Thanks Maty!
You are assiduous in ferreting out this sort of information. I have been looking for this for years since I discovered LTSpice could give the phase angle of the harmonics.
Within my limited research, I can confirm NP's findings and have found that depth of image is also related to feedback regimes. This is why I always limit my global feedback.
The AKSA story was presented to the AES some years back in Melbourne. Nothing comes from it; most people were somewhat confused by my bullet points, and those who understood did not comment on the night. This was my first public presentation since my stroke which left me aphasic, but Paul Bysouth and Graham Huon piloted me well through it.
I have said it before here but I believe all the engineering of good amps was finished fifty years ago. We are now attempting to improve audio presentation with psychoacoustic tricks, using engineering of course to implement it. Self's analysis of distortion was a watermark in amp design in the early nineties, but his approach was quantitative, not qualitative. I have tried to apply the subjective aspects of audio amplification, nothing more....... it is the last step in the chain, and once complete, it is possible to design stunning audio amplifiers with monotonic harmonic profiles, very small parts counts and very high efficiency.
I continue with my amp R&D with the wonderful help from XRK, who builds an amp every week and auditions it very carefully, measuring and then critically listening. JPS64 continues to support both of us with space-age layouts, and the forum is benefiting.
The ALPHA was completely designed using LTSpice, and studied very carefully down to every harmonic. Hundreds of permutations were analysed on the spice engine to ensure the profile was monotonically decreasing through the full range of operation.. Using hunches and a mind's eye of the schem, I delivered the completed circuit to XRK and he then quickly built it up from JPS's layout. From the first it worked very, very well and I think now that with four or five of these in our forums it is becoming clear that the amp works very well, delivering real music. Of course, nothing is new in this area of electronics, but the 'boiler plate' design techniques work very well while Spice accelerates the process very quickly.
This has been the most creative period of my life and I'm delighted to be surrounded by good friends, stable health, and a supportive family.
BTW, I just bought an old Lexus with the 4.3 litre V8 engine. Used cars are worth nothing in sophisticated consumer markets, it is one of the tragedies of our age, particularly for the auto manufacturers. The engineering in this car is cosmic, one would believe that the engine is an electric motor, it is so smooth and efficient. It is this excellence of engineering that only happens with obsessed engineers. I understand Toyota spent $980B developing this engine in the late eighties, and I can believe it. There are examples of this engine in the US with one million miles on the clock, and the engine has never been opened for major service. I couldn't be happier with my purchase!
Thank you to XRK, to JPS, and to this forum.......
Hugh
You are assiduous in ferreting out this sort of information. I have been looking for this for years since I discovered LTSpice could give the phase angle of the harmonics.
Within my limited research, I can confirm NP's findings and have found that depth of image is also related to feedback regimes. This is why I always limit my global feedback.
The AKSA story was presented to the AES some years back in Melbourne. Nothing comes from it; most people were somewhat confused by my bullet points, and those who understood did not comment on the night. This was my first public presentation since my stroke which left me aphasic, but Paul Bysouth and Graham Huon piloted me well through it.
I have said it before here but I believe all the engineering of good amps was finished fifty years ago. We are now attempting to improve audio presentation with psychoacoustic tricks, using engineering of course to implement it. Self's analysis of distortion was a watermark in amp design in the early nineties, but his approach was quantitative, not qualitative. I have tried to apply the subjective aspects of audio amplification, nothing more....... it is the last step in the chain, and once complete, it is possible to design stunning audio amplifiers with monotonic harmonic profiles, very small parts counts and very high efficiency.
I continue with my amp R&D with the wonderful help from XRK, who builds an amp every week and auditions it very carefully, measuring and then critically listening. JPS64 continues to support both of us with space-age layouts, and the forum is benefiting.
The ALPHA was completely designed using LTSpice, and studied very carefully down to every harmonic. Hundreds of permutations were analysed on the spice engine to ensure the profile was monotonically decreasing through the full range of operation.. Using hunches and a mind's eye of the schem, I delivered the completed circuit to XRK and he then quickly built it up from JPS's layout. From the first it worked very, very well and I think now that with four or five of these in our forums it is becoming clear that the amp works very well, delivering real music. Of course, nothing is new in this area of electronics, but the 'boiler plate' design techniques work very well while Spice accelerates the process very quickly.
