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wdecho

Class D

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There appears to be a lot of interest in the newer Class D offerings so I am going to start a thread on just Class D whereas not to hijack other OP on other threads on Class D amplification. I do believe Class D is going to be the wave of the future for mainstream audio retail components. I first heard about "class d" circuits over 30 years but until recently have they improved to audiophile quality. My main interest and listening is with Class A amplifiers. This is not to say that some of the class D ones I have heard do not sound good, really good. I have one the B&O Icepower board that is the most tube sounding of any I own. I also have a Sure board that is more in the lines of a good A/B amplifier. I have a diy friend in Australia that has been really praising the boards from Hifimediy.com so I ordered and received it this week. This is an impressive looking board supposedly with quality parts. It is called the T4 board and it has the option of being use with AC or DC power with better results claimed from my friend with a linear PS of which I am going to build. I have close to a dozen of the cheaper Chinese board offerings and for what they cost many do sound respectable but thin sounding in presence and soundstage is the way I describe them. The Hypex n-core is what is consider the best one available right now from what many are saying but I have not pulled the trigger on buying one because of the entry fee. 

 

Anyone wishing to comment on Class D amplification are free to post without reservations of hijacking the OP. 

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I have a few Class D boards.  The photo shows my TPA3118 "Wiener" board designed and built by gmarsh from diyaudio forum.  I purchased it at the recommendation of Rich, aka @rhing.  In the photo, it is powering a pair of La Scalas with bass reflex mod.  It sounds very good.

 

The fact that it has balanced inputs capable of accepting the balanced outputs from my Pono player appealed to me.  Soon I will take it along on a visit to @ClaudeJ1 to compare it to his HypexNcores.  Yes, I have a nice case to put it in, but I lack the time.

 

I also have a SURE TPA3110 Class D board powering my DIY boombox.  That's a duty unsuited to a tube amp.

 

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8 hours ago, wdecho said:

I have a diy friend in Australia that has been really praising the boards from Hifimediy.com so I ordered and received it this week.

What is the wattage rating on that?

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3 hours ago, CECAA850 said:

I think I found it.  180 watts per channel at 8 ohms?

Correct, but my experience with these power ratings is kinda deceiving. The power rating is at 10% THD at rated power with a lot of class D boards which in my opinion is unlistenable. I finished putting it together today and I am going to sit down and give it a listening tonight.

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5 minutes ago, wdecho said:

Correct, but my experience with these power ratings is kinda deceiving. The power rating is at 10% THD at rated power with a lot of class D boards which in my opinion is unlistenable. I finished putting it together today and I am going to sit down and give it a listening tonight.

If you have ever owned a SET amp they you will know that 10 -15% THD is not a really bad thing but what  makes this passable is the balance of the distortion spectrum. You want that to be primarily second order and followed by more even harmonic distortion rather than all or primarily odd order harmonics.

   I agree with you that such gross distortion is unacceptable especially once you become accustom to listening to amplifiers with low to no distortion. Problem is that people get sucked in to the sweet rich harmonics of lots of even order distortion just like people get sucked into the spatial qualities of dipoles, it is not real space it is an artifact but still we get sucked in. At the end of the day we all pick our poison.

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Neil "DizRotus" I have many amplifier boards on wood as yours. In fact I have a test wood case with transformer, PS section and heatsinks for trying any Class A and Class A/B build before giving it a proper home if it deserves one. Buying ready built or stuffing empty boards is not the main cost of building most amplifiers. I like to hear and test any build first before proceeding with a complete build. 

 

Moray I have many SET amplifiers and enjoy most all of them but even with SET's I would consider 10% THD too much. Fortunately with our speakers most SET's work at less even harmonic distortion figures than 10%, for most people that is. Nelson in some of his Firstwatt amplifiers intentionally introduces a small amount of 2 harmonic, around .5% is the figure that comes to mind, to give the amplifier some soul. Jean Hiraga was one of the first to proclaim an amplifier sounds best with a small amount of 2nd harmonic and a touch of 3rd. Many agree with this statement including myself. A lot of the Firstwatt clones I have built have pots where one can adjust the amount of 2nd harmonic to introduce into the mix to suit their taste. An amplifier without some 2nd harmonic is too dry and analytical for my taste. No soul. 

 

I listened to this new build last night and from the moment I first heard it on my test speakers I knew it was a keeper. I will post more on this board later. 

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Neil "DizRotus" notified me that there was some forum activity on Class D amplifiers. Like Neil, I also purchased some Class D amplifiers through a group buy at diyAudio.com offers by Gary Marsh (gmarsh). My favorite are his Wiener 2.0 Texas Instruments TPA3118 PBTL (dual mono) amps with a pair of Altec Peerless 15335A 15k:15k line level bridging transformers to convert single-ended (unbalanced) signal inputs to the differential (balanced) amplifier inputs. I also installed the high current capacity CoilCraft VER2923 output inductors. I finished the build using Duelund DCA20GA 20ga stranded Tinned Copper wire to connect the RCA inputs to the input transformers and the input transformers to the amplifier inputs. For wiring the amplifier to speaker binding posts, I used Duelund DCA16GA 16ga stranded Tinned Copper wire. My power supply is a modified Astron RS-12A regulated linear power supply delivering 13.8 VDC and 6-10A current.

