20 Watt Class A Amplifier - Bode Plot & THD
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- čas přidán 29. 01. 2021
- I will review a new 20 Watt Class A Amplifier. I'll show the Bandwidth (Bode Plot) and the THD of this amplifier. #20WattClassAamplifer, #20WClassAamplifier, #ClassAamplifier #THD #Bodeplot
Link to 20W Power Amplifier Board: amzn.to/3oB0VWW
Link to silicone lead set: amzn.to/3j23ksq
Link to Blue silicone mat: amzn.to/36qpIqD
Please use this link for the Hiraga Power supply kit:
rover.ebay.com/rover/1/711-53... Power Supply
Please use this link for Aleph 5, Class A Amplifier kit used in this project: rover.ebay.com/rover/1/711-532...
Another Aleph 5 Class A amplifier link:
rover.ebay.com/rover/1/711-53... 5 Amplifier
Bridge Rectifier with capacitors: rover.ebay.com/rover/1/711-53... with Capacitor bank
Link to Hiraga power supply kit: rover.ebay.com/rover/1/711-53... Power
Adjustable PCB holder: amzn.to/2XhH1pe
1 Ohm 3 Watt metal film resistors: amzn.to/2BO0h64
Audio Grade 220 uF 35 V capacitor: amzn.to/2BNFbET
Silver Solder: amzn.to/2Dv7wQL
Soldering Iron T12 tip: amzn.to/39MQARR
Heatsink TO-220: amzn.to/3gkO8EB
Thermal Paste: amzn.to/3i1AZ43
You can support this channel with this link to Patreon - I really do appreciate your support? This support helps me purchase the equipment I use for testing a reviews.
Patreon.com/KissAnalog
Or you can support this channel with a one time donation on PayPal at: KissAnalog@gmail.com
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Part 4: Intermodulation Distortion (IMD): • GaN Class D Review Int...
Part 3: Amplifier Distortion and THD: • GaN Class D Review Dis...
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Part 1: gain/phase plot across the audio spectrum with this GaN Class D Amplifier: • GaN Class D Review Gai...
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Seriously, why does this man only have 8.48K subs??? What phenomenal content! And I thought I knew my analog...
I love the experimental nature of the channel. Kudos to you Sir, you are a most engaging teacher. I just subbed:-)
Love your feedback!! Thank you! I appreciate you!
Thanks for amplifier testing videos
You bet! And thanks for the feedback!
Yes! Just another great Kiss Analog video.
I appreciate you;)
Hi Eddie, another awesome video and the testing was awesome.
Thank you! I appreciate your support!
great video, looking forward to the next part :)
Thanks for watching! I appreciate you!
Put both amps in the box. Biamp the output . Class A on top, Class D on the wooofer, heaven!
That’s actually a great idea;). The problem I have is my box is small. Also the guy I’m building this for has a powered sub;) He likes his music load, so I think I might go back to the Class D;)
That's a pretty good amp except for the heatsinking. If we interpolate that you'd lose another half a volt or so at 2 ohms, then (6.5V)²/2Ω = 21W. An even 20W would require 6.3V into 2Ω, which seems plausible, though THD would likely become an issue before clipping and heat may desolder components soon thereafter. 7W into 8Ω and 13W into 4Ω is plenty of power for a Class A as what good is an amp that you won't use because it turns your listening room into an oven? That might be nice in Winter, but I like to listen to music in other seasons, too ;).
There's a rule in photography that the best camera is the one that you're carrying. The corollary here is that the best sound system is the one that you're using.
7W into typical speakers will be fine unless you want a subwoofer and I would not use Class A for a sub as any minor issue with THD, linearity, and crossover lag would only ever be audible with higher frequencies. Personally, I think a good Class D built into a sub is good enough even for audiophile listening; I'd spend my limited Class A power, heat, and bucks on higher frequencies.
Thanks for the awesome feedback! I agree with your points and math! I didn’t expect to run this at 20 Watts continuously, but I did want the dynamic range;) I think I am going back to the Class D...
Hi Eddie thanks for another nice video very interesting.
So nice of you
Thanks Eddie.
