Initial impressions home demoing Dartzeel NHB-18NS

[Bergm@nn]

I've fancied giving a NHB-18NS a go in my system for quite a while based on impressions of users and overall reviews etc. So I jumped at the chance when a Mk1 unit became available, and I had the chance to hear it in my own system (with a Pass XA30.8 and AG Duo XDs).

First impression on plugging it in seem promising. Not as dynamic as I was expecting but good enough to give a few days to settle in and play with.

Two concerns have surfaced during this time -

1. Battery charging
I suspect that the batteries have ceased to operate. I followed the switching instructions from BTM to auto and only get orange when powered off and red when powered on. The unit is likely 10 years old with no record of whether the original batteries have been changed.

2. Hiss
I accept I'm using this with Avantgarde horns which are 107db sensitive, but the general hiss from both tweeter and mid horn seem obtrusive to me. Certainly louder than when I've had VTL7.5 and ARC5's etc. When playing at quite low levels 65db the hiss is quite obvious. It only recedes from my notice when the measured sound level is up about 80db.

At idle with no music playing the hiss is easily audible from my listening position 3m away.

My impression was that the Dartzeel is a pretty low noise device, so do I need to calibrate my expectations based on trying to use it with maybe speakers that are too sensitive, or does my unit/ experience sound out of the ordinary and perhaps the unit is not performing properly?

My original plan was to take this unit on and send it back for the full upgrade package to Mk2, but based on what I'm hearing so far I've not got sufficient indication/ confidence that I won't be pouring good money after bad?

If this is it, its going to have to go back.

 

[Tim Link]

This interests me because hiss amplification is a problem I have with my horns too. I understand that some pre-amps have gain settings that can be adjusted for the sensitivity of the speaker. From what I've read about this unit it does seem to have that feature. I read this on Mono & Stereo review of the product: "The NHB-18NS flexibility of the input and maximum output gain, which can be set via the menu with the balance control, offers greater adaptability than usual." I'm not sure if adjusting the maximum output gain to something lower might reduce noise.

 

[Mike Lavigne]

not sure a likely 10 years old Mk1 with dead batteries is a reference for how the 18NS can sound. if it has dead batteries might there be something else not quite right? dead batteries are not likely to lower the noise, but might raise it.

OTOH it's exactly right for what you have right there. it is what it is.

but if you want to know the objective truth, send the serial number to darTZeel or your local darTZeel distributor and find out the build date. new batteries are a few hundred dollars and easy to change if you can handle a solder gun.

my speakers are 97db efficient and i cannot hear any hiss at all from my listening position with my Mk2 18NS. my batteries are just fine. i did own a Mk1 for 11 years and never heard hiss there either, but my batteries were kept in good shape.

i do respect 107db efficiency and the consequences of noise. good to be careful about that.

 

[Bergm@nn]

I suspect that what I'm hearing is a result of perhaps too much gain in the system for the sensitivity of the horns. It takes from experience about 0.3-0.5 of a watt/ch to fill my room with sound!

The 18NS has 11 db and my Pass power amp about 26db into a 107db speaker.

So I either need a pre with little to no gain, or a power amp with little to no gain. I suspect that the lowest noise solution would be the latter.

As an experiment I inserted my Luxman 58a into the set up. You can use it as an integrated or as just pre or power. I can't find any gain figures for the unit but suspect that most the gain is coming from the power stage.

When I set up with the 18NS into the 58a (power only) the hiss was louder than 18NS into Pass.

When I set up 58a (pre out) into the Pass the hiss was less than 18NS into Pass.

As for the 18NS itself, its frustrating as I'm clearly not hearing it at its best (ie it never goes into battery mode, says its always charging without going green LED), and the system means the lack of matching makes the speakers hiss quite noticeably when playing music.

My dilemma now is -

1. Do I stick with the 18NS and get the batteries replaced/ send it for upgrade, and then look for a better matching power amp?
2. Or give the 18NS back and look elsewhere for a pre that better matches the Pass?
3. Give up on both and look for an integrated which is already 'matched' like an ASR Emitter or Grandinote etc?

 

[Bergm@nn]

Update: I changed my power amplification to a pair of low gain SIT amps and problem 2: hiss has now gone away entirely.

Still have problem 1: battery charging, and have looked into the cost of replacing these vs cost of sending unit away for complete upgrade.

 

[Mike Lavigne]

Update: I changed my power amplification to a pair of low gain SIT amps and problem 2: hiss has now gone away entirely.

Still have problem 1: battery charging, and have looked into the cost of replacing these vs cost of sending unit away for complete upgrade.

sounds like good news, progress. last time i got batteries for my Mk1 (10 years ago) they were around $250-$300. hope it's not too much more for you.

good luck on the battery thing, should not be too tough. also; there might be a software update that might improve the charging protocol. you should check with the darTZeel distributor or the factory.

 

[Bergm@nn]

Big question now is how much to consider buying this for? It is as stated a mk1 and c 10 years old.

