Which amp to build?!?

jul059

Member
2010-03-07 9:59 pm
Hello everyone!

First of all I want to say that this forum is marvellous! So much information and great designs... and because of this, I could use your help.

I want to build a power amp to use as my main stereo system. The question is which one. There are so many! Sometimes I can't even figure out how many versions of one single amp there is. For example, the DX family (the Original DX, the HRII, the Precision I, the Blame ST, etc.) Then there is also the Elliott Sound P3A, the Leach amp, etc. You probably know more amps than I do...

I would greatly appreciate your input concerning the sound quality of these amps, their strengths, their weaknesses. If you heard more than one, please compare! I am obviously also interested in numbers, so a frequency response graph, THD, TIM, and such are interesting. Also concerning the DX family, which do you recommend and why? Also please recommend any amp I have not listed.

So, which is best?
 

Jay

Banned
2003-02-11 9:02 am
Jakarta
Hello everyone!

First of all I want to say that this forum is marvellous! So much information and great designs... and because of this, I could use your help.

I want to build a power amp to use as my main stereo system. The question is which one. There are so many! Sometimes I can't even figure out how many versions of one single amp there is. For example, the DX family (the Original DX, the HRII, the Precision I, the Blame ST, etc.) Then there is also the Elliott Sound P3A, the Leach amp, etc. You probably know more amps than I do...

I would greatly appreciate your input concerning the sound quality of these amps, their strengths, their weaknesses. If you heard more than one, please compare! I am obviously also interested in numbers, so a frequency response graph, THD, TIM, and such are interesting. Also concerning the DX family, which do you recommend and why? Also please recommend any amp I have not listed.

So, which is best?

There have been many of similar questions, but as far as I know, there has been no satisfying answer because of the complexity of the answer, and because the question is too general.

You seem to know enough about amplifiers, but similar questions usually come from beginners, probably because they don't realize the complexity of the answer.

But IF what they (the questioners) really need is assistance in choosing the correct amplifier so not to waste money and time, I believe that special consultancy is required. Questioners should explain their preference of music, previous amplifiers, their previous best amps (you don't want to suggest a Citation12 to those who have built Quasi amp, do you?), their speaker, expected power level, what parts already on hand, etc etc...

I believe this kind of consultancy thread is an effective way for (mostly) beginners to choose a suitable amplifier.
 

jul059

Member
2010-03-07 9:59 pm
Thanks four your reply!

I am indeed a beginner concerning DIY Power Amplifiers, but I do know things about frequency response, impedence, Total Harmonic Distortion, Transient Intermodulation Distortion, etc. (Egineering student).

You are also right that I want assistance in choosing an amplifier so as not to waste money and especially time. I love amplifiers, but it is not (yet...) my main hobby.

So here are some infos :

I want to listen to a wide range of music (electronic, rock, pop, jazz, some classic).

I corrently use a pair of Camber speakers, ancestors of paradigm. They are 2 way vented speakers and are fairly efficient. Please note that I may have to return them to their owner, so I might have to change them.

Expected power level : Not huge. I would say 50w RMS is good.

I have owned a Cambridge Audio Azur 340A.

Also note that I am NOT interested in a class A Power Amplifier for heat reasons.

Cheers,
Julien
 

Jay

Banned
2003-02-11 9:02 am
Jakarta
Thanks four your reply!

I am indeed a beginner concerning DIY Power Amplifiers, but I do know things about frequency response, impedence, Total Harmonic Distortion, Transient Intermodulation Distortion, etc. (Egineering student).

You are also right that I want assistance in choosing an amplifier so as not to waste money and especially time. I love amplifiers, but it is not (yet...) my main hobby.

So here are some infos :

I want to listen to a wide range of music (electronic, rock, pop, jazz, some classic).

I corrently use a pair of Camber speakers, ancestors of paradigm. They are 2 way vented speakers and are fairly efficient. Please note that I may have to return them to their owner, so I might have to change them.

Expected power level : Not huge. I would say 50w RMS is good.

