Types of amplifiers, DIY

[doze84]

I don't know much about this, but I do understand that there are a lot of ways to build an amplifier.

My guess is that the implementation is more important than the type of amplifier.
I've also understood that the powersupply(the large transformator) is important.
I've understood that a lot of copper clamped to the transistors is good.

But other than that.

Are there any gnd rules?

My part-time college said he was going to build an amplifier as a side project in his electronics engineering education.

He said he was to make a push and pull type of construction.. That didn't say much to me..
Are there any constructions that are superior to others, is there anything I could recommend to him.
Are there basic mistake he clearly should avoid?
Are there any clues when picking a transformator?
Are there some brand of components that always are better than another brands in bringing out the music out?
What does it mean to have the circuit in balance?
What types of constructions have Linn used, what is Lejonklou using?
Is OP amp(at least that one i understand) another than push pull, I'm pretty lost, but I wish to give him something, since he's probably gonna put some work into this(I feel sorry for him).

I know he needs some kind of miracle for it to sound as good as a LK2, and I figure asking at Faktiskt.se would be of no use.

Feel free to contribute even though your last name isn't Lejonklou:)

[lejonklou]

Hi doze84!

My guess is that the implementation is more important than the type of amplifier.

Absolutely! Perfecting many details of any reasonably good design can bring massive improvements.

I've also understood that the powersupply(the large transformator) is important.

Yes, the power supply is important. Switch mode is the way to go, in my opinion, but it's also more complicated, so a conventional transformer is good to begin with.

I've understood that a lot of copper clamped to the transistors is good.

Aluminium is OK too. It's easy to start with a ready made heat sink and in aluminium they are not too expensive.

Are there any gnd rules?

Ground rules? As in signal ground and power ground? If yes, a good rule is to keep those two separated when applicable and possible.

He said he was to make a push and pull type of construction.. That didn't say much to me..
Are there any constructions that are superior to others, is there anything I could recommend to him.
Are there basic mistake he clearly should avoid?
Are there any clues when picking a transformator?
Are there some brand of components that always are better than another brands in bringing out the music out?
What does it mean to have the circuit in balance?
What types of constructions have Linn used, what is Lejonklou using?
Is OP amp(at least that one i understand) another than push pull, I'm pretty lost, but I wish to give him something, since he's probably gonna put some work into this(I feel sorry for him).

Don't feel sorry for him, he's on a wonderfully fascinating journey! Can't think of anything more fun.

Push-pull means the amplifier is divided into two parts, one pushing and one pulling. This is a very common design and one that I use in my power amplifiers. In addition, I also have a push-pull power supply design; one is pulling and the other is pushing. This is very rare, as it's not efficient - neither for power nor for cost. But the regulation becomes superior, so it's a choice of quality before quantity.

Then there are many different push-pull amplifier designs. Read about them before deciding!

An OP amp is a specific type of amplifier, which can be considered a basic building block. It can be used, alone or in combination with other OP amps, in an almost endless number of ways. I'm sure your friend knows a bit about this if he is studying electronics.

No, there are no brands of components that are always better than others. I recommend avoiding anything that is labelled Audio (which usually is a way to sell parts at a much higher price) and using really cheap components. Then experiment and don't worry if it blows up (just protect yourself!) Mistakes are highly valuable, try to figure each one out before moving on. That's the best way to learn and make progress.

[doze84]

Thank you for your details answer, you surely bring a lot of enlightenment to us uneducated people in this subject.

By saying I feel sorry for him, I meant that I feel sorry for him approaching this area without a compass or a map, by that I mean "tune dem". I'm sure it's a whole different thing when having a direction.

The "gnd rules" thing was just me trying to pull of a wordplay about if there are any basic rules to go by.
Maybe that was swenglish:)

Okey, yes I remember now that the switch thing is the Linn path, as I understand, at least in the later years?