First, those heat sinks aren't going to cut it. You have to use those bolt holes to add heat sinking. What I've learned with these things so far from experimenting is that the best solution is to use a fan. Something like a 12 volt fan at 6 volts just to keep the air moving but you can't really hear it. I found it significantly reduces the heat. David Hafler had a setup with his SS amps from the 80's where he ran a fan through an aluminum box with the boards attached to it that worked pretty well that I might try.
I have a Pass 3 clone board coming and I'll know more when I start experimenting with it.
What I did do is take one of those ebay Sure class D 250w x 2 amps and run my system on it. Once it broke in I liked the sound but I'm using a tube preamp design I did for AudioXpress a few years ago with a 6922 which is a neat little tube. What I'm thinking is that if I put a tube preamp with second harmonic distortion thru the class D I might get a sound that I like enough with out these class A's with 25 or 30% efficiency. Have you run any of them on Mean Well SMPS suppliers, saves all the caps and linear supply stuff.
I don't know, what do you think?
Thanks @mosfet500 I agree, these heatsinks are just convienent to mount the transistors to and for simple power tests, but any longer testing or real use - they do need to be mounted to larger heatsinks. I have a small box with fairly large heatsinks that I hope this amp will be OK with. I'll run another test to check this and do a video;)
I like your ideas of mixing technology. Also, running with switching power supplies is right down my road. I'm actually designing a power supply for that use now;)
@@KissAnalog I'm pretty much an off the shelf SMPS guy, it's a real art making them. Very interested to see what you come up with and what I can learn.
The other thing I was thinking of was a hybrid of class D and A so you could use something like Pass's 8 watt camp amp that doesn't dim your lights and a class D low end with a little crossover to bring them together. I think there were some tube/SS designs where this was done.
Great video. Thorough.
Much appreciated!
As I'm now rocking an Aleph 5 amp thanks to you, I vote for the 20W class A amp. You really need to build both so that you can compare how they sound.
Thanks Ian! I need to get some parts and a BIG heatsink/box for my Aleph 5 project. This 20 Watt seems like it will be more like 8 Watts at 8 ohms. I wonder if that is enough power for my friend who like to listen to rock with the volume turned up? I'll do another video with the power experiments.
@@KissAnalog good for tweeters @4KHz
Classic 80/90s old school British amplifier "look a like"
If you use the Class A amp, you can be a snob when you're talking with your friends! ;-)
Thanks! LOL That’s actually a big reason to do it;) This is for a friend and I wanted to give him something to brag about;)
You could add a thermal imaging camera to prove it!
Setup a nice CRC psu & a nice Toroidal transformer and your good to go.!
Thank you Mr Leamerz! Nice video BTW;)
@@KissAnalog Thanks, soon to be working on a few QA401 videos..
8W only with very efficient loudspeakers for playing rock/metal if your friend lives in a relatively quiet area.
I have 2 amps Nakamichi Compact Receiver1 @ 12w on a/d/s/ L200's and AIWA A60 @14w on L400's on my desk with a dual amp ballancer between them and for me its adequate.
My truck on the otherhand has 960W and it needs more.
Thank you for your feedback! Yes I think I have to agree. I think if I could get 12 Watts I’d be happier with it.
Your system does sound nice;)
Great video!!!!!! Could you please add the li k of these silicone multimeter test leads!!!!!! Thank you....
Yes, I will add that! Thank you! I'll add the silicone mat as well;)
Yes. After your probe video, I bought some on Ebay for about 3.50, gold very sharp points, claiming 20 amps... a class above my Fluke probes! Every thing you said: supple, sharp, comfortable, good strain relief...
I'm mesmerized by all the tip attachments that yours came with. I think that I'll order a pair.
Thank you for the probe rant: it worked!
I’m glad you like them!
T03 metal encapsulated transistors! You have my attention!!!
Oh wait, they are those 150024's!
I wonder how it's going to sound? I usually stick to the 2N3055's, even if they are Chinese made, there's a video over on John Audio Tec's channel where he tested an amplifier with those things and it was really bad! After swapping out to the possibly fake 2N3055's it came good!
I haven't watched all the video yet, I'm commenting early... I will see how it goes....
