Which of these two amps is better for a low impedance speaker?

[wainwj]

I've had it from new, but being in my second system, I doubt it's seen 100 hours use yet. I haven't noticed any significant change in its sound during this time.
The hardness/brightness might be a combination with your speakers? I've never heard, but would very much like too, obelisks. I believe that the speakers that I have mine hooked up to currently are known for being on the less harst/bright end of the spectrum. Spendor SP100 R2.
But again, reputation and spec , count for little as opposed to what you are hearing yourself.
How's the Marantz compare?

 

[Steveh]

This might be irrelevant now, but there was a time( ca. 2000?) when Shahinian recommended Creek amplification for the Obelisk mk 1.
With reference to your current(pun intended) dilemma, I would recommend the Denon. I have owned both Marantz and Denon amps(not the ones in consideration).

 

[Lawrence001]

Good to know, some Obelisk owners on the forums seem to think you need Battersea power station to get these speakers sounding right.

Intrigued to know why current delivery was a limitation into tweeters, I did some googling and it seems the issue arises due to a quirk with certain Naim amps like the Nap250 where a protection circuit can't deal with low impedance loads and therefore the speakers sound dull with them.

I'd be surprised if most normal amps struggled to power any tweeter.

 

[antonio66]

@Lawrence001 I can vouch for that after using Naim 135's with Obelisks. Sounded great until turning volume up a bit, then no sound at all due to the protection circuit kicking in on one amp or the other.

 

[HoopsOnToast]

O venerable druids of hi fi, your wisdom please. I’m currently auditioning for purchase two very good integrated amps to drive my Shahinian Obelisk Mk2 speakers.

The Obs, while rated at a nominal 6 ohms, are known to be difficult to drive because their omnidirectional supertweeters dip and hover around the 2 ohm mark.

I understand that wattage is secondary to current when it comes to an amp’s ability to handle low impedance speakers - but when I get into comparisons between the two amps I start to struggle.

Below are the power specs for each amp, benchmarked from the same source. For fun, and to keep things as objective as possible, I will for now avoid revealing the identity of the two amps and simply call them A and B.

Amplifier A: Rated 100/200w into 8/4ohm

The modest 100/200W 8/4ohm rating is exceeded to the tune of 190W/310W, with 228W, 433W, 645W and 355W achieved under dynamic conditions into 8, 4, 2 and 1ohm loads.

Continuous power (<1% THD, 8/4ohm)	190W / 310W
Dynamic power (<1% THD, 8/4/2/1ohm)	228W / 433W / 645W / 355W

Amplifier B: Rated 80w/160w into 8/4 ohm

Load tolerance is exceptional, with its 80W/160W 8/4ohm power rating being met at 2x93W and 2x180W into 8 and 4ohm loads. This 'stiff' PSU means that while there's little additional headroom under dynamic conditions there is the current available (24.9A for 10msec at <1% THD) to support a full 95W, 184W, 346W and 618W into 8, 4, 2 and 1ohm loads, respectively. So tough speaker loads will be driven with comparative ease.

Continuous power (<1% THD, 8/4ohm)	93W / 180W
Dynamic power (<1% THD, 8/4/2/1ohm)	95W / 184W / 346W / 618W

SO, Amp A doubles into 4 ohms, but beyond that starts to drop off - whereas Amp B doubles into 4 ohms and 2 ohms and has a decent stab at doubling to 1ohm!

BUT, at 2 ohm Amp A is putting out 645W, while Amp B is putting out 346W.

So my question is: which will cope/perform better with low impedance dips? In practice, does the superior underlying current stability suggested by Amp B trump the fact that Amp A can put out double the wattage of Amp B at 2ohm?

Any thoughts from the more technically minded among you would be very welcome. I am of course comparing their actual, rather than theoretical, performance at present and will share the results in due course – but I have to finish burning the buggers in first! Also, understanding the above will help me put in to context what I'm hearing.

Cheers

Steve

The PMA-2500NE is actually more powerful in lab tests with around ~130wpc/8Ohms & 210wpc/4Ohms

https://www.google.com/search?clien...iw=1536&bih=772&dpr=1.25#imgrc=wVi-Zlk_RTViNM

https://www.i-fidelity.net/testberi...ma-2500ne-denon-dcd-2500ne/labor-seite-7.html

I have had the PMA-2000IVR, PMA-2000AE and PMA-2500NE. There won't be many speakers, if any, that it wont be comfortable with unless you are in a PA setting.

