124 replies to this topic

[Onevox]

Sat next to guy on plane today who is an audio and video expert on ultra high end uses. We got into VP discussion. And he was fascinated. I wish I could have processed his info and recommendations.

 

He thinks that two mech subs, which I had been thinking about, could have phase issues between channels where they're canceling a certain amount of wavelength and reducing the effect. At lower wavelengths phase issues are more likely. He worked on tactile feedback on rides at Universal theme parks years ago and said there was a regular schedule on rides to tighten bolts because bass shakers would loosen them.    Might need to turn down my sub a bit.

Edited by Onevox, 30 August 2017 - 11:08 AM.

[rickh]

Sat next to guy on plane today who is an audio and video expert on ultra high end uses. We got into VP discussion. And he was fascinated. I wish I could have processed his info and recommendations.

 

He thinks that two mech subs, which I had been thinking about, could have phase issues between channels where they're canceling a certain amount of wavelength and reducing the effect. At lower wavelengths phase issues are more likely. He worked on tactile feedback on rides at Universal theme parks years ago and said there was a regular schedule on rides to tighten bolts because bass shakers would loosen them.    Might need to turn down my sub a bit.

Onevox,

 

Perhaps there is some truth in this and although acoustics and tactile feedback have evolved from an art to a science, I think that experimenting what sounds and feels best trumps science.  I'm not advocating the disregard to science, but merely using it only as a guideline.   I once had an old MacIntosh stereo tube amp that had a switch to throw the left speaker out of phase by 180 deg (simply reversed the polarity of one of the speakers).  Some audiophile once told me that this switch was used when the L/R speakers were far apart and the listener was closer to one speaker.  I tried it and honestly I did not think it sounded better, but other disagreed.  I think this is the same for tactile feedback and audio; it is a user preference.     

Rick

[hlr53]

I never really paid attention to my sound card inputs. I have simply plugged in my 2 Altic Lansing powered cubes and their attached sub to the green in. I just checked and found I also have orange and black inputs so I can add more speakers.

 

Gonna head over to Parts Express sometime in September and pick up some Dayton exciters (not sure which ones yet) and an amp. I'll also ask the guys while there.

Edited by hlr53, 31 August 2017 - 10:28 PM.

[mjr]

He worked on tactile feedback on rides at Universal theme parks years ago and said there was a regular schedule on rides to tighten bolts because bass shakers would loosen them.

 

Ha.  Yep, that definitely has been an issue with my tactile sub.  Even with a nut-locking washer-nut sandwich and everything tightened down, the constant vibration works things loose over time.

[Brer Frog]

 

Sat next to guy on plane today who is an audio and video expert on ultra high end uses. We got into VP discussion. And he was fascinated. I wish I could have processed his info and recommendations.

 

He thinks that two mech subs, which I had been thinking about, could have phase issues between channels where they're canceling a certain amount of wavelength and reducing the effect. At lower wavelengths phase issues are more likely. He worked on tactile feedback on rides at Universal theme parks years ago and said there was a regular schedule on rides to tighten bolts because bass shakers would loosen them.    Might need to turn down my sub a bit.

Onevox,

 

Perhaps there is some truth in this and although acoustics and tactile feedback have evolved from an art to a science, I think that experimenting what sounds and feels best trumps science.  I'm not advocating the disregard to science, but merely using it only as a guideline.   I once had an old MacIntosh stereo tube amp that had a switch to throw the left speaker out of phase by 180 deg (simply reversed the polarity of one of the speakers).  Some audiophile once told me that this switch was used when the L/R speakers were far apart and the listener was closer to one speaker.  I tried it and honestly I did not think it sounded better, but other disagreed.  I think this is the same for tactile feedback and audio; it is a user preference.     

Rick

 

 

What happened to the MacIntosh stereo tube amp? That would be priceless to have today.

[rickh]

 

 

Sat next to guy on plane today who is an audio and video expert on ultra high end uses. We got into VP discussion. And he was fascinated. I wish I could have processed his info and recommendations.

 

He thinks that two mech subs, which I had been thinking about, could have phase issues between channels where they're canceling a certain amount of wavelength and reducing the effect. At lower wavelengths phase issues are more likely. He worked on tactile feedback on rides at Universal theme parks years ago and said there was a regular schedule on rides to tighten bolts because bass shakers would loosen them.    Might need to turn down my sub a bit.

