you go with Hagtech's definition that a 3rd ground leg is required to meet the definition of balanced then a cartridge is not. However, I can't find any definitions or discussions (other than this one) that require this ground. The ones I have found discuss currents in the 2 legs as equal but in opposite directions, which a cartridge would fufill. It also seems to me that if you want to get a ground refernce involved, as soon as you hook up the leads to a differential amplifier that they could be referenced to that circuit's ground. Then again, I suppose Ralph's assertion that what really matters is the circuit and how it sounds and it doesn't matter what you call it might be the best approach. |
Hi jh, the way differential amplifiers work is that ground is ignored. Our preamps are fully differential from input to output and so the ground is merely a shield- no currents are passed through it. This helps prevent ground loops. As I mentioned, differential amps ignore ground. They have two inputs: non-inverting (positive) and inverting (negative). The differential amplifier will do nothing if the signal is the same on both inputs; it will only amplify what is *different* between the two inputs. Thus there is nothing disingenuous about the tone arm being ground- it *is* at ground and is providing a shield as the signal leaves the cartridge. Balanced inputs that are not differential are a different story- ground can play a crucial role. Differential amplifiers (a subset of balanced amplifiers) consequently offer higher performance, less complexity and lower noise. Herman, There is a tendency to try to create interpretations for all sorts of experiences that we have in the world. In the case of the SE/balanced issue, the interpretation that I am referring to is to identify sounds within the realm of SE or balanced when it is neither. Its OK to question this- I did myself for a while until I got that I had to give up the interpretive story. Then I was able to realize that sound simply is what it is and is neither SE or balanced but a series of pressure variances in the atmosphere. It is when the sound arrives at a microphone that it suddenly appears in the realm of electronics and is subject to being SE or balanced. All dynamic pickups are balanced as are capacitive pickups (although their preamps are often SE) and all the output transformers on microphones are balanced and on and on. There is merit to the argument of keeping what started balanced in that domain, but sound itself has nothing to do with this. To give you some perspective, SE signals travel in a cable with a single conductor and a ground. The ground connection is the 'return' circuit- where is the return circuit for sound itself? There is none- it is an entirely different phenomena from that of electronics. On an LP the sound is encoded in grooves due to a 3rd phenomena: a mechanical process and is again neither SE or balanced. However FWIW the cutterhead is a balanced load insofar as the amp is concerned: like all other balanced devices reversing the connections does nothing except invert phase (a property of a balanced device). If it helps at all, take a look at an Ampex 351 schematic and see how the input and output transformers are used to accept or create balanced operation. Its an eye opener: a center tap is not part of the equation... |
Hi Jeff_jones, we wondered the same thing so we put the same circuit into a more budget priced preamp to see how it works. The same advantages appeared and the phono section of our MP-3 is quiet with cartridges of 0.2mV, while at the same time having only 2 stages of gain and passively equalized. IOW the approach works on a budget too. |
Hi Hagtech, when you get a chance, take a look at the schematics for the Ampex recording equipment- something tube like the 351 electronics. What you will see is that the output has an *optional* switched center tap on the output matching transformer. The input, which is also balanced, has no center tap at all. Note that the input is conventional single-ended circuitry with a transformer to effect the balanced input. The ground is handled in a way almost identical to how it is done with a balanced phono setup. Of course, going balanced differential without the transformer offers the possibility of higher performance. If you look at solid state gear, opamps are often used as a balanced (differential) input; the technique is common. The point is in all these examples that balanced, even if it is not differential, does not require a center tap. However there is almost always three terminals (the example I gave above with two terminals was in an industrial situation) as you mentioned. In a phono system that third 'terminal' (ground) is shared between both channels. In any event, the system works. When I did this for the first time in my home system as an experiment, about 1987, I was startled at how straightforward everything behaved. Over the years I've used a variety of interconnects, some shielded, some merely braided and all have operated without a trace of hum. Grabbing the braided cable and squeezing it with your hand made absolutely no difference in the noise floor; the system seemed to all accounts impervious. The technology to operate this way has existed for decades; I am at a loss to sort out why it had not been done sooner! |
>>In a phono system that third 'terminal' (ground) is shared between both channels<< Thank you. That's the point I've been trying to make all along here. The receiver is providing the common mode reference, not the transmitter. In your case, a resistor to ground on each side of the differential input. So in this particular case, the differential circuit *does* care about ground. It is the same with mic inputs, which uses a 6.8k resistor in each leg to provide the common mode reference. The term 'phantom' power comes from the original use in telegraph lines (before telephones), where they were used in both differential and common (phantom) modes. Truly, the original balanced electrical circuit. Look, that's all I'm trying to say. A cartridge by itself is not a balanced transmitter. However, with proper receiver circuitry we can *force* it into balanced mode (which does require 3 terminals). jh |
So in this particular case, the differential circuit *does* care about ground. Well, no it doesn't. In our preamp we have two resistors because we have to have a 47K input impedance and because the tubes require a grid leak resistance- for biasing. We could have set the unit up with a pair of 1M resistors and put the 47K across the input, from pin 2 to pin 3. It would have worked as well, but it would have been more parts. When we load the cartridge, the load is applied with a single resistor from pin 2 to pin 3 of the XLR. The ground functions only as shield with no signal currents. |
>>We could have set the unit up with a pair of 1M resistors<< Exactly! For the circuit to work you *must* have a common mode connection to ground (the 3rd terminal). Or some other reference voltage similar to a ground. I don't understand why you keep trying to deny this. Just because you make the connection inside the box doesn't mean it is non-existent. If you can get your preamp to operate in balanced mode without these 47k or 1M resistors connected to ground, then send them to me and I will eat them. jh |
Forgive me, I tire of this thread. What started as an intelligent debate has devolved into childish wordplay. I must be annoying everyone as I keep repeating myself (a sign of insanity) like a broken record. I'm like a homeless bum pushing a shopping cart mumbling to myself. Seriously, didn't I just say: "...or some other reference voltage similar to ground..."? And before that: "...the receiver is providing the common mode reference..."? Maybe my posts are moderated and nobody else can see them. If so, I apologize. I had thought the see-saw analogy and the fact that the input stage is providing the common mode reference (pivot point) for the cart would make sense. Why did I bother? It's very simple. I like the truth. I don't like the way marketing can obscure and twist reality. You see, there are a few phono stages out there with XLR inputs that have pin 3 tied to ground. Hence, they actually run single-ended. Clearly that is not the case for atmasphere or bat. Just a few I won't name. The problem, as I see it, is that perpetuating this myth that a cartridge in and of itself is a balanced transmitter gives these folks a pass. Customers end up believing. Hey, it had an XLR input, right? The tragic irony here, is that the guy doing the most to benefit the disengenuous is someone who makes the effort to do it right. jh |
Hi jh, if I provide two independent floating bias supplies for the input of the preamp, I don't have to have the grid resistors go to a common point. This way the cartridge does not have a 'center tap'. Yet it still works exactly the same way- no noise running as a balanced source into our balanced differential input. It does in tact satisfy all the requirements of a balanced source. Inductors being what they are, you can create a balanced output with a transformer that is driven single-ended. And it works fine- the technique has been used for decades. Cartridges are no different in this regard. You might consider the implications- I took a look at your website and you have some impressive little goodies! |
