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  • help for amp confused noob

    I just finished building my c-note speakers two weeks ago. I have a Lepai LP-2020TI, and this is the amp I have used for all of my testing so far. I have used a 3.5mm to RCA for most testing. I started on my PC and was simply amazed with the quality of the sound. The clarity from these speakers made me feel like I was hearing music for the first time. So over the last two weeks, I have been moving the speakers around to other setups in my house for the sake of experimentation. I ended up placing them on a TV system where I am using the RCA audio out from the TV to the amp. Again, the sound was incredible. I decided that I wanted to replace the Lepai with an amp I have had for a few years so that I can use a remote for the volume. I plugged in my Sony STR-DH130 in place of the Lepai. I was shocked to find that the sound wasn't nearly as impressive as with the Lepai. My questions are: Are there any specs I can use when choosing an amplifier to make sure I am getting the best bang for my buck? What other factors might be at play that would make a $30 amplifier seem vastly superior to a $150 amp?

    Thanks in advance!

    Lepai LP-2020TI
    Specifications: • Power output: 2 x 20 watts RMS • Speaker impedance: 4-8 ohms • SNR: >102 dB • Input impedance: 47k ohms • Frequency response: 20 Hz - 22 kHz • Input sensitivity: 200 mV • Minimum THD: <0.1% • Dimensions: 4.72" D x 5.79" W x 1.65" H.

    Sony STR-DH130
    Amplifier

    POWER OUTPUT (8 Ω, 1 KHZ, THD 1%)100 W + 100 W

  • #2
    Sounds like something is wrong with your Sony. I have used similar little Chinese class D amps and they work fine for my desktop computers, but distortion is very high. I do not know what the difference you are hearing is, but the Sony should be much lower distortion and remain so at a higher volume even though it is probably a much older "chip-amp" design.

    Unfortunately, the standards for measuring and advertising electronic specs were tossed out, so they can claim almost anything they want. Curious they advertise a MINIMUM distortion where we actually want to know MAXIMUM distortion. Kind of makes buying by spec useless. Nifty little amplifier though. Just no remote you were looking for.

    Do notice in the advertisement, the included power supply only gives 15W per channel. That should actually be enough, but for 20W, you need a bigger power supply.

    So to guide you on buying, really having a good return policy if you don't like it is your only defense. Even when you move way up into high end, on paper a $300 amp may have better advertised specs than a $3000 amp. And in some cases sound better. ( Not that the $300 amp is great, just a lot of very expensive equipment is all prestige, not performance. Some is very very good).

    Comment


    • #3
      The "old school" Class AB amps are my favorite. Parts Express has a nice, reasonably priced one. The APA150
      https://www.parts-express.com/dayton...ifier--300-812
      I bought 3 of them when they were on sale a while ago.

      I think I hear a difference - wow, it's amazing!" Ethan Winer: audio myths
      "As God is my witness I'll never be without a good pair of speakers!" Scarlett O'Hara

      High value, high quality RS150/TB28-537SH bookshelf - TARGAS NLA!
      SB13/Vifa BC25SC06 MTM DCR Galeons-SB13-MTM
      My Voxel min sub Yet-another-Voxel-build

      Tangband W6-sub

      Comment


      • #4
        Glad you're enjoying your C-Notes Dravo! We use the same little Lepai and I was surprised that the TI is a clear step up from the previous 2020's. I'd start by rechecking the polarity of the speaker wires to to Sony. When I double check, I remove the wires entirely from both and work backwards from the speakers because I can hold them right in front of me. If they don't sound right on your "A" speakers see if "B" sounds any different. If they still don't sound right I think any amp or receiver that as a remote that works for you, fits the form you want and has the connections you want will have your C-Notes singing from the comfort of your easy chair!

        Comment


        • #5
          Originally posted by donradick View Post
          The "old school" Class AB amps are my favorite. Parts Express has a nice, reasonably priced one. The APA150
          https://www.parts-express.com/dayton...ifier--300-812
          I bought 3 of them when they were on sale a while ago.
          I agree, but I have one more stipulation. If consumer class speakers, then an amp with dominant pole filter stabilization. If building really good speakers, then Transient Miller compensation lifts a veil off the sound. If you don't have control of the tweeter breakup to above 40K, stick with dominant pole.

          Totally irrelevant to the OP though Do notice, he is looking for one with a remote control for the volume, so he needs an integrated with remote. Where I might look at a Cambridge or NAD, that is not what Dravoo is looking for. E-bay has some very cheap remote control "preamp"boards that could do for a DIY. Unfortunately, remote control is going to cost as much as the amp.

          The question is why the little class D sounds dramatically better than the Sony. Something is amiss. Noise floor? Hum? Distortion? It also shows for entry level, Class D has come a long way. I have not heard the best digital be able to match the best analog, but I suspect that day is coming.

