Just ordered from AliExpress 0.05 Ohm 5W source resistors.
It may take 3-4 weeks until arrives. My mosfets are very-very close matched so the resistor value will be good enough. Wires......
I may replace the teflon (silver plated) wires after if I still not satisfied! The same wires I use in my other DIY projects and there is very good.
Until that I use the the amp daily (burn in) and my work on other project.
Found out I have at home some 2200uF 16V organic / polymer caps (it belong to the USSA5 project), I may test those to.
Those who has the amplifier PCB I encourage to build the amp, Is not a bad sounding amplifier if built with care!
Me, I like to bring out the maximum from every DIY project I build......... 😎
Hi kgrlee,
Take your pick of many. Bryston 4B or 3B cubed for one. Even a Sansui AU-517 or AU-717. They run cool but are probably biased higher. Manufacturers bias amplifiers higher to cover worst case in mass production. Many I have serviced easily beat their specs biased far lower than factory bias settings. Less well designed amplifiers need the higher bias currents. No mystery here. Mosfets do tend to require higher bias currents.
The amp I have that only needs 5 mA, a SymAsym 5.3 using On Semi MJW0281 / MJW0302. You can build it a minimal cost to see for yourself. I did match semi's closely, so if you don't do that you probably will not get the same results.
There you go, challenge answered.
Take your pick of many. Bryston 4B or 3B cubed for one. Even a Sansui AU-517 or AU-717. They run cool but are probably biased higher. Manufacturers bias amplifiers higher to cover worst case in mass production. Many I have serviced easily beat their specs biased far lower than factory bias settings. Less well designed amplifiers need the higher bias currents. No mystery here. Mosfets do tend to require higher bias currents.
The amp I have that only needs 5 mA, a SymAsym 5.3 using On Semi MJW0281 / MJW0302. You can build it a minimal cost to see for yourself. I did match semi's closely, so if you don't do that you probably will not get the same results.
There you go, challenge answered.
I built the SymAsym amplifier, I tested with low bias up to 400mA to Class A.
On the end I sold it. Not mu cup of tea.
I built several Hiraga Class A, including the Le Monste. I dismantled the Class A-s and I sold the Le Monstre to Europe.
Built an Aleph 30, Class A bias (I still miss that sound),
I did not kept because I needed the enclosure for an other project (SEWA).
I dismantled the SEWA also. Good sounding but it was about 7-8 Watts per channel only + needed a separate pre-amp to.
I built an Aleph X, 100 Watt 7A / channel bias, I did not like that, not even built (finished) the second channel.
When it comes to amplifier bias or Classes the high bias not everything! The circuit, components, PS everything we use it counts. (That is my humble opinion, I built so many amps).
I built Peter Daniels Gain Clone and used it for a while (a year or so)......
I think some Single Ended Class A tend to have a nice sound. 😎
At the moment this amp running on 100mA bias (just because is a mosfet amp). I don't think it make any difference if I would run it at 500mA. Rather try some tweaks than increase the bias.......
On the end I sold it. Not mu cup of tea.
I built several Hiraga Class A, including the Le Monste. I dismantled the Class A-s and I sold the Le Monstre to Europe.
Built an Aleph 30, Class A bias (I still miss that sound),
I did not kept because I needed the enclosure for an other project (SEWA).
I dismantled the SEWA also. Good sounding but it was about 7-8 Watts per channel only + needed a separate pre-amp to.
I built an Aleph X, 100 Watt 7A / channel bias, I did not like that, not even built (finished) the second channel.
When it comes to amplifier bias or Classes the high bias not everything! The circuit, components, PS everything we use it counts. (That is my humble opinion, I built so many amps).
I built Peter Daniels Gain Clone and used it for a while (a year or so)......
I think some Single Ended Class A tend to have a nice sound. 😎
At the moment this amp running on 100mA bias (just because is a mosfet amp). I don't think it make any difference if I would run it at 500mA. Rather try some tweaks than increase the bias.......
Hi gaborbela,
It comes down to personal preference. The large majority of people prefer low distortion and low noise.
Some amplifier designs have a sonic signature (= distortion) a few prefer, and that's cool. You can achieve the same result with a clean amplifier and effects unit ahead of it. So when you say something has a "nice sound", accuracy and fidelity don't come into play, it is your personal preference. I have customers who like single ended class A, but they usually tire of them after a while. Same for just about everything you can think of. Most who love music will go for low noise and low distortion. If something sounds "dry" or "etched", it is because of other types of distortion.
I carefully matched the parts in my Symasyms. I have better amplifiers, but the quality surprised me and they are better than most commercial products. From your preferences I can see they wouldn't do it for you.
