[dburna]

I am starting a build of NCore amps soon and wanted to know what experiences (good/bad) people have had with using a passive pre-amp with the NCores.  I have been considering a short list of passives to mate with the NCores (e.g. DIY Paradise Eva-2, Akustyk resistor-ladder passive, Pass B1 Buffer) and I was wondering a few things about sound quality for this combo:

1. Did anyone feel that LDRs or a resistor-ladder were a better match?
2. What passives seemed to perform best with the NCores?
3. Were there any appreciable downsides to using a passive with the NCores?  Since the NCores have such a high input impedance, I thought that they might present close to the ideal application for passive pre-amps (making them sound as good as they can). 
4. Did dynamics suffer with a passive, especially at low levels?
5. Did anyone feel that their passive pre-amp fell short against their active "brethren"?  If so, how good a pre-amp (make, cost) did it take to better the passive?

And finally, a generic (bonus?) passive pre-amp newbie question:

6. For a resistor-ladder passive, what does the indicator (10K, 25K, 50K, 100K) stand for?  How does you know what would be the best match for one's system?


Thanks, -dB

[Rclark]

 I'll be testing with an LDR, I'll let you know how it goes.

[Chris Adams]

I built a pair of NC400s and use them with the Pass B1 that I built. Works great and sounds even better. Very dynamic. My B1 has a Goldpoint attenuator and upscale parts. The B1 with basic parts is inexpensive to build. If you do so and like it, you can always upgrade it little by little. Or, try something different.

10K, 25K, 50K, 100K is the impedance of the attenuator. Rule of thumb, impedance in should be 10x higher than the impedance feeding it.

[dburna]

10K, 25K, 50K, 100K is the impedance of the attenuator. Rule of thumb, impedance in should be 10x higher than the impedance feeding it.

Well, OK, this makes sense, but if that's the reasoning, wouldn't you want the input impedance as high as possible?  Why not 500k?  Higher?  I think I read somewhere that, in a shunt-resistor configuration, the output impedance is proportional to the input impedance -- as one goes up, so does the other.  I don't know if that's true (I could be delusional), but it might make sense as to why you wouldn't want an attenuator with an infinitely high input impedance.

Am I missing something here?  Is the above explanation correct?  Or should I just look for an attenuator with as big an input impedance as possible (more is always better?)?

Thanks to someone who can explain this one to me.

-dB

[Letitroll98]

4. Did dynamics suffer with a passive, especially at low levels?
5. Did anyone feel that their passive pre-amp fell short against their active "brethren"?  If so, how good a pre-amp (make, cost) did it take to better the passive?

I had a different opinion than my listening panel did.  I have a pre that has both passive and active options.  First, the Ncores had way more dynamics than my class A/B using a passive pre, albeit the Ncores had a 2-1 power advantage, not all that much in absolute terms, nevertheless they handled impact much better.  However the Ncores did give up some dynamics using passive compared to the active circuit.  Our differences were that I felt the active circuits added enough impact to offset the slight addition of some electronic grain or haze, the listening panel universally preferred the passive option and didn't mind the slight loss of dynamics.  These findings were consistent at high and low level listening.

Since my PS Audio pre was down for repair, the pre in question was a lowly B&K CS115.  So you don't need much of a preamp to get within shouting distance of a passive unit.  Note that in passive mode there is almost no difference between the B&K and the PS Audio.  Only in active mode does the PS Audio's quality shine brighter than the B&K.  So I would feel confident enough to say that you could pick your preferred option in preamps and not go wrong, however you wouldn't be escaping the traditional tradeoffs.     

[Chris Adams]

Well, OK, this makes sense, but if that's the reasoning, wouldn't you want the input impedance as high as possible?  Why not 500k?  Higher?  I think I read somewhere that, in a shunt-resistor configuration, the output impedance is proportional to the input impedance -- as one goes up, so does the other.  I don't know if that's true (I could be delusional), but it might make sense as to why you wouldn't want an attenuator with an infinitely high input impedance.

Am I missing something here?  Is the above explanation correct?  Or should I just look for an attenuator with as big an input impedance as possible (more is always better?)?

Thanks to someone who can explain this one to me.

-dB

Many variables involved and my modest understanding isn't enough to explain it thoroughly to you. I know there are other members who can explain; maybe one will chime in.