This has been the most creative period of my life and I'm delighted to be surrounded by good friends, stable health, and a supportive family.
BTW, I just bought an old Lexus with the 4.3 litre V8 engine. Used cars are worth nothing in sophisticated consumer markets, it is one of the tragedies of our age, particularly for the auto manufacturers. The engineering in this car is cosmic, one would believe that the engine is an electric motor, it is so smooth and efficient. It is this excellence of engineering that only happens with obsessed engineers. I understand Toyota spent $980B developing this engine in the late eighties, and I can believe it. There are examples of this engine in the US with one million miles on the clock, and the engine has never been opened for major service. I couldn't be happier with my purchase!
Thank you to XRK, to JPS, and to this forum.......
Hugh
Last edited:
Call me old
Call me old, but I have always been of the opinion that before commenting, you have to be properly informed, especially in a public forum.
Unfortunately it is something that is no longer practiced, especially in social networks. And in Spain even worse (net -I only write in English- or real life).
My new signature: "Comment is free, but facts are sacred" - C. P. Scott
Btw, you , X and JPS64 have a gift. Look at the mail.
Call me old, but I have always been of the opinion that before commenting, you have to be properly informed, especially in a public forum.
Unfortunately it is something that is no longer practiced, especially in social networks. And in Spain even worse (net -I only write in English- or real life).
My new signature: "Comment is free, but facts are sacred" - C. P. Scott
Btw, you , X and JPS64 have a gift. Look at the mail.
Last edited:
....aha aha i like it!
Hi X and Hugh and Fellas,
In the early day i was looking in forums....nothing much NEW's!
Now is started a new optional way M2 build.
Thank you for sharing result of diligently, creative work.
I was discordantly which one i should prefer.....MoFo with AKSA Pre, M2X or
Alpha....now i think X and Hugh has given new direktion, motivation.
Shorter colder days, JPS has started his stove....so on...
I have worked on layout my own Aksa Lender Pre for MoFo use, but not started.
Hi X and Hugh and Fellas,
In the early day i was looking in forums....nothing much NEW's!
Now is started a new optional way M2 build.
Thank you for sharing result of diligently, creative work.
I was discordantly which one i should prefer.....MoFo with AKSA Pre, M2X or
Alpha....now i think X and Hugh has given new direktion, motivation.
Shorter colder days, JPS has started his stove....so on...
I have worked on layout my own Aksa Lender Pre for MoFo use, but not started.
Attachments
ALPH-M2 Experiment
I had a free hour to try something, and certainly for those of you with an existing M2 and an Aksa Lender preamp in-hand already, you can try too. Takes no time at all. Cut the trace from Edcor to 10uF coupling cap C2. Cut the trace from input jack to JFET front end. Solder jumper from input pin to C2 positive terminal where trace was cut. Connect your Aksa Lender pre to the amp's RCA inputs. Turn on and enjoy.
This is the best I have heard the M2 sound - the noise and any hum is gone gone gone. Silence ears pressed to speaker cones. The music is engaging, dynamic, and with a zero global feedback power stage - very natural and with superb imaging and soundstage. This is going to be a fantastic amp.
Cut traces with Dremel tool (took 1 min), wire jumper (took 2min), re-assemble on UMS heatsink (took 10min).
Testing with 0.40x Karlsonators with 3FE25:
So the concept is now proven and I did not have to build a proto board!
I had a free hour to try something, and certainly for those of you with an existing M2 and an Aksa Lender preamp in-hand already, you can try too. Takes no time at all. Cut the trace from Edcor to 10uF coupling cap C2. Cut the trace from input jack to JFET front end. Solder jumper from input pin to C2 positive terminal where trace was cut. Connect your Aksa Lender pre to the amp's RCA inputs. Turn on and enjoy.
This is the best I have heard the M2 sound - the noise and any hum is gone gone gone. Silence ears pressed to speaker cones. The music is engaging, dynamic, and with a zero global feedback power stage - very natural and with superb imaging and soundstage. This is going to be a fantastic amp.
Cut traces with Dremel tool (took 1 min), wire jumper (took 2min), re-assemble on UMS heatsink (took 10min).
Testing with 0.40x Karlsonators with 3FE25:
So the concept is now proven and I did not have to build a proto board!