-Chris
It comes down to personal preference. The large majority of people prefer low distortion and low noise.
Some amplifier designs have a sonic signature (= distortion) a few prefer, and that's cool. You can achieve the same result with a clean amplifier and effects unit ahead of it. So when you say something has a "nice sound", accuracy and fidelity don't come into play, it is your personal preference. I have customers who like single ended class A, but they usually tire of them after a while. Same for just about everything you can think of. Most who love music will go for low noise and low distortion. If something sounds "dry" or "etched", it is because of other types of distortion.
I carefully matched the parts in my Symasyms. I have better amplifiers, but the quality surprised me and they are better than most commercial products. From your preferences I can see they wouldn't do it for you.
-Chris
One thing that was shown in the development of the SymAsym was how important PCB payout was. Also a number of other factors that normal simulators don't model. Looking at simulated performance can give you an idea if something works or not. What it can't do is tell you anything much about real world performance of the real thing. Only designed in faults.
If anyone is interested in this design, an extremely complete thread exists if you read the darned thing. This would include impressions for the real, built unit. Maybe even real measurements.
The real circuit often never performs as well as the simulated results. Many times much worse. So much depends on component matching and PCB layout (being the biggest factors). So if you are ever going to attempt to decide which circuit is better based on simulations alone, as long as the circuits in question don't have any faults, you really are on a mission to confusion. Then, if you're going to comment on which sounds better based on simulations, well. You are not speaking from a position of knowledge.
You've got to build the thing and measure it as well as listen. That is the only time you actually know anything.
If anyone is interested in this design, an extremely complete thread exists if you read the darned thing. This would include impressions for the real, built unit. Maybe even real measurements.
The real circuit often never performs as well as the simulated results. Many times much worse. So much depends on component matching and PCB layout (being the biggest factors). So if you are ever going to attempt to decide which circuit is better based on simulations alone, as long as the circuits in question don't have any faults, you really are on a mission to confusion. Then, if you're going to comment on which sounds better based on simulations, well. You are not speaking from a position of knowledge.
You've got to build the thing and measure it as well as listen. That is the only time you actually know anything.
And a lot of that depends on how the amp is compensated. Input "lag" , OPS "lead" , VAS lead (or shunt).Even the amount of miller comp. will "voice"
the amp.
Some of the older "classic" Japanese designs have a rather complicated mix of lead,lag,miller and shunt. Then there is our "new" TPC and TMC.
I like the symasym , it's "voice" is the result of it's direct shunt + loading of the VAS.
OS
Hi OS,
The other thing is that no matter how you compensate the amplifier, if the distortion products are low enough the human body can't even perceive any of it. At that point it is whatever is in the head of the observer. Even if those distortion products are something that can be heard, what is in their head often takes precedence.
Yes, earlier designs were a complicated mess for compensation. We were still learning I think. Your designs are very clean, I like them.
The other thing is that no matter how you compensate the amplifier, if the distortion products are low enough the human body can't even perceive any of it. At that point it is whatever is in the head of the observer. Even if those distortion products are something that can be heard, what is in their head often takes precedence.
Yes, earlier designs were a complicated mess for compensation. We were still learning I think. Your designs are very clean, I like them.
anatech, I'm very aware of these things. If I was a guru in my previous life, it was a DBLT Guru.
Based on that experience, I have my own prejudices on what is AUDIBLY important in amp design.
However, I'm really impressed by how LTspice simulated my previous real life (measured) experience ... assuming good PCB layout bla bla.
I'd just like to check for measured (or simmed) stuff for which I have real life correlation with DBLTs 🙂
So I'll ask again if anyone can post a LTspice model of SymAsym 5.3
Of course
Can you tell us which of these factors are important? It's a serious question.
Sure kgrlee,
You also know this then. Transistor matching and actual beta. Early effect may be different with different dies (manufacturers). Component tolerance and again some parts should be matched. PCB material normally doesn't matter greatly at <1 MHz frequencies, but copper width and thickness may. There are times a flying lead is far better than a trace. Capacitance between layers can matter also. Then vias and blind vias. Yikes!
So many things come into play at higher current levels too. Output relays if used for one. Supply voltage bounce and all kinds of things.
Then we get into resistors and capacitors. Voltage dependence and thermal changes in resistors, capacitors can also be affected by the voltage across their terminals, so dielectric can matter a great deal in certain locations. A schematic doesn't show this, not even close. Then we have decoupling near point of load. Capacitors and resistors may have higher than expected inductance, and inductors can have leakage capacitance. Heat build up and thermal gradients can also play a part. Air flow can cause LF noise in high gain input stages.
