Just about to build this amplifier for my (future) bi-amped system... I searched and found this thread... wow... It took me about 3 hours reading it entirely, very interesting and I learnt a lot! 
I really thank to all of you guys who posted a lot of useful tips and information about this amp (also useful for others amps)
I really thank to all of you guys who posted a lot of useful tips and information about this amp (also useful for others amps)
Sure,
Most of the notes I took (and what is being talked about here) were about the design of the PCB.
(Note: there is a lot of “copy & paste” quoting other members of diyaudio.com in this post; I cannot quote each user because I copied what I considered important to a notepad, and the member name was not copied…sorry for that, but I will have to re-read all the posts again to add the name, and the thread is too long!)
And a final comment, there should be some things that will not be mentioned here because I did not considered them important (or missed them..)
So here it is:
If the target is very high quality the PCB for this amp needs to be proper and under some rules; (otherwise it will work too…but will not achieve high quality)
-drivers have to be close to the outputs
-output trace together with collector resistors needs to be tight and organized and as small is possible while away from small signal input transistors
-except 100nf decoupling it could be nice to have together 100mfd /63 volt or more but closer to the outputs while the connection to ground is also as short as possible
- feedback resistor is to be connected to the output R5 22k if possible just next to the output lead
- input transistors may be located "face to face " with each other and that will give you the chance to glue them together and make them behave better since they share the same temperature
-miller capacitors C6-C4 need to be of some quality and voltage above 160volts and either mika or styroflex while as close is possible to the transistor connected
-current source for transistors 1-2 is the transistor Q3 that also needs to be as close to the input transistors 1-2
-the Vbe issue TR9 might become critical if you have plans to push the amp around and high temperatures are expected .... in this case you might want to relocate it close to the drivers either glue it to one of them so it senses temperature from; ideally one heatsink ( small piece of aluminum) that will include drivers Q5-6 and Q9 will be the best hing to do ...Q9 might sense temp from both of the drivers .
In a case the amplifier is for casual listening and not expected to be pushed around none of these is needed but yes the bias will drift depending on the level of sound and the room temperature still you might get away with it
-remember to use a big heatsink just to be on the safe side ....
-A sensitive node (to both pick-up and stray capacitance) is the feedback to the input pair (the common trace(s) connecting R4, R5 and Q2's base). Try to minimize the copper used for these connections.
-Traces - use 1.27mm traces all around apart from the power and ground traces - make those as wide as possible, at least 2.54mm wide. The bypass capacitors should also be close to the output devices.
- C7 and C3 cannot share the same thin track down to ground. C3 is signal and should connect directly on the incoming signal ground point.
- C4 and C6 should have very short tracks to Q4/Q6.
Most of the notes I took (and what is being talked about here) were about the design of the PCB.
(Note: there is a lot of “copy & paste” quoting other members of diyaudio.com in this post; I cannot quote each user because I copied what I considered important to a notepad, and the member name was not copied…sorry for that, but I will have to re-read all the posts again to add the name, and the thread is too long!)
And a final comment, there should be some things that will not be mentioned here because I did not considered them important (or missed them..)
So here it is:
If the target is very high quality the PCB for this amp needs to be proper and under some rules; (otherwise it will work too…but will not achieve high quality)
-drivers have to be close to the outputs
-output trace together with collector resistors needs to be tight and organized and as small is possible while away from small signal input transistors
-except 100nf decoupling it could be nice to have together 100mfd /63 volt or more but closer to the outputs while the connection to ground is also as short as possible
- feedback resistor is to be connected to the output R5 22k if possible just next to the output lead
- input transistors may be located "face to face " with each other and that will give you the chance to glue them together and make them behave better since they share the same temperature
-miller capacitors C6-C4 need to be of some quality and voltage above 160volts and either mika or styroflex while as close is possible to the transistor connected
-current source for transistors 1-2 is the transistor Q3 that also needs to be as close to the input transistors 1-2
-the Vbe issue TR9 might become critical if you have plans to push the amp around and high temperatures are expected .... in this case you might want to relocate it close to the drivers either glue it to one of them so it senses temperature from; ideally one heatsink ( small piece of aluminum) that will include drivers Q5-6 and Q9 will be the best hing to do ...Q9 might sense temp from both of the drivers .
In a case the amplifier is for casual listening and not expected to be pushed around none of these is needed but yes the bias will drift depending on the level of sound and the room temperature still you might get away with it
-remember to use a big heatsink just to be on the safe side ....
-A sensitive node (to both pick-up and stray capacitance) is the feedback to the input pair (the common trace(s) connecting R4, R5 and Q2's base). Try to minimize the copper used for these connections.
-Traces - use 1.27mm traces all around apart from the power and ground traces - make those as wide as possible, at least 2.54mm wide. The bypass capacitors should also be close to the output devices.
- C7 and C3 cannot share the same thin track down to ground. C3 is signal and should connect directly on the incoming signal ground point.
- C4 and C6 should have very short tracks to Q4/Q6.
There are no annotations/numbering on the esp site, to answer your Q.
'...I have been reading about matching transistors and some people says there is no need to match NPN with PNP devices...'
It is a practical requirement not to match NPN with PNP devices as you will never find these can be matched.
Gajanan Phadte
'...I have been reading about matching transistors and some people says there is no need to match NPN with PNP devices...'
It is a practical requirement not to match NPN with PNP devices as you will never find these can be matched.
Gajanan Phadte
No, the feedback resistor R5 should be as close as possible to the base of Q2, but the point at which you take feedback from the output should be at the output (after the connection of output emiter resisitors R13 and R14).
do you want a long trace with a larger signal or a long trace with a smaller signal?
I am not pcb designer, nor anything even similar, but I've been told that all feedback components should be as close as possible to the input. As always, there are different schools for everything, and your kung fu may be different from my kung fu.
No.
you are probably missing the point and i actually find your opinion rather in the arrogance side .
Rod's effort is the most well documented projects if i may say world wide ...far more you may find some other projects that are well documented but nowhere so many together .
then you are missing that 99.9% is totally and absolutely free
So i think that this type of criticism is against DIY spirit and also very bad for a person given his work to the community for free .
There is many others ''well known '' designers that offer astronomical rates for amplifiers when it comes to specs only thing you have to do is to make them work .
All of ESP circuits work and perform according given specs ..no more no less Other than the above i see this type of criticism as a very negative thing .
Sorry but what do you mean? They are numbered in the schematic circuit! (Figure 1)
Take a look:
60-80W Power Amplifier
So what do I need to match? I have been reading about some differents techniques for matching, but I can't find which devices should be matched in an amp circuit. If someone has a link or some information please let me know
Totally agree!
Anyway, michaelkiwanuka, if you don't like his designs, maybe you can give us the reasons why you don't like and what other things should be considered when choosing an amp. Not recommending it because you just don't like it is not contributiong to this forum...
Maybe someday I will build it for fun, some people says it is good the other says it is not...
But I believe Mr Rod is a good person he show us what he want that we need, sure there is secret things & that's all.
It is been a while I don't see Rode post here, maybe he doesn't care too much about it.
Andrew if you have a better way please show us, with schematic of course.
You know that my words understanding is not good
But usually I use DMM only & the result quite good
But I believe Mr Rod is a good person he show us what he want that we need, sure there is secret things & that's all.
It is been a while I don't see Rode post here, maybe he doesn't care too much about it.
Then how to match them?
Andrew if you have a better way please show us, with schematic of course.
You know that my words understanding is not good
But usually I use DMM only
& the result quite good
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