[dburna]

I installed my new NCore amp a little over a week ago.  Love it!  Thanks to Mike Galusha for a terrific assembly job.  So here's my new configuration:

Mac Mini (via Pure Music 1.6. -> AR-T Legato -> Audio-GD DAC19DSP -> NCore amp -> Horning Perikles Ultimate speakers
Small-to-medium sized room
Using almost solely using 16/44.1k files
Pure Music supplying the volume attenuation (currently set to 24-big
DAC19DSP: output impedance = 20 ohms
NCore: input impedance = 108k ohms (or something near that)
Perikles Ultimates: 96dB, 8 ohms nominal (fairly close to 8 ohms throughout the frequency range)

I have given some thought to a pre-amp in this system.  Thought about a number of options in the under $1k range (Burson Soloist, Dodd Buffer, Luminous Audio Axxiom, Pass B1 buffer, used/vintage pre-amp).  My question: do I need one?

Consider the following:
1. Gain?  Don't need it.  NCore has (26dB) gain into 96dB speakers.  Gain isn't needed, only attenuation.
2. Attenuation? Pure Music provides digital volume attenuation -- supposedly high-quality and no loss in sound quality due to use of bits 16-24 (or 24-36 bit).

Sooooooo, what am I missing without a pre-amp?  Tone?  Soundstage?  Distortion?  Not only have I taken one preamp out of the equation, but also a set of interconnects as well.

My other issue here is that I can't use any pre-amp that doesn't provide major attenuation.  In my current system, I find that I am using somewhere between 30-40dB attenuation.  I never go above -25dB in my rig.

Thanks for any insight you can provide.  If there is a GREAT sounding sub-$1k solution that would work here -- and provides at least 40dB or more attenuation -- I'd appreciate knowing about it.

-dB

[hopkins]

Am using an ADCOM GFP-750 in passive mode with great results... It has XLR inputs and outputs, and a remote. Sounds amazing with the Ncore.

[jtwrace]

Am using an ADCOM GFP-750 in passive mode with great results... It has XLR inputs and outputs, and a remote. Sounds amazing with the Ncore.

Can you share more about your system?

[hopkins]

Sure.  Alix 3D2 w/Voyage MPD > Ayre QB-9 > Adcom > Hypex Ncore > Harbeth HL Compact 7. 

[jtwrace]

Sure.  Alix 3D2 w/Voyage MPD > Ayre QB-9 > Adcom > Hypex Ncore > Harbeth HL Compact 7.

[milezone]

I'm using a Stax SRM T1W with my NCores driving KLH Nine electrostats. The preamp is essentially a balanced volume control. The result -- astounding. According to my ears, musicians perform in my living room. I'm considering building a tube buffer or active gain control with some tubes I have lying around. Anyone else using a tube buffer with their NCores? Furthermore, I run fully balanced. Does anyone know of a balanced option on the level of the lighternote/lightspeed attenuator?

[ijscobar]

No Ncore for me (yet...). I have tried using a passive pre with UCD400AD's though. Did't like it. Takes the "soul" out of the music.
Tried the Pass B1 buffer also. Liked it very much. If you don't need the gain this is a go! I needed the gain however so I built a RelaiXed 2.
This is a diy balanced pre amp. I've been using it for a couple of months now and it does very well!

http://www.eijndhoven.net/jos/relaixed/index.html

[mikeeastman]

I've had my Ncores a couple of weeks but just got them hooked up to my main system today. System not complete, waiting on buss to power front end  and new speakers ( Serenity Super 7s ) , using mac book instead of modded mini, Redwine Isaballina w/ pro upgrade and John Kenny MK3, Dodd balanced tube buffer, GR Research OB 7s. I notice a big difference with tube buffer, bigger soundstage and the music sounds much richer and fuller. will do more A/Bing when I get buss and new speakers in next couple of weeks.

[Vetnik]

Hi all,
Just finished my first nc400 mono amp.
It works fine with a tc impact twin as a dac preamp, but is not working (nly hummmmm) with my transformer based passive preamp. (Tvc).
Any thoughts would be appreciated
Thanks a lot,
Nikos

[jtwrace]

Hi all,
Just finished my first nc400 mono amp.
It works fine with a tc impact twin as a dac preamp, but is not working (nly hummmmm) with my transformer based passive preamp. (Tvc).
Any thoughts would be appreciated
Thanks a lot,
Nikos

Is the passive XLR or RCA output?  Have you checked pinout to make sure it's wired properly to the NCore?

[Vetnik]

Is the passive XLR or RCA output?  Have you checked pinout to make sure it's wired properly to the NCore?

problem solved!
one channel of my tvc was not working properly.
tvc and ncore is an ultra transparent combination...
thank you for your effort!

[jtwrace]

problem solved!
one channel of my tvc was not working properly.
tvc and ncore is an ultra transparent combination...
thank you for your effort!

Great! 

[rklein]

No Ncore for me (yet...). I have tried using a passive pre with UCD400AD's though. Did't like it. Takes the "soul" out of the music.

Depends on the passive that you use...

Randy