I know it's not strictly DIY but thought this and audio science sites the best place to get an answer. I have a vintage Rotel integrated amp from 1991. Probably cost about £100, maybe a touch more. If I were to buy or build a modern day class A/B amp of similar value, taking inflation into account, would it sound any better? What's improved in class A/B design over 30 years, if anything? Or have companies just found ways to get a decent sound with cheaper parts and we have to build our own or pay ridiculous amounts of money to get a quality amp?
Building an audio amplifier is more of a balancing act between trade-offs. On the other hand, there is our subjective perception of music received from the audio path. And whatever amplifiers are used commercial or do-it-yourself all the same, after a while there will be a desire to change the sound path. It is rather a human property to receive new impressions, and the technical development of the audio industry here only partially helps to achieve this.
I doubt if you will find any class AB amps for sale. Everything in my market offered is class D or T. As I'm sensitive about RF howling into mag phono cartridges or tape heads: I won't buy one of those.
In amps you can build, there are many designs on here that probably test better than a Rotel. Honey Badger from diyaudio supply is right up there in low HD. Whether you can hear the difference, on speakers that produce 3 to 10% harmonic distortion, I have my doubts. I'm focusing my efforts now that I have a .03% HD class AB amp, to room testing to eliminate standing waves & perhaps multiple driver speaker construction. Nobody selling speakers is specifying or guaranteeing HD anymore, that I can tell. Plus no commercial speaker in my market goes +-3b below 40 hz. I listen to organ and piano sources that go to 26 hz.
In amps you can build, there are many designs on here that probably test better than a Rotel. Honey Badger from diyaudio supply is right up there in low HD. Whether you can hear the difference, on speakers that produce 3 to 10% harmonic distortion, I have my doubts. I'm focusing my efforts now that I have a .03% HD class AB amp, to room testing to eliminate standing waves & perhaps multiple driver speaker construction. Nobody selling speakers is specifying or guaranteeing HD anymore, that I can tell. Plus no commercial speaker in my market goes +-3b below 40 hz. I listen to organ and piano sources that go to 26 hz.
There is a company called outlaw audio that sells a 7x130W AB amp for 1K. AB's still exist, you just have to look harder. Not exactly sure when it happened but switchers (D) are now the mainstream product. I'm sure other AB makers exist, have not looked in quite awhile, have a few old amps I've nowhere to put as it is.
The actual cost of the electronics is rather low.
Most the cost is the case it goes in and a power supply.
Your question is somewhat generalized
because there is very simply amplifiers or more complicated amplifiers
that can yield very low, to somewhat average or poor distortion measurements.
So it is whatever your willing to build.
A used amplifier from the 90s is a hard comparison.
Because to replicate it with equivalent new parts.
It would cost more.
To build something " new " in a used price range
doesn't really work with almost anything.
new is more expensive.
As far as the actual amplifier board and basic components.
yes you could build a much better amplifier.
again all that changes, when you add the power supply, case, preamp
protection circuits etc etc.
and also you have the option to use more expensive rugged components
compared to a mass produced amplifier
Most the cost is the case it goes in and a power supply.
Your question is somewhat generalized
because there is very simply amplifiers or more complicated amplifiers
that can yield very low, to somewhat average or poor distortion measurements.
So it is whatever your willing to build.
A used amplifier from the 90s is a hard comparison.
Because to replicate it with equivalent new parts.
It would cost more.
To build something " new " in a used price range
doesn't really work with almost anything.
new is more expensive.
As far as the actual amplifier board and basic components.
yes you could build a much better amplifier.
again all that changes, when you add the power supply, case, preamp
protection circuits etc etc.
and also you have the option to use more expensive rugged components
compared to a mass produced amplifier
All the above and more.
Personally, a class A/B amp whether it's tube or transistor, can only be made so many ways, before it becomes rediculous.
If made with quality parts AND a quality design (time-tested), it should last a lifetime.
The 1970's/80's IMO were the golden era where they perfected design.
The proof is that those amps are still in use today, and in such demand.
Personally, a class A/B amp whether it's tube or transistor, can only be made so many ways, before it becomes rediculous.
If made with quality parts AND a quality design (time-tested), it should last a lifetime.
The 1970's/80's IMO were the golden era where they perfected design.
The proof is that those amps are still in use today, and in such demand.
