Some homebrew amps do perform as well if not better than the high end manufacturers products. But in my experience many fall short, often without the builders being aware. No I do not make them aware if the short commings as a rule, I sometimes suggest improvements though
Where do you think that DIY amps most often fail to perform better than they could, or where should we be concentrating more effort?
I'd be greatfull for you experience.
Enjoy the music, take care, regards, WALKER
Where do you think that DIY amps most often fail to perform better than they could, or where should we be concentrating more effort?
I'd be greatfull for you experience.
Enjoy the music, take care, regards, WALKER
dutch diy said:Probably each DIY at some point bends one or two rules related to "safety" when using mains-power, although no serious hazards will occur from that.
Most certainly a number of DIYes over the years went listening
to heavenly music sooner than expected because of that.
However, it probably will not be a problem for the sound quality
in general, rather, some most likely bend the rules deliberately
for the reason of improving the sound.
pinkmouse said:
And what is the point in having the most wonderful sounding system, if you, or someone close to you dies because of it...
Yes, and that was meant to be implicit in the what I said, in
case somebody missed it.
Never compromise safety, especially regarding the mainsvoltage circuitry
(says one who hasn't always lived upto that in earlier projects, but I do intend on improving in that
respect.)
Actually, this is also an important thing to think about if you
build equpment for friends or sell equipment. It's one thing
if you endanger your own life, but most of us would probably
find it even worse if someone else dies because of an amp
we have designed.
Getting back on topic!
I think one of the things we miss out on is being able to compare different iterations of designs against each other.
I remember Jonathan Carr stating that he would have four or five versions of his products, each with slight changes, on the go at once, so he could check components and layouts very easily for any improvements or degradations. This isn't so practical for the DIYer, unless you're building something cheap and easy like a GainClone.
I think one of the things we miss out on is being able to compare different iterations of designs against each other.
I remember Jonathan Carr stating that he would have four or five versions of his products, each with slight changes, on the go at once, so he could check components and layouts very easily for any improvements or degradations. This isn't so practical for the DIYer, unless you're building something cheap and easy like a GainClone.
Noisy earths
I have seen a few cases where the amplifier earth was disconnected from the mains earth to cure hum problems; this is of course a dangerous habit.
I had one system brought to me to fix the mains hum. I couldn’t find any problem with the amp and had to travel to the owner’s house to check the installation. I found the main earth connection on the house had been disconnected! Even worse, the connections on all the company owned houses in the street were in the same condition, (we use an MEN, Multiple-Earth-Neutral system here). The local supply authority inspector, a good friend of mine, chased down the cause. A young and over zealous painter had just finished painting all the houses in the street, it was his job to paint the exteriors, the older painters did the insides as they were all air-conditioned. The young painter had disconnected the earth wire from the metal pipe to do a good job. A few of the residents had noticed a tingle when touching the taps but had though no more of it!
If you have a problem with noisy earths get them checked, don’t remove the symptoms, fix the problem before some gets killed. I have even heard of a local salesman suggesting that people cut off earth pins to “fix” the problem, don’t do it!
Having said that, circuit arrangement within the chassis, earthing and cable routes are common reasons why our DIY amps some times play their own tune. I agree with that!
Take care, enjoy the music, regards WALKER
I have seen a few cases where the amplifier earth was disconnected from the mains earth to cure hum problems; this is of course a dangerous habit.
I had one system brought to me to fix the mains hum. I couldn’t find any problem with the amp and had to travel to the owner’s house to check the installation. I found the main earth connection on the house had been disconnected! Even worse, the connections on all the company owned houses in the street were in the same condition, (we use an MEN, Multiple-Earth-Neutral system here). The local supply authority inspector, a good friend of mine, chased down the cause. A young and over zealous painter had just finished painting all the houses in the street, it was his job to paint the exteriors, the older painters did the insides as they were all air-conditioned. The young painter had disconnected the earth wire from the metal pipe to do a good job. A few of the residents had noticed a tingle when touching the taps but had though no more of it!
If you have a problem with noisy earths get them checked, don’t remove the symptoms, fix the problem before some gets killed. I have even heard of a local salesman suggesting that people cut off earth pins to “fix” the problem, don’t do it!
Having said that, circuit arrangement within the chassis, earthing and cable routes are common reasons why our DIY amps some times play their own tune. I agree with that!
