Well Pete, your ML 335 has an input impedence of 100K ohms, so you shouldn't have any impedence matching issues with any preamp that you choose.
Now when you say that it must have XLR in and out, do you wish the preamp to be a differential topology (balanced internally)? If so, you're probably looking for a BAT, ARC, Cary or Atma-Sphere, depending on what flavor you are looking for.
If you are just looking for XLR in and outputs, but don't care about balanced topology, there are other choices like VAC, Lamm, Modwright, again depending on what flavor you are looking for. By flavor I mean are you seeking to head towards resolution, or towards musicality? They are seperate paths. Enjoy the journey.
A good reason to go balanced is the advantage of being able to run really long interconnects, so you can place the amps close to the speakers and avoid sonic degradation on account of the speaker cables.
The balanced line system was created to get rid of interconnect cable colorations. It works really well! However in order for that to happen, The preamp must support the balanced line standards (which have been in place for decades).
Most high end audio balanced preamps do not support the standard! As a result with such preamps you will encounter variable results as far as interconnects are concerned.
Here is the standard:
1) pins are: pin 1 ground, pin 2 and 3 are signal.
2) Ground is ignored- the signal occurs only between pin 2 and 3 (this is where most high end audio preamps have a problem- as soon as there are signal currents in the shield of the cable, the construction of the cable becomes critical).
3) the cable will be a twisted pair for the signal with a shield (tied to pin one only)
4) the output of the preamp should be capable of driving a low impedance load (2000 ohms or less) without loss of voltage, without increase in distortion and without loss of bass (this is the other big area where high end audio preamps have a problem, and also results in cable sensitivity).
Note: this does not mean that the output impedance of the preamp is this value, it means that it can *drive* this value. If there is a question, both the 1KHz output impedance and the 20Hz output impedance should be well below 300 ohms!
The actual standard is 600 ohms and you will have a lot of manufacturers of balanced products tell you that since the amps being driven have a much higher input impedance, that this does not matter. Such is incorrect if you want cable immunity! It is the higher impedance nature of single-ended preamps and amps that spawned the interconnect cable industry. Such is not needed for balanced as long as the standards are used.
Now some people want proof of this sort of thing- after all what I am saying here is that the interconnect should not have an audible quality in the system. So here is the proof. The first manufacturer of high end cables was FMI in Minneapolis, Minnesota. Robert Fulton, the proprietor, created the first cables in which in was claimed that they made an improvement when installed in a system. That was the late 1970s.
However in the late 1950s, the record labels were turning out recordings that are revered to this day (the better your system gets, the better these recordings sound). In many cases the microphone signal had to go over 200 feet to get to the input of the tape recorder- how did they do that without an exotic cable? The answer is the low impedance balanced line system.
So- if you want that same cable immunity that the recording and broadcast industry has enjoyed for the last 60 years, then your preamp should support the same standard. This takes the cable out of the system equation, and also its cost.
BTW, phono cartridges are a balanced source and should enjoy the same cable immunity if set up properly. If you have ever wondered why the phono system has that extra ground wire that no other single-ended source seems to have, that is why- its actually a balanced source that is being treated as if it is single-ended, but you have to do something with that ground...
Quicksilver Full function preamp with it's extremely low output impedance is a good match with any amp. There is no need to go balanced. Think of the extra circuitry for the option of going balanced. Keep it simple.
Rrog, you have just described a common myth. What if a preamp has only 3 gain stages from LOMC input to the main output? Is that less signal circuitry or more?
If the preamp is fully differential, one advantage is that there is less noise (up to 6db) per gain stage. Overall this can mean that you can use less stages of gain.
Additionally, the cost of the interconnect cable should be considered as part of the cost of the preamp. It is not that weird these days for a single-ended set of interconnects to cost a significant fraction of the cost of the preamp. But what if you got a pair of 40 foot interconnects for only $200-$300 and they sounded as good as the best single-ended cables you ever heard? You would think audiophiles would jump on that...
As Ralph was perhaps too modest to directly recommend his own Atmasphere pre(s) I will, as well as the used Sonic Frontiers Line 3 for consideration. Both are truly balanced and have an appropriately low output impedance for this application.