Onevox,

 

Perhaps there is some truth in this and although acoustics and tactile feedback have evolved from an art to a science, I think that experimenting what sounds and feels best trumps science.  I'm not advocating the disregard to science, but merely using it only as a guideline.   I once had an old MacIntosh stereo tube amp that had a switch to throw the left speaker out of phase by 180 deg (simply reversed the polarity of one of the speakers).  Some audiophile once told me that this switch was used when the L/R speakers were far apart and the listener was closer to one speaker.  I tried it and honestly I did not think it sounded better, but other disagreed.  I think this is the same for tactile feedback and audio; it is a user preference.     

Rick

 

 

What happened to the MacIntosh stereo tube amp? That would be priceless to have today.

 

The MA 230 integrated amp (30Wx2) had an open chassis and glass bezel design ( http://www.roger-rus...mppre.htm#ma230 ).  It was destroyed during a move which I received compensation.  I miss it like an old friend. 

Edited by rickh, 02 September 2017 - 06:22 PM.

[Brer Frog]

I just bought one of those TPA3116D2 amps. Guess I'll find out how it works after it arrives from China in a month or so.

 

Not to be confused with the PAM8610 amp that I ordered last night. IOW two amps are coming.

 

The PAM8610 arrived sometime last week from a USA vendor. So did the backbox speakers.

The TPA3116D2 arrived Sept 5, only 11 days with free shipping from China. That's the fastest I've ever got anything from China.

[rickh]

 

I just bought one of those TPA3116D2 amps. Guess I'll find out how it works after it arrives from China in a month or so.

 

Not to be confused with the PAM8610 amp that I ordered last night. IOW two amps are coming.

 

The PAM8610 arrived sometime last week from a USA vendor. So did the backbox speakers.

The TPA3116D2 arrived Sept 5, only 11 days with free shipping from China. That's the fastest I've ever got anything from China.

 

Mike,

I just got around to placing the PAM8610 on my o'scope and function gen.  I could not do a distortion measurement due to an instrument malfunction, but my noise measurements showed that it is relatively quiet with a 250 kHz PWM carrier.   So I had to evaluate it using the old fashion method of attaching it to a pair of Polk bookshelf speakers and some music.  I was impressed by the big sound coming from the small size.  I also tested an even smaller version, the PAM8603 which uses a 5VDC supply and can crank out about 2.5 Watts.  Again, impressed,but not enough for Virtual Pinball.  I'll use this critter on my MAME cocktail table machine.      

[xantari]

So what are the  bad, good, best options? 

[STV]

Any reason the Lepai LP-2020Ti isn't gaining consideration?     class D, 20W, bass/treble/volume    up to 24V input    ~$25 each. 

[rickh]

Any reason the Lepai LP-2020Ti isn't gaining consideration?     class D, 20W, bass/treble/volume    up to 24V input    ~$25 each. 

STV, Yes I have this amplifier on my Wife's CPU sound system and it is awesome.  BTW- my version came with a 12VDC supply and I haven't pried it open to see if the filter caps can handle 24VDC.   As for my amplifier review, it has a bunch of graphics associated with it and I will need to convert it to a PDF.  Meanwhile, I am still doing last minute edits. 

[Onevox]

Reading about Polk audio speakers above got me wondering how you could test the quality of the game audio file? At what point does hardware resolution become moot? 

[rickh]

Folks,

 

Appears I am having technical difficulty.  This message board will not allow me to upload a PDF. 

Consequently, I am only releasing the review section.  The applicable photos are not included, use your imagination ;-).  Sorry!

 

Type of Amplifiers Chips.   Presently, there are no discrete amplifiers, they are all chip based.  Most of these amplifiers are based on the chip manufactures suggested system design making it easy to look at the applicable data sheet and specifications of the amplifier.  Most manufacturers faithfully follow the suggested application reference design When shopping for a specific amplifier type most of the systems will be identical in design, differing only in the quality of components and build. 

Below are a few amplifier chips I have evaluated:

(All ratings at 4 ohms unless specified)

·      TDA7057 - .5W per channel, 2 ea .3%THD at 12VDC (this is a real turd!)