Take care, enjoy the music, regards WALKER
Difficult Sourcing
If the quality of parts is to be considered important (which it no doubt is) and if even the combination of said parts is critical, it seems that short of copying directly an exact design from a manufacturer, down to the part number, there could be degradation. I personally have trouble convincing myself to buy a single 'brand Y' resistor from one place and a special capacitor from another. Many of my projects are behind as I refuse to place a $3 order to anybody, and if Digikey has one part and Mouser has the other, I wait until I have enough parts to order from each prior to placing my order. My gain clone project is on hold for a 4.7uf cap, and is likely to be for a month, especially if I use an esoteric vs. Xicon. And in the end, I am never likely to hear a Gain Card or even another gain clone to compare to.
To sum up, if the results of DIY are sometimes compromised, I'd suspect the order of cause is: ignorance (which part/layout/etc is most critical), financing (spending the right money in the right places) and sourcing. After that, I bet any dedicated hobbyist could eventually beat the quality of the physical assembly.
Thanks for the chance to discuss this subject.
Sandy.
If the quality of parts is to be considered important (which it no doubt is) and if even the combination of said parts is critical, it seems that short of copying directly an exact design from a manufacturer, down to the part number, there could be degradation. I personally have trouble convincing myself to buy a single 'brand Y' resistor from one place and a special capacitor from another. Many of my projects are behind as I refuse to place a $3 order to anybody, and if Digikey has one part and Mouser has the other, I wait until I have enough parts to order from each prior to placing my order. My gain clone project is on hold for a 4.7uf cap, and is likely to be for a month, especially if I use an esoteric vs. Xicon. And in the end, I am never likely to hear a Gain Card or even another gain clone to compare to.
To sum up, if the results of DIY are sometimes compromised, I'd suspect the order of cause is: ignorance (which part/layout/etc is most critical), financing (spending the right money in the right places) and sourcing. After that, I bet any dedicated hobbyist could eventually beat the quality of the physical assembly.
Thanks for the chance to discuss this subject.
Sandy.
Rather than thinking of where you are lacking compared to commercial manufacturers, wouldn't it be more productive to carefully consider your own specific design and manufacturing environment, and come up with audio designs that utilize the resources that you presently have to the fullest extent possible without overwhelming them?
Once you are satisfied that you are extracting the most possible from your present resources, the next step would be to conduct your own assessment of the areas in which your present resources are a limitation, and then devise ways to extend beyond those limitations. For example, if you don't have the ability to come up with unique but capable schematics, either study your butt off (always a good idea), or enlist the aid of a good schematic designer who can cover up for your inadequcies. If you can't design high-performance pcb layouts, again study, study, study. OTOH, book knowledge is no substitute for hands-on experience, nor can it replace clever insight and imagination.
Never forget that the schematic is an abstract and simplified version of the "real" schematic, which is determined by the board layout, componentry choice and overall physical construction. In other words, the schematic, board layout and physical construction should be revised flexibly so that what is on the board and the physical construction is as close to what is in the schematic as possible.
And if you can only make single-layer pcbs, start searching for a professional board house who is willing to make multi-layer boards in small quantities.
Regarding componentry, although a good range of high-quality active devices is important, I don't think that the choice of passive componentry is nearly as important as many audiophiles appear to believe. Using only standard electrolytics, motor-grade film caps, industrial SMD caps and metal-film resistors, as long as the schematic, board layout and physical construction are designed really well (which I admit is partly a personal evaluation), you should be able to make a design which beats the pants off 75% of all commercial designs. Componentry can be a bonus, but it can never be a replacement for good basic design.
Everyone - commercial manufacturer or amateur designer - has to start from somewhere. I know that the designs that we were doing some 16 years ago were very much less ambitious and capable than our present products.
I think that the main points are to have a general idea of what direction _you_ want to go in, understand where you are weak - the areas that hamper your progress in the direction that you wish to go in - and then set about resolving those weaknesses. No need to hurry or make haste - steady, consistent progress over time will do the trick nicely, IME.
hth, jonathan carr
Once you are satisfied that you are extracting the most possible from your present resources, the next step would be to conduct your own assessment of the areas in which your present resources are a limitation, and then devise ways to extend beyond those limitations. For example, if you don't have the ability to come up with unique but capable schematics, either study your butt off (always a good idea), or enlist the aid of a good schematic designer who can cover up for your inadequcies. If you can't design high-performance pcb layouts, again study, study, study. OTOH, book knowledge is no substitute for hands-on experience, nor can it replace clever insight and imagination.
Never forget that the schematic is an abstract and simplified version of the "real" schematic, which is determined by the board layout, componentry choice and overall physical construction. In other words, the schematic, board layout and physical construction should be revised flexibly so that what is on the board and the physical construction is as close to what is in the schematic as possible.
And if you can only make single-layer pcbs, start searching for a professional board house who is willing to make multi-layer boards in small quantities.