 

This amplifier is used with my Audio Research LS7 tube line stage and Audio Research PH5 tube phono stage preamplifiers. I also have a Dynakit Stereo 35 6BQ5/EL84 tube amp modified with Dave Gillespie's Enhanced Fixed Bias (EFB) circuit, and a McIntosh MC240 6L6GC tube amp that I recapped with Authenticap multi-section electrolytic capacitors, Ohmite Brown Devil resistors, Russian k40y-9 PIO caps, and fast/soft recovery diodes in the power and bias supplies. I love all these amplifiers with my Klipsch Forte II's, and the Class D amp can sound as holographic and liquid as my restored vintage tube amps. 

 

Prior to my recent move to Minnesota, I used this amplification with my Klipsch Forte II speakers modified with Bob Crites crossovers. Now that we are in an apartment, I lost space to bring the Forte II's into my living room listening area. I searched quite a while for small bookshelf speakers for a few months, and finally decided to purchase a pair of KEF LS50 speakers. With their Uni-Q drivers and well designed cabinets and ports, these 85dB sensitive speakers actually sound similar to my Klipsch Forte II's. they are smoother and more refined sounding than the Klipsch bookshelf monitors I auditioned. I was concerned that my amplifiers wouldn't have enough power and headroom to drive the KEF's, but once I wired up the Wiener amp to them, my concerns dissolved. This modestly powered amp was able to drive these speakers with no problems providing a full, rich presentation. I also tried my Dynakit Stereo 35 amp with the KEF's and got great results. In fact, both of my amps sounded better than the higher powered Rotel integrated amp that the dealer had with the KEF LS50's in the showroom. 

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Interesting thread - I also have tried a few of those Chinese Class D boards - I usually was impressed by their clarity, but in the long run I alsways found them a bit "lifeless". On the other hand their prices made me curious. Currently I am using a moddified TPA3116 board (yj blue-black label v2.0). This one I really like - but as mentioned - modding it made it even better (most positive I found replacing the input caps with some Lundahl transformers and fitting some CoilCraft inductors). This amp I currently use on my Khorns driven by the (also) improved preamp section of a McIntosh MA6200.

I would really like to listen to those HypexNcores - but so far I have not found anybody in my vicinity who owns those. If they really are as good as some people write they might actually be an alternative to my "favourite" amp - a Pass F5 clone with chosen parts - but that is a different story.

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I have spent some time with this amplifier and did one short A/B against one of my Firstwatt clone builds. First I want to tell everyone that might be interested in purchasing this board that there is one error on the speaker output lettering. One of the speaker outs is incorrect so one must reverse the speaker wires. It is easy to see which one if one turns the board over and follows the trace from the speaker out to the inductor. The trace going to the inductor is the positive out of the speaker. I was aware of this before I purchased the board and I thought it might have been corrected but it has not. If you hook the speakers as lettered they will be out of phase. I am not a reviewer but my hearing is pretty good for a 68 year old man but still my ears are 68 years old. At first I did not think the bass was that great but after some hours on the board it appeared to get much better. Now the bass is quick, dynamic and strong. I have always thought of breaking in SS equipment with some skepticism but I have found it can be true. Mark, who told me about this board, said the board was bright to begin with to him but I have not thought so. Maybe he just hears better than me. He claims it took around 50 hours for the highs to settle in. They sound just fine to me right now. The mids are lovely with good soundstage and presence. The soundstage is not quite as good as the Firstwatt clone class A amplifier but few SS amplifiers are. The bass was much more dynamic and quicker that the FW clone. I found this to be the case with an A/B amplifier I recently built as well. Both the D and A/B amplifier have much more power and damping factor than the FW typical 25 watts so that is probably the reason. All in all I am very satisfied with this build. I had trust in my friend Mark with his opinion of this board so I built a PS section in a utilitarian case as it's home without first testing it on a board. Great bass, quick and dynamic with lovely mids and very good soundstage and the price to build is not that much for what you will have when finished. The board has the option of just using AC so a transformer is all that is needed. I elected to build a linear PS. One may be OK to use just a switcher but I would stress a Meanwell or equivalent quality one. This is a perfect project for a beginning diy'er. My build consist of an Antek AS-4232 transformer which is a 400VA 32 V one. After filtering I measured a tad over 47V DC. A 300VA transformer would be sufficient. The board can be purchased at https://hifimediy.com/amplifiers/diy-amplifiers/T4-mundorf-amplifier   . The case is a Bud industries AC-1421 purchased at Amazon for $28. The bridge rectifier is a 35 amp one and the capacitance is 30,000uf rated at 63V. The other accessories for an amplifier build can be purchased at Parts Express. The caps and rectifier came from Mouser.  

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Remember this thread is not about diy or just my build. Any and all discussion of D amplification is welcome. I wish I were closer to Claude to compare this build to his Hypex. I look for class D to be the class of the future for the mass market manufacturers. Of course the small market of perfectionist will always want Class A whether tube or SS. I do see class D taking over the A/B market. Cheaper, cooler and smaller and now reaching audiophile standards. As far as tubes, nothing I have sounds quite like my 300B SET with our speakers. 