·      TA8201 – 14W per channel, 2 ea. 10% at 13.2VDC (Runner up to best turd)

·      TDA7297 - 8W per channel, 4 ea 10%THD @ 12VDC (Have not evaluated this)

·      TDA7379 - 11W per channel, 4 ea 10% THD@18VDC (At 12V this amp turns into a turd)

·      TDA7377 - 7W per channel, 4 ea 1% THD@16VDC, 10%THD at 4.8W using 12VDC.  (okay at low power)

·      TDA7293 - 80W per channel, 1 ea .1% THD@+/-40VDC (good amp, but needs a bipolar supply)

·      LA4635A – 8W per channel. 2 ea 3% THD@12VDC (better than the TDA7377)

·      TDA2030 - 12W per channel, 1 ea .2% THD@+/-14VDC (An inferior version of the LM1875)

·      LM1875 - 20W per channel, 1 ea .022% THD@+/-25VDC (lots of power but needs a high voltage supply)

·      TDA2050 - 20W per channel, 1 ea .02% THD@+/-18VDC (basically a LM1875 clone)

·      TA2020-020 – 18W per channel, 2 ea 1% THD @13.5VDC (a great performer)

·      PAM8403 – 3W per channel, 2 ea. 5%THD @ 5VDC (tiny, low performance)

·      PAM8610 - 10W per channel, 2 ea .1% THD@12VDC (best deal)

·      TPA3116D2 -25W per channel, 4 ea .1% THD@21VDC (clean, very capable, very cool)

 

 

Amplifiers Brands and Models.  There are too many brand names out there, as each Chinese distributor places their own name on their product.  As mentioned model names normally use the model number of the amplifier chip.  The Chinese are also known for taking obsolete brand name models and reproducing them under a generic model name.

 A good example is the LP-838.  This model is sold under the following brands Lepy, Lepei, Elegiant, RDEXP, and Lvpin.   This 2.1 amplifier is enclosed in a nice extruded aluminum case with four audio controls and a dedicated woofer amp.  A TDA7057 amplifier chip is used for left and right channels and the single channel TA8201 amp is used for the woofer.  This design has been around for over 20 years and is no longer competitive.  It is one of the lowest performing models tested.    

To the left is a LP-838.  It claims that it is HiFi.   This is by far the worst amps I have tested.

The LP-838 can confidently be called a turd, but its little brother, the LP-808 amplifier based on Sanyo’s LA4635A is a large improvement.  Although power is lacking and it has but 2 channels, the amplifier works very well at 12V, wringing out every ounce of energy to produce a clean 8W at less than 3% THD.  Distortion increases exponentially as power increases.  Actual spec shows .06% THD @ 1W and 10% at 11W.  The low impedance of this amp allows driving left and right speaker both attached to common coil subwoofer.  This amplifier produced excellent audio sound.  The only complaint is lack of dynamic headroom for transient sounds caused by the low voltage power source.  The Lepy LP-808 is very good and affordable it should not be over looked.   As with the LP-838, this model is sold under several names.

The best deal for a performance amplifier is a generic PAM8610 based two-channel system.  This reference design is an open PCBA with a single volume control.  

 

The amplifier left uses the PAM8610 Class D dual amp, conservatively rated at a clean 10W x2.  At less than $10, this is the best value for a 2 channel system hands down. -Note the tiny Heatsink-
 

 

 

The PAM8403 dual amplifier may be a diminutive size, but it is a true mighty mite offering 2.5W (actually 3W) of clean power at 5V.  Unfortunately, it’s not suitable for virtual pinball or filling a gymnasium with sound, but ideal for smaller projects.

At the left is the DROK labeled PAM8403  

 

The LP-2020A+ is an outstanding low cost amplifier based on the TA2020 Class T amplifier chip.  This amplifier produces the best 12VDC sound of any contained system and rivals amplifier costing 3x as much.  The Chinese are great about naming inferior products after brand named chips.   It is no different for the TA2020A+.   I purchased one of these amplifiers in 2014. When looking for a second one, I discovered that several customers complained that the newer amplifiers contain an inferior version of this chip.   Be careful!

To the left is a Lepai LP-2020A+

The TDA2030 and TDA2050 are another example of an older reference design.  Both chips are based on the once mighty LM1875 which has been around for over 30 years.   Unlike the inferior TDA7057, these chips still have respectful specifications, but the reputation is marred by some systems using inferior components, design and workmanship.  This system requires an external 24VDC power supply(+12V/-12V).  Many manufactures include a rectifier and filter with their systems so that the only component needed is a transformer.  Unfortunately, the size and quality of these filter caps do not compliment the amplifier, making the system undesirable.   The tech savvy can add two separate 12VDC supplies and bypass the amplifier’s diode rectifier for an awesome sounding amplifier with plenty of punch. 