I used the above amps (which are pretty much the same in the amplifier section) with ATC SCM10, Rega R9, Acoustic Energy AE2, KEF Reference 201/2 & Three-Two an no issues whatsoever.

 

[JamieMcC]

Was only looking at some specs for the Denon A110 earlier this morning where it mentions a 80W into 8ohms 160w into 4 and 328w into 2ohms

 

[culturecrammer]

I've had it from new, but being in my second system, I doubt it's seen 100 hours use yet. I haven't noticed any significant change in its sound during this time.
The hardness/brightness might be a combination with your speakers? I've never heard, but would very much like too, obelisks. I believe that the speakers that I have mine hooked up to currently are known for being on the less harst/bright end of the spectrum. Spendor SP100 R2.
But again, reputation and spec , count for little as opposed to what you are hearing yourself.
How's the Marantz compare?

Yes i had Spendors briefly and they are definitely warmish. The Obs are neutral and very transparent. They were fine with my Denon PMA850 (circa 1979) but Denon seem to be voicing their amps with more poke in the upper frequencies these days. With vinyl the A110 is wonderful - the phono stage is lovely.

I tried the Marantz to compare as I knew it would be warmer and softer up top. It is gorgeous and perfect for jazz, acoustic and classical - a velvety, inviting, intimate sound with loads of detail. But I miss the dynamism of the Denon - it’s all a bit too polite and restrained. The biggest issue I’m having with the Marantz though is how much smaller the soundstage is. Feels like my speakers have shrunk to standmounts. Surprised as others have described the soundstage as huge - unless burn in will open it up. Im only 30 hours or so in.

 

[culturecrammer]

Intrigued to know why current delivery was a limitation into tweeters, I did some googling and it seems the issue arises due to a quirk with certain Naim amps like the Nap250 where a protection circuit can't deal with low impedance loads and therefore the speakers sound dull with them.

I'd be surprised if most normal amps struggled to power any tweeter.

Yes I’ve seen this come up. Obs def like some power - particularly current - to sound their best. But I think you’re right that the issue has been overstated.

 

[culturecrammer]

This might be irrelevant now, but there was a time( ca. 2000?) when Shahinian recommended Creek amplification for the Obelisk mk 1.
With reference to your current(pun intended) dilemma, I would recommend the Denon. I have owned both Marantz and Denon amps(not the ones in consideration).

Thanks yes I’m familiar with the Creek recommendation. Why would you go for Denon over Marantz?

 

[culturecrammer]

If I could just get rid of that stridency in the upper freqs when playing digital the Denon would be perfect.

 

[culturecrammer]

I’d happily change digital sources to achieve that, but given the Ares 2 is already a fairly warm sounding DAC I‘m not sure there’s anywhere to go.

 

[culturecrammer]

i mostly listen to vinyl. Digital is mainly for enjoying my very extensive classical collection which I invested a lot of time and money in. Classical is unlistenable if upper frequency-dependent sounds like sopranos and strings do not sound natural. Classical should not be fatiguing!

 

[antonio66]

You could always look for something by Plinius in your budget, they are supposed to be a good match with Obs.

 

[wainwj]

If I could just get rid of that stridency in the upper freqs when playing digital the Denon would be perfect.

Have you tried knocking the treble back a little with the tone controls when playing digital?
Denon manual states TREBLE: 10 kHz ±8 dB
I haven't felt the need to try them on the Denon myself. But on my previous amp, a Luxman L-590 AXII, I used to do exactly this, for the reason you state.
The improvement that a small adjustment to the treble made was subtle and adequate. I could not detect any negative effect either.
I have just checked and the Luxman manual states the exact same spec of TREBLE: 10 kHz ±8 dB for its tone control also. So I'd definitely recommend trying that.
I imagine that the adjustment that I settled on with the Luxman must have been -1db or so but it made all the difference I needed.

