Best Class D or cool-running amplifier to try?

[ahofer]

My amp is a 1990s Adcom 5802, and it drives Harbeth SHL5+ (AE) speakers. I love the sound as it is now, however, I am a little worried about age-related problems in the amp damaging my speakers, and I would like to

a) get something that runs much cooler, as I now live in a Manhattan apartment and..summer.
b) investigate Class D and/or the minute differences between well-designed amps by trying a less-expensive amp against this beast

So, what amp would be best to purchase and try against the Adcom (blind, if I can recruit someone to help)?

Some requirements:
-150 watts/channel into 8 ohms minimum
-balanced interconnects
-I want to be able to return it, of course
-stable company with some quality control, to protect my speakers

I was thinking ELAC DPA-2.

 

[Ron Texas]

Look at the Emotiva PA-1 monoblocks, $630 for a pair. They use Icepower modules.

 

[amirm]

I was thinking ELAC DPA-2.

Peter is an excellent designer and that unit looks good:

Its stated specs puts its SINAD at 90 dB. You can slot it in manually in our measurement rankings so far:

So competent but not state of the art.

 

[ahofer]

I guess the Nord would be another possibility, although your experience with out-of-phase internal wiring gives me some pause. Everything else except the Benchmark is a kit, right?

 

[restorer-john]

Your Adcom is an absolute bona-fide classic, but it essentially has nothing between the output stage and the speaker. Eschewing proper protection circuitry in the interests of 'purity' and ultimate THD means you can pay the price when something goes Chernobyl in the amp.

That said, may Class D amplifiers (most) have nothing between their Mosfets and the speakers either. They rely on very fast shutdown of the power supply to protect speakers in the event of failures/faults.

I understand the heat issue, I live in Australia. The simple solution is to have a winter amp (the big Adcom) and a summer amp (some class D thing). If you are worried the Adcom may need a service or thorough going over, get it done in summer while you are using your new amp. Maybe consider March Audio's monoblocks? They are cool running.

 

[DonH56]

The Benchmark AHB2 is another possibility. Class AB amp with tracking power rails to improve efficiency.

 

[March Audio]

Sorry, probably inappropriate. Cough.

P252

https://www.marchaudio.net.au/stere...UuKjqJKwCtekbwEIl_cQze45O4BnpYsMaAu-CEALw_wcB

 

[pjug]

Maybe not as cool as cool-running as Class D but the Benchmark AHB2 might be an option with its Class H rail switching.

 

[restorer-john]

Class AB amp with tracking power rails to improve efficiency.

So is it, or isn't it?

The AHB2 uses a slightly under biased class-AB output stage with class-H tracking rails. The tracking rails kick in just above 1/3 power. The feed-forward system also keeps the class-H transitions distortion-free.

and this...

Actually this is incorrect. The supply does not produce the tracking rails. It only provides DC voltages. It is actually easier to do this with a linear supply. The main difference is that we can achieve a much better SNR with a switch-mode power supply due to the much weaker stray magnetic fields (which also happen to be at frequencies that are well above the audio band).

@DonH56, that was still a good guess! And we did discuss this in the design process. It would have been possible to generate tracking rails with a class-D amplifier, but we chose to keep the entire amplifier analog. We wanted to keep IMD and THD low and we wanted to avoid producing out-of-band noise.

My interpretation is fixed regulated SMPS rails and a transition between them for peaks. But with another FF error amp of course. Somewhat like the commutating rail amplifiers in the 1980s (NAD,Kenwood,Hitachi, Proton, Pioneer etc). So that means series connected output devices at high powers (from the HV rails).

(Hitachi HMA-8300)

"but we chose to keep the entire amplifier analog."

Except for the giant FPGA in control...

 

[Sal1950]

Wish I could understand what all this "goings on" is about.

 

[DonH56]

So is it, or isn't it?



and this...