Regarding componentry, although a good range of high-quality active devices is important, I don't think that the choice of passive componentry is nearly as important as many audiophiles appear to believe. Using only standard electrolytics, motor-grade film caps, industrial SMD caps and metal-film resistors, as long as the schematic, board layout and physical construction are designed really well (which I admit is partly a personal evaluation), you should be able to make a design which beats the pants off 75% of all commercial designs. Componentry can be a bonus, but it can never be a replacement for good basic design.
Everyone - commercial manufacturer or amateur designer - has to start from somewhere. I know that the designs that we were doing some 16 years ago were very much less ambitious and capable than our present products.
I think that the main points are to have a general idea of what direction _you_ want to go in, understand where you are weak - the areas that hamper your progress in the direction that you wish to go in - and then set about resolving those weaknesses. No need to hurry or make haste - steady, consistent progress over time will do the trick nicely, IME.
hth, jonathan carr
Jonathan,
Excellent suggestions and comments.
You do actually also touch one thing I have intended to ask
about on the forum sooner or later, so why not now? Could
you, or somebody else, point to some good resources
(preferrably on the web) about rules/guidelines for how to
do good PCB layouts? I could come up with a few things that
seem intuitively reasonable to me, but they may be wrong
and are by no means sufficient. I have tried to search the
web but everything I found seemed to be about how to
use various layout software, which is not what I want.
Excellent suggestions and comments.
You do actually also touch one thing I have intended to ask
about on the forum sooner or later, so why not now? Could
you, or somebody else, point to some good resources
(preferrably on the web) about rules/guidelines for how to
do good PCB layouts? I could come up with a few things that
seem intuitively reasonable to me, but they may be wrong
and are by no means sufficient. I have tried to search the
web but everything I found seemed to be about how to
use various layout software, which is not what I want.
Christer:
>Could you, or somebody else, point to some good resources (preferably on the web) about rules/guidelines for how to do good PCB layouts?<
Whatever you do, don't study the board layouts used in the vast majority of audio designs (including most commercial products), because as a general rule, they aren't very good. IMO, IC designers and IC applications engineers have a much better handle on good pcb layout practice.
Most of my library is in printed form (and a great deal of it is in Japanese), but here are some starters on the web.
http://www-s.ti.com/sc/psheets/sloa089/sloa089.pdf
http://www.analog.com/UploadedFiles/Application_Notes/135208865AN-202.pdf
http://www.linear.com/pdf/an47fa.pdf
http://www.old555.com/LPE/DaEtiCsuiPitdcrut.html
Burr-Brown also used to have some _very_ nice papers on system board design, (they looked like PowerPoint slide presentations), but after the merger with TI, I haven't been able to locate any URL. I may have them in some form somewhere, but I won't make any promises.
But any paper that you read is only a starting point. It is up to you to study it, digest the contents, mull over the implications, and come up with your own design approaches. Things that I now automatically consider include, total surface area and the sensitivity of the circuit as an RF antenna, trace inductances and capacitances and their effect on circuit performance and stability, common-impedance errors, noise coupling, ground and power planes, ground currents, node impedances, leakage currents and the desireability of guard rings and isolated stand-offs, and on and on.
hth, jonathan carr
>Could you, or somebody else, point to some good resources (preferably on the web) about rules/guidelines for how to do good PCB layouts?<
Whatever you do, don't study the board layouts used in the vast majority of audio designs (including most commercial products), because as a general rule, they aren't very good. IMO, IC designers and IC applications engineers have a much better handle on good pcb layout practice.
Most of my library is in printed form (and a great deal of it is in Japanese
), but here are some starters on the web.http://www-s.ti.com/sc/psheets/sloa089/sloa089.pdf
http://www.analog.com/UploadedFiles/Application_Notes/135208865AN-202.pdf
http://www.linear.com/pdf/an47fa.pdf
http://www.old555.com/LPE/DaEtiCsuiPitdcrut.html
Burr-Brown also used to have some _very_ nice papers on system board design, (they looked like PowerPoint slide presentations), but after the merger with TI, I haven't been able to locate any URL. I may have them in some form somewhere, but I won't make any promises.
But any paper that you read is only a starting point. It is up to you to study it, digest the contents, mull over the implications, and come up with your own design approaches. Things that I now automatically consider include, total surface area and the sensitivity of the circuit as an RF antenna, trace inductances and capacitances and their effect on circuit performance and stability, common-impedance errors, noise coupling, ground and power planes, ground currents, node impedances, leakage currents and the desireability of guard rings and isolated stand-offs, and on and on.
hth, jonathan carr
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