 

[culturecrammer]

Have you tried knocking the treble back a little with the tone controls when playing digital?
Denon manual states TREBLE: 10 kHz ±8 dB
I haven't felt the need to try them on the Denon myself. But on my previous amp, a Luxman L-590 AXII, I used to do exactly this, for the reason you state.
The improvement that a small adjustment to the treble made was subtle and adequate. I could not detect any negative effect either.
I have just checked and the Luxman manual states the exact same spec of TREBLE: 10 kHz ±8 dB for its tone control also. So I'd definitely recommend trying that.
I imagine that the adjustment that I settled on with the Luxman must have been -1db or so but it made all the difference I needed.

Hi, thanks for the suggestion. I don’t really like using tone controls as I always feel that they are cutting out bits of the sound. I did try it briefly with the Denon - given your positive experience I will have another go

 

[Drummerman]

I am no tech expert but I would have thought that the tweeters will draw very little, 2ohm notwithstanding.

 

[culturecrammer]

I am no tech expert but I would have thought that the tweeters will draw very little, 2ohm notwithstanding.

Being omnidirectional there are eight sets of tweeters, I wonder if this is why?

 

[culturecrammer]

What do folk think about the wisdom - or otherwise - of offsetting a synergy issue between speaker and amp by changing sources? I was wondering if going for a DAC that is warmer even than the Denafrips - say, Border Patrol or Audio Note - might cure the problem? Or is this wrongheaded and going about things back to front ?

The thing is it's fabulous with vinyl which suggests the amp/speaker are not inherently mismatched. The stridency is worst with the internal DAC (which frustratingly is fantastic on all other counts, with mind blowing scale, dynamics and resolution!), much less so with the Denafrips, so a third DAC might be less so again?

 

[culturecrammer]

You could always look for something by Plinius in your budget, they are supposed to be a good match with Obs.

Yes Plinius is often used with Obs - but they are hard to come by and zillions of squids, no?

 

[britishcomposers]

Your last observation hits the nail on the head. Denon's current DAC's are very strong in detail, so unless you have properly designed mains conditioning, such as Shunyata Research (and I don't deal in hi-fi accessories or separates, so no association with such) and matching mains leads, plus Entreq earthing boxes to combat any floating chassis voltages, plus moreover, loudspeaker cables that limit acting as antennae to an amplifier's feedback circuits (Entreq again) and you're in for all sorts of stridencies on string-tone and synthesiser recordings, simply because this is still within the budget sector, where the PSU and screening detail on what are cost-constrained items (as against expensive high-end gear) doesn't limit high-frequency noise riding on the treble detail.

Most 'regular' loudspeaker designs have overly complicated, detail absorbing, high component count circuits to achieve a linear, phase coherent response that naturally rolls-back any reveal of such, but what you have might be less veiled and thus opening-up all manner of brittle/bright details that may serve rock and pop well but less so on anything acoustical.

I am also a firm believer in second-hand Metrum Acoustic DAC's (not the Flint model though) that deployed medical profession chipsets so powerful that with no pre/post echo ringing artefacts to bear and without the usual rolled-off NOS DAC traits, courtesy of the superior components used against those that the usual culprits found in every other DAC deploy, and you'll achieve high-end silkiness and depth to your sound that found Martin Colloms rating them above all else up to £10,000.

The Denon DAC I fear is revealing a little more than just your music though and so by regularly looking on eBay for a Shunyata Research mains conditioner/multi-outlet device may well find you a bargain for less than £500 with the preferred US mains outputs on a UK or Australian voltage product. Then you can buy entry-level non-fused (always a better sound) US-sourced US C19 plug to IEC C15 plug 1.5m mains leads for around £150 apiece from private sellers across the pond. The Tellus Entreq boxes are easily found, and I made-up my own leads using yellow/green sleeving over solid-multi-core mains electrical earth wire with the requisite metal ends applied with crimping tool. These often have three earth posts: one for your power amplifier and the rest for your sources. Only the power amp, phono stage (possibly) and digital sources, plus any pre-amp are really going to need any help at fending-off the RFI/EMI noise traits. A turntable's motor is another issue that is something I've not experimented with as I can't see much logic; being that it's not attached to any audio, - though it may collect and harbour noise around it's sphere of activity within the close proximation to your headshell/cartridge as it traverses across toward the record's centre where the motor resides underneath.