I've been using balanced cables in various pro audio situations (and my hifi wherever possible) since the end of the last ice age, and I can say without a doubt there are HUGE differences among these cables. Better mic cables are better. I was recently shocked when an otherwise respected brand of balanced IC completely BLEW GIGANTIC VIRTUAL CHUNKS of treble hash in my hifi, and was quickly returned to the seller...replaced with some inexpensive AQ Diamondbacks that sound fine. Note that another single ended version of the offending (Mogami Neglex...there I said it) cable works fine for my turntable Akito din plug rig, so it has made ammends somewhat.
Atmasphere, I believe you. The whole point of true balanced should be to eliminate IC wire/wire length influences. I have a hybrid preamp with both SE and BAL outputs. I used high quality BAL cables for many years; but occasionally I would put some SE ICs between the amp and preamp and that arrangement would sound a touch better. Eventually, I moved my amp closer to the preamp and went with high quality SE ICs. I think it sounds better with SE ICs because on paper my preamp wants 20k Ohms min impedance and my amp is 22k ohms BAL looking into it. I think the SE has slightly higher impedance. My ICs also have switchable impedance settings. Is my thinking correct? My system today sounds very good with satisfying low end.
Tonywinsc, your thinking is correct. Single ended cables and preamps have no termination standard and tend to be high impedance. Under these circumstances the cable cannot be very long and how it is built has a huge effect on its sound.
Wolf_garcia, it is evident from your post that what ever balanced equipment you were using does not support the balanced standard. Your results are typical in that regard. I use Mogami Neglex all that time and have no troubles with it at all, but I am careful to use generic balanced cables onlly when I have confidence that the equipment supports its use.
Atmasphere, I use balanced outs from my DAC to balanced ins on my preamp (Kavent S-33), and it was the balanced out from the preamp to the power amp where the Mogami sounded crappy, and the balanced Diamondbacks sound great. Even the weird (but seemingly decent) "green mystery" balanced cable supplied with the Kavent sounded better than those particular Mogamis (Guitar Center...maybe they were crap?). I was surprised really as Mogamis usually sound fine (like I said, the Akito's Mogami cable sounds great) and I've used 'em as mic cables in pro audio gear for years. Go figure. I might be the only person in audio history to have a bad Mogami experience.
Wolf, I don't think so- I think it has more to do with how the cable is driven.
Unfortunately there is not a lot of information on the Kavent, but likely what is happening (as this is very common) is that the preamp puts signal current on the ground connection of the cable (If the preamp has XLR outputs and also RCAs that both work at the same time without operating a switch, then this is the case).
If it does that then you will hear pretty big differences in cables (which is not supposed to happen with balanced...). IOW it does not support the standard, but in that regard it has a lot of company. This is why there is so much confusion about balanced operation.
Atmasphere is corrent in that there is a lot of confusion about balanced operation. The proplem being that too many manufacturers do not clarify the type of operation used in their "balanced" connections.
I have been inside a lot of equipment over the years only to find some components claiming to have balanced connection simply tie pin #1 and pin #3 together. This is no more than a single ended circuit with a XLR connector. Some manufacturers do this because they don't think there is a difference between single ended and true balanced and don't beleive consumers can hear a difference. Others do it simply for marketing to those who are looking for balanced. Unfortunately, these are the products that created all the confusion and they are deceiving consumers.
All of our Purity Audio Design preamps are true balanced and do agree with others that when done properly, it will make a difference as long as it is being used with associated components that also uses true balanced circuitry.
You have to be careful not to judge say a preamp with true balanced outputs when it is feeding an amplifier that simply has pin 1 and pin 3 tied together on a XLR connector. You are not getting the benefits of balanced in such an arrangement as you are back to dealing with the ground so you cannot put any blame on the preamp. It happens far too often.
The Kavent S-33 is exactly the same preamp as a Vincent SA 93 for whatever that's worth (I might be able to find out about the outputs somehow). Although I'm not certain if the XLR outs are truly balanced (with one meter ICs it doesn't matter to me anyway, except for the fact that I like XLRs), I am certain the Mogamis sucked, which was my point. Also, hearing differences in balanced cables maybe is "not supposed to happen", but in pro audio using balanced mic cables it happens all the time.
By the way, is there any simple way to test if XLR outputs are actually balanced without a boatload of test gear?
Wow thanks for all the info. Some of it went over my head but all very usefull
Wolfman; with the amp or preamp powered off, measure resistance between pins 1 and 3 with an Ohmmeter. If you see something less than 1 Ohm then the pins are tied together like Atmasphere says. If the meter reads open (infinity) then it must be a true balanced circuit.