I'll post an update very soon... I'm not as impressed as I wanted to be;)
@@KissAnalog it kinda reminds me of the qusi complimentary amplifier that's available on eBay that a few people built but weren't impressed with! They were also based on the TO3 output transistors which I love so much but no one has tried to fix any issues that they came across! They cost only $10 - $15Au which is even cheaper in the US! I ended up getting around 5 or 6 kits but I have yet been reluctant to assemble one! It's going to happen one of these days, been thinking about getting it on video and possibly even trying to improve it if it needs it... But that's on the drawing board for now as I continue to collect the tools and space needed... I will definitely be watching any further follow up on this amplifier... See you then 🤗.
Thanks for the tip, Peter. I love 3055s!
Nice video. You didn't talk about the huge sense resistor that's in a coil configuration. I was wondering why there was an air core inductor until I saw the resister symbol on the silk screen. I guess the coil configuration provides some high frequency roll-off?
Thank you! Yes the coil is part of the Boucherot Cell;)
@@KissAnalog Ah, okay. I googled this and your picture and video came up on top of the list! :-D
I am not an amp expert but I have built a few Pass First Watt amps. They need 5U high heat sinks to stay within 50 - 55 deg. Celsius
at 30 watts, at the specified bias setting.
And class A amps run out of class A at an output that is depending of the bias setting. And afficiados think that higher bias always
sounds better, not depending on output.
I also think that a class A amp should draw around the same amount of current at all output levels. That is why it doesn´t need as
much capacity in the PSU, but needs some heavy heat sinking.
The box you have looks good, but still seems to have too little heat sink for a class A amp, with high biasing.
You say that you are not an expert - but I'd say that you have a lot of expertise:) I agree - the box I have gets very hot;) It is too hot to touch for long after about 20 min. My friend loves the sound - but I think it is too hot - but in the few hours a week that he listens to it - it is probably ok.
8w with speaker up 90 - 92db no problem !
Thanks marco!
That was an awesome test. Can you check to remove the input capacitor of class D amplifiers? and check the phase shift? I think that input capacitor itself can cause phase shift at different frequencies.
Thank you! That's a great idea - and I'm sure that you are right;)
Yes, that would be interesting. That phase shift was horrible!
Hi Eddie,
I've been saving up for a Siglent SDS1204X-E, but I'm not sure.. I am really impressed with your GW Instek.
I'm far from wealthy so I'm looking for some advice. I really would like to be able to do Bode plots. TFT is essential unless the scope is an MDO that can double as a spectrum analyzer. It must have at least 1M for TFT. Bandwidth is not critical: 100MHz would be fine. Fast slope is more important, but that's tied to bandwidth...
Finally, quick access to functions is a consideration, as I get annoyed at this digital world where functions are hidden in layers of menus and values are discrete steps set with buttons instead of rotating a knob. My Siglent SDS1052 has the multifunction knob that always changes setting as I push it in....
What would you recommend? Siglent or GW Instek? Where would you compromise on? 2 channels instead of 4? Bandwidth?
Thank you for your advice and thank you for the great channel and great useful videos!
Cheers
Mark
That's a great question #Question Mark, and thank you for it;) I do think my MDO instek is easier to use for the spectrum analyzer, and I like the larger display and dedicated vertical control knobs for each channel (makes it a bigger scope though): amzn.to/3joLMXD
The siglent SDS1104X-E is on sale right now and is a great scope. Smaller screen and the multifunction/selection knob is a bit squirrly, and the FFT, like most scope, is not as easy/fast to use as the SA of the Instek MDO, but the MDO is a bit pricer.
Let me know what you decide.
@@KissAnalog Thanks, Eddie. Unfortunately, where I live the Siglent is not on sale.i think that I'll save up for a two channel GW MDO with the generator for the Bode plots. I'm afraid being pennywise and pound foolish...
Funny... I thought that the squirly multifunction knob would have been only on the low end scopes... pity. Actually, my Siglent also does not have a really great display in that the grids are too thick and too bright and the overall image is rough. Maybe I'm just spoiled with my combiscope pm3984b...
Thanks for the advice and the great videos.
Cheers
Mark
Sir can you uploaded pdf for this project ?