          A comment on specs. Sure, 100, or 150W sounds impressive, but pay attention to folks like Nelson Pass who strive to get the first watt correct. A 20W amp is likely more than enough for the OP. As an example, I down-sized from two Parasound 1200s , active crossovers and Berhringer 2000 on the subs to my own 60W MOSFET and plate amp. Sound? Yes, a tiny tiny difference at orchestra levels. Consider the old 1200 Mk II is one of the finest amps ever built price-no-object. Messing with my friends, while I had a stack of Hafler 200's I demo'd my system to a friend and fellow speaker builder. He was impressed with the power. Well, unbeknownst to him, I was really running a 30W Creek on the mains.

          Dravo does have me tempted to try one of these new digital amps on my desktop instead of my old chip-amp.

          Comment


          • #6
            Originally posted by tvrgeek View Post

            I agree, but I have one more stipulation. If consumer class speakers, then an amp with dominant pole filter stabilization. If building really good speakers, then Transient Miller compensation lifts a veil off the sound. If you don't have control of the tweeter breakup to above 40K, stick with dominant pole.

            Totally irrelevant to the OP though Do notice, he is looking for one with a remote control for the volume, so he needs an integrated with remote. Where I might look at a Cambridge or NAD, that is not what Dravoo is looking for. E-bay has some very cheap remote control "preamp"boards that could do for a DIY. Unfortunately, remote control is going to cost as much as the amp.

            The question is why the little class D sounds dramatically better than the Sony. Something is amiss. Noise floor? Hum? Distortion? It also shows for entry level, Class D has come a long way. I have not heard the best digital be able to match the best analog, but I suspect that day is coming.

            A comment on specs. Sure, 100, or 150W sounds impressive, but pay attention to folks like Nelson Pass who strive to get the first watt correct. A 20W amp is likely more than enough for the OP. As an example, I down-sized from two Parasound 1200s , active crossovers and Berhringer 2000 on the subs to my own 60W MOSFET and plate amp. Sound? Yes, a tiny tiny difference at orchestra levels. Consider the old 1200 Mk II is one of the finest amps ever built price-no-object. Messing with my friends, while I had a stack of Hafler 200's I demo'd my system to a friend and fellow speaker builder. He was impressed with the power. Well, unbeknownst to him, I was really running a 30W Creek on the mains.

            Dravo does have me tempted to try one of these new digital amps on my desktop instead of my old chip-amp.
            I agree on the watts thingie. My main amp is now a Marantz HTR with 50 clean watts/channel. Plenty of power for my needs.
            As far as Class D amps, PE is carrying Icepower, which is pretty groovy.
            https://www.parts-express.com/icepow...-170w--326-214

            I think I hear a difference - wow, it's amazing!" Ethan Winer: audio myths
            "As God is my witness I'll never be without a good pair of speakers!" Scarlett O'Hara

            High value, high quality RS150/TB28-537SH bookshelf - TARGAS NLA!
            SB13/Vifa BC25SC06 MTM DCR Galeons-SB13-MTM
            My Voxel min sub Yet-another-Voxel-build

            Tangband W6-sub

            Comment


            • #7
              I would check to see if you've 'altered' any of the settings on the Sony amp if there are any.

              Remember playing a cassette with the Dolby off, realizing it, then turning it on.... and then being disappointed with the lack of high end... it just sounded a bit duller, even if the tape hiss was more predominant. Adjusting the bass and tremble controls on the Lepai up a bit and then using the button to turn off the 'boost' can make music sound a bit lifeless in the same way. I suspect you may have to tweak the controls a bit on the Sony.

              TomZ
              *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
              *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

              *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

              Comment


              • #8
                Originally posted by tvrgeek View Post
                The question is why the little class D sounds dramatically better than the Sony. Something is amiss. Noise floor? Hum? Distortion? It also shows for entry level, Class D has come a long way. I have not heard the best digital be able to match the best analog, but I suspect that day is coming.

                Dravo does have me tempted to try one of these new digital amps on my desktop instead of my old chip-amp.
                Originally posted by donradick View Post
                As far as Class D amps, PE is carrying Icepower, which is pretty groovy.
                tvrgeek - I know you have mentioned in a few posts about the current state of Class D amps. I have not heard all of these, but based on widely accepted reviews the Purifi and Hypex n-core are world-class amps, but also not cheap. The Icepower are good as well as amps from www.classdaudio.com/ although these are getting a little out of date.

                If you are interested in "trying" one, the TPA3255 (and less easy to find TPA3251) are supposed to be quite good for the money when implemented well, but the problem is the abundance of cheap poorly implemented designs from China. 3e Audio sells boards on eBay for about $70 (he has a website but it's not great) that are supposed to be quite good and there is a DIY designed TPA3255 Reference board with a group buy at diyaudio.com.