To the left is a 2.1 system based on the TDA2030.  The unshielded cable and diminutive size of the two filter caps compromise the performance potential of this system.

 

 

 

Another common system is the TDA7377 and TDA7379.  These are mediocre performing amplifiers that are good for 5W.   The example I evaluated uses a separate PCBA for the controls.  An unshielded cable is required between both PCBAs.  These unshielded wires pick up unwanted noise.    Similar amplifiers can be had with both boards integrated which eliminate this shortcoming.   4W of quality power is sufficient for most arcade applications.  Both systems can be run at 16VDC which highly recommended.   Both models are on par with the LP-808 amplifier based on Sanyo’s LA4635A. 

At the left is a TDA7377 2.1 system amplifier.  The separate control board allows easy cabinet mounting.

 

For transient response, low distortion, low power dissipation, and relevant features look no further than an amplifier based on the class D TPA3116D2.   Simply, it is the best amplifier I have tested.   This system provides two 25W channels for L and R, and two bridged amps to produce 50W for a subwoofer.  It comes complete with a treble, bass and volume control all for $15.  The only complaint I have is that the output filter circuitry prevent this system from driving lower impedance loads.  A 24V 80 watt supply will set you back $18.  In all, this is a cracking deal. 

 

To the left is the mighty 2.1 TPA3116D2. 

Edited by rickh, 08 September 2017 - 03:36 PM.

[Brer Frog]

I did a trial hookup of the PAM8610 amp to the 2” speakers I got from Parts Express & everything works. The amp’s power supply & audio jacks are a bit too close to each other & the 2 corresponding plugs are slightly wedged together. I’ll just file them down a bit.

Not sure if I’m overdriving anything or if it’s just that my 12V “wall wart” power supply is not up to snuff since it’s only 1250 mA. My old cheap Dell PC speakers seem cleaner when played loud & they’re powered by a 12V 600mA supply. The PE speakers seem brighter so maybe I’m just hearing stuff normally muffled by the Dell speakers. I tried to run the PAM8610 amp at somewhere near the middle of its volume control setting in order to limit current draw. I’ll have to play with it a bit.

[rickh]

I did a trial hookup of the PAM8610 amp to the 2” speakers I got from Parts Express & everything works. The amp’s power supply & audio jacks are a bit too close to each other & the 2 corresponding plugs are slightly wedged together. I’ll just file them down a bit.

Not sure if I’m overdriving anything or if it’s just that my 12V “wall wart” power supply is not up to snuff since it’s only 1250 mA. My old cheap Dell PC speakers seem cleaner when played loud & they’re powered by a 12V 600mA supply. The PE speakers seem brighter so maybe I’m just hearing stuff normally muffled by the Dell speakers. I tried to run the PAM8610 amp at somewhere near the middle of its volume control setting in order to limit current draw. I’ll have to play with it a bit.

When I tested this amplifier, I used a 3 amp supply, It sounded good driving a pair of Sony book shelf speakers.  It was on par with the paired Sony amp. With a 1.25 amp supply you should have 7.5 watts available per channel (which should be more than enough).  It would be interesting to measure the supply voltage when playing steady music material.  

[Brer Frog]

I'll see what I can determine regarding the supply voltage under load.

 

Do you have any idea from your testing what input signal strength it takes to drive the PAM8610 to full output power? Or what the max input signal is before overdriving the amp?

[rickh]

I'll see what I can determine regarding the supply voltage under load.

 

Do you have any idea from your testing what input signal strength it takes to drive the PAM8610 to full output power? Or what the max input signal is before overdriving the amp?

I can certainly do that, but it might take a few days.  I'll see if I can provide a few screen shots of the oscilloscope (both input/output) too.  In the meantime, if you have a multimeter, measure the DC voltage across each L/R speaker and input.  I failed to mention that that many of these new amplifiers are DC input, which means that they do not have a DC blocking input capacitor.  This is a dual sided sword, as these DC amps may have enhanced/flat lower frequency response, but a DC bias on the input will eat up your available power. The TDA2030 and LM1875 based amplifiers are notoriously known to exhibit problem which rooted from the poor application reference design.  

Edited by rickh, 19 September 2017 - 11:45 AM.