I have owned a Cambridge Audio Azur 340A.

Also note that I am NOT interested in a class A Power Amplifier for heat reasons.

Cheers,
Julien

First, there are tube amps, bipolar amps, mosfet amps....

The theorists will say that it doesn't matter what device you use, it is how you use it. But you can not make good sound from light bulb as amplifying devices!

Tube amps are slow and musical. Bipolar amps are fast, and that is also a minor part of musicality. Mosfet amp stands in the middle, doesn't have specific strength. Most of the time mosfet amps are lousy amps. Only a few people that seem to be attached to the sound of mosfet, including myself. VMOSFET doesn't work well in class-B amplifier. The best I have heard is in the stochino, but it is too complicated (slew rate about 300V/us). For class-B it must be LMOSFET, but the price may be high, only for mosfet lovers :D

So if you prefer the sound of a mosfet, many JLH amps are musical sounding. Search for Mooly amplifier, it is also based on JLH work, only one pair of LMOSFET per channel to give 60W. If you need fast class-B mosfet amplifier, there is new thread about Goldmund amplifier. I'm in the process of building it. But it uses 3 pairs per channel, and the remaining transistors might be difficult to find.

Bipolar amps are not my preference. I rarely like them. But Sanken 2922 output transistors seem to have bass similar to mosfet, and I prefer the sound that doesn't "hurt" my ears, hence any low PIM/TIM designs such as the Leach amplifier. Or scaled-up version of Otala amp (20W?) if any.
 
As you seem to feel that you need 50 watts or so, why don't you build a chipamp?
They can be dirt simple, easy to build, pretty economical and don't give much away in overall sound quality. A LM 3875 or a 3886 chip will get you in the neighborhood of your power requirements. With the money you'll save, you can begin to upgrade other parts of your system.

Best Regards,
TerryO
 

Jay

Banned
2003-02-11 9:02 am
Jakarta
As you seem to feel that you need 50 watts or so, why don't you build a chipamp?
They can be dirt simple, easy to build, pretty economical and don't give much away in overall sound quality. A LM 3875 or a 3886 chip will get you in the neighborhood of your power requirements. With the money you'll save, you can begin to upgrade other parts of your system.

Best Regards,
TerryO

Possible option. But you have to search for your "future" amp first so you can invest in a proper transformer (the output voltage).

May be because transformer is the most expensive part, and that you may build another amp in the future, you should pick amplifier that uses the most "common" rail voltage. And your quality supply caps should not be underrated in the future project :D
 

jul059

Member
2010-03-07 9:59 pm
Ok thanks everyone.

I never gave the chipamp much thought. Perhaps it's a good option. But which implementation is recommended? I guess the one specified by the manufacturer is good. I found this : PA100 DIY 2x LM3886 in parallel gainclone audio amplifier. What do you think?

gaetan8888,
Concerning the Dx, can you explain me the differences in the different versions? I guess the "plain" Dx is the one most commonly built, but I'm not sure.

also, I think I read that the Baby AKSA is a "tweaker's dream". considering that I do not have access to all the equipment I might need, is it a good idea for me to start building it?
 
First, there are tube amps, bipolar amps, mosfet amps....

The theorists will say that it doesn't matter what device you use, it is how you use it. But you can not make good sound from light bulb as amplifying devices!

True, but a good triode amplifier stage is hard to beat with sand. But components made from sand are cheaper, use a safe voltage level, more efficient, and not nearly as fragile. I agree with the 'theorists', but it is important to note that all those different devices work in different ways with different properties and have to be used differently.

Vertical mosfet class AB can be made to sound very neutral with very little distortion but it is not so straight forward. It requires local correction loops and is more complex than typical LIN BJT circuits, at least if you want to do it right. Most people are scared of the complexity, but for a beginner, simplicity is better.:) So stick with devices that are more suited to a simpler design.
 