My ML 433 and ARC LS27 are a great match. A used LS 27 should just fit within the top end of your price range.
Wolf, I bet your preamp is balanced. But like a lot of modern studio gear, the outputs are probably set up so that the non-inverting occurs between pin 2 and pin 1 (ground) while the inverting output occurs between pin 3 and pin 1.
How it *should* work to get cable immunity is that the signal occur between pin 2 and pin 3 while pin 1 is ignored and only used for shield. But today a large amount of studio gear ignores this grounding issue, thus you are hearing differences in cables in the studio. Trust me on this one- the reason the balanced line system came into existence was to solve that very problem. I can do into the history of it if you like; but in a nutshell what is happening is that if you hear differences in cables then the equipment does not support the standard.
My pro mixers with balanced, low impedence ins and outs certainly "support the standard" or I wouldn't be able to use 100' snakes for clean signal...Better mic cables do sound better in my experience, as I noticed when recording music for a TV show we used to do...I was recording direct to digital with a Mackie board using a high sensitivity phantom powered condensor mic and used very good headphones...the better cables were clearly better sounding.
Ralph (Atmasphere), thanks for what as I see it is really excellent info and background, including the proof that is provided in your first post above, which strikes me as extremely persuasive. A few days ago I provided a link to that post in a couple of the ongoing cable threads.
Wolf, keep in mind that even if the equipment has very low output impedance and very good drive capability, it does not meet the standard if it connects XLR pin 1 to circuit ground, as opposed to chassis.
As Ralph indicated, and as is indicated in Figure 1b and some of the text in this paper
, it is very common for pro equipment (as well as consumer equipment) to connect pin 1 to circuit ground, in violation of the standard.
Ralph, is there any threshold that can be defined for how low the resistance that may be designed into a component between circuit ground and chassis ground can be without defeating the purposes of the standard?
Also, to eliminate interconnect cable differences is it necessary that the component output actually BE driving a low load impedance (2000 ohms or less, to use your figure), or is it just necessary that it be CAPABLE of doing that?
Thanks again. Best regards,
I'm gathering all my pro gear together tonight to talk to it about "violating the standard." I need to know what violations are taking place and why, and will include tip/ring/sleeve jacks and all my outboard gear...it won't be pretty.
Wolf, don't take any guff from any of those components. Tell them they better toe the line, or else!
Hi Al, I've not seen anything that defines a resistance to ground as a standard. I know that you can have some, as long as the circuit does not put current through it.
But I think the classic example is that of an output transformer, as one might see in a Neumann microphone. In this case the transformer is driving the output with its secondary, which is a single winding without a center tap. One side of the winding is pin 2 and the other side is pin 3. Ground is simply the circuit ground of the mic, but has no continuity to pin 2 or 3. IOW the transformer output is floating.
You touched on an interesting point about the load vs the capability to drive that load. I have found that the capacity to drive the load plays a huge role, about 80% but for that last bit of cable artifact to go away the load must be there as well. Flipping the coin over- if the capacity to drive the load is absent, then its moot and there will be cable colorations.
I remember back in the 1990s Stereophile published some letters to the editor from an audio engineer who was basically taking audiophiles and the high end audio industry to task because as he put it 'cables don't make a difference' and its all 'snake oil'. I think Stereophile published the letter mostly because of the humor value as everyone knows that cables do make a difference, but what neither party really made clear is that the engineer was working almost exclusively with balanced cables while audiophiles were using single ended.
I'm a very low-tech guy, but my McIntosh C220 (actually a tube-hybrid pre) has XLR outputs, and plays fine using RCA cables (18' runs!) with my Odyssey Audio HT3 SS amp. No bass roll-off. And it worked well also with Arion Audio RS-500 class D monoblocks I had temporarily (fantastic amps, btw). The C-220 lists for ~$4K.
Bondmanp, if the long runs are a problem, it will be a rolloff in the highs that is the issue.
Yes, Atmasphere, you are correct. By no bass roll-off, I guess I meant impedance mismatches, which is what I experienced with a C-J PV-11. The McIntosh restored the bottom octave. A better match, I suppose. But I don't think I am suffering any high frequency roll-off, either.
Hi Pete, I'm in the same mess ! Have a ML 336 and I want to pare with a tube pre amp. My focus is now on Manley 300B Neoclassic or on the Cary Audio Slp 05. Both very good looking, and well reviewed, but actually I haven't heard any of those.
Does anyone made a comparison ?