Very well Alex you added the missing caps. The 470K resistor in the input marked green is connected to main ground will it be better to be connected to the lifted GND? Also 56K resistor marked red needs to be connected right after the 1uF cap and then to the lifted GND now is wrong.
On the picture is the TO220 version can you please post the TO126 version?
If you fix that I think we will be ready for VER2.0 🙂
On the picture is the TO220 version can you please post the TO126 version?
If you fix that I think we will be ready for VER2.0 🙂
Attachments
Last edited:
Alex if will be a big problem to fix the 470K resistor leave it - it is not absolutely needed.
It is recommended but not critical circuit will work well without it.
It is recommended but not critical circuit will work well without it.
According to this simulated with lower value resistor and when the value go under 2K it seems THD get a bit lower. How will this correspond with reality?
What will be right value for R36 1K maybe or not?
Regards!
R36 magnifies the affect of parasitic capacitance and Early effect in the cascode transistor. This will be observed as a modulation of the cascode voltage while playing. What you have done is to contaminate the cascode reference with the signal you were trying to eliminate in the first place. You can bypass the resistor entirely. If this causes instability, add a small 1k trimmer as R36 and adjust it until you are satisfied with the stability. Then measure the resistance and substitute a fixed resistor. It would not be strange if a small resistor say 50-330R were needed here; but not a large one.
In reality the affect on distortion could be better or worse than simulations show, depending on simulation quality and prototype layout. At low Vce, the transistor will enter quasi-saturation, and this will cause extra distortion not predicted by simulation (models do not include quasi-saturation). You may never discover it unless you test your amp at high volumes. The 10k resistor will make this effect worse.
In reality the affect on distortion could be better or worse than simulations show, depending on simulation quality and prototype layout. At low Vce, the transistor will enter quasi-saturation, and this will cause extra distortion not predicted by simulation (models do not include quasi-saturation). You may never discover it unless you test your amp at high volumes. The 10k resistor will make this effect worse.
Thanks very much for the explanation! Example with the trimmer is very good will play a bit with 1k trimmer and see what will happens but let first PCB get ready and make the new build.
Regards!
Regards!
This is where it is useful to scope the actual design for real as well as simulate it. Scoping wouldn't show changes in absolute distortion though.
I wouldn't like to say really... perhaps experiment with the ref volts (zener) as well as the resistor value. There are always trade offs and compromises.
I wouldn't like to say really... perhaps experiment with the ref volts (zener) as well as the resistor value. There are always trade offs and compromises.
Today I played a bit with the ready board. Found the problem with the hum it was a leaky cap in my test power supply 😡 After replacing hum disappeared 🙂 Also fixed the reversed diode and tested with lower value resistor for R36. Decreased it first to 390R and then to 68R. With 390R sound was more detailed and crystal clear and can't hear any difference between 390R and 68R. Well decreasing the resistance makes HF response better. Probably will leave the 68R for this resistor.
My hands are itchy now for building VER2.0 and can't wait 🙂
My hands are itchy now for building VER2.0 and can't wait 🙂
Alex now everything looks OK 🙂 we are ready for VER2.0 You can post now B&W files for TO126 drivers version and I will be ready for etching.
Keantoken all listed here are not fakes for sure: Transistors | Comet Electronics
Keantoken all listed here are not fakes for sure: Transistors | Comet Electronics
The MJE340/350 are popular and apparently sound good, but they do not have good specs and are known for "sticking". You may replace them with a better part and see if you prefer them or not. I would replace them with BD139/140 or 2SA1220/C2690. Higher Hfe parts will work better for a CCS because of reduced base leakage. There will be more options if you resort to SMD parts.
Well I'm just a hobby person and make this amp just for fun and I'm not familiar with SMD parts - never used them and never used or created SMD board so will stay with conventional devices. BD139/140 are good but Vce is only 80V is my +/-50V supply not too much for them. I already was suggested that can use bd139 for VAS because it don't "sees" the 100V from the supply and used it but this does not apply for the other ones.
Last edited:
What speakers are you using this amp on ?
How do you think it compares to other amps you have tried/owned etc ?
How do you think it compares to other amps you have tried/owned etc ?
I newer owned a commercial amp. I do use a small 35-40W/8R Pioneer speakers and listening music on this: http://www.diyaudio.com/forums/solid-state/171882-what-you-think-about-schematic.html At first instance this one seems to have better HF response than my current one but will confirm that later.
