Musings on Class D .... is it actually 'there' now? Should we all be using it?

[George47]

If anyone is interested I did a review of the Nord stereo power amps.

They are very good....http://www.hifiwigwam.com/nord-one-u...lifier-review/

The amps use the NC500 modules with individual SMPS. Colin uses discrete regulators and has put a socket on the board to allow the cheap op-amps to be swapped out. I found the Sonic Imagery op amps suited me best, others prefer the Burson. And as it is made on the UK the price is more palatable than an import. Acoustic Imagery make a similar mono version but without the discrete regulators or the ability to swap the op amps.

[SLS]

Having installed a Devialet Expert Pro 250 yesterday I might be biased. It employed an A/D hybrid system. It just does everything well in a very understated way. What was particularly impressive was how much better it is compared to the previous Le 250 version.

It does some sounds, in particular kettle drum, with spectacular realism, that is astounding. I use Harbeth SHL5+ that use an 8" mid-bass driver, proving to me at least that massive speakers are not required for a massive sound.

[Sherwood]

I can strongly recommend the Nuprime STA-9 power amps! I am currently using a pair to drive Magneplanar 1.7 speakers. I am speaking as an owner of a good quality valve power amp (Art Audio Quintet) and several other good solid state units. I have come to the STA-9s via an earlier Nuforce amp which unfortunately expired on me whilst I was working in Northern Vietnam and which was not cost effective to repair (I still have it in a cupboard somewhere). The Nuforce was extremely good and able to drive my earlier Magneplanar MG12s very well. However, the Nuprime is significantly better than the Nuforce on every dimension: detail, dynamics, imaging, transient response. Bass is both deep and tuneful with timbres resolved superbly and vocals sound very natural. On first encounter it might seem to some to be a little rolled off in the treble, but extended listening has convinced me that this is not the case: it is just very smooth, rather valve like. I did try using a single STA-9 with my Maggies and it acquitted itself extremely well. Impressive at this price point.

I suspect that many of those who decry digital amps, have not heard the best designs. Yes, some of the budget Tripath designs are excellent for the price (i have a few myself) but they are not in the same league as the new generation of digital and PWM amps.

Geoff

[agk]

I thoroughly enjoyed the couple I've owned.

It seems that op amps are the new valves.

[montesquieu]

I can strongly recommend the Nuprime STA-9 power amps! I am currently using a pair to drive Magneplanar 1.7 speakers. I am speaking as an owner of a good quality valve power amp (Art Audio Quintet) and several other good solid state units. I have come to the STA-9s via an earlier Nuforce amp which unfortunately expired on me whilst I was working in Northern Vietnam and which was not cost effective to repair (I still have it in a cupboard somewhere). The Nuforce was extremely good and able to drive my earlier Magneplanar MG12s very well. However, the Nuprime is significantly better than the Nuforce on every dimension: detail, dynamics, imaging, transient response. Bass is both deep and tuneful with timbres resolved superbly and vocals sound very natural. On first encounter it might seem to some to be a little rolled off in the treble, but extended listening has convinced me that this is not the case: it is just very smooth, rather valve like. I did try using a single STA-9 with my Maggies and it acquitted itself extremely well. Impressive at this price point.

I suspect that many of those who decry digital amps, have not heard the best designs. Yes, some of the budget Tripath designs are excellent for the price (i have a few myself) but they are not in the same league as the new generation of digital and PWM amps.

Geoff

Funny you should say that - look what just turned up today - Nuprime STA-9. Just one as I wanted to get a feel for it though if I like it I might well buy another and monoblock (290w per Tannoy should be quite entertaining). The plan is to tide me over till I get the big Radford back from restoration.

This is Class A (JFET) into Class D (though there seem to be some particularly analogue methods at work in the implementation). I've only had 30mins with it so far and I'm rather impressed, bass is very solid, highs clean enough, not sure about midrange warmth, inner detail or presentation of space vs the Radford but I'll let the thing warm up and play in first - it's fresh new out of the box.

[Firebottle]

Quite a contrast in size there Tom, looking forward to your further impressions

[Sherwood]

Funny you should say that - look what just turned up today - Nuprime STA-9. Just one as I wanted to get a feel for it though if I like it I might well buy another and monoblock (290w per Tannoy should be quite entertaining). The plan is to tide me over till I get the big Radford back from restoration.

This is Class A (JFET) into Class D (though there seem to be some particularly analogue methods at work in the implementation). I've only had 30mins with it so far and I'm rather impressed, bass is very solid, highs clean enough, not sure about midrange warmth, inner detail or presentation of space vs the Radford but I'll let the thing warm up and play in first - it's fresh new out of the box.

Tom,

I am not entirely convinced about burn in with electronics (it certainly does apply to speakers) but it took a couple of days for my STA-9s to "bed in".

I am guessing that the single STA-9 in stereo mode will be a fantastic match to your Tannoys. I tried one of mine in that configuration with my single driver Alnico speakers and the bass extension and slam was impressive (try Rickie Lee Jones "Under the Boardwalk").

However, the sound in mono mode is somewhat different. Obviously, the extra power comes into play, but the quality of the sound changes too. Musical timbres are easy to discern and the unit just sounds more valve like. I am not qualified to speculate on the technical reasons for the change but switching back and forth a couple of times confirmed the difference. What I have also discovered is the difference that balanced XLR inputs make. The immediate difference is the increase in loudness for any given volume setting. Other than that everything just seems a little more etched, more dynamic, and the already incredible (low) noise floor drops even further. I now plan to buy longer XLRs and switch to short speaker cables (<0.5m) with the STA-9s underneath the Maggies. For that I need to design and manufacture an alternative stand for the Maggies that will raise them by about 6inches and angle them a few degrees backward. Any ideas from the engineeringly gifted out there ........

Geoff