I never gave the chipamp much thought. Perhaps it's a good option. But which implementation is recommended? I guess the one specified by the manufacturer is good. I found this : PA100 DIY 2x LM3886 in parallel gainclone audio amplifier. What do you think?

The National Semiconductor "Overture Series" are excellent designs by top engineers. It would be hard to miss by building one of these. There are also numerous internet designs and PC boards for even more designs. You can build a low power version with an LM1875 chip and Radio Shack parts for around $50 or so, utilizing the time-honored "Dead Bug style" and have a very decent 18-22 watt amp. It doesn't take much time, effort or money and can sound very nice indeed.

It really depends on what you want to do, how much experience and money you have and what your final goal actually is.

Best Regards,
TerryO
 
Ok thanks everyone.

I never gave the chipamp much thought. Perhaps it's a good option. But which implementation is recommended? I guess the one specified by the manufacturer is good. I found this : PA100 DIY 2x LM3886 in parallel gainclone audio amplifier. What do you think?

gaetan8888,
Concerning the Dx, can you explain me the differences in the different versions? I guess the "plain" Dx is the one most commonly built, but I'm not sure.

also, I think I read that the Baby AKSA is a "tweaker's dream". considering that I do not have access to all the equipment I might need, is it a good idea for me to start building it?


Hello

The Dx plain version are the first one made by Destroyer X, it's the easyer to made, there is better version, like the Dx precision, Dx HR2, Dx Blame ES, etc but they need more work to made them. For a first amp the Dx plain version are recommended.

You can build the Baby AKSA without tweaking.

If you want a very well document amp, build the Dx plain version. Greg made a very well documented web page about all Dx amps, schematics, pcb, hints, etc, to made the amp, here is the link;

Greg's Web Site

Bye

Gaetan
 

Jay

Banned
2003-02-11 9:02 am
Jakarta
True, but a good triode amplifier stage is hard to beat with sand. But components made from sand are cheaper, use a safe voltage level, more efficient, and not nearly as fragile. I agree with the 'theorists', but it is important to note that all those different devices work in different ways with different properties and have to be used differently.

Vertical mosfet class AB can be made to sound very neutral with very little distortion but it is not so straight forward. It requires local correction loops and is more complex than typical LIN BJT circuits, at least if you want to do it right. Most people are scared of the complexity, but for a beginner, simplicity is better.:) So stick with devices that are more suited to a simpler design.

I agree with both theorists/objectivists and subjectivists :cool:

It is very expensive to use tube device properly, I mean to achieve an acceptable subjective performance in areas where tubes are lacking. Just to mention a few:

(1) Power and speaker damping. What speakers are the options, especially to go DIY? I have used Lowther DX2. Cheaper full range drivers especially, can easily hurts my ears.

(2) Speed. This is where I gave up. Even big/expensive tube amps not "fast" enough for certain music.

Vertical mosfet class AB can be made to sound very neutral with very little distortion but it is not so straight forward. It requires local correction loops and is more complex than typical LIN BJT circuits, at least if you want to do it right. Most people are scared of the complexity, but for a beginner, simplicity is better.:) So stick with devices that are more suited to a simpler design.

Which design you have in mind? I might build it because I know you.

I build my 300V/us stochino amp point-to-point! I'm not scared of complexity, unless when I realize that it may affect the outcome. From poor implementation due to the absence of an oscilloscope, to unknown distortion induced by complex schematic.

And subjective sound quality measure such as "NEUTRAL" is never exist in my book. My ears know only "MUSICAL" and "NON-FATIGUING". These subjective measures are still difficult to explain. Some think "MUSICALITY" is about distortion spectrum. Judging from my experience with loudspeaker, I think FATIGUE has high correlation with phase problem, something that is often overlooked in amplifier design, because they prioritize other measures (such as THD???)
 

Jay

Banned
2003-02-11 9:02 am
Jakarta
I never gave the chipamp much thought. Perhaps it's a good option. But which implementation is recommended? I guess the one specified by the manufacturer is good.

