Hello
Recently I have build VSSA amp (shaan version bit modyfied) and I am very happy with it.
I had few irfp240/9140 pairs in stock so I decided to build another version (as I am not an expert some upgrades may be needed).
Bellow schematic, board, and measurements. The measurements were done on prototyp board and all components weren't matchet (just taken stright from the box).
Bias is stable, cold amp seted to 100mA (15C) hot amp 92mA (78C), I didnt have irf540/530 so I used irf840 instead. I think that amp can use bit higher power supply than +/-35V.
Amp is playing really good.
Thanks to LazyCat and Shaan
Ps
I was thinking If it would be recommended to leave 0,1R source resistors and put 47R gate resistors instead 100R ?
My sound card is not the top notch and is creating some high order harmonics artefacts (there are present at the same place on different amplifiers measurements).
Recently I have build VSSA amp (shaan version bit modyfied) and I am very happy with it.
I had few irfp240/9140 pairs in stock so I decided to build another version (as I am not an expert some upgrades may be needed).
Bellow schematic, board, and measurements. The measurements were done on prototyp board and all components weren't matchet (just taken stright from the box).
Bias is stable, cold amp seted to 100mA (15C) hot amp 92mA (78C), I didnt have irf540/530 so I used irf840 instead. I think that amp can use bit higher power supply than +/-35V.
Amp is playing really good.
Thanks to LazyCat and Shaan
Ps
I was thinking If it would be recommended to leave 0,1R source resistors and put 47R gate resistors instead 100R ?
My sound card is not the top notch and is creating some high order harmonics artefacts (there are present at the same place on different amplifiers measurements).
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Very nice VSSA variant! I was curious about a HEXFET version of the VSSA. I see you used CCSs as well.
cute and nice measurements 🙂 Out of curiosity what was the output power for the 3 different THD you show ?
I moved the vas stage under the board. There are 2 caps added just before each o/p transistor. Places for fuses if someone are going to use them.
I have tested the amp how it would react in case of one of burned fuse.
If the ''core'' of the amp is permanently supplied there is no DC at the output, so there is safe to use fuse protection in the amp.
I have tested the amp how it would react in case of one of burned fuse.
If the ''core'' of the amp is permanently supplied there is no DC at the output, so there is safe to use fuse protection in the amp.
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Hi Borys,
Nice to see vssa variant. How does SQ compare to 2sj162/2sk1058? Can I use IRF540/IRF9540? Thank you.
Regards,
Boyet
I am not able to compare sq at the moment but I must say that irfp version sound excellent, only one think I can notice is that bass is bit different.
I You can use any hexfets I think 540/9540 will be ok.
I You can use any hexfets I think 540/9540 will be ok.
Nice!
I've got some N-channel IRFP250N only.
Could anyone draw a variant of this circuit to fit only N-channel hexfet outputs?
Thanks!
I've got some N-channel IRFP250N only.
Could anyone draw a variant of this circuit to fit only N-channel hexfet outputs?
Thanks!
These are some excellent test results Borys! Especially the THD measurements. Can I ask which Hantek you used to do these tests? There are several of them, and I know some have better reviews than others.
Can I ask which Hantek you used to do these tests? There are several of them, and I know some have better reviews than others.
I am using portable dso1060 scope as I work a lot on the cars.
I must upgrade my sound card and function generator. The amp is made without matching any of the components - just stright from the bag parts.
There are eagle files anyway.
I can maybe draw the n-channel version but I do not want to upload not tested version.
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THX
If Ill have some free time I am going to put 2nd pair of o/p tranies and lift up the supply voltage, but I must do some tests first.
Regards
Yeah, there's always something better you can upgrade to (chuckle). I had a National instruments DAQ card and some LabView apps that did an excellent job, but none of that stuff worked with Windows 7 or later (sigh). I would be interested in comparing some notes on that, because I feel a bit handicapped with just my standalone scopes.
The input pairs I am using on my version of Shaan's PeeCeeBee were matched. Feedback resistors also. Nothing else. KSA/KSC pair cannot be matched in D/E versions, and I think there is no point matching the mosfets. I did adjust the gate R values however, according to the gate capacitance of the mosfets, similar to what LC did.
Frankly, I am surprised the harmonic distortion measured as low as it did. Again, good job!
Currently I am working on upgraded more powerfull version of FET-hex amplifier.
The new version has code name BG2-fet.
It will have 2 pair of outputs (or more). One of forum meber advised to add double bootstrap for vas stage, and so far is working great.
There psu voltage is not wasted anymore. At the moment I have only 80W transformer so further test and developments will be required after Ill get bigger buddy.
Bellow results:
THD
Measurement is allways with amplitude 20V just to compare all my amps. Unfortunetly my sound card has some artefacts on measurements, I hope I will have time to upgrade it.
boot21-Clipping
Output voltage on 8R load vs vas bootstrapped voltage
boot23 and 24
Supply voltage vs output voltsge 8R load, as you can see amplifier is very very efficiednt (thanks to raven and mr zbig from my forum).
boot25
Sypply voltage vs 50Hz square - you can see my 80W transformer has drop the load 😛
boot26
Clipping vs bootstrap again
boot28
some RNB song
boot27
Here I have small question - from approx 4kHz the bootstrapp is starting to collapse a bit, I do not know If I have to be woory about it cause the power spectrum of music signal for higher F is not as high as for lower F's.
BG2-fet
The test amp itself (temporarly with one pair of outputs and no source resistors - there will be a time for them further)
The new version has code name BG2-fet.
It will have 2 pair of outputs (or more). One of forum meber advised to add double bootstrap for vas stage, and so far is working great.
There psu voltage is not wasted anymore. At the moment I have only 80W transformer so further test and developments will be required after Ill get bigger buddy.
Bellow results:
THD
Measurement is allways with amplitude 20V just to compare all my amps. Unfortunetly my sound card has some artefacts on measurements, I hope I will have time to upgrade it.
boot21-Clipping
Output voltage on 8R load vs vas bootstrapped voltage
boot23 and 24
Supply voltage vs output voltsge 8R load, as you can see amplifier is very very efficiednt (thanks to raven and mr zbig from my forum).
boot25
Sypply voltage vs 50Hz square - you can see my 80W transformer has drop the load 😛
boot26
Clipping vs bootstrap again
boot28
some RNB song
boot27
Here I have small question - from approx 4kHz the bootstrapp is starting to collapse a bit, I do not know If I have to be woory about it cause the power spectrum of music signal for higher F is not as high as for lower F's.
BG2-fet
The test amp itself (temporarly with one pair of outputs and no source resistors - there will be a time for them further)
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