Not sure much has in terms of circuit design. With technologies things like surface mount has made strides with for instance IMS pcbs available allowing novel thermal designs for power electronics.
And perhaps these days SMPS would be prefered allowing considerable weight savings.
RFI rejection has become more important with so many wireless devices around the home.
I have tried to design many topology class AB amplifiers. Not all of those I built by my self. Some built by local audio community here. They think all my amplifiers sound different although some of them used cheap speakers.
It is not only about how low THD of the amplifier, but about harmonic profile of the distortion, intermodulation distortion, phase intermodulation distortion, thermal distortion, slew limiting distortion, signal to noise ratio, etc. If you think all class AB amplifier sound the same may be: 1. your listening skill is not good enough, 2. You have very bad acoustic room. 3. You have very bad recording (signal source). 4. You have very bad speakers.
It is not only about how low THD of the amplifier, but about harmonic profile of the distortion, intermodulation distortion, phase intermodulation distortion, thermal distortion, slew limiting distortion, signal to noise ratio, etc. If you think all class AB amplifier sound the same may be: 1. your listening skill is not good enough, 2. You have very bad acoustic room. 3. You have very bad recording (signal source). 4. You have very bad speakers.
I agree with bimo for the most part, you will not see any of the improvements in the commercial market but there has been huge strides in AB design in DIY. I do not care for most older AB amps, I am eager to hear how the replacement to Honey Badger will sound. Since I live in a warm climate I find A amps a challenge in the summer. I am also going to try a newer Class D amp as well.
Bill
Bill
Thanks for your reply - I'm not looking to replicate my Rotel, I just wonder if I can do better with modern tech. If technology has moved on, and most importantly, it sounds better, then I'm open to any modern class a/b design. I have a 3e Audio class D and don't particularly like the sound and it also interferes with my FM and my DAB radios. I'm not sure if the switching power supply has somethingto do with it. I like tubes but even my 6 watt SET amp is too hot in the British summer, so class A is out whether it's tubes or ss. As far as taste is concerned, I prefer warmth to lean.
So I'd like to build a 100w in 8 ohms power amp with a linear power supply and decent parts but nothing too expensive, say under £500 / $600. The main problem is that I need a kit with a good instruction manual, I've only built one amp- a Bottlehead S.E.x headphone amp, which was easy as the instructions took me through every stage. I don't need DAC or bluetooth, or a remote, so hopefully my money will go to the important parts and I'll get a better sound than buying a £500 shop amp. That's my logic anyway. Am open to all suggestions. Cheers
The Honey Badger is probably what you're looking for. But, just the case and heatsinks will eat half your budget. Maybe find a used non-working amp for really cheap (or free) and use its case/heatsinks.
I find that these days, most class AB amps are biased so cold they are basically class B. The devices might dissipate a watt at idle whereas in my tube designs, that number is between 15W and 40W...
FWIW, if I was going to design and build a solid state AB amp, I'd use depletion MOSFETs from IXYS. I build an SE amp using them and it sounds really nice.
FWIW, if I was going to design and build a solid state AB amp, I'd use depletion MOSFETs from IXYS. I build an SE amp using them and it sounds really nice.
Silicon is much cheaper than it was 40 years ago. So, you will see current mirrors and cascode LTP and VAS, and lots of silicon used in the OPS. Small transistors now cost pennies, so designers are free to use as many as they like. You will also see symmetric IPS although there are problems with that idea. You see amplifiers with way more stages and transistors than actually improve performance. So called CFAs are very popular even though that is actually a back-step in circuit topology, but perhaps not as a symmetric IPS with a servo. OPS are usually cross coupled, which is only viable on complimentary OPS, because PNP power transistors are now common and cheap. Older power transistors had serious SOA problems and not only are new devices better, but new versions of old favorites are also better. I think some of these "new" topologies were the secrets of HK's impressive square waves, including a folded cascode VAS. Crown and Phase Linear etc tried to use op-amps as IPS but that leads to feedback stability problem so those are rare today. MOSFETs were new then and today linear MOSFET amps usually use "lateral" MOSFETs because they have good thermal performance and low vto. However, the market for MOSFETs is mostly in switching applications so lateral MOSFETs are not so easy to buy. Class-AB falls between audiophile class-A amps and consumer class-D amps but I think they will be around for a while yet.