Are there any clues when picking a transformator, as of what core material or any branding proved to be better or you have a specific, transformator from a specific company to recommend? IS the tourqe of minor or major importance when sticking it to the chassie?
Is AC always better than DC in audio equipment?

I think my first attempt will be to help him understand tune dem. Maybe record different audio equipment and try to point out the difference in the musical flow. F ex a really bad and expeinsive cd-player/streamer vs a really good and cheap one. But until he gets that, it would be nice if he got started off right.

[lejonklou]

By saying I feel sorry for him, I meant that I feel sorry for him approaching this area without a compass or a map, by that I mean "tune dem". I'm sure it's a whole different thing when having a direction.

I see! Well, without a direction, none of your recommendations matter, do they?

Are there any clues when picking a transformator, as of what core material or any branding proved to be better or you have a specific, transformator from a specific company to recommend? IS the tourqe of minor or major importance when sticking it to the chassie?

All this depends on what he wants to build. Imagine your friend wants to build a car and instead of transformers, we're discussing wheels. Are the wheels important? Yes, certainly! Is there any type or brand that is better than the others? Well, that depends on what car he is building. An SUV will need different wheels than a three-wheeled Messerschmidt. Same thing with amplifiers, there are many types and sizes. You don't start with a particular transformer, you get one that suits your needs.

Is AC always better than DC in audio equipment?

I am not sure what you mean by this.

I think my first attempt will be to help him understand tune dem.

Yes! Deciding what is good and what is bad is THE most important thing of all.

[matthias]

IMO, the best amplification would be to have a preamp without any attenuation, which provides a variable voltage gain up to 30 or more volts in combination with a zero gain power amplifier.

KR

Matt

[hcl]

IMO, the best amplification would be to have a preamp without any attenuation, which provides a variable voltage gain up to 30 or more volts in combination with a zero gain power amplifier.

KR

Matt

A pretty cool idea. Out of the box thinking.

[matthias]

IMO, the best amplification would be to have a preamp without any attenuation, which provides a variable voltage gain up to 30 or more volts in combination with a zero gain power amplifier.
KR
Matt

A pretty cool idea. Out of the box thinking.

Thanks, hcl,
I searched the web, but such a pre/power combo does not exist. In an all analogue pathway attenuation of a signal has to be avoided at all cost. The job of the preamp is to do all the voltage gain and the job of the power amp is to deliver the current. After reading Fredriks post.......

An odd thing in HiFi systems is that the power amps amplify the signal by a fixed amount (in Linns models it's always been 27 times). This means that on volume settings less than 80, you are actually reducing the signal strength in the preamp and then increasing it in the power amp. This is probably not the best way to optimise quality in the system, but it's a standard in the industry. My last power amp proto had an amplification of 10 times, but it could be designed differently - and perhaps better - with zero gain.

........I hoped that Fredrik would come up with such a combo. Maybe somewhere in the future........

KR

Matt

[lejonklou]

IMO, the best amplification would be to have a preamp without any attenuation, which provides a variable voltage gain up to 30 or more volts in combination with a zero gain power amplifier.

Yes, this is a good idea! And you don't have to wait for it, Matthias, as I've already done it.

The only problem is that these are not the best versions of Tundra and Sagatun. Because while in theory it makes perfect sense to never attenuate a signal, in practice one finds that many circuits can be made to perform much better with a certain amount of gain in them. Even if the signal then needs to be attenuated, before or after the gain. How can this be better? Because it increases stability.

For instance, the Tundra with zero gain could not compete with the Tundra with 10x gain. Those 10x are not there to make the amp seem common, but because they help the circuits stay rock steady during all conditions. The zero gain version is a nervous and less musical beast.

In the preamp, the story is similar (and by coincidence, the result happens to suit the fact the the poweramp sounds better with some gain): If the goal is optimal musical performance, gain can't be a constant, it needs to be a variable among others. And sometimes an attenuation followed by a gain performs better than a simple stage of zero gain. It depends on circumstances and details.