Sir use lm4562 based preamp for better result
Thank you for the tip! I appreciate you!!
I'm looking for exactly what you are saying. I am triamping, 20 watts is more than enough for any tweeter and the unit I am going to use has 95 db @ 1 watt. Where can I get a kit such as you have. I used to work at Motorola Semi and On Semi is now bigger than Motorola! I would like to use Audio Note 10000mF for the power supply. I used to have the 25w/ch Pioneer M-22 (ALOT OF HEAT 100% bias).
Thanks for the great feedback! I appreciate you!
What is the amp board, where did you get ir
There's a great price on this now at this link; amzn.to/3xxfvEi
Use that Class A into that box with nice heatsink
It did turn out nice:)
So this amp is pretty bad for speakers, OK for headphones (overpowered for that). Does the THD get so high because there's no feedback, or are there other factors as well?
This project has gone on for a number of videos. I have finished the amp now so I'll put out a video to show the final project;)
It is advisable to see the electrical diagram and if it did not exist, then re-engineer it. I would also like to note that the basis for criticism should be the low cost of the device.. As for myself, I upgrade everything and almost any audio device can be significantly improved despite the greed of the manufacturer.🙂
Hi sir am from India. Aleph M 12w is good?
Great to hear from our friends in India! Yes I think it is;)
Bias voltage please show
Thanks for asking. I’ll do this again but here is a video that shows bias: czcams.com/video/jonOEyUftpM/video.html
How come it only has one potentiometer? Being a Class A, shouldn't it have adjustable midpoint voltage and DC offset adjustment as well... I have something similar from eBay which cost $15Au for two mono boards and it has both adjustments which gives me the freedom to choose my own operational voltage! Although it's not using the T03's but they can be swapped in if that's what I wanted...
The opamp might be just a buffer? I would do a quick check of the AC input voltage and compare it to the opamp output voltage, a little bit of gain never really hurt anyone LoL...
Class A becomes more efficient at louder volume, not because it's using less power, but because it's turning more of the power consumption into music instead of heat LoL...
The amplifier looks good at first glance but I'm not so sure about it now, those transistors are capable of some pretty high switching frequencies but it somehow seems to be irrelevant to making music with these one's, I would probably look for an amplifier that's based on the 2N3055 transistors, I can't remember which class A amplifier I got for $15Au, but it didn't use the TO220's but instead the TO92's although I could be wrong, if you are interested, I can find the exact details!!! It's only rated for 10W but can go higher with bigger transistors and cooling plus capacitors that will suit the voltage that you are planning on using, the PCBs are apox 2 inch square each!
Yeah they are really small! But 10W of old school RMS power really knows how to rock a room.. I ended up getting heatsinks that are designed to be mounted on either side of an enclosure, they had all the TO3 holes drilled out and they came with TO3 sockets just in case you ever need to swap out the transistors for whatever reason... They make life easier... The smaller PCB board allows for better fit for the power supply and even an active speaker protection circuit...
Anyway, see how you go! Great video, I love anything about amplifiers especially if it's got TO3's in it.
Thanks Peter - great feedback! Looking at the resistors around the OpAmp, I think you are right - it is a buffer. I found more issues though... I'll post a new video very soon. One problem I have with this is that it has no info and the masking makes it very difficult to reverse engineer.
@@KissAnalog it's most likely a straight copy of an older design.. if you have a look around at the old classics, you might find the schematic....
It could have a CCS circuit for variable bias settings... And the other pot is for voltage? Or vice versa (automatic VAs type thing).
what is the wattage of the speaker...???
In this test I used a 200 Watt resistor, is that what you are asking?
@@KissAnalog
how many watts of speakers are you using?
Ask yourself. What would I meaning your patron Joey Strong do?
Thanks Joey!!
@@KissAnalog hahahaha I'm bored man. Renovating our kitchen and sprained both ankles at the same time.......