Then forget the chipamp! It looks simple, but actually there are many of them, with different quality, and it is difficult to guess which one is suitable for anyone. But whichever you choose, it always has limitation in the high frequency, something that will matter for those who has experience with better high frequency sounds.

National gave an application example in their pdf. For 3886 and 3876 there is single supply implementation which is not popular (probably because of the cap in the output). May be a little unstable but they sound good.

The good think about the chip amp is, when your main amplifier is under tweaking, or you are designing a new speaker, you can use the chip amp which has been equipped with security measures. Nice backup.
 

klinko16

Member
2010-08-04 4:20 am
~~~~~~~~~~~~~~~~~~~~~~snip~~~~~~~~~~~~
You can build a low power version with an LM1875 chip and Radio Shack parts for around $50 or so, utilizing the time-honored "Dead Bug style" and have a very decent 18-22 watt amp. It doesn't take much time, effort or money and can sound very nice indeed.
~~~~~~~~~~~~~~~~~snip~~~~~~~~~~~~~~~~~~~
Best Regards,
TerryO

As a follow uo on the above there's a current and pretty nice thread about building a LM1875 amp over on AudioKarma:

LM1875 integrated Chip Amp with external PSU - AudioKarma.org Home Audio Stereo Discussion Forums

Best Regards,
TerryO
 
Tube amps are slow and musical. Bipolar amps are fast, and that is also a minor part of musicality. Mosfet amp stands in the middle, doesn't have specific strength. Most of the time mosfet amps are lousy amps.

what does 'slow' mean ? the only tube amp I've built sounds superior to all the solid state amps I've heard or built. However, tube amps do produce heat and heat was discounted as something to avoid.

what does 'fast' mean ? There are many different topologies of bipolar amps spanning a huge range of performance and sound. Many of the best commercial amps are using bipolar devices and there are many great DIY amps available

you say mosfet amps sound lousy most of the time ? this is a huge over-generalization perhaps !?




I want to build a power amp to use as my main stereo system. The question is which one.


My 2c of advice: you'll probably have so much fun that this won't be the last DIY amp you build so don't worry too much about choosing which one to build - I doubt you'll be disappointed

1) Get a decent chasis for your amplifier. Nothing worse than putting in many hours of work to feel it looks too amateurish at the end of the day. You will feel very much happier if the chasis is of good quality and has enough space for you to lay out the parts neatly and wire it up neatly. I wouldn't underestimate the pride and satisfaction of a neatly done job. You may want to practice your metal working skills before hacking holes and the like in a new chasis if you've not done much like this before. Another option is to get an old amplifier of ebay/junk store and re-use the chasis. You might even be able to re-use the knobs and power supply transformer etc.

2) Lavish as much care about the power supply design as the amplifier itself. The current flowing through your speakers also flows through the power supply and the quality of the power supply will affect the quality of the sound. A nicely done power supply in a good chasis is a great starting point - you can always replace / upgrade the amplifier module at a later time.

3) Trust your ears more than opinions and reviews. Ultimately, it's best if you have the time, money and interest to build more than one amplifier as you'll learn a great deal and discover what you like and what you don't like.

4) Speakers make a huge difference to the sound. A speaker I built which I don't like the sound of on my commercial solid state amp sounds gorgeous on my tube amp. There are many reasons why speakers add their own personality not least because they can interact with the amplifier itself. If you have settled on a particular set of speakers then you can at least test your DIY amplifiers with a consistent speaker type as you make adjustments etc.

Some of my own impressions:

DX/AKSA - I've built something similar - excellent overall sound and no reason this type of amplifier should not be able to fully satisfy your needs. The DX HII(?) - the one with CFP LTP - has a clearer sound and better bass but not as nice in my view (a bit harsh). If you like to follow the DX type of design I suggest doing some reading on the forum to read about the different versions for yourself as some of the more recent versions may be better options and Carlos and others building these amplifiers will be around to help you. If you don't want to make your own PCB then ask on the relevant threads to see if somebody can help you out.
 
