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Khornukopia

Class D amplifiers are cool

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=== last night I stumbled on the audio site - “audio science review” where the site founder runs many DAC, Class D and standard AB amps through rigorous testing looking for the good/bad in the designs output. Interesting site, and after reading his background/credentials I find his “opinions” are fact based. 

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19 hours ago, DizRotus said:

 

I know you mean this as a compliment, but I have a different take on your comment.   To me, amps shouldn’t sound tube-like or digital, they should sound like the music they are reproducing.  After years of enjoying several excellent tube amps, I’ve switched totally to class-D.

 

If by accurately reproducing the source material with zero noise, high dynamics, full frequency range, and great separation sounds “digital,” then I’m all for it.

 

None of my high quality tube amps sounded as good as my balanced class-D chip amps.  Others may disagree, but I don’t consider “digital” as a negative adjective.

 

YMMV

 

Hello,

 

My post was probably too short. I appreciate some digital amps for these qualities, but at the end I miss something related to the tones that don't have enough colors and variety (for my tastes). From this perspective I prefer usually SET amps, but you are right, what you win on tones and low level, you loose it on other parts. It's a choice.

With the Spec, which is also a D class but with an analog implementation, it seems that you have the best of the both worlds: zero noise, dynamic, strong bass, nice low level and a colorful sound (rich tones).

 

I am just at the beginning with this amp, so it needs to be confirmed when the system will be setup correctly, but what I have today is very promising. I should received a better source these days. Let's see.

 

Best

Ugo

 

 

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On 9/25/2019 at 7:04 AM, ClaudeJ1 said:

But why overpay … ??

 

I probably wouldn't, but people like to have different things to choose from, and many folks think the Macs are attractive looking.

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3 hours ago, Khornukopia said:

 

I probably wouldn't, but people like to have different things to choose from, and many folks think the Macs are attractive looking.

Except for the A800 I just got yesterday and put into service right away on subwoofer, (so I can see the power meters), all my class D amps are not visible, even the Ncore amps where I added potentiometers at the front end (see my next post as to why).

 

Why? because there is absolutely Zero Need to ever LOOK at a power amp that will never approach voltage clipping or current overload on an all horn system. The new 4K Godzilla movie takes my 97-100 db/watt Tapped Horn subs for an extreme workout, and the highest the LED power meters ever read was -6 db. on the new amp.

 

Subs are where 99% of my power goes as the rest of the system is 100 db/watt efficient (8 channels of Super Heresy's, Unity Summation Aperture Horns, etc.), so in my case, there is no need to ever have power meters there. In fact I use el cheapo TI Chip amps on the surrounds, since the mains take most of the power there, like less than 10 watts, vs. 400 WPC for the subs. As of yesterday, all of my amplifiers are class D. The new A800 has improved my bass resolution beyond what I had before, which was well demonstrated for a room full of Klipsch people brought over by Dizrotus. IOW, this class D upgrade made something impressive even better, by an audible smidge.

 

But hey, if someone want to ever pay more than the cost of a state of the art Hypex amp for mains just to LOOK at them, then they have more money to waste than even the above average "Klipschead" on this forum, including this one!

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On 8/23/2019 at 10:36 AM, avguytx said:

So just how good is this little Class D amp for $28 from ebay?  Anyone mess with these?  Kind of intrigued for the money just to tinker with it.

 

https://www.ebay.com/itm/Mini-Class-D-Power-Amplifier-HiFi-Stereo-2-0-Channel-Digital-Audio-Amp-50W-50W/262315996089

 

s-l1600.jpg

I had two of those running my Jubilees (106-110 db/watt) with TADs/K402's up to 124 db peaks on drum recordings, THAT's how good they are.

 

Currently I run 3 of them on 6 surround channels of my all-horn, all Class D Atmos setup. How's THAT for an endorsement!!

 

They are driven by a Yamaha Pre Pro. The best thing about these is that there's a volume Potentiometer to knock DOWN the relative gain at the front end, forcing the Yamaha to work it's output voltage in the range that would be required by typical "industry standard", non-Klipsch,  86 db/watt speakers, rather than 100 db/watt speakers I have. This increases the Signal to Noise ratio substantially. It's a SYSTEMS approach with horns, guys, let's not forget that.

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Hey All,

 

I wanted to purchase an Aiyima TPA3255 2.0 amp through eBay, but the seller in China could not ship the amp due to the COVID-19 virus outbreak. They were great about it and promptly refunded my payment. That left me with the choice to purchase the Aiyima TPA3251 2.0 amp through Amazon.com who had some inventory of these amps in the US. I had to purchase a Mean Well LRS-200-36 switching power supply to power this amp since it does not come with a power supply. I had to dial down the power supply's output to 30VDC since the power rail capacitors on the Aiyima amp are rated at 35V. I've had great results with a Mean Well LRS-350-48 switching power supply powering my Texas Instruments TPA3255EVM Class D amplifier.