How much do we think is reasonable in £GBP?

 

[uber2]

I ran avantgarde 107db with XA-25 and Nagra Classic Pre (-120db noise floor)
Although AG always played best with tube amps imho.
Once hiss is heard its quite annoying.

 

[Zeotrope]

My custom horns are ~102dB efficient and I sit 3m/10’ away. With Kondo tube pre and amp, some hiss was heard, but it was very faint.
With the Zeel 18NS and 108, there is still some hiss; but it seems to be lower.
What I don’t understand is why the hiss/background noise changes - sometimes it’s about +1dB higher. Why?
I’m now investigating the Zee 50ohm BNC cable, as it is in close proximity to AC cords at some places, and moving it may be linked to the increase in background noise. Not sure how well shielded that BNC cable is?

 

[Mike Lavigne]

My custom horns are ~102dB efficient and I sit 3m/10’ away. With Kondo tube pre and amp, some hiss was heard, but it was very faint.
With the Zeel 18NS and 108, there is still some hiss; but it seems to be lower.
What I don’t understand is why the hiss/background noise changes - sometimes it’s about +1dB higher. Why?
I’m now investigating the Zee 50ohm BNC cable, as it is in close proximity to AC cords at some places, and moving it may be linked to the increase in background noise. Not sure how well shielded that BNC cable is?

my Evolution Acoustics MM7's are 97db efficient; my ears are 95" away, no audible hiss. i do use Evolution Acoustics 7.5m 'zeel' BNC's from pre to dart 468 amps which have multiple (5) AC cords crossing them. these BNC's are very robust, stiff and heavy.....don't know about shielding. never heard any variable hiss or a random 1db gain in hiss.

i do have an 11 meter run of old style darTZeel 'zeel' BNC's running across my room to my RTR King Cello repro amp for my Studers. never noticed any hiss from that either. it does cross three AC cords.

 

[Zeotrope]

Thanks Mike. Good to hear, but my horns are significantly more sensitive than your towers.

I will continue to look into the routing of the ZeeL BNC cable. I am also early in the break-in process of these new crossovers, which could be causing it…

 

[Mike Lavigne]

Thanks Mike. Good to hear, but my horns are significantly more sensitive than your towers.

I will continue to look into the routing of the ZeeL BNC cable. I am also early in the break-in process of these new crossovers, which could be causing it…

View attachment 96868

those are beautiful. are those copper/lead cylinders for resonance control? Walker pucks? i have a set i use but mine are all beat up from spike marks.

 

[Zeotrope]

those are beautiful. are those copper/lead cylinders for resonance control? Walker pucks? i have a set i use but mine are all beat up from spike marks.

Thanks! No, everything you see is a component: capacitor, resistor, or inductor. Nothing for resonance control, other than the thick walnut board.

 

[Audiophile Bill]

those are beautiful. are those copper/lead cylinders for resonance control? Walker pucks? i have a set i use but mine are all beat up from spike marks.

Look like Dueland caps to me, Mike

 

[Zeotrope]

Look like Dueland caps to me, Mike

Yup. Duelund CAST Tinned-Copper caps. Great reviews on them from Jeff Day, among others.
These were built by Tony at Humble Homemade HiFi. Highly recommended!
Everyone should at least take a look at their existing crossovers - it’s one of the best price-performance improvements you can make. First, move it outboard, if it’s currently built into the speaker.
Second, improve the components.
Mine are still running in (it’s a long break-in time, unfortunately), but the difference vs my stock metal foil cap and ceramic resistor crossover is huge (realism, soundstage).

 

[Audiophile Bill]

Yup. Duelund CAST Tinned-Copper caps. Great reviews on them from Jeff Day, among others.
These were built by Tony at Humble Homemade HiFi. Highly recommended!
Everyone should at least take a look at their existing crossovers - it’s one of the best price-performance improvements you can make. First, move it outboard, if it’s currently built into the speaker.
Second, improve the components.
Mine are still running in (it’s a long break-in time, unfortunately), but the difference vs my stock metal foil cap and ceramic resistor crossover is huge (realism, soundstage).

Look beautifully finished - enjoy. Love the attention to detail. You could consider larger diameter wire (or ribbon) or different cores (lots of options) on the inductors in time too.

 

[Zeotrope]

I did confirm that my DarTZeel 50 ohm BNC cable will pickup background noise if close to AC cables. I have the latest (thickest) version. Perhaps it won’t be noticeable in your system: I have >100dB sensitive horns that I sit only 3m/10’ away from.
Careful distancing of the BNC cable from AC cables yielded a small (~0.1dB) but noticeable reduction in background noise.

 

[Bergm@nn]

Off to have a new set of replacement batteries fitted to the 18NS tomorrow

As I'm likely to pay the balance off on the unit too, I'm rather hoping that listening to the unit via battery power as intended makes a reasonable audible difference!