First and foremost, I'd like to offer my huge thanks/appreciation to Hugh and XRK (and whoever else was involved) for this wonderful project. Sometimes we take it for granted that we have all these nice projects, but in the end, without designers willing to share their knowledge and expertise, many of us would never be able to have such great projects/opportunities. So THANK YOU! 🙂
Do
Do
Thank you, Do! It was a team effort - Hugh conceived the circuit, JPS64 did the superb layout and Vunce was instrumental in the verification of the circuit. I hope you enjoy the sound. Happy listening over the holidays!
Do, what a great build, your artwork is impeccable. Great perseverance on the team effort to figure out problems. The touch button looks great.
@other builders also: I am looking for a push/touch button that would connect to a fused mains inlet and also to a soft start board. Is this type of power on called a single pole double throw? Not quite sure what I should be searching for. Thanks for the help.
MM
@other builders also: I am looking for a push/touch button that would connect to a fused mains inlet and also to a soft start board. Is this type of power on called a single pole double throw? Not quite sure what I should be searching for. Thanks for the help.
MM
I came across this description of 'Class A' sound in a TAS write-up of the Gryphon Antileon EVO amp:
"Conclusion
Class A amplifiers are sometimes characterized as smooth and sweet, yet lacking treble openness, dynamic impact, and excitement. The Gryphon Antileon EVO’s triumph is delivering the great virtues of Class A operation—seductive warmth, liquid textures, and a sense of ease—but with tremendous speed and dynamic authority along with a visceral excitement and energy. Its warm harmonic richness and absence of grain and glare reveal the beauty of tone colors in a way that is nothing short of seductive."
I am damn sure my AN 4R doesn't lack treble openness or dynamic impact or excitement - so I'm wondering where Robert Harley would've got this idea from?
Andy
"Conclusion
Class A amplifiers are sometimes characterized as smooth and sweet, yet lacking treble openness, dynamic impact, and excitement. The Gryphon Antileon EVO’s triumph is delivering the great virtues of Class A operation—seductive warmth, liquid textures, and a sense of ease—but with tremendous speed and dynamic authority along with a visceral excitement and energy. Its warm harmonic richness and absence of grain and glare reveal the beauty of tone colors in a way that is nothing short of seductive."
I am damn sure my AN 4R doesn't lack treble openness or dynamic impact or excitement - so I'm wondering where Robert Harley would've got this idea from?
Andy
If anyone is interested in building an Alpha Nirvana for another member who contacted me who doesn’t have time but will pay to have someone make it for him, please send me a PM. Must be in continental US to keep shipping costs reasonable. We are talking full chassis tested and ready to run. I’ll connect you guys.
Do, thank you for your lovely email. We all have an ego, and I love it when people build my designs, and all involved in the Alpha Nirvana, JPS, Vunce, Jan Hovland, and our MC X (should we now describe him as MCX?), are grateful that people are interested in our work and derive happiness from it.
For myself, and given my love of technology and my admiration for the US of my youth, I regret not moving to the US to live in my twenties. It would have put me in the centre of technology and spurred me to greater things. However, that's all the past, my present sadness is that I can't meet my many North American friends, including you, one of the most skilled builders I have seen in this industry.
Ciao,
Hugh
For myself, and given my love of technology and my admiration for the US of my youth, I regret not moving to the US to live in my twenties. It would have put me in the centre of technology and spurred me to greater things. However, that's all the past, my present sadness is that I can't meet my many North American friends, including you, one of the most skilled builders I have seen in this industry.
Ciao,
Hugh
Hugh, I think you live in one of the nicest countries in the world, actually the only country I would move to without having to think twice! I traveled around there for a couple of months in -03, loved it so much I tried to get a job to be able to stay, but it did not work out at the time, and I have not been there since. Maybe my regret is not moving to Oz 😉
Thank you RF, that is food for thought; I'm quite happy spending my last years here, and I know that Australia is an excellent country, but for some years I had the wanderlust, and spent much time in Indonesia - another, but overpopulated, country.
Hugh
Hugh
@Hugh
That's a very heart warming compliment coming from someone who has been in the industry for so many years, I don't know what to say than a big thank you! Now that I have your Class A amp, I'm only missing one of your AB Class amplifiers in my collection, but I will get there!
