I found relevant post from Bonsai regarding the frequency in the OLG plot (cursor2):
https://www.diyaudio.com/community/...as-a-small-sizzling-sound.411503/post-7697842
"Sevey, 200 kHz ILGF is too low because it means you are throwing away high frequency loop gain and therefore the opportunity to reduce distortion. For your amp I would aim for between 1-2 MHz - so if you used 100pF Cdom caps in the above plot, try changing them to about 47-68 pF. For phase margin, it is recommended you aim for >60 deg. With an output coil (which you have), you can even go lower, but I'd just stick with >60 deg for this amp and you should be okay."
The whole thread mentioned above is very educational.
If Bonsai is right, 14MHz frequency is way too high in the OLG plot.
Not saying the amp won't work, but it's not optimal...
Making an amp stable, is the most important (and difficult) aspect of designing an amp.... Not Thd, not power, but stability.
https://www.diyaudio.com/community/...as-a-small-sizzling-sound.411503/post-7697842
"Sevey, 200 kHz ILGF is too low because it means you are throwing away high frequency loop gain and therefore the opportunity to reduce distortion. For your amp I would aim for between 1-2 MHz - so if you used 100pF Cdom caps in the above plot, try changing them to about 47-68 pF. For phase margin, it is recommended you aim for >60 deg. With an output coil (which you have), you can even go lower, but I'd just stick with >60 deg for this amp and you should be okay."
The whole thread mentioned above is very educational.
If Bonsai is right, 14MHz frequency is way too high in the OLG plot.
Not saying the amp won't work, but it's not optimal...
Making an amp stable, is the most important (and difficult) aspect of designing an amp.... Not Thd, not power, but stability.
No question there if Bonsai is right but he mentions unity gain frequency from 1-2 MHz as a goal.
Current Choctaw design is in the ballpark, while having good phase margin.
@coacharnold
What speakers do you have?
10 Watt is suitable for sensitive speakers.
For less sensitive speakers I recommend Sioux https://www.diyaudio.com/community/threads/sioux-26-watt-opa552-with-diamond-buffer-output.417095/
What speakers do you have?
10 Watt is suitable for sensitive speakers.
For less sensitive speakers I recommend Sioux https://www.diyaudio.com/community/threads/sioux-26-watt-opa552-with-diamond-buffer-output.417095/
@lineup I was looking to build a small powered desktop amp to power the small Optimus speakers on my computer desk. I originaly looked at mosfet design, then ran into this project. I'm not exactly sure of the specs of these speakers so I don't know the sensitivity but I know they don't require much. I'm open to any ideas, this project just looked interesting. ...checking out your link now.... thanks and sorry for the slow reply
T
T
@coacharnold
It sounds those small speakers would suit this project.
I am waiting for @ZoltanChivay to post some files.
It sounds those small speakers would suit this project.
I am waiting for @ZoltanChivay to post some files.
You may think it is black magic but it is not. Follow Lineup's instructions and you will be fine.
I think that tomorrow, maybeafter tomorrow the PCB will reach me
I will try to build and test a prototype during the weekend
I will try to build and test a prototype during the weekend
A little effort and it worked!
There was no big boom and no magic smoke!
😆
For now, a quick test on an 8 Ohm resistance load
It looks like nothing is oscillating
20 kHz edges are slightly softened
10 kHz looks very good
That's it for today
Tomorrow a test of 8 Ohm +100nF
If it's OK, I'll listen to some music
There was no big boom and no magic smoke!
😆
For now, a quick test on an 8 Ohm resistance load
It looks like nothing is oscillating
20 kHz edges are slightly softened
10 kHz looks very good
That's it for today
Tomorrow a test of 8 Ohm +100nF
If it's OK, I'll listen to some music
Attachments
I think this is fitting in the thread subject.
It was 1994 or 94 when at office I built amp very similar to last schematics in post #208. It took extremely little time, not undermining the fact that those day or two I did not deserve my salary 🙂
It played at work happily for few years. Later at home I never used it with main set up, but it was always dug out from the shelf whenever small amp was needed, for kitchen, garden, missing one for active setup test..... whatever. In any case, it was and is used.
The build is not fantastic, diagram was never made, nor was PCB, never measured, just hooked from parts at hand, but it plays w/o complaint
Main difference from Choctaw are:
It was 1994 or 94 when at office I built amp very similar to last schematics in post #208. It took extremely little time, not undermining the fact that those day or two I did not deserve my salary 🙂
It played at work happily for few years. Later at home I never used it with main set up, but it was always dug out from the shelf whenever small amp was needed, for kitchen, garden, missing one for active setup test..... whatever. In any case, it was and is used.
The build is not fantastic, diagram was never made, nor was PCB, never measured, just hooked from parts at hand, but it plays w/o complaint
Main difference from Choctaw are:
- it uses vertical mosfets IRF532 and IRF9530.
- Instead R3 and R4 there is bias with temp compensation
- instead of R9 and R10 there are current sources (at least I think when looking from above 🙂
- TLE2027 was used as opamp, not because I think it was best at time, but because I had couple at hand.
this is all cooking very well, thanks for the update @ZoltanChivay. I'm looking forward to building this thing.
To build the amplifier I used:
2x12V 225VA toroidal transformer (overkill!)
2x10000uf ELNA as main caps
MUR840 diodes on the radiator (they are not warm)
Decoupling capacitors around the OP-AMP- 47uF Nichicon FG, 100nf Philips and 100n COG Murata (smd)
The capacitor in the feedback loop is Nichicon KA
Standard resistors 1% MOX
Input cap is Obbligato copper -good and not expensive
Power transistors - 2SK1058 / 2SJ162
I did a few quick listening tests
I have 92dB / 8Ohm speakers with a 15 inch woofer
There is no shortage of power!
Oscar Pettiford double bass sounds rich and authoritative
Female vocals (Dinah Washington, Nina Simone) sound great
I'll be listening to this for a while
Really good little amp!
2x12V 225VA toroidal transformer (overkill!)
2x10000uf ELNA as main caps
MUR840 diodes on the radiator (they are not warm)
Decoupling capacitors around the OP-AMP- 47uF Nichicon FG, 100nf Philips and 100n COG Murata (smd)
The capacitor in the feedback loop is Nichicon KA
Standard resistors 1% MOX
Input cap is Obbligato copper -good and not expensive
Power transistors - 2SK1058 / 2SJ162
I did a few quick listening tests
I have 92dB / 8Ohm speakers with a 15 inch woofer
There is no shortage of power!
Oscar Pettiford double bass sounds rich and authoritative
Female vocals (Dinah Washington, Nina Simone) sound great
I'll be listening to this for a while
Really good little amp!