Attachments
Last edited:
Hi X and Hugh and Fellas,
In the early day i was looking in forums....nothing much NEW's!
Now is started a new optional way M2 build.
Thank you for sharing result of diligently, creative work.
I was discordantly which one i should prefer.....MoFo with AKSA Pre, M2X or
Alpha....now i think X and Hugh has given new direktion, motivation.
Shorter colder days, JPS has started his stove....so on...
I have worked on layout my own Aksa Lender Pre for MoFo use, but not started.
Hi Bangla H, your layout looks very nice. You gave me a set of Quasi boards (Prasi layout) a while back and that’s how I got started working with Hugh. Let me know if you would like a set of Aksa Lender Preamp main board and daughter boards. I’ll send them out today if possible.
Cheers,
X
This is going to be a fun project. So we are starting to see some design features starting to materialize.
1. Reuse Aksa Lender daughter boards from preamp.
2. Have on board 65v DC-DC step up cap Mx and CRC on board for Aksa Lender Pre front end. Step up is on a smaller TO220 style daughter board.
3. +/-27v rails and big IXYS outputs for 35w.
4. Optionally, one can use 24v rails and usual IRFPs for a 25w amp.
5. Aiming for UMS heatsink spacing bolt holes - not sure if we can do it.
6. On board underhung diode bridge cooled by main heatsink.
7. On board CRCRCRC filter for rails.
8. Dual monoblock requiring 4 sets of trafo secondaries (dual toroidal or one with four secondaries).
1. Reuse Aksa Lender daughter boards from preamp.
2. Have on board 65v DC-DC step up cap Mx and CRC on board for Aksa Lender Pre front end. Step up is on a smaller TO220 style daughter board.
3. +/-27v rails and big IXYS outputs for 35w.
4. Optionally, one can use 24v rails and usual IRFPs for a 25w amp.
5. Aiming for UMS heatsink spacing bolt holes - not sure if we can do it.
6. On board underhung diode bridge cooled by main heatsink.
7. On board CRCRCRC filter for rails.
8. Dual monoblock requiring 4 sets of trafo secondaries (dual toroidal or one with four secondaries).
Thank you for very kind offer X.
But will wait with patience what's moving here next time.
To work on other projects i have just ordered 140 € parts....
I will look if i can make a M2X + ALender layout, of course much simpler as....
how Hugh wrote very right...." space-age layouts"...yupp!
Regards.
But will wait with patience what's moving here next time.
To work on other projects i have just ordered 140 € parts....
I will look if i can make a M2X + ALender layout, of course much simpler as....
how Hugh wrote very right...." space-age layouts"...yupp!
Regards.
For those folks not familiar with the Aksa Lender Preamp, here is an example of the core amp daughterboard that JPS64 designed. We have this in 3 variants: through hole, SMT chip resistors, or SMT mini MELF resistors. They are interchangeable as have same card edge connector.
Here is the high power through hole version (can drive headphones):
Assuming we want to drive the M2 output stage to 30Vpp (about 11wrms) then here is the front ends performance. We will have to see if the M2 can keep up but seems that we were getting similar but higher values of THD on simulation:
Here is the high power through hole version (can drive headphones):
Assuming we want to drive the M2 output stage to 30Vpp (about 11wrms) then here is the front ends performance. We will have to see if the M2 can keep up but seems that we were getting similar but higher values of THD on simulation:
Last edited:
I would probably search for or invent a way to rejigger the front end, so that it uses the ±23V dual rail supplies of the MOSFET follower output stage. Instead of having (+48, GND) for the front end and (+23, -23) for the output stage. A matter of personal taste I suppose.
Be sure that the capacitor which connects these two pieces, "C3a", is rated for at least (Vfrontend + Vneg_MOSFET) which is about 75 volts. You don't want this cap to overvoltage and short out while the three power supplies are turning on. Or turning off.
You may also want to consider output muting, to proactively eliminate any turn on thumps or turn off bangs that may or may not arise from three power supplies waking up and going to sleep at different rates.
Be sure that the capacitor which connects these two pieces, "C3a", is rated for at least (Vfrontend + Vneg_MOSFET) which is about 75 volts. You don't want this cap to overvoltage and short out while the three power supplies are turning on. Or turning off.