The wife and I are building a little robot so I'm gonna set up a test jig and create a custom c++ header and associated class to go with the android app I made to control it. Then she can feel super smart just using function calls from the robot object haha. She can also set a 555 in astable mode haha
You could run a higher quiescent current at around 3.2A and a large heatsink for the heat dissipation as stated on the design spec sheet for the original JLH 2003. Of course this design is an upgrade for electrostatic speakers, and as for the outputs being NPN/PNP of your amp, as opposed to NPN/NPN of the JLH, is it class A? It would be a shame to miss its true potential. czcams.com/video/D_b-i4VSjYc/video.html
Thanks for the great feedback! I have tried a higher current but it doesn't seem to improve the THD specs, so I am trying to find a balance between how much current vs how hot I can let the chassis run;)
@@KissAnalog Yeah that's what I have been doing. I have more to do, my next project is to work on the 2003 circuits which I have built already and have 1000 va 25v supply x4, I'm building 4 monoblocks. I will make video's and upload them to youtube and send you a link.
Nice video! Thumbs Up, but ... Class-A - I don't know. Class-A doesn't sound any better than Class-D. Seems wasteful of energy and space. It's OK for demonstration, but wholly unnecessary today.
Thank you! I have to agree with you;) I think I’m going with the class D;)
A typical Chinese rated amplifier. No one in the HiFi world uses a 2 ohm load. 8 watts into an average efficency speaker will give you a poor dynamic range. Given the same qaulity of amplifier, more power always sounds more alive and dynamic. Most amplifiers have a sweat spot in sound, normally about 75% of maximum power. So you are always far from the dreadful sound of clipping. With only 8 watts you are never far from clipping, unless you only use it for low level background music.
I guess you can always use it to heat the room. That heatsink, I think was made to screw to a larger sink, looked abit small to me, I could smell the heat here in New Zealand.
Thank you @Michael Beeny I agree with you! I was worried about the dynamic range. I think mistakenly I refer to it as power level, and it is, but secondarily. What is really important, is how high can the signal (voltage) swing (dynamics). So, if the amp cannot swing very high without clipping (even transient), then it will sound badly. One big problem is Amps are rated in power (constant or rms) so even though 20 Watts mights seem OK, the transients could be higher. So, if it is limited by heat that is one thing, but if it is limited by voltage / clipping - that is another...
Yes, I like that this small heatsink is provided to capture all the parts and make it easier to mount to a larger heatsink. Nice idea I think;)
Great to hear from New Zealand!
Yes i noticed that as well Mike. Those to3's must be roasty toasty!!
About the 2ohm rating.... I have never come across a 2ohm speaker. Even 4ohms... I've only used 4ohm speaker in cars. I base everything on 8 ohms.
THD 0.15% seriously any cheap amp can. I make ABclass amps that reach THD ~0.006%
Thanks for your feedback. I think THD gets over rated as a spec - mostly because it is just a simple spec that is understood by many - to a certain degree. It is highly debated if anyone can hear distortion as low as 0.1%, so if you want to 10x that you can say 0.01% is beyond human hearing. Also, most THD is done at 1 Watt, so 1% THD is very difficult to hear. I want to learn what the right about of THD is actually the goal, and at what power levels. Also, by using lots of negative feedback to get low THD - what are the compromises?
@@KissAnalog I think 4 transistor snake oil amplifier will sound better when spent fortune for it. Hunting odd/even harmonics in amplifiers will make one song sound great but ruin the rest with some weird sound artifacts (music is harmonics, I think if boost/add wrong ones) 2nd 3rd harmonic amplitude usually standout on inaudible average 0.1%THD . If source is MP3... then doesnt matter (but bad amplifier could make even worse if there is bad harmonic and boost it even more
People wasting theirs money selecting this kinds higher THD amplifier circuit, no protection, cheap to3 transistor ss body about 5cents per nos
Better TDA2030A/TDA2040
Thanks! Yes the TDA parts are more efficient too, but they are Class A/B. I know there are many choices for integrated devices with more built in protection, but I don't see these for Class A.
Yes you can just about get 8watts into 8 ohms from a TDA2030A on a good day.
I built a TDA2030 amp once, and it was great, but I wouldn't call it hifi...
USE WHATS THE ORIGINAL PUREST CLASS A. BESIDES. CLASS D HALF THE INFO IS MISSING
Class A is the purest, but it is so inefficient. I hope Class D evolves to the point that it is hard to hear the difference.