 

IMG_0826.thumb.jpg.063d75995ed6a06172596f195a62c848.jpg


I connected this amp to my main system using my Audio Research LS7 tube line stage preamp and modified Klipsch Forte II speakers. This is where I started my critical music listening and discovered that the right and left channels are reversed, so I switched my right and left hand RCA interconnect connections. My reference power amplifiers are a rebuilt McIntosh MC240 vacuum tube amp and Pass DIY Sony VFET Class A solid state amp I built with the diyAudio.com store kit offered several years ago.

Both of my reference amps are excellent and I am quite pleased with the low distortion and highly musical performances of both amps in my system. I connected the Aiyima Class D amp to the Audio Research preamp and my speakers, and I have to say this little amp is impressive. First of all, it is very quiet with no music playing through it. I held my ear close to my efficient Klipsch speakers and didn't hear any hiss or other noise.

 

Unlike the Texas Instruments TPA3255EVM amplifier, this amp only supports the use of single ended inputs. I'm sure the amp could be modified to accept balanced inputs, but XLR and TRS balanced connectors are too large to fit inside the compact enclosure. All that said, I like this Aiyima amp so much, I am now considering selling my Texas Instruments TPA3255EVM amp.

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47 minutes ago, rhing said:

I like this Aiyima amp so much, I am now considering selling my Texas Instruments TPA3255EVM amp.

 

What do you prefer about it Rich?

 

I'm so pleased with my balanced TPA3255EVM I can't imagine replacing it.  I feel some of my appreciation is attributable to the balanced capacity.  The balanced output from my Pono--which functions as pre-amp, DAP, & DAC--is fed to the 3255 and a pair of Class D iNuke 1000dsp amps powering my subs.  I go to meetings now so no more "last" amps.  Nonetheless, I'm curious about your impressions.

 

TPA3225EVM.thumb.jpg.f97482699864649f59c534ceac680069.jpg

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For your setup with the balanced connections to the Pono Player, you are set with the best solution in the Texas Instruments TPA-32xx Class D amplification.
 

I prefer the Aiyima for its compact simplicity and the very dead silent background. It has a built-in protection against the thumps/pops on power-up and power-down. I no longer have to be concerned with using the reset switch on the TI TPA3255EVM to mute and unmute the amp. I also wanted to roll op amps to see the effects on sound quality. The amp as-is is a keeper, at less than $50 sans power supply, it is quite a bargain for an amp capable of powering low-medium to high sensitivity speakers. 
 

BD2A76C1-7C73-4A7F-AA0B-0A1EEC4DFE63.thumb.jpeg.7b6736a31a06fd59ff51d7f5707b5a8a.jpeg

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Thanks for the feedback @rhing.  FWIW,  neither my TPA3118 Wiener nor my TPA3255 EVM have any thumps or pops at on or off.  I’ve never had to use the reset on the 3255.  Both are dead silent at idle and between tracks.  Putting an ear to an efficient idling tweeter reveals dead silence, whether K77/T35, K76, et al or DE 120.

 

Please continue to share your projects and impressions.  I feel I’m now totally immunized against further infection.

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4 hours ago, rhing said:

I had to purchase a Mean Well LRS-200-36 switching power supply to power this amp since it does not come with a power supply. I had to dial down the power supply's output to 30VDC since the power rail capacitors on the Aiyima amp are rated at 35V.

 

 

 

How did you drop down the voltage; an output pot adjust (like most switchers)?

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I’m not certain about the Mean Well LRS-200-36, I’ll defer to Rich @rhing on that.  I suspect it’s similar to my Mean Well LRS-350-48 which is adjustable for output voltage.

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6 hours ago, Blvdre said:

 

How did you drop down the voltage; an output pot adjust (like most switchers)?

Yes. There is an output pot on the Mean Well to make that adjustment. 

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I have had a chance to roll op amps in this little, yet powerful, amp:

  • Texas Instruments OPA1622
  • Burr-Brown OPA627AU

In comparison to the stock Texas Instruments NE5532 dual op amps, both significantly improved the sound quality in terms of creating a larger, deeper soundstage, better frequency response at the extremes, and improved detail. Both sets of op amps required 2-3 hours to really settle in. Since both types were mounted on DIP8 adapters, they were very easy to plug into the DIP8 sockets. On the other hand, removing the stock TI NE5532 op amps with their soft metal legs was more challenging and I ended up mangling the legs of one of them that would not come out of the socket easily. 
 

After much listening, I prefer the Burr-Brown OPA627AU op amps. The presentation is tonally rich and the bass energy was equal to my Pass DIY Sony VFET Class A SS amp and rebuilt McIntosh MC240 tube amp. The soundstage is life-size with really good separation of performers. The midrange and treble are very smooth with no brightness sometimes associated with Class D amps. In all, a very high quality amp, power supply, and optional op amps can be had for less than $100 to power Klipsch speakers. 

7CBF1C8A-27A4-458E-B59D-2CF339F5D278.jpeg

6D0B68F2-A4EE-4064-8985-83BC488468B0.jpeg

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18 hours ago, rhing said:
  • Texas Instruments OPA1622
  • Burr-Brown OPA627AU

 

The difference I see is the two circuit boards about 3/4" square, correct?, and the TI is the upper picture and the B-B is the lower picture? 

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Have you tried an LME49720? Still available in a DIP.

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