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Thanks for sharing some of your listening experiences. I also believe that Class D amps will be the future - basically because they strike me as cheaper to produce. What I have found that power supplies with these boards matter - personally I use a Meanwell unit with a relatively high switching frequency. But that might not be the best there is. I think the proof of the pudding - like with all equipment - is how much one enjoys listening in the long run. Often a piece of equipment that initially sound find begins to be tiring after a while - until now this isn't the case with my D amp.

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17 minutes ago, dubai2000 said:

 What I have found that power supplies with these boards matter - personally I use a Meanwell unit with a relatively high switching frequency. But that might not be the best there is. 

My friend Mark believes strongly on a linear supply with D boards. I mentioned the Hypex to him but he did not consider it because of the linear PS. I favor a linear over a switcher myself. Why not try a linear with your board and post your results. 

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I power mine with batteries recharged by a small solar panel.  

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I actually tried a linear PS but prefer the Meanwell - the sound is clearer, crisper - but pay attention to polarity - with the horns it made a tonal difference how you plugged the Meanwell in - wrong polarity seems to add harshness to the sound.

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 Straying a bit from Class D but power supplies in general can and do  make or break  a good amplifier design. I have a pair of Nelson Pass Amp Camps Class A built by Justin Weber that are truly nothing short of phenomenal. And according to Justin it's because of the giant regulated linear power supplies he used on Each block. The power supply chassis are twice the size of the actual amp. He said the little computer style wall wart power supply designed for the amps made them just barely acceptable. I can saw that in direct comparison with a genuine NP First Watt F3 JFET the Camps give no ground to the F3. And if I had to choose to her only one I think the Camps I would keep. They sound really ally nice through Jubes and LS. 

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I did a brief one song comparison of this D amp against what I consider my standard in sound  the 300B SET I built and it made a respectable showing. The significant difference is the soundstage at lower volumes. When you lower the volume of this build the soundstage shrinks towards the wall but with good accuracy. When turned up the difference in soundstage diminishes. I have found this to be the case with all the SS A/B and D amplifiers I have heard against more expensive class A tube or SS. I tend to listen at a louder volume than most, at least that is what my friends say, so it is not deal breaker most of the time. I am well satisfied and find myself wanting to listen more. Non fatiguing after hours of use. 

 

I thought I would add that some even like the more against the wall sound. I think it is because that is what they are more use to hearing with most retail amplifiers for the masses. 

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Interesting update - personally I find "tone" most important - that is does a piece of equipment render to tone/colour of instruments, voices in a way that strikes me as realistic and is not fatiguing - an example would be the sound of many Coltrane recordings - on some gear the tone becomes quite unpleasant after a while - and in that respect my clone F5 rules (albeit on different speakers). I played some Coltrane last night on my Horns with Class D board - pretty good - though I wonder if a different chip might not be even more musical - thus I am hoping more people chime in with their listening experiences.

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6 hours ago, dubai2000 said:

Interesting update - personally I find "tone" most important - that is does a piece of equipment render to tone/colour of instruments, voices in a way that strikes me as realistic and is not fatiguing - an example would be the sound of many Coltrane recordings - on some gear the tone becomes quite unpleasant after a while - and in that respect my clone F5 rules (albeit on different speakers). I played some Coltrane last night on my Horns with Class D board - pretty good - though I wonder if a different chip might not be even more musical - thus I am hoping more people chime in with their listening experiences.

This build and description as I said is not a review but a work in progress. I compared it to a recently built A/B amplifier using some boards off Ebay called MX50 one can buy for $20 shipped with 100 watts per channel but requires a much more expensive PS section. As for as "tone" I prefer the A/B build over the D board. I have already compared the MX50 build against my Firstwatt F7 clone collaboration built with other diy'ers help at the diyaudio forum. I say collaboration because the official schematic of the F7 has not been published. There is a big difference in sound quality between the F7 clone and either the D or A/B build. Class A is still class A with all its drawbacks. I just now compared the F7 against the new D and there is a big gap. This is not to say the D sounds bad, it does not. In fact it is a respectable amplifier with better bass than any of my Firstwatt builds, of which I now have 6 complete working ones. But the D falls behind in "tone", presence, and soundstage of the Firstwatt F7. Right now it is the only other Firstwatt clone I have compared it to besides the V-fet. It might get better with 50 hours on it but right now it probably sounds as good or better than most $1000 and under retail SS amplifiers. I still say it is a worthy first time diy amplifier project. Give it a try with a Meanwell switcher to make it simple. For those that put more emphasis on quick, sharp strong bass with decent mids and highs might really like it over some other amps. 

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Thanks for the detailed description. Obviously comparing a cheap Class D board with a Firstwatt DIY amp is a bit unfair - pricewise. So that there is a difference in quality doesn't really surprise. But I agree that those Class D boards are really very good - especially for their costs - and if one is able to mod them a bit. What interests me how Hypex or IcePower amps might fare in a comparison like the one posted by wdecho.

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