And there's another very important part: The high voltages required in the power amp (to drive the loudspeaker) are not optimal when controlling input selection and volume. In recent years, a flood of magnificent new low voltage components have been released, usually aimed at the computer market. In comparison, very few new high voltage components are introduced. In practice, this makes a preamp that can deliver 30 volts or more inferior to one that only needs to handle a few volts.

So although the idea of never attenuating an analogue signal is a good one, it's one of those theoretical rules that needs to be broken if the goal is to optimize musicality.

I like theories, but never cling to them. That includes anything I may have stated above! :)

[matthias]

Fredrik,
thank you for these very interesting insights.

KR
Matt

[lejonklou]

Thanks for bringing it up, Matthias!

I had almost forgotten how convinced I was that the high gain preamp and zero gain power amp was the best solution. It feels clean and makes sense. Then practical circuits reveal the limitations.

This is similar to balanced signals. Rejecting possible interference feels good and the signal to noise ratio should increase. Then practical circuits reveal that they're more noisy, not less.

[matthias]

Fredrik,

after the very successful launch of Sagatun Mono do you have plans for a Phono Mono amp, perhaps Phono MC?

Matt

[lejonklou]

after the very successful launch of Sagatun Mono do you have plans for a Phono Mono amp, perhaps Phono MC?

Yes, that would be nice.

With two completely MONO phono stages, the left and right signal and their respective grounds would be completely separated from the two windings in the cartridge all the way to the left and right loudspeaker. They would never meet, anywhere. I'd like to hear what effect that could have! Maybe it's important, maybe it isn't.

At the moment, I am stuck with the input stage of the MC phono stage. I have an idea of how it should work in a beautiful way, but it doesn't.

[matthias]

At the moment, I am stuck with the input stage of the MC phono stage. I have an idea of how it should work in a beautiful way, but it doesn't.

What do you think about the LCR type phono stages, which seem to be well reputed in an all Linn environment:

http://www.pinkfishmedia.net/forum/show ... p?t=142968 ?

Matt

[lejonklou]

What do you think about the LCR type phono stages, which seem to be well reputed in an all Linn environment

I have never tried making a phono stage with the eq based on an LCR circuit. I find that inductors are usually way more problematic than capacitors, but perhaps I haven't tried hard enough. :)

[doze84]

By saying I feel sorry for him, I meant that I feel sorry for him approaching this area without a compass or a map, by that I mean "tune dem". I'm sure it's a whole different thing when having a direction.

I see! Well, without a direction, none of your recommendations matter, do they?

Well, I was kind of hoping to raise the lowest level of possible outcome for him, before he gets the method. But I guess, it's too many details in this process, for any specific advice to make any major difference .

Are there any clues when picking a transformator, as of what core material or any branding proved to be better or you have a specific, transformator from a specific company to recommend? IS the tourqe of minor or major importance when sticking it to the chassie?

All this depends on what he wants to build. Imagine your friend wants to build a car and instead of transformers, we're discussing wheels. Are the wheels important? Yes, certainly! Is there any type or brand that is better than the others? Well, that depends on what car he is building. An SUV will need different wheels than a three-wheeled Messerschmidt. Same thing with amplifiers, there are many types and sizes. You don't start with a particular transformer, you get one that suits your needs.

Is AC always better than DC in audio equipment?

I am not sure what you mean by this.

Thank you, I get that now, transformator comes after other overlaying decisions.

I'm not sure either, I was thinking that some were AC powered amplifiers and some were DC powered amplifiers, inside. That must be true in the power stage. Car amplfiers are DC and living room amplifiers AC. But are there any that work with AC all the way? Opamps seems to want a minus and a plus power DC, T-amps seems to be DC all the way too.

I think my first attempt will be to help him understand tune dem.

Yes! Deciding what is good and what is bad is THE most important thing of all.

[/quote]
True.

I had to spend some more time studying electronics just to be able to talk about this, without coming across as the most ignorant person on the planet. I still might, but it actually made me want to try some more experimenting for my self.

