If you have high sensitivity (for example 100dB) speakers and listen its at 50mW power (632mV RMS on 8R), at the listening position (usually from 6feet from two loudspeaker) generate 84.8dB sound pressure (SPL) calculation.
Your listening corresponds more than the noise of the busy street.
40dB is the quite library room.
So 632mV signal on loudspeaker, and you want 0.1mV noise (hum) level.
It's 76dB signal to noise ratio at 50mW .... at full (2W) power is 92dB!
Are you sure this is the biggest problem?
Right. At 0.48mV I’m thinking I am pretty close to limits of the power supply design no matter what I do to the grounding on this amp.
Measured at my seating position I probably average around 65 to 70dB.
0.48mV ripple at speaker is inaudible at 1 meter even with 101dB speakers. Of course ripple is higher at normal listening volume settings…measures 1.2mV at typical 70dB listening levels. Still completely inaudible.
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Very true!l … But where is the fun in that? 😜
For me, this post was about learning best practices and grounding theory from those with much greater knowledge than myself. Thanks to you and others I accomplished this goal. Of course, still more to learn.
2nd Mono Block
I tried to incorporate what I learned from the group in the second monoblock. Still a couple of wire “swoops“ trying to stay clear of the rectifier/first cap wires. Maybe overkill?
Gone is the star ground in the corner. (The tag strip is there for the chassis ground and in case I want to add a resistor and capacitor) Also tried to incorporate proper “transformer-first cap-rectifier” connections.
The white wire is one continuous piece of 16 gauge. I cut the insulation and pulled apart, then threaded through widened holes in cap connectors. I was going to use 14 gauge, but it just wouldn’t fit. Do overs I would probably notch the tops of the cap connectors and lay the wire in.
With this configuration, radial caps would’ve made more sense on the driver filters.
Better? Worse? Let me know what you think!
Thank you everyone for the help so far!
I tried to incorporate what I learned from the group in the second monoblock. Still a couple of wire “swoops“ trying to stay clear of the rectifier/first cap wires. Maybe overkill?
Gone is the star ground in the corner. (The tag strip is there for the chassis ground and in case I want to add a resistor and capacitor) Also tried to incorporate proper “transformer-first cap-rectifier” connections.
The white wire is one continuous piece of 16 gauge. I cut the insulation and pulled apart, then threaded through widened holes in cap connectors. I was going to use 14 gauge, but it just wouldn’t fit. Do overs I would probably notch the tops of the cap connectors and lay the wire in.
With this configuration, radial caps would’ve made more sense on the driver filters.
Better? Worse? Let me know what you think!
Thank you everyone for the help so far!
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Allowed driver filter cap electrolytes to form for a few days before measuring.
The ripple at speaker terminal measures 0.30mV.
A 38% improvement over the first mono block which measures 0.48mV!
I call that a win!
A pretty basic filter, but I guess I had not reached the theoretical limit of the design after all!
Possibly more to go, but I am quite happy with this improvement with a few simple wiring changes. Not too bad for an AC heated DHT.
Thanks all…Especially euro and sUMMER for hanging in there with me!
Nothing is “basic” if you don’t know.
The ripple at speaker terminal measures 0.30mV.
A 38% improvement over the first mono block which measures 0.48mV!
I call that a win!
A pretty basic filter, but I guess I had not reached the theoretical limit of the design after all!
Possibly more to go, but I am quite happy with this improvement with a few simple wiring changes. Not too bad for an AC heated DHT.
Thanks all…Especially euro and sUMMER for hanging in there with me!
Nothing is “basic” if you don’t know.
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I was always taught that NOTHING else should be attached at the IEC connector ground point. Place an extra screw/nut/washer adjacent to it for the remaining connections. This is a safety issue to insure the ground to chassis connection is never disconnected when moving other connections.
IIRC, this is in a safety standard, possibly UL60950. I don't have my copies now that I am retired.
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