Still don't have full impression of this amp because don't have two working channels to try , don't have the full +/-50V supply testing with a small 100VA trafo which gives me a +/-25VDC just to check that the board have no mistakes.
Most people will ask me why I just not buy a commercial amp and doing this.
Answer is simple - what I'm going to do when it get broken? Repair will cost like new one because today amps have very complex schematics that I can't manage. Here is a common practice when service can't provide one part for you because they know well that parts like STK chips for example are all fakes here to refuse to repair it if you don't find that part by yourself and all responsibility comes to you. Other thing - when the service technician can't find the right part or any suitable replacement it puts what it have and don't give a damn about complementary pairs I've seen a repaired amp with one BD139 driver and the other was MJE350 but most people don't know that and are happy that amp is working again. So I prefer to have some amp that can make and fix with available original parts and not to trow up every time when get damaged because this happens.
One interesting fact - today most nations celebrate St. Valentine's day but here we celebrate the St. Triphon's day or the day of the vine. All vine producers or enthusiasts with small farms like me have celebration today.There are also a people that celebrate the love day or both vine and love day together but for me is the vine day so I want to say a BIG CHEERS EVERYONE
Still don't have full impression of this amp because don't have two working channels to try , don't have the full +/-50V supply testing with a small 100VA trafo which gives me a +/-25VDC just to check that the board have no mistakes.
Most people will ask me why I just not buy a commercial amp and doing this.
Answer is simple - what I'm going to do when it get broken? Repair will cost like new one because today amps have very complex schematics that I can't manage. Here is a common practice when service can't provide one part for you because they know well that parts like STK chips for example are all fakes here to refuse to repair it if you don't find that part by yourself and all responsibility comes to you. Other thing - when the service technician can't find the right part or any suitable replacement it puts what it have and don't give a damn about complementary pairs I've seen a repaired amp with one BD139 driver and the other was MJE350 but most people don't know that and are happy that amp is working again. So I prefer to have some amp that can make and fix with available original parts and not to trow up every time when get damaged because this happens.
One interesting fact - today most nations celebrate St. Valentine's day but here we celebrate the St. Triphon's day or the day of the vine. All vine producers or enthusiasts with small farms like me have celebration today.There are also a people that celebrate the love day or both vine and love day together but for me is the vine day so I want to say a BIG CHEERS EVERYONE
Last edited:
Thanks 🙂
Building your own will far outperform any STK type amp and of course there is the satisfaction of doing it. I have owned a couple of commercial ones in the past but would always DIY now.
So I see this design is a development of your earlier one... V2.00 to begin with 😉
Building your own will far outperform any STK type amp and of course there is the satisfaction of doing it. I have owned a couple of commercial ones in the past but would always DIY now.
So I see this design is a development of your earlier one... V2.00 to begin with 😉
I can't call absolutely mine it is like to claim that I discovered the hot water 🙂
I made it using someone else ideas but stick them together the way I like. Of course made some mistakes but here are people knowing much more than me and they guided me trough the building process and still doing it so thank you very very much for this.
The older amp sounds really nice and will make it a PCB some day and rebuild it because now is on veroboard and deserves a better thing 🙂
I made it using someone else ideas but stick them together the way I like. Of course made some mistakes but here are people knowing much more than me and they guided me trough the building process and still doing it so thank you very very much for this.
The older amp sounds really nice and will make it a PCB some day and rebuild it because now is on veroboard and deserves a better thing 🙂
As with all things electronic compromises have to be made, I think if you compare minor problem like base leakage which is easily remedied to what youd get with a very reduced Early voltage in case of the bd´s youd change opinion.
The bd´s would cause a big PSRR drop, higher distortion at frequencies at, below and around 1khz, more assymetric drive to the drivers causing higher levels of crossover distortion. The only benefit would be that it has lower Cob having lower high frequency THD.
Another fact to keep in mind is that the MJE´s are not manufactured the same way as they were back when they were concieved, in practice they display much improved characteristics from the parts which first appeared. No one has bothered to update datasheets. This is the case also with components like 2n3055, 2n3771 mj15003 etc.
Thanks for the info Homemodder. Maybe Astankov could get a realistic idea of CCS behavior at normal voltages with these parts with Cordell's models, as Cordell developed them from real, measured devices.
Problem with spice is that models have fundamental flaws, you wouldnt see all the effects till you put the circuit on a scope. First you should look at all the flaws associated to the early voltage, the breakdown parameters and the kirk effect to get a better undestanding of the limits the simulations will show.
- Status
- Not open for further replies.