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what does 'slow' mean ? the only tube amp I've built sounds superior to all the solid state amps I've heard or built. However, tube amps do produce heat and heat was discounted as something to avoid.

what does 'fast' mean ? There are many different topologies of bipolar amps spanning a huge range of performance and sound. Many of the best commercial amps are using bipolar devices and there are many great DIY amps available

you say mosfet amps sound lousy most of the time ? this is a huge over-generalization perhaps !?

Hello

Tube amp do not have the spray of thd spectrum, especialy hf thd, that we find in some types of transistors amps.

Did you made a 300B tube amp ?

But some topology of transistors amps can sound very musical. And matching ltp transistors, using a fast and low cob VAS trany, using a phase lead cap and keeping a low nfb factor will help a lot.

Mosfet amps need a minimum of bias to sound better, we can see it at the image of a graphic from Nelson Pass. If you use mosfet with a higher bias you will have a better sound, that's why the Nelson Pass's First Watt and Pass Lab mosfet amps sound so good.

Bye

Gaetan
 

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Jay

Banned
2003-02-11 9:02 am
Jakarta
what does 'slow' mean ? the only tube amp I've built sounds superior to all the solid state amps I've heard or built.

I understand the sound I hear better than I understand electronics theory. To describe a "slow" sound is not that easy unless you can hear what I hear, or we both have the same experience hearing the "slow" thing.

But technically I think it relates to trans-conductance and/or slew rate. If you cannot perceive it, it's normal, many can't. One of the reason is because it can only be heard in a "limited" circumstances (it's music and system dependent).

When I used tube amp, I changed my speakers to full range drivers, and I changed my music to vocals. Tube amps will have no problem playing Eva Cassidy, Don Williams, Sarah McLachlan, Leonard Cohen, Jachinta, etc. But when it has to play low frequency with quick transient, I perceived a "slow" sound. May be because the tube cannot slew a high current quickly, to complete a bass note attack (Even the power supply cannot have enough capacitance).

you say mosfet amps sound lousy most of the time ? this is a huge over-generalization perhaps !?

What will you expect from class-B mosfet amps, especially in the past? Even now many designers when they try to design their best class-B amp, they turn to bipolar. Just ask what is their best design, it will be bipolar. Pavel Dudek may prefer his vertical mosfet design, but if you like your tube amp that much, you will not like his amp for sure.

Now let's look at Nelson Pass class-A designs. He can achieve such a high quality sound with simplicity. But it has a limit. Many cannot hear the difference in mosfet capacitance. But for me, the capacitance is clearly the limitation of a mosfet amp. Very easy to hear, even in the output stage running in class-A.

What if the mosfet is in input or driver stage? Even worse!! BOZ, Aleph, D1, etc. JLH used VN1210M, Alex Nikitin cleverly choose ZVP3310A in follower configuration, but many new designers use IRF610 and higher capacitance devices! Some even use IRLD123 in the input stage. If you can't hear the problem, I can. Some others can hear the problem but don't know where it comes from.

Good or bad is relative. In intermediate level, bipolar amps are often better than mosfet amps. In ultra high end level, mosfet amps still has to work very hard with its capacitance problem (thus non-linearity, distortion etc).

this won't be the last DIY amp you build so don't worry too much about choosing which one to build - I doubt you'll be disappointed

I think that the more you are after a high end system, the more disappointment you will have, up until you reach a certain level, where you have wasted so much time and money to understand the problem :cheers:
 
Hi, I've been thinking about building a multi channel amp from kit form purchased from ebay. supposedly they claim it is a current feedback amp, and if true, that seems to me to be an obvious choice. The current feedback topology has square wave response out to 1Mhz, and was invented by Mark Alexander of Analog Devices.
2 X DELUXE HI-FI CURRENT FEEDBACK POWER AMPLIFIER KIT! on eBay (end time 20-Oct-10 21:55:35 BST)

This kit you bought on eBay how does it sound? Can you share your listening experince?

Thank you.

Regards,
Paulo.