One last question on livingroom power amps.
I've gotten the impression that most of the circuits are for filtering and trying to get rid of noise, what's your take on this? I would guess you would say, as little filtering as possible, because it affects the sound. But I guess some filtering of the power signal and some filtering of the sound-signal is needed, do you apply any EQ:ing on the signal?


For my personal experimenting:

I would like to be able to build a battery driven (pre)amplifying cuircut(1v output) together with a bluetooth receiver, that can power an external amp, bluetoothspeakers(using 3.5 plugg) or headphones.

I've come across a handfull of fully assembled bluetooth receivers that are musically better than the output on the iPhone, so I know it´s possible. For example this Biltema thing in the bargains section. But only a few bluetooth chips seems to have audio out on them (meaning dac is included in the chip).

My take on this would be a little opamp, cuircut

-I would put it on a breadboard, and order some of the different bluetooth-chips that are available(with dac included in the chip).
-Power it with a 18650 battey.
-Make a simple basic opamp schematic
-Try different opamps.
-Try different gains, and filters etc

In what order will things impact the musicality, in other words where should I put most of my effort.

1. Soldering, (after breadboard prototyping)
2. Type of opamp
3. Boardlyout, the way the lanes are drawn.
4. Type of headphone connector
5. Pick of gain
6. Filtering battery-power.
7.etc
8.
9.
etc

Maybe my questions are really novice, but I´m hoping to get started somewhere and not to walk into too many unnecessary pitfalls.

I'm very thankful for every single advice on this matter.

[lejonklou]

I'm not sure either, I was thinking that some were AC powered amplifiers and some were DC powered amplifiers, inside. That must be true in the power stage. Car amplfiers are DC and living room amplifiers AC. But are there any that work with AC all the way? Opamps seems to want a minus and a plus power DC, T-amps seems to be DC all the way too.

Almost all amplifiers run on DC. In the car they run off the DC of the battery. In the "living room amp", the power supply converts mains AC to a suitable DC voltage.

I've gotten the impression that most of the circuits are for filtering and trying to get rid of noise, what's your take on this? I would guess you would say, as little filtering as possible, because it affects the sound. But I guess some filtering of the power signal and some filtering of the sound-signal is needed, do you apply any EQ:ing on the signal?

Sure, filtering and suppressing noise can take up a major part of an amplifier circuit. There is often a simple way of building a circuit, and then you can improve it by adding extra parts. In the end you might end up with a circuit that has ten times as many components as you started with. But the extra parts can also introduce new problems, so it's a good idea to keep things reasonably simple.

No, I don't apply any EQ on the signal. As flat as possible and a good rule of thumb is to keep it flat a decade outside the audible frequency range. We can hear roughly 20-20,000 Hz, so try keeping it flat between 2 and 200,000 Hz.

-I would put it on a breadboard, and order some of the different bluetooth-chips that are available(with dac included in the chip).
-Power it with a 18650 battey.
-Make a simple basic opamp schematic
-Try different opamps.
-Try different gains, and filters etc

Sounds like a cool project!

In what order will things impact the musicality, in other words where should I put most of my effort.

1. Soldering, (after breadboard prototyping)
2. Type of opamp
3. Boardlyout, the way the lanes are drawn.
4. Type of headphone connector
5. Pick of gain
6. Filtering battery-power.

7. Trying different circuit designs might be the most important of all.

3 is really important and often underrated.

2 is important, but often overrated. If you stick with one type of OP amp and try everything with it, you'll eventually learn how to make it sound good. If you then change to another OP amp, you'll need to start over again, getting to know how it "likes" to be treated.

[rowlandhills]

When you refer to "different circuit designs" do you mean different physical layouts of the same logical circuit?

[lejonklou]

When you refer to "different circuit designs" do you mean different physical layouts of the same logical circuit?

No, that was point 3, wasn't it?

I meant different logical circuits.