                Comment


                • #9
                  Again, the sound was incredible. I decided that I wanted to replace the Lepai with an amp I have had for a few years so that I can use a remote for the volume. I plugged in my Sony STR-DH130 in place of the Lepai. I was shocked to find that the sound wasn't nearly as impressive as with the Lepai. My questions are: Are there any specs I can use when choosing an amplifier to make sure I am getting the best bang for my buck? What other factors might be at play that would make a $30 amplifier seem vastly superior to a $150 amp?


                  There aren't any differences in specs between the amps you are using that would explain the magnitude of difference you are hearing as long as they are functioning properly. Really needs to be wiring, damaged connectors/wiring or settings as Tom suggested.😉

                  Comment


                  • #10
                    a4, Doing some searching today. I see Parasound in selling one now. Hard to think John would put his name on one if it was not up to snuff. ClassDaudio is new to me. The ICE blocks are fine for subs or desktops, probably just fine for 99% of the typical AVR users out there and what a revolution for cars, but no where near a good AB for high end. My ears of course and by good, that is a select few. Let me think: 1200 Mk II, Aragon, Levinson 27 was no slouch, there was an early small Krell that was really good, and of course my own MOSFET. If they are up to, say the old 800 series Rotels, then I would say ready for prime time. Just not for my main yet.

                    I used a Behringer on my subs in the last house and it did fine. I tried it on the mains, and barely made it across the room to turn it off. Sounded like a cheap PA. Well, it IS a cheap PA. So cheap if you were on the road you could afford a couple in the box in case of a failure! But it was cleaner than my O-audio plates. A bowed upright just goes a little off as it moves from my mains to my sub, so something new is in order. I was looking at the Dayton DSP plates, but their lack of specifications worries me. 1% THD, but that's at rated. Drop 5% power and they are probably .1, but they don't say.

                    I noticed by some of the specs out there, how one must interpret THD in totally different way for class D as they seem to follow a bathtub curve. Where I think they are falling down is in the first watt as a result of the bit-length. I listen to a lot of classical guitar so that first bit has to be very very good. Female vocalists with little accompaniment is another. Just a guitar or piano. I hope by the time I need a new amp, I wil be so old I won't care any more. Sigh. probably time to re-cap my MOSFET though. It is about 10 years old. I can tell I need to work on my Nak CA5 preamp. It's original.

                    Still does not answer Dravo's question. How do we set him up with a decent inexpensive integrated with remote control? Pieces are all out there on e-bay, but how much fab he can do I do not know. Does someone put one of these new boards in a box with a remote cheap?

                    Comment


                    • #11
                      Maybe this is something that fits the bill.
                      https://www.amazon.com/Wireless-Blue...0&s=aht&sr=1-1

                      Comment


                      • #12
                        Or https://www.amazon.com/S-M-S-L-Infin...&s=aht&sr=1-20 S.M.S.L SA300

                        has a sub out for a powered sub, so a 2.1

                        Comment


                        • #13
                          Originally posted by tvrgeek View Post
                          Snippety... Where I think they are falling down is in the first watt as a result of the bit-length. ...snip
                          There's a common misunderstanding of class D right there. They're not digital, so there is no bit depth. They operate as PWM devices, like a switching power supply. You may still be quite right though, since the pulse width for low level signals for the first watt are very narrow which may contribute to the elevated THD (just guessing).

                          Checking out the common and cheap example TPA3116 chip data sheet, there is a little bathtub curve in the THD vs. output power mostly dependent on the measurement frequency. I wonder why that chip has a problem with 6kHz that doesn't show up at 1 and 20kHz. That seems odd.
                          Electronics engineer, woofer enthusiast, and musician.
                          Wogg Music
                          Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

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                          • #14
                            Yea, I was trying to be simple. I took a class many years ago from Tektronix on digitizing when scopes first came out. Back then there was a big debate between bit rate and word length. When they asked me what I need in my lab, the answer was "yes". ( We were dealing with intermittent signals in the ns range.) I don't remember the details as it was like 35 years ago.

                            Looked at the data sheet. Very odd indeed. I don't understand it. One would need to plot the distortion in 3D. I would expect higher distortion when approaching LSB, and higher when approaching Nyquist. Maybe some sort of IM with the clock?

                            How it handles peaks could be another difference. A flat line clip is going to be really horrible due to the harmonics. Some smarts to compress in a non linear function maybe, but that would show up measured as HD even though it might sound good. Well, I understand analog. Two key features: enough outputs and method of compensation. We know how to make them measure good (Self) or sound good ( Curl, Pass). Spice tells me almost all I need to know. ( Except my attempt to model a spark plug. Darn that is a difficult problem)

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                            • #15
                              We are getting way off topic here, but did some googleing. Seems the Hypex based amps don't have those issues as the TI based ones, but they cost as much as equivalent class AB. Case, power supply, assembly, markup for every change of hands. A nice one winds up $1200 and up. That's my learning for today. Sticking with what I know.

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