You may also want to consider output muting, to proactively eliminate any turn on thumps or turn off bangs that may or may not arise from three power supplies waking up and going to sleep at different rates.
Thanks, Mark Johnson for the suggestions. We have been debating whether or not to run the front end single rail or dual rail. The preamp is single rail, and the ALPHA 20 and ALPHA BB have the dual rail variant to be consistent with given PSU dual rails. We could do that here I suppose, but I wanted to be able to re-use the old tech already developed and that was the single rail preamp daughterboard. Let me think about it. You were not the first to suggest this. However, filtering of the main rails from the front end really needs to be done well to keep it clean as the SE Class A nature of the front end picks up any variations in the power supply as noise.
If we went dual rail, we would basically start from the ALPHA 20 layout and replace the PMOS Aleph output stage with the M2 output stage. Here is the schematic for the same Aksa Lender front end but implemented in dual rail and with global feedback:
Btw, here is how the Teabag M2 output stage measures with the Aksa Lender preamp front end for 2.85Vrms into 8ohms. Nice profile but the M2 output is higher in overall THD - but at 0.04% and dominant H2 and H3 -16dB less, and nothing else - this should sound really nice - and it does. Since it is a no global feedback design, it is expected that the distortion will be a bit higher but that's quite alright as the profile looks wonderful.
If we went dual rail, we would basically start from the ALPHA 20 layout and replace the PMOS Aleph output stage with the M2 output stage. Here is the schematic for the same Aksa Lender front end but implemented in dual rail and with global feedback:
Btw, here is how the Teabag M2 output stage measures with the Aksa Lender preamp front end for 2.85Vrms into 8ohms. Nice profile but the M2 output is higher in overall THD - but at 0.04% and dominant H2 and H3 -16dB less, and nothing else - this should sound really nice - and it does. Since it is a no global feedback design, it is expected that the distortion will be a bit higher but that's quite alright as the profile looks wonderful.
Attachments
Last edited:
Since you are discarding 2/3rds of the M2 anyway, why not throw away its "No Feedback" arrangement too? You can quite readily include the output stage inside the feedback loop of the overall amplifier. Or arrange a couple of jumpers / DIPswitches which allow you to listen to the amplifier BOTH ways: (1) output stage not included in NFB loop; (2) output stage yes included in NFB loop. Maybe your preference will be a complete surprise.
By the way, this is a small tweak upon the WHAMMY headphone amplifier, with lower value source resistors (thus higher standing bias current) and WHAMMY's 4N35 optoisolator biasing loop. Replace the IC opamp with discretes, done.
_
By the way, this is a small tweak upon the WHAMMY headphone amplifier, with lower value source resistors (thus higher standing bias current) and WHAMMY's 4N35 optoisolator biasing loop. Replace the IC opamp with discretes, done.
_
Last edited:
Good idea about NFB selector switch. Maybe we should build amps as modules and allow interchange of any input stage with any output stage. I know Vzaichenko is building his amps that way. Since you mention throwing away 2/3rds of the M2, it’s not for lack of trying. I really did try to like it and get it to work for 2 years. Even added mu-metal shielding. That was a pricey sheet of metal foil and helped but still not quiet to my standards. But the problems all revolved around the magic middle third - the Edcor autoformer. People are so enamored with it but what I hear once that is bypassed and use of a regular transistor to provide voltage gain is a complete change in dynamics and clarity with a huge decrease in noise. This amp is now finally silent. The soundstage and engagement are very nice. But hey, it’s my amp and I should do what I like to make it sound better to my tastes. I suspect others who try this will like it too based on the measured harmonic profile.
Last edited:
Phoenician follower
If you replace the pre-amp with a step up audio transformer you get My Phoenician follower
the Phoenician follower
If you replace the pre-amp with a step up audio transformer you get My Phoenician follower
the Phoenician follower
Attachments
Hi X, I understand your reason for doing this current exercise. But by leaving out the autoformer, aren't you also eliminating that part of the circuit which gives the M2 it's unique, warm and chalky sound? That is exactly what has drawn me to the M2 in the first place. I'm not implying that it will not sound good, just that it's probably not going to sound like an M2 anymore.
Absolutely! And after having built the AKSA Lender Preamp, I have a lot of respect for your judgement and approach to topologies and making it sound exceptional. Go for it. I can't wait to see how this plays out.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.