Building an ultimate low power class A amplifier – my way

Hi tombo56

I really like the design of this amplifier, it looks like it will be in hard control and easy swinging.
I also like the possibility of summer setting as we get 30°+ ambient in the summer here.

Looking at ordering the pcb; the default
pcb thickness is 1.6
outer copper weight is 1oz
inner copper weight is 0.5 oz
Is there any benefit of increasing any of these values?
( apart from paying more :unsure: )

I guess that the other values are ok as default,
apart from the layer sequence.

rebone
 
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s there any benefit of increasing any of these values?
Hi rebone,
Any benefit from inner layers at 1 oz is doubtful. Though, I did use 1 oz for all layers as my build was to be an ultimate.
With low total dissipation, this amplifier doesn't really need summer bias setting except in case of very small heatsinks and very high environment temperatures.
 
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Hi -

It looks like there is a nice bit of interest in the project.

@tombo56, if you are OK with it, I'll be happy to sell my extra boards to those in the USA (shipping outside the US is likely more expensive than the boards). $5 per board + (typically) $7 for shipping in the USA. I don't want to put them in the swap meet or anything, it's your project / your property.

I ordered the specs below. Edited to put in correct specs vs picture and easier to read...

Outer Copper 2 oz
Inner Copper 0.5 oz
Green
HASL
 
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@tombo56, if you are OK with it, I'll be happy to sell my extra boards to those in the USA
And I'll be happy as well. :)
This is a completely free project as I don't sell PCBs.

Regarding 2 oz for outer layers, it would be better to order PCBs with 1 oz for all layers. Price would be likely the same or even lower. Where it matters (output stage power and loudspeaker output, I use all 4 layers in parallel (where possible).
 
Hi tombo56

I really like the design of this amplifier, it looks like it will be in hard control and easy swinging.
I also like the possibility of summer setting as we get 30°+ ambient in the summer here.

Looking at ordering the pcb; the default
pcb thickness is 1.6
outer copper weight is 1oz
inner copper weight is 0.5 oz
Is there any benefit of increasing any of these values?
( apart from paying more :unsure: )

I guess that the other values are ok as default,
apart from the layer sequence.

rebone
here it is the setup if you order as the "developer" choose
here:
 
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Just one last checkup.
Thank you!
Did you check PCB layers sequence as shown at the post #16.
I did not. I had it in my notes, but... DOH!
AFAIK, JLCPCB will automatically assign the correct sequence but it is better to be sure.
This is how it is displayed in their Gerber viewer for the boards I ordered. I made an effort to do a quick continuity check against the schematic to be sure the boards matched. They seem to, but if there is anything I could/should do to be more confident that they're proper, please let me know. I don't mind it so much for me... but I've already had a few people contact me about boards. I want to be very sure I didn't goof. The board viewer doesn't show the file associated with each layer. I made an effort, by uploading the Gerber again and clicking to view various layers... I admit that it's better if someone more skilled takes a look.

Thank you!

All layers
1704466460888.png


Top layer only
1704466594799.png

Inner1 layer only
1704466655868.png

Inner2 Layer Only
1704466720205.png

Bottom Layer Only
1704466755203.png
 
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Yes there is Gary... Baby Bliss was born and first sound heard on 1/8/24. Today she was moved to the main rig. The front panel power switch and standby LED indicator still need to be drilled and tidy up some internal wiring. My original plan was to build the Bliss boards and assemble a quickie wood plank amp so I can listen right away. But I'm also parallel building the F6 Diamond and thought these amps should have a proper home when in use. So out came the big chassis and all the bells and whistles, SSR soft start, momentary pushbutton switch, SSR DC protection boards with delay on and instant off controlled by the soft start board and over temperature cut off (not that Bliss would ever reach the temp threshold).
So the process took much longer than expected, but well worth the wait. Today was really the first time I listened to my go to test tracks.
System chain:
MacMini w/linear psu conversion as music server-->Homebrew NOS AD1862 DAC-->Topping Pre90 (most neutral preamp I have now)-->Bliss Amp-->Tang Band W8-2314 in TL enclosure. Impressions from my short time with Bliss are very good. The speakers disappear and the soundstage is wide, Tool's 'Chocolate Chip Trip' sounds spooky - super impressive! I use London Grammer's 'Hey Now' track to sleuth out any low frequency issues. The bass output is strong and controlled, no "flabbyness" whatsoever, doesn't seem like a low power amp. Looking forward to clocking many more hours on Bliss, it's been hard to walk out of the living room with the music playing.
Fantastic creation Tombo56!! Bliss ROCKS!
A few porn pics attached here :yes:
 

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Congratulations on the superb build. It is as a Lego like platform where building blocks can be easily exchanged. Hopefully, your ‘merican room is big enough for the soundstage. Mine is somewhere at the neighbor. :)
Seems that we agree, coaxial drivers are a way to go for the good soundstage.

Make sure that resistors at the safety ground PCB (that small GLB marked one) are at least 100R They serve to break external ground loops formed by grounding wires in power cords and prevent signal to travel, between audio components, partially through power cord grounding wires. Full safety is maintained by the diode bridges.
 
Make sure that resistors at the safety ground PCB (that small GLB marked one) are at least 100R They serve to break external ground loops formed by grounding wires in power cords and prevent signal to travel, between audio components, partially through power cord grounding wires.

Why would you get "external ground loops formed by grounding wires in power cords"?

Yes, the earth wire in the power cord going to each component should be attached to the component's case (for safety reasons) - but if the signal ground is entirely separate from mains earth ... how do you get a (signal) earth loop?
 
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Amplifier ground, which is also a signal ground, is for safety reasons mandatory connected (in most cases with10R NTC, sometimes direct) to the chassis and every chassis is connected to the power earth safety wire. Power cords connect audio components to the same power earth ground point. Those wires form a parallel connection to the signal interconnection ground wires and signal distribution (through ground) is determined by impedances of those parallel connections. Draw a diagram and it will be clear.

Resistors from signal to the chassis ground, increase impedance in that unwanted signal branch. Diode bridge in parallel to R, allows use of high R value while safety is not compromised. Knowledgeable members like jneutron are explaining this for years. But it seems that it doesn't get through.
 
Hi Vunce, based on your 1st pic in post #175 and the discussion after it about earth/grounding, can you elaborate for us how you have wired your chassis. I see you have an earth stud on the chassis (with paint removed) that is directly connected to the earth terminal on the IEC mains input connector. Then you have 2 other wires from that stud that disappear under the PSU assembly. You then have a small square pcb next to it fitted with diode bridges, caps, resistors etc that appears to be a GND lift board or similar.

Can you explain for us here how you have this wired and do you have details or a link to that pcb ( I have not seen it before), that also might explain its operation and may even have the gerber files available. This might go a long way to answering some of the questions that arise around this subject.