There is so much involved in a physical product. It takes a team of engineers to get it right, or a really old, really experienced designer! lol!
I don't know if I caught it all, but that is off the top of my head. Only the very best professional simulators and models can capture this, or do montecarlo sims with parts.
You also know this then. Transistor matching and actual beta. Early effect may be different with different dies (manufacturers). Component tolerance and again some parts should be matched. PCB material normally doesn't matter greatly at <1 MHz frequencies, but copper width and thickness may. There are times a flying lead is far better than a trace. Capacitance between layers can matter also. Then vias and blind vias. Yikes!
So many things come into play at higher current levels too. Output relays if used for one. Supply voltage bounce and all kinds of things.
Then we get into resistors and capacitors. Voltage dependence and thermal changes in resistors, capacitors can also be affected by the voltage across their terminals, so dielectric can matter a great deal in certain locations. A schematic doesn't show this, not even close. Then we have decoupling near point of load. Capacitors and resistors may have higher than expected inductance, and inductors can have leakage capacitance. Heat build up and thermal gradients can also play a part. Air flow can cause LF noise in high gain input stages.
There is so much involved in a physical product. It takes a team of engineers to get it right, or a really old, really experienced designer! lol!
I don't know if I caught it all, but that is off the top of my head. Only the very best professional simulators and models can capture this, or do montecarlo sims with parts.
I still using the amplifier every day after I made some (more) improvement!
Also ordered lower value Source resistors, I wait on those to arrive to do some more tweak.
I bypassed the capacitor bank with Russian 20uF foil caps and replaced the Blue Alps with the small green potentiometer (in this set up is better).
That improved the sound a lot, now it has enough deep bass and air/separation between the instruments.
Yes I plan to build the amp into an enclosure!
Also ordered lower value Source resistors, I wait on those to arrive to do some more tweak.
I bypassed the capacitor bank with Russian 20uF foil caps and replaced the Blue Alps with the small green potentiometer (in this set up is better).
That improved the sound a lot, now it has enough deep bass and air/separation between the instruments.
Yes I plan to build the amp into an enclosure!
Hi Gaborbela,
Do you have a list of major changes that you implenented in the amp to make sure others building this in the future get it right?
This is the CFH9CX layout right?
Thanks
Do you have a list of major changes that you implenented in the amp to make sure others building this in the future get it right?
This is the CFH9CX layout right?
Thanks
Yes that is based on your schematics / circuit marked "This is how I built."
When I finish I will mention all the modification I made. Right now I Ohmited the front regulator, I use 10uF Silmic on the input.
On board I use a pair 330uF Panasonic FC and one pair 220uF Nichicon FG capacitors. (that is what I had!)
For the low voltage (16V) I choose 2200uF Panasonic FM type Bypassed with 3.3uF ERO capacitors
The more influence on the sound came from the power supply 33 000uF /rail bypassed by 20uF Russian Foil caps, and from the green potentiometer.
To me the Blue Alps tend to sound muddy & dull.
I plan to lower the source resistors value, my mosfets matched virtually identical, still waiting for the resistors.
One more thing for VAS I used Hitachi transistors. HIT 2SB1109 & 2SD1609 (original Japanese)
When I finish I will mention all the modification I made. Right now I Ohmited the front regulator, I use 10uF Silmic on the input.
On board I use a pair 330uF Panasonic FC and one pair 220uF Nichicon FG capacitors. (that is what I had!)
For the low voltage (16V) I choose 2200uF Panasonic FM type Bypassed with 3.3uF ERO capacitors
The more influence on the sound came from the power supply 33 000uF /rail bypassed by 20uF Russian Foil caps, and from the green potentiometer.
To me the Blue Alps tend to sound muddy & dull.
I plan to lower the source resistors value, my mosfets matched virtually identical, still waiting for the resistors.
One more thing for VAS I used Hitachi transistors. HIT 2SB1109 & 2SD1609 (original Japanese)
Just to be clear. I use this type of Russian capacitors as a bypass capacitor on the PS capacitor bank.
Picture for illustration. I used 20uF. Also I use Rifa paper 0.1uF caps.
I will wait to build the amp into the enclosure after I test the lower value Source resistors.
The PCB needs to be removed from the heatsink.
I listen to the amp every day and really enjoy her!
I am satisfied with the sound but I already ordered those resistors. Let's test them, why not.
Picture for illustration. I used 20uF. Also I use Rifa paper 0.1uF caps.
I will wait to build the amp into the enclosure after I test the lower value Source resistors.
The PCB needs to be removed from the heatsink.
I listen to the amp every day and really enjoy her!
I am satisfied with the sound but I already ordered those resistors. Let's test them, why not.