Like Rallyfinnen says, Autralia is such a nice country. I really wanna go there and visit one day. It is on my bucket list for sure!
All the best!!
Do
That's a very heart warming compliment coming from someone who has been in the industry for so many years, I don't know what to say than a big thank you! Now that I have your Class A amp, I'm only missing one of your AB Class amplifiers in my collection, but I will get there!
Like Rallyfinnen says, Autralia is such a nice country. I really wanna go there and visit one day. It is on my bucket list for sure!
All the best!!
Do
I fired up my amp(s) first time today! I'm running dual mono in a re-purposed enclosure. Have not measured Iq except when I was first powered the modules from 20V bench supply, and it was abt 1,7A (a little low?), but I guess that should stay the same even with the higher voltages.
I'm running simple rectifiers and caps (33mF/rail/channel), transformers are 250VA Toroidy's with 22VAC secondaries, makes 29,5VDC rails loaded. Simple as that at the moment.
There is a little bit of hum, but nothing I can hear from listening position. Thinking of cutting some traces on the PCB's to be able to feed the front end from cap MX previously installed in the enclosure. If there ever will be an update to this PCB, maybe add cap MX for the front to the list? A lot neater than doing it on the main rails I think.
DC offset is a couple of mV with the trimmers in end position, have not kept track of offset with temperature yet, but input pairs are thermally connected.
No HF filtering caps mounted yet (want to do some square wave testing first).
I want to avoid speaker relays if possible, but there is a pretty solid thump at turn on, similar to some old single rail amps with output caps.. Maybe I can live with that, since it seems to be a 'soft' thump.
I have been running the amp in the garage a couple of hours earlier to see that it seemed ok thermally, and heat sinks seem ok, but I think I need to improve cooling for the rectifiers. I could not resist bringing the amp home to give it a listen, and it's playing as I write.
First impression is that it's pumping more bass, almost like I added BR ports on the speakers, same impression on the garage speakers. It also seems I turn it up louder with this amp.. Will give it some time before I comment more on the sound.
Thank you guys for your work on this one!
Picture from assembly earlier today. Needs a lot of finishing up still, but I was eager to test 🙂
I'm running simple rectifiers and caps (33mF/rail/channel), transformers are 250VA Toroidy's with 22VAC secondaries, makes 29,5VDC rails loaded. Simple as that at the moment.
There is a little bit of hum, but nothing I can hear from listening position. Thinking of cutting some traces on the PCB's to be able to feed the front end from cap MX previously installed in the enclosure. If there ever will be an update to this PCB, maybe add cap MX for the front to the list? A lot neater than doing it on the main rails I think.
DC offset is a couple of mV with the trimmers in end position, have not kept track of offset with temperature yet, but input pairs are thermally connected.
No HF filtering caps mounted yet (want to do some square wave testing first).
I want to avoid speaker relays if possible, but there is a pretty solid thump at turn on, similar to some old single rail amps with output caps.. Maybe I can live with that, since it seems to be a 'soft' thump.
I have been running the amp in the garage a couple of hours earlier to see that it seemed ok thermally, and heat sinks seem ok, but I think I need to improve cooling for the rectifiers. I could not resist bringing the amp home to give it a listen, and it's playing as I write.
First impression is that it's pumping more bass, almost like I added BR ports on the speakers, same impression on the garage speakers. It also seems I turn it up louder with this amp.. Will give it some time before I comment more on the sound.
Thank you guys for your work on this one!
Picture from assembly earlier today. Needs a lot of finishing up still, but I was eager to test 🙂
Attachments
Very nice build, different than the regular cases.
For the small hum have you connected the power supply ground to mains earth through a 10ohm resistor or a loop breaker circuit ?
Or a ground lifter bridge.
For the small hum have you connected the power supply ground to mains earth through a 10ohm resistor or a loop breaker circuit ?
Or a ground lifter bridge.
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Very nice RF, compact, good layout. Rectifiers always get very hot on Class A; you'd be doing more than 1.35W constant dissipation on each leg with 1.7A+ and usually around Vak of 0.8V.
Try the earth loop, ten ohm resistor from input/coax/fb shunt signal ground to power ground, perhaps one on each module.
Thank you for building the Alpha!!
Hugh
Try the earth loop, ten ohm resistor from input/coax/fb shunt signal ground to power ground, perhaps one on each module.
