As long as you don't push them too hard, it can be a bit surprising how good many of these little amps can actually sound. Of course then you start to wonder how good it can get... In our own work on class D amps (we have a design entirely our own) I've come to the conclusion that power amps based on tubes are on life support.
Class D amplifier with TPA 3250 board
Hello,
I'm new to this forum. I recently purchased my endgame setup comprised of Closer Acoustics Ogy speakers (91 SPL), REL T5X subwoofer and a custom hand built tube amplifier with EL34 tubes. The tube amplifier is giving me trouble with hissing noises, so it's constantly at the artisan's workshop. Since my speakers are extremely efficient, I was wondering about smaller amplifiers as an escape route (if the artisan can't fix the amp, he surely can). The Octavio Amp looks nice on paper. So does the Atoll IN80. Is one obviously better than the other for my revealing speakers?
Folks on another forum I shall not name seem to heavily imply that all amplifiers should sound the same (or very similar). They rave about these cheap tiny Topping/Aiyima amplifiers with class D TPA 3250 amplifier boards. These same boards are used in Genelec active monitors, so they must be good? I'm flustered because there no direct comparisons between these TPA 32xx amplifiers and more conventional/expensive branded amplifiers. The same folks on the forum I shall not name imply that I'm a dunce for spending so much money on a tube amplifier (quote: it's a distortion factory and it can't play grindcore metal music so it sucks). If it weren't for the hiss I wouldn't post here.
Can I cheap class D amp replace a custom hand-wired EL34 tube amplifier for extremely revealing Closer Acoustics Ogy speakers?
Showing 6 responses by atmasphere
@timlub That came from the specs published by the manufacturer of the chips: TA2024 10% at full power (10W) TA2020 10% at full power (13W) TA2022 10% at full power (125W) Tk2050 10% at full power (117W) TAS5613 10% at full power (150W) TAS5630 10% at full power (160W 8Ohms) ...and so on; in fact I've yet to see any class D chip that did not spec 10% at full power. Typically they are operated at considerably less than full power, but if you are looking at specs and power is one of those things in which you're interested, its a good idea to look closely to see what the claim actually is. In the case of the raw chips this isn't such a big deal since a designer has to implement the design and will spec the resulting amplifier when that's done. But I've noticed a lot of the Chinese offerings tend to state the '10% full power spec' when the power supply accompanying the amp won't support it- if you don't watch it, you'll think you're buying a more powerful amp and one of a lot less distortion. IMO its a bit misleading. |
@kokakolia Seriously, getting an amp to be quiet on a speaker that's only 91 dB should be a walk in the park! 15W seems surprisingly low for a speaker rated with that low sensitivity FWIW! |
If you drive the sub from the preamp, yes.
That's not high efficiency! That's a moderate efficiency; you enter high efficiency territory when the speaker is about 97dB or higher. If you are listening nearfield I can understand using such low power. In a typical American room you'd want about 50-60 Watts to make a speaker of that efficiency play properly. The only conversion from AC to DC I can think of for the amp (to which you referred above) would be creating a DC power supply for the filaments of the tubes in the amp. FWIW this is sending up a bit of a warning flag for me. We use AC filaments in almost all of our amps and they are plenty quiet enough to use on horn speakers. In addition, if you are getting a hum from the filaments of the tubes, the hum would be 50Hz and not 100Hz (because its induced at the line frequency)! So while I am keeping all this in abeyance, I must admit to having lost some faith in your 'artisan'. Of course this is all hearsay... |
One thing to watch in these less expensive amps is the bass response. Not unlike what Radio Shack did with some of their lower powered amps back in the early 1970s, a lot of them I've looked at have the low frequencies curtailed- likely for the same reason Radio Shack did this so long ago, to prevent bass notes from gobbling up amplifier power. |
@kokakolia Tube amps can play grindcore just fine! Since this is a buzz (not a hum, hum in France would be 50Hz only; since you have 100Hz you probably also have artifacts you can hear in the tweeters) and not a hiss there may be things you can do. The first thing to do is find out if, when you short the amplifier's inputs, does the amp still make the sound? Or does it only make it when the amp has something connected to its inputs? If you can answer those questions we might be able to make some progress without any serious investment. With regards to the TPA3250 and other chip-based class D amps, I think if you look at their specs you'll (and those over at ASR) you'll be surprised to find their distortion at full output is about 10%, more than your tube amp! I've got the Topping amp (the little '30 Watt' unit) and its quite boring to listen to- almost to make you think that specs are more important than the music 😁 Which they are not. You need good specs to get the music right and plain and simple, while those chip based class D amps do some things fairly well, their specs suck. This is not to say class D does not work! But chip based class D amps don't represent the class of operation... So answer my questions above and let's see if progress can be made.
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