AudioCircle
Other Stuff => Archived Circles => Hypex Owners Circle => Topic started by: forkliftHIFI on 14 Jul 2014, 02:54 am
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A few months back I almost ordered a Peachtree Nova 125 w/D5 speakers but didn't go through with it and went on a research binge.
So far I've put in for a pair of Sierra Towers w/RAAL tweeters from Ascend Acoustics. 90 db/w efficient, 6 ohm nominal, 4.5 ohm minimum impedance. 300 w maximum recommended continuous power. The nc400 appeared to be an ideal match for these and I have commissioned one of the build services for a stereo nc400.
My decision now is passive preamp or active. Strongly considering a Goldpoint balanced passive pre or one of the several LDR type passives. Also considering an oppo bdp-105 which would serve as a sort of dac source and passive pre. Cost is obviously a factor or I'd go all out on a high end balanced active preamp. That said is there any significant performance hit from using a single ended preamp with RCA/XLR conversion cables?
Any advice would be appreciated.
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Good choices so far. (I bought one of the first pairs of Ascend Acoustics CBM-170 and still love them in my little A/V system.)
Don't worry about sound quality differences between XLR (balanced) vs RCA (unbalanced) cabling or the converters. The XLR locking connectors are nice and the gear that offers XLR is typically better stuff (build quality, higher cost) but XLR is not needed for typical home use unless you are planning on long parallel runs of multiple cables (think stadium concerts or studios full of gear). Due to my gear I've got both on hand (same wire/vendor) and can't tell a sonic difference.
The issues with passives relate mostly to system matching and the need for buffering. Some systems need the extra dynamics of active. Some cables provide an impedance mismatch which can mute high frequencies. Some amps need greater input signal strength than the sources can provide. And some audiophiles (tube fans mostly) want to be able to flavor the sound by introducing the pre-amp (or just have the easy accommodation for multiple sources).
I own Channel Island Audio Hypex based digital mono-block power amps and had one of their passives (which is the only style of pre-amp they've ever sold), but stepped attenuators that work best connected at the amp inputs (search Scott Endler who also custom made all my cables for very reasonable cost) sounded better (both had excellent volume controls). They are cheaper but limits you to one input at a time unless you plug and unplug sources. Active pre-amp (solid state) sounded better yet in my system (unfortunately true due to higher cost).
As you obviously have a computer, you should consider using it as your source and adding music playback software (like JRiver, Pure Music, or Audirvana) and trying a nice DAC like a Schiit BiFrost ($349 - 519 and upgradable/"future proofed") without a pre-amp. Or step up to a nicer DAC ($2000 Benchmark DAC2 HGC, $1700 Mytek 192, or $1200 Oppo HA-1 for instance) that can handle DSD and all PCM modes plus has multiple inputs, headphone outputs, volume control, and remote.
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Go Tortuga. For the money, it is very nice sounding.
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I have the Hypex nc400 mono blocks in cases from Aluminati Sound. I have had good success pairing these with a Wyred 4 Sound STP-SE preamplifier which is a passive/active design (has a great volume control). These are driving Von Schweikert VR4jrs that are soon to be replaced by Vapor Audio Joule Blacks.
Don P.
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Don't worry about sound quality differences between XLR (balanced) vs RCA (unbalanced) cabling or the converters. The XLR locking connectors are nice and the gear that offers XLR is typically better stuff (build quality, higher cost) but XLR is not needed for typical home use unless you are planning on long parallel runs of multiple cables (think stadium concerts or studios full of gear). Due to my gear I've got both on hand (same wire/vendor) and can't tell a sonic difference.
The difference between balanced and unbalanced is not really in connectors (despite the historical fact that balanced tends to use XLR's). The main difference comes from the differential input stage that offers common mode rejection and ground isolation. You can get most of the benefit of the differential input stage even when using an unbalanced source.
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I used an unbalanced battery powered LDR for a while and now use a balanced Emotiva XDA 2 with an Emotiva CMX2 power filter, Emotiva X series XLR cables and Emotiva X series power cables. Lotta Emotiva in my system, lol, and the NC400's are astounding.
Will also add these amps have never been switched off, been a couple years now, and they also pulled double audiocircle tours cross country. These amps are as reliable and consistent and maintenance free as you could please. They also sip mere single digit wattage at idle. Dream amps.