[Brer Frog]

Rick,

I checked the 12V wall wart power supply under no signal to the PAM8610, with maximum volume on amp & PC, and various in between settings. The supply remained at 12.4V all the time. I used one of those cheap $23 DSO138 oscilloscope kits that I built a couple years ago. That way I could see if the wall wart was maintaining a real DC output & it was. But now I wonder if I should have played around with the time base setting in case any anomalies showed up under different settings. Let me show you what I observed so far.

I connected one channel of the amp to a 7 ohm resistor that was cobbled together (closest I could get to 8 ohms). The PC volume was set at the half way point and I experimented with the amplifier’s volume. I fed the amp a 1 KHz audio signal. The signal across the load resistor was noisy & distorted even at very low levels. The first photo shows the typical output signal with the amp’s volume set anywhere from low to somewhere in the middle. If I turned it up a bit more the signal got really distorted as shown in the second photo. IOW even at relatively low to medium volume levels the signal was crappy looking.

I’ll have to check the signal going into the amp. In the meantime, looking at the photos, could all that noise be caused by the class D switching amp? Have you seen anything like that when reviewing all those little amplifiers?

 

Mike

 

 IMG_101B.jpg   127.81KB   14 downloads     IMG_105.jpg   58.92KB   10 downloads

[rickh]

Rick,

I checked the 12V wall wart power supply under no signal to the PAM8610, with maximum volume on amp & PC, and various in between settings. The supply remained at 12.4V all the time. I used one of those cheap $23 DSO138 oscilloscope kits that I built a couple years ago. That way I could see if the wall wart was maintaining a real DC output & it was. But now I wonder if I should have played around with the time base setting in case any anomalies showed up under different settings. Let me show you what I observed so far.

I connected one channel of the amp to a 7 ohm resistor that was cobbled together (closest I could get to 8 ohms). The PC volume was set at the half way point and I experimented with the amplifier’s volume. I fed the amp a 1 KHz audio signal. The signal across the load resistor was noisy & distorted even at very low levels. The first photo shows the typical output signal with the amp’s volume set anywhere from low to somewhere in the middle. If I turned it up a bit more the signal got really distorted as shown in the second photo. IOW even at relatively low to medium volume levels the signal was crappy looking.

I’ll have to check the signal going into the amp. In the meantime, looking at the photos, could all that noise be caused by the class D switching amp? Have you seen anything like that when reviewing all those little amplifiers?

 

Mike

 

IMG_101B.jpg    IMG_105.jpg

Those Windows O'scopes are really handy.  Let me tell you what is going on here.  The PAM8610 is a class D amp.  As such, it uses a 250kHz based PWM.  Since your scope has only a 200 kHz limited bandwidth, it filters out this higher frequency, allowing you to see most of the original content. However, I suspect you might be seeing some aliasing.  My scope has higher band width so I use a home made low pass filter so I can see the waveform. So I have the opposite problem.   If I have time tonight and give you some waveforms and we can compare notes.    

[Brer Frog]

Rick,

You mentioned a Windows O'scope. What I have is a JYE Tech oscilloscope kit & it does have the 200KHz bandwidth as you mentioned.
http://www.jyetech.c...dScope/e138.php

Here are a few photos & observations regarding the 12V supply on the PAM8610.

First one is the 1KHz input signal at the amp’s input. The PC’s volume is all the way up & the signal looks pretty good.
 IMG_2862C.jpg   106.4KB   9 downloads

 

Second one is the 12V power supply not connected to anything other than the scope. Minimal noise, some of which is probably from the cheap oscilloscope.
 IMG_2869C2.jpg   91.34KB   8 downloads

 

Third photo is the 12V connected to the amplifier & measured at the amp. The audio is connected but the amp’s volume is all the way down.
 IMG_2881C.jpg   103KB   7 downloads

 

Fourth also shows 12V on amp but with both PC and amp volume at 50%. Increasing the amp’s volume control past the half point does increase the noise, but not as rapidly.
 IMG_2884C.jpg   111.47KB   8 downloads

 

It appears that just powering up the amplifier generates noise on the 12V supply.

 

I did connect a 36 ohm resistance across the 12V wall wart in order to put a load on it & see how it held up. That did add a little noise compared to no load, but nowhere near what connecting the amplifier did. I tried to take a photo but needed another hand to hold everything in place & hold the camera at the same time.

Edited by Brer Frog, 21 September 2017 - 08:11 AM.