Nice to see someone try this out! Was discussing this possibility on another thread, any demos /pictures of it that you could post? What speaker are you using?
Cheers
Cheers
Hi ,
very nice work , I like it! post any pictures?'
It would be better to use a much smaller cap than 47,000 uF on yer power input. That large value is useful for 50-60 Hz unregulated linear PS! the PS using a laptop replacement SMPS is operating at > 40,000 Hz AND is most probably regulated (good) Too large values can indeed upset the negative feedback loop inside a SMPS (bad). For best results try values in the 100's uF range designed for SMPS. use a common mode choke to clean up stray PS hash once you attached O-scopes and see some signals.
very nice work , I like it! post any pictures?'
It would be better to use a much smaller cap than 47,000 uF on yer power input. That large value is useful for 50-60 Hz unregulated linear PS! the PS using a laptop replacement SMPS is operating at > 40,000 Hz AND is most probably regulated (good) Too large values can indeed upset the negative feedback loop inside a SMPS (bad). For best results try values in the 100's uF range designed for SMPS. use a common mode choke to clean up stray PS hash once you attached O-scopes and see some signals.
I was expecting to see a replacement MOSFET fitted into an old practice amp holding B+ at 160 V.
This one is Hi-Fi
This one is Hi-Fi
I am using 1x12 Celestion V30 speaker 8 Ohm. You can find pictures of ACA amp in this thread: http://www.diyaudio.com/forums/pass-labs/215392-amp-camp-amp-aca.html
Here is the original article of ACA amplifer by Nelson Pass:
http://www.diyaudio.com/forums/diyaudio-com-articles/214808-amp-camp-amp-1-a.html
Mind you, that there is bias mod for ACA which makes the idle current 1.5A. In the original article the mod is not included, so measurements are little worse with 1A bias.
You can use different power mosfets than IRFP240. I haven´t tried any others, but it could be interesting to use some with lower capacitances (and gm also).
It sounds better than DIY build of class A EL34 guitar amplifier (Hi-Octane by AX84).
For preamp I recommend you AMT Legend amps series (JFET preamps).
Anyway design is very simple and I don´t think there is more to tweak or change.
http://www.diyaudio.com/forums/diyaudio-com-articles/214808-amp-camp-amp-1-a.html
Mind you, that there is bias mod for ACA which makes the idle current 1.5A. In the original article the mod is not included, so measurements are little worse with 1A bias.
You can use different power mosfets than IRFP240. I haven´t tried any others, but it could be interesting to use some with lower capacitances (and gm also).
It sounds better than DIY build of class A EL34 guitar amplifier (Hi-Octane by AX84).
For preamp I recommend you AMT Legend amps series (JFET preamps).
Anyway design is very simple and I don´t think there is more to tweak or change.
Hi Kacernator,
Nice speaker that. Yes am aware of ACA, just wondered if you built using the PCB or did own setup. Did you mount it in the ACA style enclosure, or musical amp style enclosure?
Nice speaker that. Yes am aware of ACA, just wondered if you built using the PCB or did own setup. Did you mount it in the ACA style enclosure, or musical amp style enclosure?
Apparently the 1.5 A bias mod will lower the distortion somewhat, which for guitar amp purpose may not even be as ''desirable''?... Another tweak would be to run with reduced NFB or possibly adjustable (100K range)? Accordingly to Mr. Pass design, he has come up with another amp that is simple and stable even without feedback. I've got some of the parts, but not the PCB or time to build yet.
Just having you comparing the ACA with a AX84 High Octane makes me want to fire up the soldering iron! Better you say.. that should be quite good!
Cheers
Just having you comparing the ACA with a AX84 High Octane makes me want to fire up the soldering iron! Better you say.. that should be quite good!
Cheers
I build ACA using P2P construction on tag board. I have used small heatsink with fan. Enclosure is just small metal box.
I have tried disconnecting the NFB and the sound was worse! As I am using high gain preamp the less distortion in poweramp the better for me.
At first I was using 19V power adapter, but felt the sound is little bit too dark. With 24V power supply it sounds much livier, has better punch and reacts better to playing. I didn´t tried higher voltage, because dissipation would be very high and it is very hard to find higher voltage laptop PSU than 24V.
Which another amp from Nelson Pass are you talking about?
I have tried disconnecting the NFB and the sound was worse! As I am using high gain preamp the less distortion in poweramp the better for me.
At first I was using 19V power adapter, but felt the sound is little bit too dark. With 24V power supply it sounds much livier, has better punch and reacts better to playing. I didn´t tried higher voltage, because dissipation would be very high and it is very hard to find higher voltage laptop PSU than 24V.
Which another amp from Nelson Pass are you talking about?
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I am glad you got good result with it ''as is'', was thinking of increasing feedback resistor somewhat, but as of yet not much time to build. So thank you for giving us some impression of the results.
NP mentioned the ACA design could go well up to a 24 V rail. And using high gain jfet preamp, I am sure you have enough ''stuff'' going on there in the pre stage.
OP on other thread was looking at F6, I suggested trying an ACA for the lower parts count to do some preliminary investigating before committing to the bigger F6 build.
NP mentioned the ACA design could go well up to a 24 V rail. And using high gain jfet preamp, I am sure you have enough ''stuff'' going on there in the pre stage.
OP on other thread was looking at F6, I suggested trying an ACA for the lower parts count to do some preliminary investigating before committing to the bigger F6 build.
Why F6? Why bother with input transformer?
There are also more topological possibilites - PLH, Aleph or LTP to VAS to MOSFET follower.
BUT ACA is as simple and easy as it gets and 5W with high efficiency guitar speaker is VERY loud for home use.
There are also more topological possibilites - PLH, Aleph or LTP to VAS to MOSFET follower.
BUT ACA is as simple and easy as it gets and 5W with high efficiency guitar speaker is VERY loud for home use.
Hello Kacerinator,
Hope you can put a demo up here for the ACA. More needs to be done in this area.
I could answer that previous question about that input transfo.. but I have asked that question in person to Mr Pass, and it is not my design so respectively leave that to the designer to respond. I have my subjective (very good) opinion about it all, but not for me to respond with an answer.
You have gone down that road of good SS design, and wish you very well with it.
Hope you can put a demo up here for the ACA. More needs to be done in this area.
I could answer that previous question about that input transfo.. but I have asked that question in person to Mr Pass, and it is not my design so respectively leave that to the designer to respond. I have my subjective (very good) opinion about it all, but not for me to respond with an answer.
You have gone down that road of good SS design, and wish you very well with it.
Updated schematics
Some minor tweaks in PSU of OPAMP and mainly change in speaker outputs to maintain same damping factor into different loads.
Rocktron in their Velocity guitar poweramps took another approach to damping factor. They have very low output impedance amplifier and in the preamp are EQ controls for bass and treble simulate frequency response of low-damped guitar speaker.
So there is another posibility - change topology of this little class A amplifier to something with source follower to obtain low output impedance and design EQ controls.
Some minor tweaks in PSU of OPAMP and mainly change in speaker outputs to maintain same damping factor into different loads.
Rocktron in their Velocity guitar poweramps took another approach to damping factor. They have very low output impedance amplifier and in the preamp are EQ controls for bass and treble simulate frequency response of low-damped guitar speaker.
So there is another posibility - change topology of this little class A amplifier to something with source follower to obtain low output impedance and design EQ controls.
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