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Differential can sound much different than single ended. True balanced outputs eliminate the even harmonics. The even harmonics can add to the musical pleasure of the music for some people. The odd harmonics are not lost and they are the least musical part of the music. A lot of the flavor that people prefer with tubes comes from the even harmonics. You will lose a lot of the benefit of tubes with true tube differential outputs. Low distortion solid state differential dacs and preamps work well with balanced outputs. If you like tube sound then go single ended if the tube preamp has true balanced outputs.
Bob
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True balanced outputs eliminate the even harmonics.
What properly designed modern preamp has audible levels of harmonic distortion?
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I would think the OP would be more interested in preamp suggestions rather than a debate of balanced vs. single ended. Just my humble opinion.
Don P.
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That said is there any significant performance hit from using a single ended preamp with RCA/XLR conversion cables?
You might read starting at page 12 here. (http://www.hypex.nl/docs/NC400_datasheet.pdf)
12.2 Input configuration
The second major cause of extraneous noise and distortion is common-impedance coupling between
power wiring and signal connections. This is caused by the use of ground-referenced signalling (aka
single-ended or unbalanced transmission), which unfortunately is the predominant method of
interfacing consumer-grade audio equipment. As a result the ground circuit becomes an inseparable
part of the signal path and any currents flowing through the ground circuit affect the audio signal.
Ground loops cannot fundamentally be avoided. Star grounding only works at low frequencies. The
longer the wires to the “star”, the lower the frequency at which supply decoupling becomes
ineffective. The maximum permissible trace length of decoupling capacitors in class D amplifiers is
measured in millimetres and the value of the decoupling capacitances is large. To make a long story
short: you cannot connect the audio signal using a single wire and hope to solve the ensuing drama
using star grounding. It won’t work.
12.2.1 Way of looking at it when you’re only familiar with unbalanced wiring.
The solution adopted by the NC400 is a floating input, consisting of a “hot” and a “cold” connection,
which can be connected to the source like the primary of an isolation transformer. This breaks any
current flow that might otherwise flow in the audio cable. You would never directly connect the cold
pin of the input connector to the ground pin in the same way as you would never locally ground
input of an isolation transformer because it would no longer provide isolation.
Note that this isolation is not absolute. Differentials of more than a few 100mV should be avoided.
Because of this, some current path should be provided using a third wire. Any current that flows
through that wire is current that’s no longer flowing through your audio cable, and which is now
harmless.
Source Amp
Figure 1: The basic idea behind a differential (floating) input.
12.2.2 Way of looking at it if you’re used to working with balanced connections.
The NC400 has a balanced input.
12.3 Acceptable wiring schemes for amplifier chassis
The differential input permits a wide range of robust scenarios for hum-free connection, of which
three will be shown. We would like to urge users not to venture into the unknown before having tried
one of the proven good ones.
12.3.1 Vastly preferred setup: XLR input.
Regardless of whether the remainder of your audio system has balanced connections or not, the very
best way to wire the input of the NC400 is to leverage the advantage of its balanced input. You can
get almost all of the quality improvement afforded by balanced connections even with an
unbalanced source, provided that you have a balanced input.
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You won't find a more transparent preamp than the Tortuga unit...I should add that I have owned TVC units in copper and silver (Bent), as well as the Placette. The LDR units were a noticeable improvement, one that I was not expecting....
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take a LOOK at Bent Audio AVC-1 preamp or the Tap
http://www.bentaudio.com/index2.html
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Also read up on the Placette Remote Volume Control and the Passive Linestage
http://www.placetteaudio.com/Reviews.htm
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take a LOOK at Bent Audio AVC-1 preamp or the Tap
http://www.bentaudio.com/index2.html
I did a comparison here:
http://www.audiocircle.com/index.php?topic=119915.msg1308586#msg1308586
Best,
Anand.
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To me it appears you are cost conscious, if so, my strong advice would be to avoid a preamp entirely unless you really need to switch between multiple sources easily.
The NC-400 are easily driven directly by most DACs with volume controls. There is nothing wrong with digital volume controls at all, as long is one is using them in a properly gain matched set up. With proper gain matching, critical listening will take place in the upper range of the VC, resulting in no loss of resolution.