Thank you for building the Alpha!!
Hugh
Thank you! Something I put together from some old heatsinks and sheet metal, a true DIY case 🙂 Maybe it reflects the owner, I might be a bit different myself 😉 It actually has ok WAF when it's assembled,
I have cheated, secondary side of the transformer is not grounded 🙂 Both channels are floating, only the input ground is connecting them, minimizing risk of ground loops (transformers and case are grounded though).
I think the small hum is simply from the ripple from my simple supplies. From memory the amp PCB's have HBR's.
@Hugh: I only have some small caps between signal grounds to case at the input connectors. I still have a lot to fix before it's finished..
I have cheated, secondary side of the transformer is not grounded 🙂 Both channels are floating, only the input ground is connecting them, minimizing risk of ground loops (transformers and case are grounded though).
I think the small hum is simply from the ripple from my simple supplies. From memory the amp PCB's have HBR's.
@Hugh: I only have some small caps between signal grounds to case at the input connectors. I still have a lot to fix before it's finished..
Very nice work RF! Those are unique looking heatsinks. I like the low profile case with toroidal trafos on the outside. Interesting design. Your PSU has no CRC, just C’s and that might be the hum you are hearing. The front end doesn’t need a cap Mx, it’s the output stage really. Try adding even a 15,000uF cap after the trafo and 0.22ohm resistor between that and the current cap you have. That should quiet it down substantially. Or if you want, try the SLB power supply and the amp will be silent and hum free. I would ground PSU through a 10ohm NTC to chassis. That might also reduce the hum.
Thank you! I think the heat sinks are from some RF-equipment, I got them from a EMC-engineer at work.
I think the hum is caused by the simple PSU as you say, however, from simulation it looked like hum could be improved by abt 30dB by smoothing only the supply to the the front end, actually only negative rail would do it. we discussed it with Hugh a few pages earlier.
Since I already have a small cap-mx in the case, that's what I would like to try first, Everything else takes up more space, and there is not so much, especially in the 'power box' at the back.
I think I could even live with it as is, since I can only hear the hum with my ear next to the woofer.
/Sam
I think the hum is caused by the simple PSU as you say, however, from simulation it looked like hum could be improved by abt 30dB by smoothing only the supply to the the front end, actually only negative rail would do it. we discussed it with Hugh a few pages earlier.
Since I already have a small cap-mx in the case, that's what I would like to try first, Everything else takes up more space, and there is not so much, especially in the 'power box' at the back.
I think I could even live with it as is, since I can only hear the hum with my ear next to the woofer.
/Sam
I'm cutting some traces for my separate front end supply, and just saw that C101 (HF cap at input) is shunting to power ground and not signal ground. Is this by design? Just thinking some HF could be fed to the input from the 'dirty' ground?
That’s the RF filter cap, you want that shunted to analog 0v ground for most effective attenuation. That’s clean unlifted ground. Dirty ground is on other side of the NTC connected to PE tab. I suppose you could try moving it but I generally connect that to 0v ground.
Ok, I'll leave it as is. (Sorry, RF is the correct term, I was thinking High Frequencies)
I did a quick startup after connecting the cap-mx to the front end, but just based on my hearing as measurement, it did nothing to the hum.
@Hugh:
I'm intrigued by R123/C121, I guess this combo has some (maybe a lot?) effect on the sound character of the amp, and I would like to play around with them and listen just out of curiosity.
Do they affect the stability of the amp, or are they only there for tuning the sound? Since my tian-probe gives me weird results, I can't simulate it.. Could I bother you with simulating two variants? One without these connected, and one with C121 shorted but R123 still in place? I guess this should give the extremes, and everything in between should probably be safe?
I did a quick startup after connecting the cap-mx to the front end, but just based on my hearing as measurement, it did nothing to the hum.
@Hugh:
I'm intrigued by R123/C121, I guess this combo has some (maybe a lot?) effect on the sound character of the amp, and I would like to play around with them and listen just out of curiosity.
Do they affect the stability of the amp, or are they only there for tuning the sound? Since my tian-probe gives me weird results, I can't simulate it.. Could I bother you with simulating two variants? One without these connected, and one with C121 shorted but R123 still in place? I guess this should give the extremes, and everything in between should probably be safe?