My interpretation is fixed regulated SMPS rails and a transition between them for peaks. But with another FF error amp of course. Somewhat like the commutating rail amplifiers in the 1980s (NAD,Kenwood,Hitachi, Proton, Pioneer etc). So that means series connected output devices at high powers (from the HV rails).

View attachment 29615
(Hitachi HMA-8300)

"but we chose to keep the entire amplifier analog."

Except for the giant FPGA in control...

Guess we'd have to ask him... What I thought he said was the power supply itself is a conventional SMPS that feeds linear regulators that do the voltage stepping/tracking/whatever. So I think we are on the same page?

The point was to offer another amp with a different approach to running cool than class D.

I've been averaging 70+ hours the last few weeks, brain is fuzzy.

 

[pjug]

I guess I don't feel like I need to understand exactly how they implemented this - the improved efficiency is a good thing, right? Also, I think it interesting that they did not push this as far as they might have. It would be interesting to know what efficiency would be possible with just a little drop in performance. From http://everythingaudionetwork.blogspot.com/2014/10/audiophile-review-benchmark-ahb2-stereo.html

•Siau said that certain THX design elements allow him to make the amp as efficient as possible, but the AHB2 design was optimized for low distortion and low noise.
“It was not optimized for the highest possible efficiency that could be achieved with the new THX topology,” Siau explained. “Nevertheless the AHB2 is much more efficient than a conventional Class AB design.

 

[pjug]

Sorry, probably inappropriate. Cough.

P252

https://www.marchaudio.net.au/stere...UuKjqJKwCtekbwEIl_cQze45O4BnpYsMaAu-CEALw_wcB

Wow your prices are very good, and these look very nice. Have you sent an amp to Amir yet?

 

[March Audio]

Wow your prices are very good, and these look very nice. Have you sent an amp to Amir yet?

Its been on the to do list for a while. I have reserved some amps to go to Amir in the next few weeks. I just need to catch up on a small of a backlog at the moment (good problem to have )

 

[maty]

ELAC DPA-2 -> Hypex UCD400LP modules

https://www.hifi-journal.de/news/34-verstaerker/658-elac-alchemy-serie-erstmals-abgelichtet

 

[maty]

My amp is a 1990s Adcom 5802.

Adcom 5802 Amplifier Repair And Restoration

http://www.vintageaudioaddict.com/adcom_5802/adcom_5802.htm

If it were mine, I would update/check it and add the protection modules for the speakers, which are cheap.

Find a good technician and reliable in your area, asking in the audio forums of your country. Already put, the electrolytic capacitors are changed.

https://www.hifiengine.com/manual_library/adcom/gfa-5802.shtml

 

[maty]

New York? And Adcom, then you have a good time reading: https://hoppesbrain.com/

Before making a decision and spending money inform yourself well and without hurry.

 

[maty]

Harbeth Super HL5plus loudspeaker

https://www.stereophile.com/content/harbeth-super-hl5plus-loudspeaker-measurements

[ The Harbeth is specified as having a sensitivity of 86dB/W/m, and my estimate of its voltage sensitivity was the same: 86dB(B)/2.83V/m. Though this is 1dB or so below average, I commend Harbeth for not inflating this specification. Although the Super HL5plus has a specified impedance of 6 ohms, my measurement (fig.1) indicates that the speaker's impedance remains above 8 ohms for almost all of the audioband, and that the electrical phase angle remains relatively small. The HL5plus will therefore be an easy load for the partnering amplifier to drive, and a good match for tubed designs.

 

[March Audio]

"but we chose to keep the entire amplifier analog."

Except for the giant FPGA in control...

That cought my eye, it implies class d is digital, which it is not.

 

[maty]

In your case, I would not buy NOW any class D amplifier at this time. It would hold until next year to know what sound quality the Purifi 1ET400A offer.

https://www.audiosciencereview.com/...easurements-of-purifi-1et400a-amplifier.7984/

If you do not want to wait and, living in the US, you have two / three very interesting options, with a 30-day trial period two of them. One class D and others class AB.