Going direct also allows one to take advantage of balanced operation, whereas something like a balanced Bent TAP will add considerable additional expense.
An example of a DAC with an excellent VC is the Wyred 4 Sound DAC 2.
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What properly designed modern preamp has audible levels of harmonic distortion?
Sorry to take so long to reply. Tube preamps can have fairly high distortion. As an example, Stereophile states the total harmonic distortion of my Calypso preamp to be about .2 percent at one volt output single ended. It also gives about .02 percent differentially. My Calypso was rated Class A by Stereophile.
Bob
Edit: I prefer to listen to my Calypso in the single ended mode even though the distortion is higher. In the differential mode, I prefer to bypass my Calypso entirely and just use the solid state differential output of my DAC/preamp.
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I would think the OP would be more interested in preamp suggestions rather than a debate of balanced vs. single ended. Just my humble opinion.
The OP specifically asked:
is there any significant performance hit from using a single ended preamp
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Tube preamps can have fairly high distortion.
True. And that distortion is often quoted as the main reason some people prefer tubes. I just find pairing tubes with a nc400 a somewhat odd choice, given that the nc400 is designed for extremely low distortion.
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Thank you guys all very much! You have given me lots of great information to consider.
After much research, at the high end of things I would very much like try try a Tortuga LDR or Bent AVC-1. Downsides are that XLR versions of either are very expensive.
Since I don't have a DAC yet, purchasing a balanced DAC will also be considerable added expense.
As a compromise how about getting a regular RCA Tortuga and a relatively inexpensive DAC like a Schiit Audio Bitfrost. Then I basically just connect the Tortuga to the ncore with the shortest XLR to RCA conversion cable I can find? Also use the shortest possible RCA connections between the DAC and the Tortuga.
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I would like to add that the Ncores were amazing with the unbalanced, Warpspeed LDR on battery. The only reason I switched to the XDA 2 was because I was dropping my ERC 2 cdp for a PS4, which forces optical input the Warpspeed lacks. Btw a PS4 with Music Unlimited is a pretty nice transport for digital music. Actually matched my cdp. The ERC 2 was sweet through , I may buy a 3.
The XDA 2 also gives me a remote and a rather decent headphone amp. But otherwise for sound quality I loved the Warpspeed. Don't think it matters that much. Choose whichever pre optimizes your source the best.
I'll eventually replace the XDA 2 with a Dual Core 2.0 on a high end supply and a separate stereo headphone amp, probably tubes, just to have some.
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As a compromise how about getting a regular RCA Tortuga and a relatively inexpensive DAC like a Schiit Audio Bitfrost. Then I basically just connect the Tortuga to the ncore with the shortest XLR to RCA conversion cable I can find? Also use the shortest possible RCA connections between the DAC and the Tortuga.
Sounds like a good solution - and as I wrote, with the differential input of the nc400, you get most of the benefits of balanced even with an unbalanced source - see Figure 3 under paragraph 12.3.1 in the nc400 data sheet.
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As you don't have a DAC yet, I suggest you try out a Exasound DAC, the volume control works very very well.
DSD256 playback with the transparency the NCore gives a simply glorious sound
Check out the Exasound thread at computer audiophile
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I would second...third...fourth all the comments about DAC-->nCore directly. You don't need a preamp if you have a DAC with a good volume control.
I have an Emotiva DC-1 that works very well (you can find these used for less than $400)... and have the LHLabs Geek Pulse X ordered to try.
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I have an Emotiva DC-1 that works very well (you can find these used for less than $400)
The current price for the DC-1 has been reduced to $499 shipped, and is apparently popular enough at the price that reservations are being taken for the next production run.
Steve
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Presently using a DC-1 with newly finished NC400s- no complaints!
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First the speakers came in. Then the preamp. Today the ncore stereo unit arrived. Here is the result.
(http://www.audiocircle.com/image.php?id=103899)
(http://www.audiocircle.com/image.php?id=103900)
Compared to what I was using before, and to anything I've actually heard before, all I can say is "Wow." It just plays so effortlessly. Can't turn it up right now as there are people asleep but tomorrow morning it's on.
I will probably make a new post or add some more once I rearrange and it's all finalized. Still haven't got a DAC, just using the computers soundcard.